diff --git a/include/input/Input.h b/include/input/Input.h
index d4defa8..389b1bd 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -356,8 +356,6 @@
     float getAxisValue(int32_t axis) const;
     status_t setAxisValue(int32_t axis, float value);
 
-    void scale(float globalScale);
-
     // Scale the pointer coordinates according to a global scale and a
     // window scale. The global scale will be applied to TOUCH/TOOL_MAJOR/MINOR
     // axes, however the window scaling will not.
diff --git a/libs/gui/ISurfaceComposer.cpp b/libs/gui/ISurfaceComposer.cpp
index 53721cf..0436758 100644
--- a/libs/gui/ISurfaceComposer.cpp
+++ b/libs/gui/ISurfaceComposer.cpp
@@ -123,11 +123,11 @@
         return remote()->transact(BnSurfaceComposer::CAPTURE_DISPLAY, data, &reply);
     }
 
-    status_t captureDisplay(uint64_t displayOrLayerStack,
+    status_t captureDisplay(DisplayId displayId,
                             const sp<IScreenCaptureListener>& captureListener) override {
         Parcel data, reply;
         data.writeInterfaceToken(ISurfaceComposer::getInterfaceDescriptor());
-        SAFE_PARCEL(data.writeUint64, displayOrLayerStack);
+        SAFE_PARCEL(data.writeUint64, displayId.value);
         SAFE_PARCEL(data.writeStrongBinder, IInterface::asBinder(captureListener));
 
         return remote()->transact(BnSurfaceComposer::CAPTURE_DISPLAY_BY_ID, data, &reply);
@@ -281,9 +281,14 @@
             NO_ERROR) {
             std::vector<uint64_t> rawIds;
             if (reply.readUint64Vector(&rawIds) == NO_ERROR) {
-                std::vector<PhysicalDisplayId> displayIds(rawIds.size());
-                std::transform(rawIds.begin(), rawIds.end(), displayIds.begin(),
-                               [](uint64_t rawId) { return PhysicalDisplayId(rawId); });
+                std::vector<PhysicalDisplayId> displayIds;
+                displayIds.reserve(rawIds.size());
+
+                for (const uint64_t rawId : rawIds) {
+                    if (const auto id = DisplayId::fromValue<PhysicalDisplayId>(rawId)) {
+                        displayIds.push_back(*id);
+                    }
+                }
                 return displayIds;
             }
         }
@@ -1296,12 +1301,15 @@
         }
         case CAPTURE_DISPLAY_BY_ID: {
             CHECK_INTERFACE(ISurfaceComposer, data, reply);
-            uint64_t displayOrLayerStack = 0;
+            uint64_t value;
+            SAFE_PARCEL(data.readUint64, &value);
+            const auto id = DisplayId::fromValue(value);
+            if (!id) return BAD_VALUE;
+
             sp<IScreenCaptureListener> captureListener;
-            SAFE_PARCEL(data.readUint64, &displayOrLayerStack);
             SAFE_PARCEL(data.readStrongBinder, &captureListener);
 
-            return captureDisplay(displayOrLayerStack, captureListener);
+            return captureDisplay(*id, captureListener);
         }
         case CAPTURE_LAYERS: {
             CHECK_INTERFACE(ISurfaceComposer, data, reply);
@@ -1368,9 +1376,9 @@
         }
         case GET_PHYSICAL_DISPLAY_TOKEN: {
             CHECK_INTERFACE(ISurfaceComposer, data, reply);
-            PhysicalDisplayId displayId(data.readUint64());
-            sp<IBinder> display = getPhysicalDisplayToken(displayId);
-            reply->writeStrongBinder(display);
+            const auto id = DisplayId::fromValue<PhysicalDisplayId>(data.readUint64());
+            if (!id) return BAD_VALUE;
+            reply->writeStrongBinder(getPhysicalDisplayToken(*id));
             return NO_ERROR;
         }
         case GET_DISPLAY_STATE: {
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index aa93808..1bb6393 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -2125,12 +2125,12 @@
     return s->captureDisplay(captureArgs, captureListener);
 }
 
-status_t ScreenshotClient::captureDisplay(uint64_t displayOrLayerStack,
+status_t ScreenshotClient::captureDisplay(DisplayId displayId,
                                           const sp<IScreenCaptureListener>& captureListener) {
     sp<ISurfaceComposer> s(ComposerService::getComposerService());
     if (s == nullptr) return NO_INIT;
 
-    return s->captureDisplay(displayOrLayerStack, captureListener);
+    return s->captureDisplay(displayId, captureListener);
 }
 
 status_t ScreenshotClient::captureLayers(const LayerCaptureArgs& captureArgs,
diff --git a/libs/gui/include/gui/ISurfaceComposer.h b/libs/gui/include/gui/ISurfaceComposer.h
index cb04689..c420e4a 100644
--- a/libs/gui/include/gui/ISurfaceComposer.h
+++ b/libs/gui/include/gui/ISurfaceComposer.h
@@ -114,6 +114,11 @@
 
     using EventRegistrationFlags = Flags<EventRegistration>;
 
+    template <typename T>
+    struct SpHash {
+        size_t operator()(const sp<T>& k) const { return std::hash<T*>()(k.get()); }
+    };
+
     /*
      * Create a connection with SurfaceFlinger.
      */
@@ -237,24 +242,17 @@
      * The subregion can be optionally rotated.  It will also be scaled to
      * match the size of the output buffer.
      */
-    virtual status_t captureDisplay(const DisplayCaptureArgs& args,
-                                    const sp<IScreenCaptureListener>& captureListener) = 0;
+    virtual status_t captureDisplay(const DisplayCaptureArgs&,
+                                    const sp<IScreenCaptureListener>&) = 0;
 
-    virtual status_t captureDisplay(uint64_t displayOrLayerStack,
-                                    const sp<IScreenCaptureListener>& captureListener) = 0;
-
-    template <class AA>
-    struct SpHash {
-        size_t operator()(const sp<AA>& k) const { return std::hash<AA*>()(k.get()); }
-    };
+    virtual status_t captureDisplay(DisplayId, const sp<IScreenCaptureListener>&) = 0;
 
     /**
      * Capture a subtree of the layer hierarchy, potentially ignoring the root node.
      * This requires READ_FRAME_BUFFER permission. This function will fail if there
      * is a secure window on screen
      */
-    virtual status_t captureLayers(const LayerCaptureArgs& args,
-                                   const sp<IScreenCaptureListener>& captureListener) = 0;
+    virtual status_t captureLayers(const LayerCaptureArgs&, const sp<IScreenCaptureListener>&) = 0;
 
     /* Clears the frame statistics for animations.
      *
diff --git a/libs/gui/include/gui/SurfaceComposerClient.h b/libs/gui/include/gui/SurfaceComposerClient.h
index 0940e9d..86f1b63 100644
--- a/libs/gui/include/gui/SurfaceComposerClient.h
+++ b/libs/gui/include/gui/SurfaceComposerClient.h
@@ -623,12 +623,9 @@
 
 class ScreenshotClient {
 public:
-    static status_t captureDisplay(const DisplayCaptureArgs& captureArgs,
-                                   const sp<IScreenCaptureListener>& captureListener);
-    static status_t captureDisplay(uint64_t displayOrLayerStack,
-                                   const sp<IScreenCaptureListener>& captureListener);
-    static status_t captureLayers(const LayerCaptureArgs& captureArgs,
-                                  const sp<IScreenCaptureListener>& captureListener);
+    static status_t captureDisplay(const DisplayCaptureArgs&, const sp<IScreenCaptureListener>&);
+    static status_t captureDisplay(DisplayId, const sp<IScreenCaptureListener>&);
+    static status_t captureLayers(const LayerCaptureArgs&, const sp<IScreenCaptureListener>&);
 };
 
 // ---------------------------------------------------------------------------
diff --git a/libs/gui/tests/Surface_test.cpp b/libs/gui/tests/Surface_test.cpp
index ea8c295..7002adf 100644
--- a/libs/gui/tests/Surface_test.cpp
+++ b/libs/gui/tests/Surface_test.cpp
@@ -752,21 +752,19 @@
     }
     status_t setActiveColorMode(const sp<IBinder>& /*display*/,
         ColorMode /*colorMode*/) override { return NO_ERROR; }
-    status_t captureDisplay(const DisplayCaptureArgs& /* captureArgs */,
-                            const sp<IScreenCaptureListener>& /* captureListener */) override {
-        return NO_ERROR;
-    }
     void setAutoLowLatencyMode(const sp<IBinder>& /*display*/, bool /*on*/) override {}
     void setGameContentType(const sp<IBinder>& /*display*/, bool /*on*/) override {}
-    status_t captureDisplay(uint64_t /*displayOrLayerStack*/,
-                            const sp<IScreenCaptureListener>& /* captureListener */) override {
+
+    status_t captureDisplay(const DisplayCaptureArgs&, const sp<IScreenCaptureListener>&) override {
         return NO_ERROR;
     }
-    virtual status_t captureLayers(
-            const LayerCaptureArgs& /* captureArgs */,
-            const sp<IScreenCaptureListener>& /* captureListener */) override {
+    status_t captureDisplay(DisplayId, const sp<IScreenCaptureListener>&) override {
         return NO_ERROR;
     }
+    status_t captureLayers(const LayerCaptureArgs&, const sp<IScreenCaptureListener>&) override {
+        return NO_ERROR;
+    }
+
     status_t clearAnimationFrameStats() override { return NO_ERROR; }
     status_t getAnimationFrameStats(FrameStats* /*outStats*/) const override {
         return NO_ERROR;
diff --git a/libs/input/Input.cpp b/libs/input/Input.cpp
index 649a140..e8c05e5 100644
--- a/libs/input/Input.cpp
+++ b/libs/input/Input.cpp
@@ -253,10 +253,6 @@
     scaleAxisValue(*this, AMOTION_EVENT_AXIS_TOOL_MINOR, globalScaleFactor);
 }
 
-void PointerCoords::scale(float globalScaleFactor) {
-    scale(globalScaleFactor, globalScaleFactor, globalScaleFactor);
-}
-
 void PointerCoords::applyOffset(float xOffset, float yOffset) {
     setAxisValue(AMOTION_EVENT_AXIS_X, getX() + xOffset);
     setAxisValue(AMOTION_EVENT_AXIS_Y, getY() + yOffset);
diff --git a/libs/nativedisplay/AChoreographer.cpp b/libs/nativedisplay/AChoreographer.cpp
index 0edb213..e7bd977 100644
--- a/libs/nativedisplay/AChoreographer.cpp
+++ b/libs/nativedisplay/AChoreographer.cpp
@@ -306,8 +306,9 @@
         // Fortunately, these events are small so sending packets across the
         // socket should be atomic across processes.
         DisplayEventReceiver::Event event;
-        event.header = DisplayEventReceiver::Event::Header{DisplayEventReceiver::DISPLAY_EVENT_NULL,
-                                                           PhysicalDisplayId(0), systemTime()};
+        event.header =
+                DisplayEventReceiver::Event::Header{DisplayEventReceiver::DISPLAY_EVENT_NULL,
+                                                    PhysicalDisplayId::fromPort(0), systemTime()};
         injectEvent(event);
     }
 }
diff --git a/libs/nativewindow/include/android/hardware_buffer.h b/libs/nativewindow/include/android/hardware_buffer.h
index d93a84c..d5e7cb2 100644
--- a/libs/nativewindow/include/android/hardware_buffer.h
+++ b/libs/nativewindow/include/android/hardware_buffer.h
@@ -556,6 +556,7 @@
                                    int32_t* _Nonnull outBytesPerPixel,
                                    int32_t* _Nonnull outBytesPerStride) __INTRODUCED_IN(29);
 
+
 /**
  * Get the system wide unique id for an AHardwareBuffer.
  *
diff --git a/libs/ui/Android.bp b/libs/ui/Android.bp
index 74d17ce..5a118ec 100644
--- a/libs/ui/Android.bp
+++ b/libs/ui/Android.bp
@@ -137,7 +137,6 @@
         "HdrCapabilities.cpp",
         "PixelFormat.cpp",
         "PublicFormat.cpp",
-        "Size.cpp",
         "StaticDisplayInfo.cpp",
     ],
 
diff --git a/libs/ui/Size.cpp b/libs/ui/Size.cpp
deleted file mode 100644
index d2996d1..0000000
--- a/libs/ui/Size.cpp
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * Copyright 2019 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <ui/Size.h>
-
-namespace android::ui {
-
-const Size Size::INVALID{-1, -1};
-const Size Size::EMPTY{0, 0};
-
-} // namespace android::ui
diff --git a/libs/ui/include/ui/DisplayId.h b/libs/ui/include/ui/DisplayId.h
index f196ab9..9120972 100644
--- a/libs/ui/include/ui/DisplayId.h
+++ b/libs/ui/include/ui/DisplayId.h
@@ -38,12 +38,22 @@
 
     uint64_t value;
 
+    // For deserialization.
+    static constexpr std::optional<DisplayId> fromValue(uint64_t);
+
+    // As above, but also upcast to Id.
+    template <typename Id>
+    static constexpr std::optional<Id> fromValue(uint64_t value) {
+        if (const auto id = Id::tryCast(DisplayId(value))) {
+            return id;
+        }
+        return {};
+    }
+
 protected:
     explicit constexpr DisplayId(uint64_t id) : value(id) {}
 };
 
-static_assert(sizeof(DisplayId) == sizeof(uint64_t));
-
 inline bool operator==(DisplayId lhs, DisplayId rhs) {
     return lhs.value == rhs.value;
 }
@@ -80,11 +90,8 @@
 
     // TODO(b/162612135) Remove default constructor
     PhysicalDisplayId() = default;
-    // TODO(b/162612135) Remove constructor
-    explicit constexpr PhysicalDisplayId(uint64_t id) : DisplayId(id) {}
 
     constexpr uint16_t getManufacturerId() const { return static_cast<uint16_t>(value >> 40); }
-
     constexpr uint8_t getPort() const { return static_cast<uint8_t>(value); }
 
 private:
@@ -96,10 +103,9 @@
     explicit constexpr PhysicalDisplayId(DisplayId other) : DisplayId(other) {}
 };
 
-static_assert(sizeof(PhysicalDisplayId) == sizeof(uint64_t));
-
 struct VirtualDisplayId : DisplayId {
     using BaseId = uint32_t;
+
     // Flag indicating that this virtual display is backed by the GPU.
     static constexpr uint64_t FLAG_GPU = 1ULL << 61;
 
@@ -163,10 +169,23 @@
     explicit constexpr HalDisplayId(DisplayId other) : DisplayId(other) {}
 };
 
+constexpr std::optional<DisplayId> DisplayId::fromValue(uint64_t value) {
+    if (const auto id = fromValue<PhysicalDisplayId>(value)) {
+        return id;
+    }
+    if (const auto id = fromValue<VirtualDisplayId>(value)) {
+        return id;
+    }
+    return {};
+}
+
+static_assert(sizeof(DisplayId) == sizeof(uint64_t));
+static_assert(sizeof(HalDisplayId) == sizeof(uint64_t));
 static_assert(sizeof(VirtualDisplayId) == sizeof(uint64_t));
+
+static_assert(sizeof(PhysicalDisplayId) == sizeof(uint64_t));
 static_assert(sizeof(HalVirtualDisplayId) == sizeof(uint64_t));
 static_assert(sizeof(GpuVirtualDisplayId) == sizeof(uint64_t));
-static_assert(sizeof(HalDisplayId) == sizeof(uint64_t));
 
 } // namespace android
 
diff --git a/libs/ui/include/ui/Size.h b/libs/ui/include/ui/Size.h
index f1e8252..ecc192d 100644
--- a/libs/ui/include/ui/Size.h
+++ b/libs/ui/include/ui/Size.h
@@ -23,103 +23,70 @@
 #include <type_traits>
 #include <utility>
 
-namespace android {
-namespace ui {
+namespace android::ui {
 
-// Forward declare a few things.
-struct Size;
-bool operator==(const Size& lhs, const Size& rhs);
-
-/**
- * A simple value type representing a two-dimensional size
- */
+// A simple value type representing a two-dimensional size.
 struct Size {
-    int32_t width;
-    int32_t height;
+    int32_t width = -1;
+    int32_t height = -1;
 
-    // Special values
-    static const Size INVALID;
-    static const Size EMPTY;
+    constexpr Size() = default;
 
-    // ------------------------------------------------------------------------
-    // Construction
-    // ------------------------------------------------------------------------
-
-    Size() : Size(INVALID) {}
     template <typename T>
-    Size(T&& w, T&& h)
-          : width(Size::clamp<int32_t, T>(std::forward<T>(w))),
-            height(Size::clamp<int32_t, T>(std::forward<T>(h))) {}
-
-    // ------------------------------------------------------------------------
-    // Accessors
-    // ------------------------------------------------------------------------
+    constexpr Size(T w, T h) : width(clamp<int32_t>(w)), height(clamp<int32_t>(h)) {}
 
     int32_t getWidth() const { return width; }
     int32_t getHeight() const { return height; }
 
-    template <typename T>
-    void setWidth(T&& v) {
-        width = Size::clamp<int32_t, T>(std::forward<T>(v));
-    }
-    template <typename T>
-    void setHeight(T&& v) {
-        height = Size::clamp<int32_t, T>(std::forward<T>(v));
-    }
-
-    // ------------------------------------------------------------------------
-    // Assignment
-    // ------------------------------------------------------------------------
-
-    void set(const Size& size) { *this = size; }
-    template <typename T>
-    void set(T&& w, T&& h) {
-        set(Size(std::forward<T>(w), std::forward<T>(h)));
-    }
-
-    // Sets the value to INVALID
-    void makeInvalid() { set(INVALID); }
-
-    // Sets the value to EMPTY
-    void clear() { set(EMPTY); }
-
-    // ------------------------------------------------------------------------
-    // Semantic checks
-    // ------------------------------------------------------------------------
-
     // Valid means non-negative width and height
     bool isValid() const { return width >= 0 && height >= 0; }
 
     // Empty means zero width and height
-    bool isEmpty() const { return *this == EMPTY; }
+    bool isEmpty() const;
 
-    // ------------------------------------------------------------------------
-    // Clamp Helpers
-    // ------------------------------------------------------------------------
-
-    // Note: We use only features available in C++11 here for compatibility with
-    // external targets which include this file directly or indirectly and which
-    // themselves use C++11.
-
-    // C++11 compatible replacement for std::remove_cv_reference_t [C++20]
     template <typename T>
-    using remove_cv_reference_t =
-            typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+    void setWidth(T v) {
+        width = clamp<int32_t>(v);
+    }
+
+    template <typename T>
+    void setHeight(T v) {
+        height = clamp<int32_t>(v);
+    }
+
+    void set(Size size) { *this = size; }
+
+    template <typename T>
+    void set(T w, T h) {
+        set(Size(w, h));
+    }
+
+    // Sets the value to kInvalidSize
+    void makeInvalid();
+
+    // Sets the value to kEmptySize
+    void clear();
+
+    // TODO: Replace with std::remove_cvref_t in C++20.
+    template <typename T>
+    using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<T>>;
 
     // Takes a value of type FromType, and ensures it can be represented as a value of type ToType,
     // clamping the input value to the output range if necessary.
     template <typename ToType, typename FromType>
-    static Size::remove_cv_reference_t<ToType>
-    clamp(typename std::enable_if<
-            std::numeric_limits<Size::remove_cv_reference_t<ToType>>::is_specialized &&
-                    std::numeric_limits<Size::remove_cv_reference_t<FromType>>::is_specialized,
-            FromType>::type v) {
-        using BareToType = remove_cv_reference_t<ToType>;
-        using BareFromType = remove_cv_reference_t<FromType>;
-        static constexpr auto toHighest = std::numeric_limits<BareToType>::max();
-        static constexpr auto toLowest = std::numeric_limits<BareToType>::lowest();
-        static constexpr auto fromHighest = std::numeric_limits<BareFromType>::max();
-        static constexpr auto fromLowest = std::numeric_limits<BareFromType>::lowest();
+    static constexpr remove_cvref_t<ToType> clamp(FromType v) {
+        using BareToType = remove_cvref_t<ToType>;
+        using ToLimits = std::numeric_limits<BareToType>;
+
+        using BareFromType = remove_cvref_t<FromType>;
+        using FromLimits = std::numeric_limits<BareFromType>;
+
+        static_assert(ToLimits::is_specialized && FromLimits::is_specialized);
+
+        constexpr auto toHighest = ToLimits::max();
+        constexpr auto toLowest = ToLimits::lowest();
+        constexpr auto fromHighest = FromLimits::max();
+        constexpr auto fromLowest = FromLimits::lowest();
 
         // Get the closest representation of [toLowest, toHighest] in type
         // FromType to use to clamp the input value before conversion.
@@ -127,37 +94,35 @@
         // std::common_type<...> is used to get a value-preserving type for the
         // top end of the range.
         using CommonHighestType = std::common_type_t<BareToType, BareFromType>;
+        using CommonLimits = std::numeric_limits<CommonHighestType>;
 
         // std::make_signed<std::common_type<...>> is used to get a
         // value-preserving type for the bottom end of the range, except this is
         // a bit trickier for non-integer types like float.
-        using CommonLowestType =
-                std::conditional_t<std::numeric_limits<CommonHighestType>::is_integer,
-                                   std::make_signed_t<std::conditional_t<
-                                           std::numeric_limits<CommonHighestType>::is_integer,
-                                           CommonHighestType, int /* not used */>>,
-                                   CommonHighestType>;
+        using CommonLowestType = std::conditional_t<
+                CommonLimits::is_integer,
+                std::make_signed_t<std::conditional_t<CommonLimits::is_integer, CommonHighestType,
+                                                      int /* not used */>>,
+                CommonHighestType>;
 
         // We can then compute the clamp range in a way that can be later
         // trivially converted to either the 'from' or 'to' types, and be
-        // representabile in either.
-        static constexpr auto commonClampHighest =
-                std::min(static_cast<CommonHighestType>(fromHighest),
-                         static_cast<CommonHighestType>(toHighest));
-        static constexpr auto commonClampLowest =
-                std::max(static_cast<CommonLowestType>(fromLowest),
-                         static_cast<CommonLowestType>(toLowest));
+        // representable in either.
+        constexpr auto commonClampHighest = std::min(static_cast<CommonHighestType>(fromHighest),
+                                                     static_cast<CommonHighestType>(toHighest));
+        constexpr auto commonClampLowest = std::max(static_cast<CommonLowestType>(fromLowest),
+                                                    static_cast<CommonLowestType>(toLowest));
 
-        static constexpr auto fromClampHighest = static_cast<BareFromType>(commonClampHighest);
-        static constexpr auto fromClampLowest = static_cast<BareFromType>(commonClampLowest);
+        constexpr auto fromClampHighest = static_cast<BareFromType>(commonClampHighest);
+        constexpr auto fromClampLowest = static_cast<BareFromType>(commonClampLowest);
 
         // A clamp is needed only if the range we are clamping to is not the
         // same as the range of the input.
-        static constexpr bool isClampNeeded =
+        constexpr bool isClampNeeded =
                 (fromLowest != fromClampLowest) || (fromHighest != fromClampHighest);
 
         // If a clamp is not needed, the conversion is just a trivial cast.
-        if (!isClampNeeded) {
+        if constexpr (!isClampNeeded) {
             return static_cast<BareToType>(v);
         }
 
@@ -170,34 +135,46 @@
 
         // Otherwise clamping is done by using the already computed endpoints
         // for each type.
-        return (v <= fromClampLowest)
-                ? toClampLowest
-                : ((v >= fromClampHighest) ? toClampHighest : static_cast<BareToType>(v));
+        if (v <= fromClampLowest) {
+            return toClampLowest;
+        }
+
+        return v >= fromClampHighest ? toClampHighest : static_cast<BareToType>(v);
     }
 };
 
-// ------------------------------------------------------------------------
-// Comparisons
-// ------------------------------------------------------------------------
+constexpr Size kInvalidSize;
+constexpr Size kEmptySize{0, 0};
 
-inline bool operator==(const Size& lhs, const Size& rhs) {
+inline void Size::makeInvalid() {
+    set(kInvalidSize);
+}
+
+inline void Size::clear() {
+    set(kEmptySize);
+}
+
+inline bool operator==(Size lhs, Size rhs) {
     return lhs.width == rhs.width && lhs.height == rhs.height;
 }
 
-inline bool operator!=(const Size& lhs, const Size& rhs) {
-    return !operator==(lhs, rhs);
+inline bool Size::isEmpty() const {
+    return *this == kEmptySize;
 }
 
-inline bool operator<(const Size& lhs, const Size& rhs) {
+inline bool operator!=(Size lhs, Size rhs) {
+    return !(lhs == rhs);
+}
+
+inline bool operator<(Size lhs, Size rhs) {
     // Orders by increasing width, then height.
     if (lhs.width != rhs.width) return lhs.width < rhs.width;
     return lhs.height < rhs.height;
 }
 
 // Defining PrintTo helps with Google Tests.
-static inline void PrintTo(const Size& size, ::std::ostream* os) {
-    *os << "Size(" << size.width << ", " << size.height << ")";
+inline void PrintTo(Size size, std::ostream* stream) {
+    *stream << "Size(" << size.width << ", " << size.height << ')';
 }
 
-} // namespace ui
-} // namespace android
+} // namespace android::ui
diff --git a/libs/ui/tests/DisplayId_test.cpp b/libs/ui/tests/DisplayId_test.cpp
index 1d908b8..8ddee7e 100644
--- a/libs/ui/tests/DisplayId_test.cpp
+++ b/libs/ui/tests/DisplayId_test.cpp
@@ -32,6 +32,9 @@
     EXPECT_FALSE(GpuVirtualDisplayId::tryCast(id));
     EXPECT_TRUE(PhysicalDisplayId::tryCast(id));
     EXPECT_TRUE(HalDisplayId::tryCast(id));
+
+    EXPECT_EQ(id, DisplayId::fromValue(id.value));
+    EXPECT_EQ(id, DisplayId::fromValue<PhysicalDisplayId>(id.value));
 }
 
 TEST(DisplayIdTest, createPhysicalIdFromPort) {
@@ -43,6 +46,9 @@
     EXPECT_FALSE(GpuVirtualDisplayId::tryCast(id));
     EXPECT_TRUE(PhysicalDisplayId::tryCast(id));
     EXPECT_TRUE(HalDisplayId::tryCast(id));
+
+    EXPECT_EQ(id, DisplayId::fromValue(id.value));
+    EXPECT_EQ(id, DisplayId::fromValue<PhysicalDisplayId>(id.value));
 }
 
 TEST(DisplayIdTest, createGpuVirtualId) {
@@ -52,6 +58,9 @@
     EXPECT_FALSE(HalVirtualDisplayId::tryCast(id));
     EXPECT_FALSE(PhysicalDisplayId::tryCast(id));
     EXPECT_FALSE(HalDisplayId::tryCast(id));
+
+    EXPECT_EQ(id, DisplayId::fromValue(id.value));
+    EXPECT_EQ(id, DisplayId::fromValue<GpuVirtualDisplayId>(id.value));
 }
 
 TEST(DisplayIdTest, createHalVirtualId) {
@@ -61,6 +70,9 @@
     EXPECT_FALSE(GpuVirtualDisplayId::tryCast(id));
     EXPECT_FALSE(PhysicalDisplayId::tryCast(id));
     EXPECT_TRUE(HalDisplayId::tryCast(id));
+
+    EXPECT_EQ(id, DisplayId::fromValue(id.value));
+    EXPECT_EQ(id, DisplayId::fromValue<HalVirtualDisplayId>(id.value));
 }
 
 } // namespace android::ui
diff --git a/libs/ui/tests/Size_test.cpp b/libs/ui/tests/Size_test.cpp
index 5f75aea..acef47f 100644
--- a/libs/ui/tests/Size_test.cpp
+++ b/libs/ui/tests/Size_test.cpp
@@ -93,9 +93,8 @@
     }
 
     {
-        const auto& s = Size::INVALID;
-        EXPECT_FALSE(s.isValid());
-        EXPECT_FALSE(s.isEmpty());
+        EXPECT_FALSE(kInvalidSize.isValid());
+        EXPECT_FALSE(kInvalidSize.isEmpty());
     }
 
     {
@@ -112,9 +111,8 @@
     }
 
     {
-        const auto& s = Size::EMPTY;
-        EXPECT_TRUE(s.isValid());
-        EXPECT_TRUE(s.isEmpty());
+        EXPECT_TRUE(kEmptySize.isValid());
+        EXPECT_TRUE(kEmptySize.isEmpty());
     }
 
     {
diff --git a/services/automotive/display/AutomotiveDisplayProxyService.cpp b/services/automotive/display/AutomotiveDisplayProxyService.cpp
index d6fc695..d205231 100644
--- a/services/automotive/display/AutomotiveDisplayProxyService.cpp
+++ b/services/automotive/display/AutomotiveDisplayProxyService.cpp
@@ -34,7 +34,10 @@
     sp<IBinder> displayToken = nullptr;
     sp<SurfaceControl> surfaceControl = nullptr;
     if (it == mDisplays.end()) {
-        displayToken = SurfaceComposerClient::getPhysicalDisplayToken(PhysicalDisplayId(id));
+        if (const auto displayId = DisplayId::fromValue<PhysicalDisplayId>(id)) {
+            displayToken = SurfaceComposerClient::getPhysicalDisplayToken(*displayId);
+        }
+
         if (displayToken == nullptr) {
             ALOGE("Given display id, 0x%lX, is invalid.", (unsigned long)id);
             return nullptr;
@@ -157,7 +160,11 @@
     HwDisplayConfig activeConfig;
     HwDisplayState  activeState;
 
-    auto displayToken = SurfaceComposerClient::getPhysicalDisplayToken(PhysicalDisplayId(id));
+    sp<IBinder> displayToken;
+    if (const auto displayId = DisplayId::fromValue<PhysicalDisplayId>(id)) {
+        displayToken = SurfaceComposerClient::getPhysicalDisplayToken(*displayId);
+    }
+
     if (displayToken == nullptr) {
         ALOGE("Given display id, 0x%lX, is invalid.", (unsigned long)id);
     } else {
diff --git a/services/inputflinger/dispatcher/Entry.cpp b/services/inputflinger/dispatcher/Entry.cpp
index 881024f..8d6bd8a 100644
--- a/services/inputflinger/dispatcher/Entry.cpp
+++ b/services/inputflinger/dispatcher/Entry.cpp
@@ -176,10 +176,11 @@
     }
     return StringPrintf("KeyEvent(deviceId=%d, eventTime=%" PRIu64
                         ", source=0x%08x, displayId=%" PRId32 ", action=%s, "
-                        "flags=0x%08x, keyCode=%d, scanCode=%d, metaState=0x%08x, "
+                        "flags=0x%08x, keyCode=%s(%d), scanCode=%d, metaState=0x%08x, "
                         "repeatCount=%d), policyFlags=0x%08x",
                         deviceId, eventTime, source, displayId, KeyEvent::actionToString(action),
-                        flags, keyCode, scanCode, metaState, repeatCount, policyFlags);
+                        flags, KeyEvent::getLabel(keyCode), keyCode, scanCode, metaState,
+                        repeatCount, policyFlags);
 }
 
 void KeyEntry::recycle() {
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/DisplayCreationArgs.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/DisplayCreationArgs.h
index 633668e..526e7da 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/DisplayCreationArgs.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/DisplayCreationArgs.h
@@ -21,13 +21,10 @@
 #include <string>
 
 #include <ui/DisplayId.h>
-#include <ui/PixelFormat.h>
 #include <ui/Size.h>
 #include <ui/StaticDisplayInfo.h>
 
-#include "DisplayHardware/DisplayIdentification.h"
 #include "DisplayHardware/PowerAdvisor.h"
-#include "DisplayIdGenerator.h"
 
 namespace android::compositionengine {
 
@@ -37,23 +34,13 @@
  * A parameter object for creating Display instances
  */
 struct DisplayCreationArgs {
-    struct Physical {
-        DisplayId id;
-        ui::DisplayConnectionType type;
-    };
+    DisplayId id;
 
-    // Required for physical displays. Gives the HWC display id for the existing
-    // display along with the connection type.
-    std::optional<Physical> physical;
+    // Unset for virtual displays
+    std::optional<ui::DisplayConnectionType> connectionType;
 
     // Size of the display in pixels
-    ui::Size pixels = ui::Size::INVALID;
-
-    // Pixel format of the display
-    ui::PixelFormat pixelFormat = static_cast<ui::PixelFormat>(PIXEL_FORMAT_UNKNOWN);
-
-    // True if virtual displays should be created with the HWC API if possible
-    bool useHwcVirtualDisplays = false;
+    ui::Size pixels = ui::kInvalidSize;
 
     // True if this display should be considered secure
     bool isSecure = false;
@@ -67,9 +54,6 @@
 
     // Debugging. Human readable name for the display.
     std::string name;
-
-    // Generator for IDs of virtual displays, which are backed by the GPU.
-    DisplayIdGenerator<GpuVirtualDisplayId>* gpuVirtualDisplayIdGenerator;
 };
 
 /**
@@ -80,8 +64,13 @@
 public:
     DisplayCreationArgs build() { return std::move(mArgs); }
 
-    DisplayCreationArgsBuilder& setPhysical(DisplayCreationArgs::Physical physical) {
-        mArgs.physical = physical;
+    DisplayCreationArgsBuilder& setId(DisplayId id) {
+        mArgs.id = id;
+        return *this;
+    }
+
+    DisplayCreationArgsBuilder& setConnectionType(ui::DisplayConnectionType connectionType) {
+        mArgs.connectionType = connectionType;
         return *this;
     }
 
@@ -90,22 +79,6 @@
         return *this;
     }
 
-    DisplayCreationArgsBuilder& setPixelFormat(ui::PixelFormat pixelFormat) {
-        mArgs.pixelFormat = pixelFormat;
-        return *this;
-    }
-
-    DisplayCreationArgsBuilder& setUseHwcVirtualDisplays(bool useHwcVirtualDisplays) {
-        mArgs.useHwcVirtualDisplays = useHwcVirtualDisplays;
-        return *this;
-    }
-
-    DisplayCreationArgsBuilder& setGpuVirtualDisplayIdGenerator(
-            DisplayIdGenerator<GpuVirtualDisplayId>& generator) {
-        mArgs.gpuVirtualDisplayIdGenerator = &generator;
-        return *this;
-    }
-
     DisplayCreationArgsBuilder& setIsSecure(bool isSecure) {
         mArgs.isSecure = isSecure;
         return *this;
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/RenderSurfaceCreationArgs.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/RenderSurfaceCreationArgs.h
index a8d372c..4110346 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/RenderSurfaceCreationArgs.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/RenderSurfaceCreationArgs.h
@@ -24,21 +24,17 @@
 
 struct ANativeWindow;
 
-namespace android {
-
-namespace compositionengine {
-
-class Display;
+namespace android::compositionengine {
 
 /**
  * A parameter object for creating RenderSurface instances
  */
 struct RenderSurfaceCreationArgs {
     // The initial width of the surface
-    int32_t displayWidth;
+    int32_t displayWidth = -1;
 
     // The initial height of the surface
-    int32_t displayHeight;
+    int32_t displayHeight = -1;
 
     // The ANativeWindow for the buffer queue for this surface
     sp<ANativeWindow> nativeWindow;
@@ -46,22 +42,16 @@
     // The DisplaySurface for this surface
     sp<DisplaySurface> displaySurface;
 
-    size_t maxTextureCacheSize;
+    // The maximum size of the renderengine::ExternalTexture cache
+    size_t maxTextureCacheSize = 0;
+
+private:
+    friend class RenderSurfaceCreationArgsBuilder;
+
+    // Not defaulted to disable aggregate initialization.
+    RenderSurfaceCreationArgs() {}
 };
 
-/**
- * A helper for setting up a RenderSurfaceCreationArgs value in-line.
- * Prefer this builder over raw structure initialization.
- *
- * Instead of:
- *
- *   RenderSurfaceCreationArgs{1000, 1000, nativeWindow, displaySurface}
- *
- * Prefer:
- *
- *  RenderSurfaceCreationArgsBuilder().setDisplayWidth(1000).setDisplayHeight(1000)
- *      .setNativeWindow(nativeWindow).setDisplaySurface(displaySurface).Build();
- */
 class RenderSurfaceCreationArgsBuilder {
 public:
     RenderSurfaceCreationArgs build() { return std::move(mArgs); }
@@ -75,11 +65,11 @@
         return *this;
     }
     RenderSurfaceCreationArgsBuilder& setNativeWindow(sp<ANativeWindow> nativeWindow) {
-        mArgs.nativeWindow = nativeWindow;
+        mArgs.nativeWindow = std::move(nativeWindow);
         return *this;
     }
     RenderSurfaceCreationArgsBuilder& setDisplaySurface(sp<DisplaySurface> displaySurface) {
-        mArgs.displaySurface = displaySurface;
+        mArgs.displaySurface = std::move(displaySurface);
         return *this;
     }
 
@@ -92,5 +82,4 @@
     RenderSurfaceCreationArgs mArgs;
 };
 
-} // namespace compositionengine
-} // namespace android
+} // namespace android::compositionengine
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/Display.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/Display.h
index 54e91ae..bb540ea 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/Display.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/Display.h
@@ -80,19 +80,13 @@
 
     // Internal
     virtual void setConfiguration(const compositionengine::DisplayCreationArgs&);
-    virtual std::optional<DisplayId> maybeAllocateDisplayIdForVirtualDisplay(ui::Size,
-                                                                             ui::PixelFormat) const;
     std::unique_ptr<compositionengine::OutputLayer> createOutputLayer(const sp<LayerFE>&) const;
 
-    // Testing
-    void setDisplayIdForTesting(DisplayId displayId);
-
 private:
     bool mIsVirtual = false;
     bool mIsDisconnected = false;
     DisplayId mId;
     Hwc2::PowerAdvisor* mPowerAdvisor = nullptr;
-    DisplayIdGenerator<GpuVirtualDisplayId>* mGpuVirtualDisplayIdGenerator;
 };
 
 // This template factory function standardizes the implementation details of the
diff --git a/services/surfaceflinger/CompositionEngine/src/Display.cpp b/services/surfaceflinger/CompositionEngine/src/Display.cpp
index 953eb76..be28449 100644
--- a/services/surfaceflinger/CompositionEngine/src/Display.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/Display.cpp
@@ -50,36 +50,14 @@
 Display::~Display() = default;
 
 void Display::setConfiguration(const compositionengine::DisplayCreationArgs& args) {
-    mIsVirtual = !args.physical;
+    mId = args.id;
+    mIsVirtual = !args.connectionType;
     mPowerAdvisor = args.powerAdvisor;
     editState().isSecure = args.isSecure;
     editState().displaySpace.bounds = Rect(args.pixels);
     setLayerStackFilter(args.layerStackId,
-                        args.physical &&
-                                args.physical->type == ui::DisplayConnectionType::Internal);
+                        args.connectionType == ui::DisplayConnectionType::Internal);
     setName(args.name);
-    mGpuVirtualDisplayIdGenerator = args.gpuVirtualDisplayIdGenerator;
-
-    if (args.physical) {
-        mId = args.physical->id;
-    } else {
-        std::optional<DisplayId> id;
-        if (args.useHwcVirtualDisplays) {
-            id = maybeAllocateDisplayIdForVirtualDisplay(args.pixels, args.pixelFormat);
-        }
-        if (!id) {
-            id = mGpuVirtualDisplayIdGenerator->nextId();
-        }
-        LOG_ALWAYS_FATAL_IF(!id, "Failed to generate display ID");
-        mId = *id;
-    }
-}
-
-std::optional<DisplayId> Display::maybeAllocateDisplayIdForVirtualDisplay(
-        ui::Size pixels, ui::PixelFormat pixelFormat) const {
-    auto& hwc = getCompositionEngine().getHwComposer();
-    return hwc.allocateVirtualDisplay(static_cast<uint32_t>(pixels.width),
-                                      static_cast<uint32_t>(pixels.height), &pixelFormat);
 }
 
 bool Display::isValid() const {
@@ -102,23 +80,16 @@
     return mId;
 }
 
-void Display::setDisplayIdForTesting(DisplayId displayId) {
-    mId = displayId;
-}
-
 void Display::disconnect() {
     if (mIsDisconnected) {
         return;
     }
 
     mIsDisconnected = true;
-    if (const auto id = GpuVirtualDisplayId::tryCast(mId)) {
-        mGpuVirtualDisplayIdGenerator->markUnused(*id);
-        return;
+
+    if (const auto id = HalDisplayId::tryCast(mId)) {
+        getCompositionEngine().getHwComposer().disconnectDisplay(*id);
     }
-    const auto halDisplayId = HalDisplayId::tryCast(mId);
-    LOG_FATAL_IF(!halDisplayId);
-    getCompositionEngine().getHwComposer().disconnectDisplay(*halDisplayId);
 }
 
 void Display::setColorTransform(const compositionengine::CompositionRefreshArgs& args) {
diff --git a/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp b/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
index e12cb57..1a7f75f 100644
--- a/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
@@ -14,10 +14,6 @@
  * limitations under the License.
  */
 
-// TODO(b/129481165): remove the #pragma below and fix conversion issues
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wextra"
-
 #include <cmath>
 
 #include <compositionengine/DisplayColorProfileCreationArgs.h>
@@ -60,12 +56,12 @@
 using testing::SetArgPointee;
 using testing::StrictMock;
 
-constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId{42};
-// TODO(b/160679868) Use VirtualDisplayId
-constexpr PhysicalDisplayId VIRTUAL_DISPLAY_ID = PhysicalDisplayId{43};
-constexpr int32_t DEFAULT_DISPLAY_WIDTH = 1920;
-constexpr int32_t DEFAULT_DISPLAY_HEIGHT = 1080;
-constexpr int32_t DEFAULT_LAYER_STACK = 123;
+constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(123u);
+constexpr HalVirtualDisplayId HAL_VIRTUAL_DISPLAY_ID{456u};
+constexpr GpuVirtualDisplayId GPU_VIRTUAL_DISPLAY_ID{789u};
+
+constexpr ui::Size DEFAULT_RESOLUTION{1920, 1080};
+constexpr uint32_t DEFAULT_LAYER_STACK = 42;
 
 struct Layer {
     Layer() {
@@ -94,8 +90,6 @@
     public:
         using impl::Display::injectOutputLayerForTest;
         virtual void injectOutputLayerForTest(std::unique_ptr<compositionengine::OutputLayer>) = 0;
-
-        using impl::Display::maybeAllocateDisplayIdForVirtualDisplay;
     };
 
     // Uses a special implementation with key internal member functions set up
@@ -169,21 +163,19 @@
 
     DisplayCreationArgs getDisplayCreationArgsForPhysicalHWCDisplay() {
         return DisplayCreationArgsBuilder()
-                .setPhysical({DEFAULT_DISPLAY_ID, ui::DisplayConnectionType::Internal})
-                .setPixels({DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_HEIGHT})
-                .setPixelFormat(static_cast<ui::PixelFormat>(PIXEL_FORMAT_RGBA_8888))
+                .setId(DEFAULT_DISPLAY_ID)
+                .setConnectionType(ui::DisplayConnectionType::Internal)
+                .setPixels(DEFAULT_RESOLUTION)
                 .setIsSecure(true)
                 .setLayerStackId(DEFAULT_LAYER_STACK)
                 .setPowerAdvisor(&mPowerAdvisor)
                 .build();
     }
 
-    DisplayCreationArgs getDisplayCreationArgsForNonHWCVirtualDisplay() {
+    DisplayCreationArgs getDisplayCreationArgsForGpuVirtualDisplay() {
         return DisplayCreationArgsBuilder()
-                .setUseHwcVirtualDisplays(false)
-                .setGpuVirtualDisplayIdGenerator(mGpuDisplayIdGenerator)
-                .setPixels({DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_HEIGHT})
-                .setPixelFormat(static_cast<ui::PixelFormat>(PIXEL_FORMAT_RGBA_8888))
+                .setId(GPU_VIRTUAL_DISPLAY_ID)
+                .setPixels(DEFAULT_RESOLUTION)
                 .setIsSecure(false)
                 .setLayerStackId(DEFAULT_LAYER_STACK)
                 .setPowerAdvisor(&mPowerAdvisor)
@@ -195,7 +187,6 @@
     StrictMock<renderengine::mock::RenderEngine> mRenderEngine;
     StrictMock<mock::CompositionEngine> mCompositionEngine;
     sp<mock::NativeWindow> mNativeWindow = new StrictMock<mock::NativeWindow>();
-    RandomDisplayIdGenerator<GpuVirtualDisplayId> mGpuDisplayIdGenerator;
 };
 
 struct PartialMockDisplayTestCommon : public DisplayTestCommon {
@@ -247,9 +238,9 @@
     EXPECT_EQ(DEFAULT_DISPLAY_ID, display->getId());
 }
 
-TEST_F(DisplayCreationTest, createNonHwcVirtualDisplay) {
-    auto display = impl::createDisplay(mCompositionEngine,
-                                       getDisplayCreationArgsForNonHWCVirtualDisplay());
+TEST_F(DisplayCreationTest, createGpuVirtualDisplay) {
+    auto display =
+            impl::createDisplay(mCompositionEngine, getDisplayCreationArgsForGpuVirtualDisplay());
     EXPECT_FALSE(display->isSecure());
     EXPECT_TRUE(display->isVirtual());
     EXPECT_TRUE(GpuVirtualDisplayId::tryCast(display->getId()));
@@ -262,17 +253,15 @@
 using DisplaySetConfigurationTest = PartialMockDisplayTestCommon;
 
 TEST_F(DisplaySetConfigurationTest, configuresInternalSecurePhysicalDisplay) {
-    mDisplay->setConfiguration(
-            DisplayCreationArgsBuilder()
-                    .setUseHwcVirtualDisplays(true)
-                    .setPhysical({DEFAULT_DISPLAY_ID, ui::DisplayConnectionType::Internal})
-                    .setPixels(ui::Size(DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_WIDTH))
-                    .setPixelFormat(static_cast<ui::PixelFormat>(PIXEL_FORMAT_RGBA_8888))
-                    .setIsSecure(true)
-                    .setLayerStackId(DEFAULT_LAYER_STACK)
-                    .setPowerAdvisor(&mPowerAdvisor)
-                    .setName(getDisplayNameFromCurrentTest())
-                    .build());
+    mDisplay->setConfiguration(DisplayCreationArgsBuilder()
+                                       .setId(DEFAULT_DISPLAY_ID)
+                                       .setConnectionType(ui::DisplayConnectionType::Internal)
+                                       .setPixels(DEFAULT_RESOLUTION)
+                                       .setIsSecure(true)
+                                       .setLayerStackId(DEFAULT_LAYER_STACK)
+                                       .setPowerAdvisor(&mPowerAdvisor)
+                                       .setName(getDisplayNameFromCurrentTest())
+                                       .build());
 
     EXPECT_EQ(DEFAULT_DISPLAY_ID, mDisplay->getId());
     EXPECT_TRUE(mDisplay->isSecure());
@@ -283,17 +272,15 @@
 }
 
 TEST_F(DisplaySetConfigurationTest, configuresExternalInsecurePhysicalDisplay) {
-    mDisplay->setConfiguration(
-            DisplayCreationArgsBuilder()
-                    .setUseHwcVirtualDisplays(true)
-                    .setPhysical({DEFAULT_DISPLAY_ID, ui::DisplayConnectionType::External})
-                    .setPixels(ui::Size(DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_WIDTH))
-                    .setPixelFormat(static_cast<ui::PixelFormat>(PIXEL_FORMAT_RGBA_8888))
-                    .setIsSecure(false)
-                    .setLayerStackId(DEFAULT_LAYER_STACK)
-                    .setPowerAdvisor(&mPowerAdvisor)
-                    .setName(getDisplayNameFromCurrentTest())
-                    .build());
+    mDisplay->setConfiguration(DisplayCreationArgsBuilder()
+                                       .setId(DEFAULT_DISPLAY_ID)
+                                       .setConnectionType(ui::DisplayConnectionType::External)
+                                       .setPixels(DEFAULT_RESOLUTION)
+                                       .setIsSecure(false)
+                                       .setLayerStackId(DEFAULT_LAYER_STACK)
+                                       .setPowerAdvisor(&mPowerAdvisor)
+                                       .setName(getDisplayNameFromCurrentTest())
+                                       .build());
 
     EXPECT_EQ(DEFAULT_DISPLAY_ID, mDisplay->getId());
     EXPECT_FALSE(mDisplay->isSecure());
@@ -303,25 +290,17 @@
     EXPECT_FALSE(mDisplay->isValid());
 }
 
-TEST_F(DisplaySetConfigurationTest, configuresHwcBackedVirtualDisplay) {
-    EXPECT_CALL(mHwComposer,
-                allocateVirtualDisplay(DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_WIDTH,
-                                       Pointee(Eq(static_cast<ui::PixelFormat>(
-                                               PIXEL_FORMAT_RGBA_8888)))))
-            .WillOnce(Return(VIRTUAL_DISPLAY_ID));
+TEST_F(DisplaySetConfigurationTest, configuresHalVirtualDisplay) {
+    mDisplay->setConfiguration(DisplayCreationArgsBuilder()
+                                       .setId(HAL_VIRTUAL_DISPLAY_ID)
+                                       .setPixels(DEFAULT_RESOLUTION)
+                                       .setIsSecure(false)
+                                       .setLayerStackId(DEFAULT_LAYER_STACK)
+                                       .setPowerAdvisor(&mPowerAdvisor)
+                                       .setName(getDisplayNameFromCurrentTest())
+                                       .build());
 
-    mDisplay->setConfiguration(
-            DisplayCreationArgsBuilder()
-                    .setUseHwcVirtualDisplays(true)
-                    .setPixels(ui::Size(DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_WIDTH))
-                    .setPixelFormat(static_cast<ui::PixelFormat>(PIXEL_FORMAT_RGBA_8888))
-                    .setIsSecure(false)
-                    .setLayerStackId(DEFAULT_LAYER_STACK)
-                    .setPowerAdvisor(&mPowerAdvisor)
-                    .setName(getDisplayNameFromCurrentTest())
-                    .build());
-
-    EXPECT_EQ(VIRTUAL_DISPLAY_ID, mDisplay->getId());
+    EXPECT_EQ(HAL_VIRTUAL_DISPLAY_ID, mDisplay->getId());
     EXPECT_FALSE(mDisplay->isSecure());
     EXPECT_TRUE(mDisplay->isVirtual());
     EXPECT_EQ(DEFAULT_LAYER_STACK, mDisplay->getState().layerStackId);
@@ -329,47 +308,17 @@
     EXPECT_FALSE(mDisplay->isValid());
 }
 
-TEST_F(DisplaySetConfigurationTest, configuresNonHwcBackedVirtualDisplayIfHwcAllocationFails) {
-    EXPECT_CALL(mHwComposer,
-                allocateVirtualDisplay(DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_WIDTH,
-                                       Pointee(Eq(static_cast<ui::PixelFormat>(
-                                               PIXEL_FORMAT_RGBA_8888)))))
-            .WillOnce(Return(std::nullopt));
+TEST_F(DisplaySetConfigurationTest, configuresGpuVirtualDisplay) {
+    mDisplay->setConfiguration(DisplayCreationArgsBuilder()
+                                       .setId(GPU_VIRTUAL_DISPLAY_ID)
+                                       .setPixels(DEFAULT_RESOLUTION)
+                                       .setIsSecure(false)
+                                       .setLayerStackId(DEFAULT_LAYER_STACK)
+                                       .setPowerAdvisor(&mPowerAdvisor)
+                                       .setName(getDisplayNameFromCurrentTest())
+                                       .build());
 
-    mDisplay->setConfiguration(
-            DisplayCreationArgsBuilder()
-                    .setUseHwcVirtualDisplays(true)
-                    .setGpuVirtualDisplayIdGenerator(mGpuDisplayIdGenerator)
-                    .setPixels(ui::Size(DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_WIDTH))
-                    .setPixelFormat(static_cast<ui::PixelFormat>(PIXEL_FORMAT_RGBA_8888))
-                    .setIsSecure(false)
-                    .setLayerStackId(DEFAULT_LAYER_STACK)
-                    .setPowerAdvisor(&mPowerAdvisor)
-                    .setName(getDisplayNameFromCurrentTest())
-                    .build());
-
-    EXPECT_TRUE(GpuVirtualDisplayId::tryCast(mDisplay->getId()));
-    EXPECT_FALSE(mDisplay->isSecure());
-    EXPECT_TRUE(mDisplay->isVirtual());
-    EXPECT_EQ(DEFAULT_LAYER_STACK, mDisplay->getState().layerStackId);
-    EXPECT_FALSE(mDisplay->getState().layerStackInternal);
-    EXPECT_FALSE(mDisplay->isValid());
-}
-
-TEST_F(DisplaySetConfigurationTest, configuresNonHwcBackedVirtualDisplayIfShouldNotUseHwc) {
-    mDisplay->setConfiguration(
-            DisplayCreationArgsBuilder()
-                    .setUseHwcVirtualDisplays(false)
-                    .setGpuVirtualDisplayIdGenerator(mGpuDisplayIdGenerator)
-                    .setPixels(ui::Size(DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_WIDTH))
-                    .setPixelFormat(static_cast<ui::PixelFormat>(PIXEL_FORMAT_RGBA_8888))
-                    .setIsSecure(false)
-                    .setLayerStackId(DEFAULT_LAYER_STACK)
-                    .setPowerAdvisor(&mPowerAdvisor)
-                    .setName(getDisplayNameFromCurrentTest())
-                    .build());
-
-    EXPECT_TRUE(GpuVirtualDisplayId::tryCast(mDisplay->getId()));
+    EXPECT_EQ(GPU_VIRTUAL_DISPLAY_ID, mDisplay->getId());
     EXPECT_FALSE(mDisplay->isSecure());
     EXPECT_TRUE(mDisplay->isVirtual());
     EXPECT_EQ(DEFAULT_LAYER_STACK, mDisplay->getState().layerStackId);
@@ -476,7 +425,7 @@
 TEST_F(DisplaySetColorModeTest, doesNothingForVirtualDisplay) {
     using ColorProfile = Output::ColorProfile;
 
-    auto args = getDisplayCreationArgsForNonHWCVirtualDisplay();
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
     std::shared_ptr<impl::Display> virtualDisplay = impl::createDisplay(mCompositionEngine, args);
 
     mock::DisplayColorProfile* colorProfile = new StrictMock<mock::DisplayColorProfile>();
@@ -521,7 +470,11 @@
 TEST_F(DisplayCreateRenderSurfaceTest, setsRenderSurface) {
     EXPECT_CALL(*mNativeWindow, disconnect(NATIVE_WINDOW_API_EGL)).WillRepeatedly(Return(NO_ERROR));
     EXPECT_TRUE(mDisplay->getRenderSurface() == nullptr);
-    mDisplay->createRenderSurface(RenderSurfaceCreationArgs{640, 480, mNativeWindow, nullptr});
+    mDisplay->createRenderSurface(RenderSurfaceCreationArgsBuilder()
+                                          .setDisplayWidth(640)
+                                          .setDisplayHeight(480)
+                                          .setNativeWindow(mNativeWindow)
+                                          .build());
     EXPECT_TRUE(mDisplay->getRenderSurface() != nullptr);
 }
 
@@ -551,25 +504,25 @@
 
 using DisplaySetReleasedLayersTest = DisplayWithLayersTestCommon;
 
-TEST_F(DisplaySetReleasedLayersTest, doesNothingIfNotHwcDisplay) {
-    auto args = getDisplayCreationArgsForNonHWCVirtualDisplay();
-    std::shared_ptr<impl::Display> nonHwcDisplay = impl::createDisplay(mCompositionEngine, args);
+TEST_F(DisplaySetReleasedLayersTest, doesNothingIfGpuDisplay) {
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
+    std::shared_ptr<impl::Display> gpuDisplay = impl::createDisplay(mCompositionEngine, args);
 
     sp<mock::LayerFE> layerXLayerFE = new StrictMock<mock::LayerFE>();
 
     {
         Output::ReleasedLayers releasedLayers;
         releasedLayers.emplace_back(layerXLayerFE);
-        nonHwcDisplay->setReleasedLayers(std::move(releasedLayers));
+        gpuDisplay->setReleasedLayers(std::move(releasedLayers));
     }
 
     CompositionRefreshArgs refreshArgs;
     refreshArgs.layersWithQueuedFrames.push_back(layerXLayerFE);
 
-    nonHwcDisplay->setReleasedLayers(refreshArgs);
+    gpuDisplay->setReleasedLayers(refreshArgs);
 
-    const auto& releasedLayers = nonHwcDisplay->getReleasedLayersForTest();
-    ASSERT_EQ(1, releasedLayers.size());
+    const auto& releasedLayers = gpuDisplay->getReleasedLayersForTest();
+    ASSERT_EQ(1u, releasedLayers.size());
 }
 
 TEST_F(DisplaySetReleasedLayersTest, doesNothingIfNoLayersWithQueuedFrames) {
@@ -585,7 +538,7 @@
     mDisplay->setReleasedLayers(refreshArgs);
 
     const auto& releasedLayers = mDisplay->getReleasedLayersForTest();
-    ASSERT_EQ(1, releasedLayers.size());
+    ASSERT_EQ(1u, releasedLayers.size());
 }
 
 TEST_F(DisplaySetReleasedLayersTest, setReleasedLayers) {
@@ -599,7 +552,7 @@
     mDisplay->setReleasedLayers(refreshArgs);
 
     const auto& releasedLayers = mDisplay->getReleasedLayersForTest();
-    ASSERT_EQ(2, releasedLayers.size());
+    ASSERT_EQ(2u, releasedLayers.size());
     ASSERT_EQ(mLayer1.layerFE.get(), releasedLayers[0].promote().get());
     ASSERT_EQ(mLayer2.layerFE.get(), releasedLayers[1].promote().get());
 }
@@ -610,15 +563,15 @@
 
 using DisplayChooseCompositionStrategyTest = PartialMockDisplayTestCommon;
 
-TEST_F(DisplayChooseCompositionStrategyTest, takesEarlyOutIfNotAHwcDisplay) {
-    auto args = getDisplayCreationArgsForNonHWCVirtualDisplay();
-    std::shared_ptr<Display> nonHwcDisplay =
+TEST_F(DisplayChooseCompositionStrategyTest, takesEarlyOutIfGpuDisplay) {
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
+    std::shared_ptr<Display> gpuDisplay =
             createPartialMockDisplay<Display>(mCompositionEngine, args);
-    EXPECT_TRUE(GpuVirtualDisplayId::tryCast(nonHwcDisplay->getId()));
+    EXPECT_TRUE(GpuVirtualDisplayId::tryCast(gpuDisplay->getId()));
 
-    nonHwcDisplay->chooseCompositionStrategy();
+    gpuDisplay->chooseCompositionStrategy();
 
-    auto& state = nonHwcDisplay->getState();
+    auto& state = gpuDisplay->getState();
     EXPECT_TRUE(state.usesClientComposition);
     EXPECT_FALSE(state.usesDeviceComposition);
 }
@@ -700,12 +653,12 @@
 
 using DisplayGetSkipColorTransformTest = DisplayWithLayersTestCommon;
 
-TEST_F(DisplayGetSkipColorTransformTest, checksCapabilityIfNonHwcDisplay) {
+TEST_F(DisplayGetSkipColorTransformTest, checksCapabilityIfGpuDisplay) {
     EXPECT_CALL(mHwComposer, hasCapability(hal::Capability::SKIP_CLIENT_COLOR_TRANSFORM))
             .WillOnce(Return(true));
-    auto args = getDisplayCreationArgsForNonHWCVirtualDisplay();
-    auto nonHwcDisplay{impl::createDisplay(mCompositionEngine, args)};
-    EXPECT_TRUE(nonHwcDisplay->getSkipColorTransform());
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
+    auto gpuDisplay{impl::createDisplay(mCompositionEngine, args)};
+    EXPECT_TRUE(gpuDisplay->getSkipColorTransform());
 }
 
 TEST_F(DisplayGetSkipColorTransformTest, checksDisplayCapability) {
@@ -852,11 +805,11 @@
 
 using DisplayPresentAndGetFrameFencesTest = DisplayWithLayersTestCommon;
 
-TEST_F(DisplayPresentAndGetFrameFencesTest, returnsNoFencesOnNonHwcDisplay) {
-    auto args = getDisplayCreationArgsForNonHWCVirtualDisplay();
-    auto nonHwcDisplay{impl::createDisplay(mCompositionEngine, args)};
+TEST_F(DisplayPresentAndGetFrameFencesTest, returnsNoFencesOnGpuDisplay) {
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
+    auto gpuDisplay{impl::createDisplay(mCompositionEngine, args)};
 
-    auto result = nonHwcDisplay->presentAndGetFrameFences();
+    auto result = gpuDisplay->presentAndGetFrameFences();
 
     ASSERT_TRUE(result.presentFence.get());
     EXPECT_FALSE(result.presentFence->isValid());
@@ -885,9 +838,9 @@
     EXPECT_EQ(presentFence, result.presentFence);
 
     EXPECT_EQ(2u, result.layerFences.size());
-    ASSERT_EQ(1, result.layerFences.count(&mLayer1.hwc2Layer));
+    ASSERT_EQ(1u, result.layerFences.count(&mLayer1.hwc2Layer));
     EXPECT_EQ(layer1Fence, result.layerFences[&mLayer1.hwc2Layer]);
-    ASSERT_EQ(1, result.layerFences.count(&mLayer2.hwc2Layer));
+    ASSERT_EQ(1u, result.layerFences.count(&mLayer2.hwc2Layer));
     EXPECT_EQ(layer2Fence, result.layerFences[&mLayer2.hwc2Layer]);
 }
 
@@ -933,66 +886,66 @@
 }
 
 TEST_F(DisplayFinishFrameTest, skipsCompositionIfNotDirty) {
-    auto args = getDisplayCreationArgsForNonHWCVirtualDisplay();
-    std::shared_ptr<impl::Display> nonHwcDisplay = impl::createDisplay(mCompositionEngine, args);
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
+    std::shared_ptr<impl::Display> gpuDisplay = impl::createDisplay(mCompositionEngine, args);
 
     mock::RenderSurface* renderSurface = new StrictMock<mock::RenderSurface>();
-    nonHwcDisplay->setRenderSurfaceForTest(std::unique_ptr<RenderSurface>(renderSurface));
+    gpuDisplay->setRenderSurfaceForTest(std::unique_ptr<RenderSurface>(renderSurface));
 
     // We expect no calls to queueBuffer if composition was skipped.
     EXPECT_CALL(*renderSurface, queueBuffer(_)).Times(0);
 
-    nonHwcDisplay->editState().isEnabled = true;
-    nonHwcDisplay->editState().usesClientComposition = false;
-    nonHwcDisplay->editState().layerStackSpace.content = Rect(0, 0, 1, 1);
-    nonHwcDisplay->editState().dirtyRegion = Region::INVALID_REGION;
+    gpuDisplay->editState().isEnabled = true;
+    gpuDisplay->editState().usesClientComposition = false;
+    gpuDisplay->editState().layerStackSpace.content = Rect(0, 0, 1, 1);
+    gpuDisplay->editState().dirtyRegion = Region::INVALID_REGION;
 
     CompositionRefreshArgs refreshArgs;
     refreshArgs.repaintEverything = false;
 
-    nonHwcDisplay->finishFrame(refreshArgs);
+    gpuDisplay->finishFrame(refreshArgs);
 }
 
 TEST_F(DisplayFinishFrameTest, performsCompositionIfDirty) {
-    auto args = getDisplayCreationArgsForNonHWCVirtualDisplay();
-    std::shared_ptr<impl::Display> nonHwcDisplay = impl::createDisplay(mCompositionEngine, args);
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
+    std::shared_ptr<impl::Display> gpuDisplay = impl::createDisplay(mCompositionEngine, args);
 
     mock::RenderSurface* renderSurface = new StrictMock<mock::RenderSurface>();
-    nonHwcDisplay->setRenderSurfaceForTest(std::unique_ptr<RenderSurface>(renderSurface));
+    gpuDisplay->setRenderSurfaceForTest(std::unique_ptr<RenderSurface>(renderSurface));
 
     // We expect a single call to queueBuffer when composition is not skipped.
     EXPECT_CALL(*renderSurface, queueBuffer(_)).Times(1);
 
-    nonHwcDisplay->editState().isEnabled = true;
-    nonHwcDisplay->editState().usesClientComposition = false;
-    nonHwcDisplay->editState().layerStackSpace.content = Rect(0, 0, 1, 1);
-    nonHwcDisplay->editState().dirtyRegion = Region(Rect(0, 0, 1, 1));
+    gpuDisplay->editState().isEnabled = true;
+    gpuDisplay->editState().usesClientComposition = false;
+    gpuDisplay->editState().layerStackSpace.content = Rect(0, 0, 1, 1);
+    gpuDisplay->editState().dirtyRegion = Region(Rect(0, 0, 1, 1));
 
     CompositionRefreshArgs refreshArgs;
     refreshArgs.repaintEverything = false;
 
-    nonHwcDisplay->finishFrame(refreshArgs);
+    gpuDisplay->finishFrame(refreshArgs);
 }
 
 TEST_F(DisplayFinishFrameTest, performsCompositionIfRepaintEverything) {
-    auto args = getDisplayCreationArgsForNonHWCVirtualDisplay();
-    std::shared_ptr<impl::Display> nonHwcDisplay = impl::createDisplay(mCompositionEngine, args);
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
+    std::shared_ptr<impl::Display> gpuDisplay = impl::createDisplay(mCompositionEngine, args);
 
     mock::RenderSurface* renderSurface = new StrictMock<mock::RenderSurface>();
-    nonHwcDisplay->setRenderSurfaceForTest(std::unique_ptr<RenderSurface>(renderSurface));
+    gpuDisplay->setRenderSurfaceForTest(std::unique_ptr<RenderSurface>(renderSurface));
 
     // We expect a single call to queueBuffer when composition is not skipped.
     EXPECT_CALL(*renderSurface, queueBuffer(_)).Times(1);
 
-    nonHwcDisplay->editState().isEnabled = true;
-    nonHwcDisplay->editState().usesClientComposition = false;
-    nonHwcDisplay->editState().layerStackSpace.content = Rect(0, 0, 1, 1);
-    nonHwcDisplay->editState().dirtyRegion = Region::INVALID_REGION;
+    gpuDisplay->editState().isEnabled = true;
+    gpuDisplay->editState().usesClientComposition = false;
+    gpuDisplay->editState().layerStackSpace.content = Rect(0, 0, 1, 1);
+    gpuDisplay->editState().dirtyRegion = Region::INVALID_REGION;
 
     CompositionRefreshArgs refreshArgs;
     refreshArgs.repaintEverything = true;
 
-    nonHwcDisplay->finishFrame(refreshArgs);
+    gpuDisplay->finishFrame(refreshArgs);
 }
 
 /*
@@ -1017,23 +970,26 @@
     NiceMock<mock::CompositionEngine> mCompositionEngine;
     sp<mock::NativeWindow> mNativeWindow = new NiceMock<mock::NativeWindow>();
     sp<mock::DisplaySurface> mDisplaySurface = new NiceMock<mock::DisplaySurface>();
+
     std::shared_ptr<Display> mDisplay = impl::createDisplayTemplated<
             Display>(mCompositionEngine,
                      DisplayCreationArgsBuilder()
-                             .setPhysical({DEFAULT_DISPLAY_ID, ui::DisplayConnectionType::Internal})
-                             .setPixels({DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_HEIGHT})
-                             .setPixelFormat(static_cast<ui::PixelFormat>(PIXEL_FORMAT_RGBA_8888))
+                             .setId(DEFAULT_DISPLAY_ID)
+                             .setConnectionType(ui::DisplayConnectionType::Internal)
+                             .setPixels(DEFAULT_RESOLUTION)
                              .setIsSecure(true)
                              .setLayerStackId(DEFAULT_LAYER_STACK)
                              .setPowerAdvisor(&mPowerAdvisor)
-                             .build()
+                             .build());
 
-    );
     impl::RenderSurface* mRenderSurface =
             new impl::RenderSurface{mCompositionEngine, *mDisplay,
-                                    RenderSurfaceCreationArgs{DEFAULT_DISPLAY_WIDTH,
-                                                              DEFAULT_DISPLAY_HEIGHT, mNativeWindow,
-                                                              mDisplaySurface}};
+                                    RenderSurfaceCreationArgsBuilder()
+                                            .setDisplayWidth(DEFAULT_RESOLUTION.width)
+                                            .setDisplayHeight(DEFAULT_RESOLUTION.height)
+                                            .setNativeWindow(mNativeWindow)
+                                            .setDisplaySurface(mDisplaySurface)
+                                            .build()};
 };
 
 TEST_F(DisplayFunctionalTest, postFramebufferCriticalCallsAreOrdered) {
@@ -1049,6 +1005,3 @@
 
 } // namespace
 } // namespace android::compositionengine
-
-// TODO(b/129481165): remove the #pragma below and fix conversion issues
-#pragma clang diagnostic pop // ignored "-Wextra"
\ No newline at end of file
diff --git a/services/surfaceflinger/CompositionEngine/tests/MockHWComposer.h b/services/surfaceflinger/CompositionEngine/tests/MockHWComposer.h
index cd2d09e..72de0b1 100644
--- a/services/surfaceflinger/CompositionEngine/tests/MockHWComposer.h
+++ b/services/surfaceflinger/CompositionEngine/tests/MockHWComposer.h
@@ -39,15 +39,19 @@
     HWComposer();
     ~HWComposer() override;
 
-    MOCK_METHOD2(setConfiguration, void(HWC2::ComposerCallback*, int32_t));
+    MOCK_METHOD1(setCallback, void(HWC2::ComposerCallback*));
     MOCK_CONST_METHOD3(getDisplayIdentificationData,
                        bool(hal::HWDisplayId, uint8_t*, DisplayIdentificationData*));
     MOCK_CONST_METHOD1(hasCapability, bool(hal::Capability));
     MOCK_CONST_METHOD2(hasDisplayCapability, bool(HalDisplayId, hal::DisplayCapability));
 
-    MOCK_METHOD3(allocateVirtualDisplay,
-                 std::optional<DisplayId>(uint32_t, uint32_t, ui::PixelFormat*));
+    MOCK_CONST_METHOD0(getMaxVirtualDisplayCount, size_t());
+    MOCK_CONST_METHOD0(getMaxVirtualDisplayDimension, size_t());
+    MOCK_METHOD4(allocateVirtualDisplay,
+                 bool(HalVirtualDisplayId, ui::Size, ui::PixelFormat*,
+                      std::optional<PhysicalDisplayId>));
     MOCK_METHOD2(allocatePhysicalDisplay, void(hal::HWDisplayId, PhysicalDisplayId));
+
     MOCK_METHOD1(createLayer, std::shared_ptr<HWC2::Layer>(HalDisplayId));
     MOCK_METHOD4(getDeviceCompositionChanges,
                  status_t(HalDisplayId, bool, std::chrono::steady_clock::time_point,
diff --git a/services/surfaceflinger/CompositionEngine/tests/RenderSurfaceTest.cpp b/services/surfaceflinger/CompositionEngine/tests/RenderSurfaceTest.cpp
index 9aeb290..431cc93 100644
--- a/services/surfaceflinger/CompositionEngine/tests/RenderSurfaceTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/RenderSurfaceTest.cpp
@@ -14,12 +14,6 @@
  * limitations under the License.
  */
 
-// TODO(b/129481165): remove the #pragma below and fix conversion issues
-#include "renderengine/ExternalTexture.h"
-#include "ui/GraphicBuffer.h"
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wextra"
-
 #include <cstdarg>
 #include <cstdint>
 
@@ -32,14 +26,16 @@
 #include <compositionengine/mock/NativeWindow.h>
 #include <compositionengine/mock/OutputLayer.h>
 #include <gtest/gtest.h>
+#include <renderengine/ExternalTexture.h>
 #include <renderengine/mock/RenderEngine.h>
+#include <ui/GraphicBuffer.h>
 
 namespace android::compositionengine {
 namespace {
 
 constexpr int32_t DEFAULT_DISPLAY_WIDTH = 1920;
 constexpr int32_t DEFAULT_DISPLAY_HEIGHT = 1080;
-constexpr DisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId(123u);
+constexpr DisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(123u);
 const std::string DEFAULT_DISPLAY_NAME = "Mock Display";
 
 using testing::_;
@@ -67,9 +63,12 @@
     sp<mock::NativeWindow> mNativeWindow = new StrictMock<mock::NativeWindow>();
     sp<mock::DisplaySurface> mDisplaySurface = new StrictMock<mock::DisplaySurface>();
     impl::RenderSurface mSurface{mCompositionEngine, mDisplay,
-                                 RenderSurfaceCreationArgs{DEFAULT_DISPLAY_WIDTH,
-                                                           DEFAULT_DISPLAY_HEIGHT, mNativeWindow,
-                                                           mDisplaySurface}};
+                                 RenderSurfaceCreationArgsBuilder()
+                                         .setDisplayWidth(DEFAULT_DISPLAY_WIDTH)
+                                         .setDisplayHeight(DEFAULT_DISPLAY_HEIGHT)
+                                         .setNativeWindow(mNativeWindow)
+                                         .setDisplaySurface(mDisplaySurface)
+                                         .build()};
 };
 
 /*
@@ -367,11 +366,8 @@
 
     mSurface.flip();
 
-    EXPECT_EQ(501, mSurface.getPageFlipCount());
+    EXPECT_EQ(501u, mSurface.getPageFlipCount());
 }
 
 } // namespace
 } // namespace android::compositionengine
-
-// TODO(b/129481165): remove the #pragma below and fix conversion issues
-#pragma clang diagnostic pop // ignored "-Wextra"
\ No newline at end of file
diff --git a/services/surfaceflinger/DisplayDevice.cpp b/services/surfaceflinger/DisplayDevice.cpp
index 0f18235..ca4b6ab 100644
--- a/services/surfaceflinger/DisplayDevice.cpp
+++ b/services/surfaceflinger/DisplayDevice.cpp
@@ -70,13 +70,14 @@
         mIsPrimary(args.isPrimary) {
     mCompositionDisplay->editState().isSecure = args.isSecure;
     mCompositionDisplay->createRenderSurface(
-            compositionengine::
-                    RenderSurfaceCreationArgs{ANativeWindow_getWidth(args.nativeWindow.get()),
-                                              ANativeWindow_getHeight(args.nativeWindow.get()),
-                                              args.nativeWindow, args.displaySurface,
-                                              static_cast<size_t>(
-                                                      SurfaceFlinger::
-                                                              maxFrameBufferAcquiredBuffers)});
+            compositionengine::RenderSurfaceCreationArgsBuilder()
+                    .setDisplayWidth(ANativeWindow_getWidth(args.nativeWindow.get()))
+                    .setDisplayHeight(ANativeWindow_getHeight(args.nativeWindow.get()))
+                    .setNativeWindow(std::move(args.nativeWindow))
+                    .setDisplaySurface(std::move(args.displaySurface))
+                    .setMaxTextureCacheSize(
+                            static_cast<size_t>(SurfaceFlinger::maxFrameBufferAcquiredBuffers))
+                    .build());
 
     if (!mFlinger->mDisableClientCompositionCache &&
         SurfaceFlinger::maxFrameBufferAcquiredBuffers > 0) {
diff --git a/services/surfaceflinger/DisplayDevice.h b/services/surfaceflinger/DisplayDevice.h
index bf249cd..33c2563 100644
--- a/services/surfaceflinger/DisplayDevice.h
+++ b/services/surfaceflinger/DisplayDevice.h
@@ -103,15 +103,21 @@
     bool needsFiltering() const;
     ui::LayerStack getLayerStack() const;
 
-    // Returns the physical ID of this display. This function asserts the ID is physical and it
-    // shouldn't be called for other display types, e.g. virtual.
+    DisplayId getId() const;
+
+    // Shorthand to upcast the ID of a display whose type is known as a precondition.
     PhysicalDisplayId getPhysicalId() const {
-        const auto displayIdOpt = PhysicalDisplayId::tryCast(getId());
-        LOG_FATAL_IF(!displayIdOpt);
-        return *displayIdOpt;
+        const auto id = PhysicalDisplayId::tryCast(getId());
+        LOG_FATAL_IF(!id);
+        return *id;
     }
 
-    DisplayId getId() const;
+    VirtualDisplayId getVirtualId() const {
+        const auto id = VirtualDisplayId::tryCast(getId());
+        LOG_FATAL_IF(!id);
+        return *id;
+    }
+
     const wp<IBinder>& getDisplayToken() const { return mDisplayToken; }
     int32_t getSequenceId() const { return mSequenceId; }
 
diff --git a/services/surfaceflinger/DisplayHardware/ComposerHal.cpp b/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
index 1cbcf59..caf0294 100644
--- a/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
+++ b/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
@@ -211,9 +211,8 @@
     return unwrapRet(ret, 0);
 }
 
-Error Composer::createVirtualDisplay(uint32_t width, uint32_t height,
-            PixelFormat* format, Display* outDisplay)
-{
+Error Composer::createVirtualDisplay(uint32_t width, uint32_t height, PixelFormat* format,
+                                     std::optional<Display>, Display* outDisplay) {
     const uint32_t bufferSlotCount = 1;
     Error error = kDefaultError;
     if (mClient_2_2) {
diff --git a/services/surfaceflinger/DisplayHardware/ComposerHal.h b/services/surfaceflinger/DisplayHardware/ComposerHal.h
index 0619b8c..b525e63 100644
--- a/services/surfaceflinger/DisplayHardware/ComposerHal.h
+++ b/services/surfaceflinger/DisplayHardware/ComposerHal.h
@@ -18,6 +18,7 @@
 #define ANDROID_SF_COMPOSER_HAL_H
 
 #include <memory>
+#include <optional>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ -94,8 +95,8 @@
     virtual Error executeCommands() = 0;
 
     virtual uint32_t getMaxVirtualDisplayCount() = 0;
-    virtual Error createVirtualDisplay(uint32_t width, uint32_t height, PixelFormat* format,
-                                       Display* outDisplay) = 0;
+    virtual Error createVirtualDisplay(uint32_t width, uint32_t height, PixelFormat*,
+                                       std::optional<Display> mirror, Display* outDisplay) = 0;
     virtual Error destroyVirtualDisplay(Display display) = 0;
 
     virtual Error acceptDisplayChanges(Display display) = 0;
@@ -341,7 +342,7 @@
 
     uint32_t getMaxVirtualDisplayCount() override;
     Error createVirtualDisplay(uint32_t width, uint32_t height, PixelFormat* format,
-                               Display* outDisplay) override;
+                               std::optional<Display> mirror, Display* outDisplay) override;
     Error destroyVirtualDisplay(Display display) override;
 
     Error acceptDisplayChanges(Display display) override;
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.h b/services/surfaceflinger/DisplayHardware/HWC2.h
index fae95e7..871465d 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.h
+++ b/services/surfaceflinger/DisplayHardware/HWC2.h
@@ -56,20 +56,16 @@
 // Implement this interface to receive hardware composer events.
 //
 // These callback functions will generally be called on a hwbinder thread, but
-// when first registering the callback the onHotplugReceived() function will
+// when first registering the callback the onComposerHalHotplug() function will
 // immediately be called on the thread calling registerCallback().
-//
-// All calls receive a sequenceId, which will be the value that was supplied to
-// HWC2::Device::registerCallback(). It's used to help differentiate callbacks
-// from different hardware composer instances.
 struct ComposerCallback {
-    virtual void onHotplugReceived(int32_t sequenceId, hal::HWDisplayId, hal::Connection) = 0;
-    virtual void onRefreshReceived(int32_t sequenceId, hal::HWDisplayId) = 0;
-    virtual void onVsyncReceived(int32_t sequenceId, hal::HWDisplayId, int64_t timestamp,
-                                 std::optional<hal::VsyncPeriodNanos>) = 0;
-    virtual void onVsyncPeriodTimingChangedReceived(int32_t sequenceId, hal::HWDisplayId,
-                                                    const hal::VsyncPeriodChangeTimeline&) = 0;
-    virtual void onSeamlessPossible(int32_t sequenceId, hal::HWDisplayId) = 0;
+    virtual void onComposerHalHotplug(hal::HWDisplayId, hal::Connection) = 0;
+    virtual void onComposerHalRefresh(hal::HWDisplayId) = 0;
+    virtual void onComposerHalVsync(hal::HWDisplayId, int64_t timestamp,
+                                    std::optional<hal::VsyncPeriodNanos>) = 0;
+    virtual void onComposerHalVsyncPeriodTimingChanged(hal::HWDisplayId,
+                                                       const hal::VsyncPeriodChangeTimeline&) = 0;
+    virtual void onComposerHalSeamlessPossible(hal::HWDisplayId) = 0;
 
 protected:
     ~ComposerCallback() = default;
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index 36876dc..32f04e5 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -38,7 +38,6 @@
 #include <utils/Trace.h>
 
 #include "../Layer.h" // needed only for debugging
-#include "../SurfaceFlinger.h"
 #include "../SurfaceFlingerProperties.h"
 #include "ComposerHal.h"
 #include "HWC2.h"
@@ -83,25 +82,22 @@
 
 class ComposerCallbackBridge : public hal::IComposerCallback {
 public:
-    ComposerCallbackBridge(ComposerCallback* callback, int32_t sequenceId,
-                           bool vsyncSwitchingSupported)
-          : mCallback(callback),
-            mSequenceId(sequenceId),
-            mVsyncSwitchingSupported(vsyncSwitchingSupported) {}
+    ComposerCallbackBridge(ComposerCallback* callback, bool vsyncSwitchingSupported)
+          : mCallback(callback), mVsyncSwitchingSupported(vsyncSwitchingSupported) {}
 
-    Return<void> onHotplug(hal::HWDisplayId display, hal::Connection conn) override {
-        mCallback->onHotplugReceived(mSequenceId, display, conn);
+    Return<void> onHotplug(hal::HWDisplayId display, hal::Connection connection) override {
+        mCallback->onComposerHalHotplug(display, connection);
         return Void();
     }
 
     Return<void> onRefresh(hal::HWDisplayId display) override {
-        mCallback->onRefreshReceived(mSequenceId, display);
+        mCallback->onComposerHalRefresh(display);
         return Void();
     }
 
     Return<void> onVsync(hal::HWDisplayId display, int64_t timestamp) override {
         if (!mVsyncSwitchingSupported) {
-            mCallback->onVsyncReceived(mSequenceId, display, timestamp, std::nullopt);
+            mCallback->onComposerHalVsync(display, timestamp, std::nullopt);
         } else {
             ALOGW("Unexpected onVsync callback on composer >= 2.4, ignoring.");
         }
@@ -111,8 +107,7 @@
     Return<void> onVsync_2_4(hal::HWDisplayId display, int64_t timestamp,
                              hal::VsyncPeriodNanos vsyncPeriodNanos) override {
         if (mVsyncSwitchingSupported) {
-            mCallback->onVsyncReceived(mSequenceId, display, timestamp,
-                                       std::make_optional(vsyncPeriodNanos));
+            mCallback->onComposerHalVsync(display, timestamp, vsyncPeriodNanos);
         } else {
             ALOGW("Unexpected onVsync_2_4 callback on composer <= 2.3, ignoring.");
         }
@@ -120,20 +115,18 @@
     }
 
     Return<void> onVsyncPeriodTimingChanged(
-            hal::HWDisplayId display,
-            const hal::VsyncPeriodChangeTimeline& updatedTimeline) override {
-        mCallback->onVsyncPeriodTimingChangedReceived(mSequenceId, display, updatedTimeline);
+            hal::HWDisplayId display, const hal::VsyncPeriodChangeTimeline& timeline) override {
+        mCallback->onComposerHalVsyncPeriodTimingChanged(display, timeline);
         return Void();
     }
 
     Return<void> onSeamlessPossible(hal::HWDisplayId display) override {
-        mCallback->onSeamlessPossible(mSequenceId, display);
+        mCallback->onComposerHalSeamlessPossible(display);
         return Void();
     }
 
 private:
-    ComposerCallback* mCallback;
-    const int32_t mSequenceId;
+    ComposerCallback* const mCallback;
     const bool mVsyncSwitchingSupported;
 };
 
@@ -145,8 +138,9 @@
 
 HWComposer::HWComposer(std::unique_ptr<Hwc2::Composer> composer)
       : mComposer(std::move(composer)),
+        mMaxVirtualDisplayDimension(static_cast<size_t>(sysprop::max_virtual_display_dimension(0))),
         mUpdateDeviceProductInfoOnHotplugReconnect(
-                android::sysprop::update_device_product_info_on_hotplug_reconnect(false)) {}
+                sysprop::update_device_product_info_on_hotplug_reconnect(false)) {}
 
 HWComposer::HWComposer(const std::string& composerServiceName)
       : HWComposer(std::make_unique<Hwc2::impl::Composer>(composerServiceName)) {}
@@ -155,7 +149,7 @@
     mDisplayData.clear();
 }
 
-void HWComposer::setConfiguration(HWC2::ComposerCallback* callback, int32_t sequenceId) {
+void HWComposer::setCallback(HWC2::ComposerCallback* callback) {
     loadCapabilities();
     loadLayerMetadataSupport();
 
@@ -164,10 +158,9 @@
         return;
     }
     mRegisteredCallback = true;
-    sp<ComposerCallbackBridge> callbackBridge(
-            new ComposerCallbackBridge(callback, sequenceId,
-                                       mComposer->isVsyncPeriodSwitchSupported()));
-    mComposer->registerCallback(callbackBridge);
+
+    mComposer->registerCallback(
+            sp<ComposerCallbackBridge>::make(callback, mComposer->isVsyncPeriodSwitchSupported()));
 }
 
 bool HWComposer::getDisplayIdentificationData(hal::HWDisplayId hwcDisplayId, uint8_t* outPort,
@@ -243,38 +236,49 @@
     return true;
 }
 
-std::optional<DisplayId> HWComposer::allocateVirtualDisplay(uint32_t width, uint32_t height,
-                                                            ui::PixelFormat* format) {
-    if (SurfaceFlinger::maxVirtualDisplaySize != 0 &&
-        (width > SurfaceFlinger::maxVirtualDisplaySize ||
-         height > SurfaceFlinger::maxVirtualDisplaySize)) {
-        ALOGE("%s: Display size %ux%u exceeds maximum dimension of %" PRIu64, __FUNCTION__, width,
-              height, SurfaceFlinger::maxVirtualDisplaySize);
-        return {};
+size_t HWComposer::getMaxVirtualDisplayCount() const {
+    return mComposer->getMaxVirtualDisplayCount();
+}
+
+size_t HWComposer::getMaxVirtualDisplayDimension() const {
+    return mMaxVirtualDisplayDimension;
+}
+
+bool HWComposer::allocateVirtualDisplay(HalVirtualDisplayId displayId, ui::Size resolution,
+                                        ui::PixelFormat* format,
+                                        std::optional<PhysicalDisplayId> mirror) {
+    if (!resolution.isValid()) {
+        ALOGE("%s: Invalid resolution %dx%d", __func__, resolution.width, resolution.height);
+        return false;
     }
 
-    const auto displayId = mVirtualIdGenerator.nextId();
-    if (!displayId) {
-        ALOGE("%s: No remaining virtual displays", __FUNCTION__);
-        return {};
+    const uint32_t width = static_cast<uint32_t>(resolution.width);
+    const uint32_t height = static_cast<uint32_t>(resolution.height);
+
+    if (mMaxVirtualDisplayDimension > 0 &&
+        (width > mMaxVirtualDisplayDimension || height > mMaxVirtualDisplayDimension)) {
+        ALOGE("%s: Resolution %ux%u exceeds maximum dimension %zu", __func__, width, height,
+              mMaxVirtualDisplayDimension);
+        return false;
     }
 
-    hal::HWDisplayId hwcDisplayId = 0;
+    std::optional<hal::HWDisplayId> hwcMirrorId;
+    if (mirror) {
+        hwcMirrorId = fromPhysicalDisplayId(*mirror);
+    }
+
+    hal::HWDisplayId hwcDisplayId;
     const auto error = static_cast<hal::Error>(
-            mComposer->createVirtualDisplay(width, height, format, &hwcDisplayId));
-    if (error != hal::Error::NONE) {
-        ALOGE("%s: Failed to create HWC virtual display", __FUNCTION__);
-        mVirtualIdGenerator.markUnused(*displayId);
-        return {};
-    }
+            mComposer->createVirtualDisplay(width, height, format, hwcMirrorId, &hwcDisplayId));
+    RETURN_IF_HWC_ERROR_FOR("createVirtualDisplay", error, displayId, false);
 
     auto display = std::make_unique<HWC2::impl::Display>(*mComposer.get(), mCapabilities,
                                                          hwcDisplayId, hal::DisplayType::VIRTUAL);
     display->setConnected(true);
-    auto& displayData = mDisplayData[*displayId];
+    auto& displayData = mDisplayData[displayId];
     displayData.hwcDisplay = std::move(display);
     displayData.isVirtual = true;
-    return displayId;
+    return true;
 }
 
 void HWComposer::allocatePhysicalDisplay(hal::HWDisplayId hwcDisplayId,
@@ -670,13 +674,6 @@
 void HWComposer::disconnectDisplay(HalDisplayId displayId) {
     RETURN_IF_INVALID_DISPLAY(displayId);
     auto& displayData = mDisplayData[displayId];
-
-    // If this was a virtual display, add its slot back for reuse by future
-    // virtual displays
-    if (displayData.isVirtual) {
-        mVirtualIdGenerator.markUnused(*HalVirtualDisplayId::tryCast(displayId));
-    }
-
     const auto hwcDisplayId = displayData.hwcDisplay->getId();
 
     // TODO(b/74619554): Select internal/external display from remaining displays.
@@ -983,10 +980,6 @@
     }
 }
 
-uint32_t HWComposer::getMaxVirtualDisplayCount() const {
-    return mComposer->getMaxVirtualDisplayCount();
-}
-
 } // namespace impl
 } // namespace android
 
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index d0c0c11..cd6f9f5 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -39,7 +39,6 @@
 #include <utils/StrongPointer.h>
 #include <utils/Timers.h>
 
-#include "DisplayIdGenerator.h"
 #include "DisplayIdentification.h"
 #include "DisplayMode.h"
 #include "HWC2.h"
@@ -101,7 +100,7 @@
 
     virtual ~HWComposer();
 
-    virtual void setConfiguration(HWC2::ComposerCallback* callback, int32_t sequenceId) = 0;
+    virtual void setCallback(HWC2::ComposerCallback*) = 0;
 
     virtual bool getDisplayIdentificationData(hal::HWDisplayId, uint8_t* outPort,
                                               DisplayIdentificationData* outData) const = 0;
@@ -109,9 +108,16 @@
     virtual bool hasCapability(hal::Capability) const = 0;
     virtual bool hasDisplayCapability(HalDisplayId, hal::DisplayCapability) const = 0;
 
-    // Attempts to allocate a virtual display and returns its ID if created on the HWC device.
-    virtual std::optional<DisplayId> allocateVirtualDisplay(uint32_t width, uint32_t height,
-                                                            ui::PixelFormat*) = 0;
+    virtual size_t getMaxVirtualDisplayCount() const = 0;
+    virtual size_t getMaxVirtualDisplayDimension() const = 0;
+
+    // Attempts to allocate a virtual display on the HWC. The maximum number of virtual displays
+    // supported by the HWC can be queried in advance, but allocation may fail for other reasons.
+    // For virtualized compositors, the PhysicalDisplayId is a hint that this virtual display is
+    // a mirror of a physical display, and that the screen should be captured by the host rather
+    // than guest compositor.
+    virtual bool allocateVirtualDisplay(HalVirtualDisplayId, ui::Size, ui::PixelFormat*,
+                                        std::optional<PhysicalDisplayId> mirror) = 0;
 
     virtual void allocatePhysicalDisplay(hal::HWDisplayId, PhysicalDisplayId) = 0;
 
@@ -246,7 +252,7 @@
 
     ~HWComposer() override;
 
-    void setConfiguration(HWC2::ComposerCallback* callback, int32_t sequenceId) override;
+    void setCallback(HWC2::ComposerCallback*) override;
 
     bool getDisplayIdentificationData(hal::HWDisplayId, uint8_t* outPort,
                                       DisplayIdentificationData* outData) const override;
@@ -254,9 +260,11 @@
     bool hasCapability(hal::Capability) const override;
     bool hasDisplayCapability(HalDisplayId, hal::DisplayCapability) const override;
 
-    // Attempts to allocate a virtual display and returns its ID if created on the HWC device.
-    std::optional<DisplayId> allocateVirtualDisplay(uint32_t width, uint32_t height,
-                                                    ui::PixelFormat*) override;
+    size_t getMaxVirtualDisplayCount() const override;
+    size_t getMaxVirtualDisplayDimension() const override;
+
+    bool allocateVirtualDisplay(HalVirtualDisplayId, ui::Size, ui::PixelFormat*,
+                                std::optional<PhysicalDisplayId>) override;
 
     // Called from SurfaceFlinger, when the state for a new physical display needs to be recreated.
     void allocatePhysicalDisplay(hal::HWDisplayId, PhysicalDisplayId) override;
@@ -402,7 +410,6 @@
 
     void loadCapabilities();
     void loadLayerMetadataSupport();
-    uint32_t getMaxVirtualDisplayCount() const;
 
     std::unordered_map<HalDisplayId, DisplayData> mDisplayData;
 
@@ -416,8 +423,7 @@
     std::optional<hal::HWDisplayId> mExternalHwcDisplayId;
     bool mHasMultiDisplaySupport = false;
 
-    RandomDisplayIdGenerator<HalVirtualDisplayId> mVirtualIdGenerator{getMaxVirtualDisplayCount()};
-
+    const size_t mMaxVirtualDisplayDimension;
     const bool mUpdateDeviceProductInfoOnHotplugReconnect;
 };
 
diff --git a/services/surfaceflinger/DisplayIdGenerator.h b/services/surfaceflinger/DisplayIdGenerator.h
index e7c69a8..9791a25 100644
--- a/services/surfaceflinger/DisplayIdGenerator.h
+++ b/services/surfaceflinger/DisplayIdGenerator.h
@@ -27,23 +27,16 @@
 
 namespace android {
 
-template <typename T>
+// Generates pseudo-random IDs of type GpuVirtualDisplayId or HalVirtualDisplayId.
+template <typename Id>
 class DisplayIdGenerator {
 public:
-    virtual std::optional<T> nextId() = 0;
-    virtual void markUnused(T id) = 0;
-
-protected:
-    ~DisplayIdGenerator() {}
-};
-
-template <typename T>
-class RandomDisplayIdGenerator final : public DisplayIdGenerator<T> {
-public:
-    explicit RandomDisplayIdGenerator(size_t maxIdsCount = std::numeric_limits<size_t>::max())
+    explicit DisplayIdGenerator(size_t maxIdsCount = std::numeric_limits<size_t>::max())
           : mMaxIdsCount(maxIdsCount) {}
 
-    std::optional<T> nextId() override {
+    bool inUse() const { return !mUsedIds.empty(); }
+
+    std::optional<Id> generateId() {
         if (mUsedIds.size() >= mMaxIdsCount) {
             return std::nullopt;
         }
@@ -51,8 +44,7 @@
         constexpr int kMaxAttempts = 1000;
 
         for (int attempts = 0; attempts < kMaxAttempts; attempts++) {
-            const auto baseId = mDistribution(mGenerator);
-            const T id(baseId);
+            const Id id{mDistribution(mGenerator)};
             if (mUsedIds.count(id) == 0) {
                 mUsedIds.insert(id);
                 return id;
@@ -62,14 +54,18 @@
         LOG_ALWAYS_FATAL("Couldn't generate ID after %d attempts", kMaxAttempts);
     }
 
-    void markUnused(T id) override { mUsedIds.erase(id); }
+    void releaseId(Id id) { mUsedIds.erase(id); }
 
 private:
     const size_t mMaxIdsCount;
 
-    std::unordered_set<T> mUsedIds;
+    std::unordered_set<Id> mUsedIds;
+
+    // Pseudo-random with random seed, in contrast to physical display IDs, which are stable
+    // across reboots. The only ISurfaceComposer exposure for these IDs is a restricted API
+    // for screencap, so there is little benefit in making them unpredictable.
     std::default_random_engine mGenerator{std::random_device()()};
-    std::uniform_int_distribution<typename T::BaseId> mDistribution;
+    std::uniform_int_distribution<typename Id::BaseId> mDistribution;
 };
 
-} // namespace android
\ No newline at end of file
+} // namespace android
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 7085eaf..34ad96c 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -294,7 +294,6 @@
 // ---------------------------------------------------------------------------
 int64_t SurfaceFlinger::dispSyncPresentTimeOffset;
 bool SurfaceFlinger::useHwcForRgbToYuv;
-uint64_t SurfaceFlinger::maxVirtualDisplaySize;
 bool SurfaceFlinger::hasSyncFramework;
 int64_t SurfaceFlinger::maxFrameBufferAcquiredBuffers;
 uint32_t SurfaceFlinger::maxGraphicsWidth;
@@ -357,8 +356,6 @@
 
     useHwcForRgbToYuv = force_hwc_copy_for_virtual_displays(false);
 
-    maxVirtualDisplaySize = max_virtual_display_dimension(0);
-
     maxFrameBufferAcquiredBuffers = max_frame_buffer_acquired_buffers(2);
 
     maxGraphicsWidth = std::max(max_graphics_width(0), 0);
@@ -434,10 +431,6 @@
     ALOGI_IF(mPropagateBackpressureClientComposition,
              "Enabling backpressure propagation for Client Composition");
 
-    property_get("debug.sf.enable_hwc_vds", value, "0");
-    mUseHwcVirtualDisplays = atoi(value);
-    ALOGI_IF(mUseHwcVirtualDisplays, "Enabling HWC virtual displays");
-
     property_get("ro.surface_flinger.supports_background_blur", value, "0");
     bool supportsBlurs = atoi(value);
     mSupportsBlur = supportsBlurs;
@@ -578,6 +571,59 @@
     setTransactionFlags(eDisplayTransactionNeeded);
 }
 
+void SurfaceFlinger::enableHalVirtualDisplays(bool enable) {
+    auto& generator = mVirtualDisplayIdGenerators.hal;
+    if (!generator && enable) {
+        ALOGI("Enabling HAL virtual displays");
+        generator.emplace(getHwComposer().getMaxVirtualDisplayCount());
+    } else if (generator && !enable) {
+        ALOGW_IF(generator->inUse(), "Disabling HAL virtual displays while in use");
+        generator.reset();
+    }
+}
+
+VirtualDisplayId SurfaceFlinger::acquireVirtualDisplay(ui::Size resolution, ui::PixelFormat format,
+                                                       ui::LayerStack layerStack) {
+    if (auto& generator = mVirtualDisplayIdGenerators.hal) {
+        if (const auto id = generator->generateId()) {
+            std::optional<PhysicalDisplayId> mirror;
+
+            if (const auto display = findDisplay([layerStack](const auto& display) {
+                    return !display.isVirtual() && display.getLayerStack() == layerStack;
+                })) {
+                mirror = display->getPhysicalId();
+            }
+
+            if (getHwComposer().allocateVirtualDisplay(*id, resolution, &format, mirror)) {
+                return *id;
+            }
+
+            generator->releaseId(*id);
+        } else {
+            ALOGW("%s: Exhausted HAL virtual displays", __func__);
+        }
+
+        ALOGW("%s: Falling back to GPU virtual display", __func__);
+    }
+
+    const auto id = mVirtualDisplayIdGenerators.gpu.generateId();
+    LOG_ALWAYS_FATAL_IF(!id, "Failed to generate ID for GPU virtual display");
+    return *id;
+}
+
+void SurfaceFlinger::releaseVirtualDisplay(VirtualDisplayId displayId) {
+    if (const auto id = HalVirtualDisplayId::tryCast(displayId)) {
+        if (auto& generator = mVirtualDisplayIdGenerators.hal) {
+            generator->releaseId(*id);
+        }
+        return;
+    }
+
+    const auto id = GpuVirtualDisplayId::tryCast(displayId);
+    LOG_ALWAYS_FATAL_IF(!id);
+    mVirtualDisplayIdGenerators.gpu.releaseId(*id);
+}
+
 std::vector<PhysicalDisplayId> SurfaceFlinger::getPhysicalDisplayIds() const {
     Mutex::Autolock lock(mStateLock);
 
@@ -736,8 +782,13 @@
                     .build()));
     mCompositionEngine->setTimeStats(mTimeStats);
     mCompositionEngine->setHwComposer(getFactory().createHWComposer(mHwcServiceName));
-    mCompositionEngine->getHwComposer().setConfiguration(this, getBE().mComposerSequenceId);
+    mCompositionEngine->getHwComposer().setCallback(this);
     ClientCache::getInstance().setRenderEngine(&getRenderEngine());
+
+    if (base::GetBoolProperty("debug.sf.enable_hwc_vds"s, false)) {
+        enableHalVirtualDisplays(true);
+    }
+
     // Process any initial hotplug and resulting display changes.
     processDisplayHotplugEventsLocked();
     const auto display = getDefaultDisplayDeviceLocked();
@@ -1596,16 +1647,11 @@
     return 0;
 }
 
-void SurfaceFlinger::onVsyncReceived(int32_t sequenceId, hal::HWDisplayId hwcDisplayId,
-                                     int64_t timestamp,
-                                     std::optional<hal::VsyncPeriodNanos> vsyncPeriod) {
-    ATRACE_NAME("SF onVsync");
+void SurfaceFlinger::onComposerHalVsync(hal::HWDisplayId hwcDisplayId, int64_t timestamp,
+                                        std::optional<hal::VsyncPeriodNanos> vsyncPeriod) {
+    ATRACE_CALL();
 
     Mutex::Autolock lock(mStateLock);
-    // Ignore any vsyncs from a previous hardware composer.
-    if (sequenceId != getBE().mComposerSequenceId) {
-        return;
-    }
 
     if (const auto displayId = getHwComposer().toPhysicalDisplayId(hwcDisplayId)) {
         auto token = getPhysicalDisplayTokenLocked(*displayId);
@@ -1656,16 +1702,11 @@
     setDesiredActiveMode({refreshRate.getModeId(), event});
 }
 
-void SurfaceFlinger::onHotplugReceived(int32_t sequenceId, hal::HWDisplayId hwcDisplayId,
-                                       hal::Connection connection) {
-    ALOGI("%s(%d, %" PRIu64 ", %s)", __FUNCTION__, sequenceId, hwcDisplayId,
+void SurfaceFlinger::onComposerHalHotplug(hal::HWDisplayId hwcDisplayId,
+                                          hal::Connection connection) {
+    ALOGI("%s(%" PRIu64 ", %s)", __func__, hwcDisplayId,
           connection == hal::Connection::CONNECTED ? "connected" : "disconnected");
 
-    // Ignore events that do not have the right sequenceId.
-    if (sequenceId != getBE().mComposerSequenceId) {
-        return;
-    }
-
     // Only lock if we're not on the main thread. This function is normally
     // called on a hwbinder thread, but for the primary display it's called on
     // the main thread with the state lock already held, so don't attempt to
@@ -1682,26 +1723,19 @@
     setTransactionFlags(eDisplayTransactionNeeded);
 }
 
-void SurfaceFlinger::onVsyncPeriodTimingChangedReceived(
-        int32_t sequenceId, hal::HWDisplayId /*display*/,
-        const hal::VsyncPeriodChangeTimeline& updatedTimeline) {
+void SurfaceFlinger::onComposerHalVsyncPeriodTimingChanged(
+        hal::HWDisplayId, const hal::VsyncPeriodChangeTimeline& timeline) {
     Mutex::Autolock lock(mStateLock);
-    if (sequenceId != getBE().mComposerSequenceId) {
-        return;
-    }
-    mScheduler->onNewVsyncPeriodChangeTimeline(updatedTimeline);
+    mScheduler->onNewVsyncPeriodChangeTimeline(timeline);
 }
 
-void SurfaceFlinger::onSeamlessPossible(int32_t /*sequenceId*/, hal::HWDisplayId /*display*/) {
+void SurfaceFlinger::onComposerHalSeamlessPossible(hal::HWDisplayId) {
     // TODO(b/142753666): use constraints when calling to setActiveModeWithConstraints and
     // use this callback to know when to retry in case of SEAMLESS_NOT_POSSIBLE.
 }
 
-void SurfaceFlinger::onRefreshReceived(int sequenceId, hal::HWDisplayId /*hwcDisplayId*/) {
+void SurfaceFlinger::onComposerHalRefresh(hal::HWDisplayId) {
     Mutex::Autolock lock(mStateLock);
-    if (sequenceId != getBE().mComposerSequenceId) {
-        return;
-    }
     repaintEverythingForHWC();
 }
 
@@ -2192,11 +2226,10 @@
             mFpsReporter->dispatchLayerFps();
         }
         hdrInfoListeners.reserve(mHdrLayerInfoListeners.size());
-        for (auto& [key, value] : mHdrLayerInfoListeners) {
-            if (value && value->hasListeners()) {
-                auto listenersDisplay = getDisplayById(key);
-                if (listenersDisplay) {
-                    hdrInfoListeners.emplace_back(listenersDisplay->getCompositionDisplay(), value);
+        for (const auto& [displayId, reporter] : mHdrLayerInfoListeners) {
+            if (reporter && reporter->hasListeners()) {
+                if (const auto display = getDisplayDeviceLocked(displayId)) {
+                    hdrInfoListeners.emplace_back(display->getCompositionDisplay(), reporter);
                 }
             }
         }
@@ -2622,10 +2655,10 @@
         ALOGE_IF(status != NO_ERROR, "Unable to query width (%d)", status);
         status = state.surface->query(NATIVE_WINDOW_HEIGHT, &resolution.height);
         ALOGE_IF(status != NO_ERROR, "Unable to query height (%d)", status);
-        int intPixelFormat;
-        status = state.surface->query(NATIVE_WINDOW_FORMAT, &intPixelFormat);
+        int format;
+        status = state.surface->query(NATIVE_WINDOW_FORMAT, &format);
         ALOGE_IF(status != NO_ERROR, "Unable to query format (%d)", status);
-        pixelFormat = static_cast<ui::PixelFormat>(intPixelFormat);
+        pixelFormat = static_cast<ui::PixelFormat>(format);
     } else {
         // Virtual displays without a surface are dormant:
         // they have external state (layer stack, projection,
@@ -2635,17 +2668,18 @@
 
     compositionengine::DisplayCreationArgsBuilder builder;
     if (const auto& physical = state.physical) {
-        builder.setPhysical({physical->id, physical->type});
+        builder.setId(physical->id);
+        builder.setConnectionType(physical->type);
+    } else {
+        builder.setId(acquireVirtualDisplay(resolution, pixelFormat, state.layerStack));
     }
+
     builder.setPixels(resolution);
-    builder.setPixelFormat(pixelFormat);
     builder.setIsSecure(state.isSecure);
     builder.setLayerStackId(state.layerStack);
     builder.setPowerAdvisor(&mPowerAdvisor);
-    builder.setUseHwcVirtualDisplays(mUseHwcVirtualDisplays);
-    builder.setGpuVirtualDisplayIdGenerator(mGpuVirtualDisplayIdGenerator);
     builder.setName(state.displayName);
-    const auto compositionDisplay = getCompositionEngine().createDisplay(builder.build());
+    auto compositionDisplay = getCompositionEngine().createDisplay(builder.build());
     compositionDisplay->setLayerCachingEnabled(mLayerCachingEnabled);
 
     sp<compositionengine::DisplaySurface> displaySurface;
@@ -2654,33 +2688,30 @@
     sp<IGraphicBufferConsumer> bqConsumer;
     getFactory().createBufferQueue(&bqProducer, &bqConsumer, /*consumerIsSurfaceFlinger =*/false);
 
-    DisplayId displayId = compositionDisplay->getId();
-
     if (state.isVirtual()) {
-        const auto virtualId = VirtualDisplayId::tryCast(displayId);
-        LOG_FATAL_IF(!virtualId);
-        sp<VirtualDisplaySurface> vds =
-                new VirtualDisplaySurface(getHwComposer(), *virtualId, state.surface, bqProducer,
-                                          bqConsumer, state.displayName);
-
-        displaySurface = vds;
-        producer = vds;
+        const auto displayId = VirtualDisplayId::tryCast(compositionDisplay->getId());
+        LOG_FATAL_IF(!displayId);
+        auto surface = sp<VirtualDisplaySurface>::make(getHwComposer(), *displayId, state.surface,
+                                                       bqProducer, bqConsumer, state.displayName);
+        displaySurface = surface;
+        producer = std::move(surface);
     } else {
         ALOGE_IF(state.surface != nullptr,
                  "adding a supported display, but rendering "
                  "surface is provided (%p), ignoring it",
                  state.surface.get());
-        const auto physicalId = PhysicalDisplayId::tryCast(displayId);
-        LOG_FATAL_IF(!physicalId);
-        displaySurface = new FramebufferSurface(getHwComposer(), *physicalId, bqConsumer,
-                                                state.physical->activeMode->getSize(),
-                                                ui::Size(maxGraphicsWidth, maxGraphicsHeight));
+        const auto displayId = PhysicalDisplayId::tryCast(compositionDisplay->getId());
+        LOG_FATAL_IF(!displayId);
+        displaySurface =
+                sp<FramebufferSurface>::make(getHwComposer(), *displayId, bqConsumer,
+                                             state.physical->activeMode->getSize(),
+                                             ui::Size(maxGraphicsWidth, maxGraphicsHeight));
         producer = bqProducer;
     }
 
     LOG_FATAL_IF(!displaySurface);
-    const auto display = setupNewDisplayDeviceInternal(displayToken, compositionDisplay, state,
-                                                       displaySurface, producer);
+    const auto display = setupNewDisplayDeviceInternal(displayToken, std::move(compositionDisplay),
+                                                       state, displaySurface, producer);
     mDisplays.emplace(displayToken, display);
     if (!state.isVirtual()) {
         dispatchDisplayHotplugEvent(display->getPhysicalId(), true);
@@ -2696,7 +2727,10 @@
     auto display = getDisplayDeviceLocked(displayToken);
     if (display) {
         display->disconnect();
-        if (!display->isVirtual()) {
+
+        if (display->isVirtual()) {
+            releaseVirtualDisplay(display->getVirtualId());
+        } else {
             dispatchDisplayHotplugEvent(display->getPhysicalId(), false);
         }
     }
@@ -2725,17 +2759,26 @@
                                            const DisplayDeviceState& drawingState) {
     const sp<IBinder> currentBinder = IInterface::asBinder(currentState.surface);
     const sp<IBinder> drawingBinder = IInterface::asBinder(drawingState.surface);
+
+    // Recreate the DisplayDevice if the surface or sequence ID changed.
     if (currentBinder != drawingBinder || currentState.sequenceId != drawingState.sequenceId) {
-        // changing the surface is like destroying and recreating the DisplayDevice
         getRenderEngine().cleanFramebufferCache();
+
         if (const auto display = getDisplayDeviceLocked(displayToken)) {
             display->disconnect();
+            if (display->isVirtual()) {
+                releaseVirtualDisplay(display->getVirtualId());
+            }
         }
+
         mDisplays.erase(displayToken);
+
         if (const auto& physical = currentState.physical) {
             getHwComposer().allocatePhysicalDisplay(physical->hwcDisplayId, physical->id);
         }
+
         processDisplayAdded(displayToken, currentState);
+
         if (currentState.physical) {
             const auto display = getDisplayDeviceLocked(displayToken);
             setPowerModeInternal(display, hal::PowerMode::ON);
@@ -2831,6 +2874,7 @@
     // Commit layer transactions. This needs to happen after display transactions are
     // committed because some geometry logic relies on display orientation.
     if ((transactionFlags & eTraversalNeeded) || mForceTraversal || displayTransactionNeeded) {
+        mForceTraversal = false;
         mCurrentState.traverse([&](Layer* layer) {
             uint32_t trFlags = layer->getTransactionFlags(eTransactionNeeded);
             if (!trFlags && !displayTransactionNeeded) return;
@@ -4601,7 +4645,8 @@
 
     StringAppendF(&result, " PRESENT_TIME_OFFSET=%" PRId64, dispSyncPresentTimeOffset);
     StringAppendF(&result, " FORCE_HWC_FOR_RBG_TO_YUV=%d", useHwcForRgbToYuv);
-    StringAppendF(&result, " MAX_VIRT_DISPLAY_DIM=%" PRIu64, maxVirtualDisplaySize);
+    StringAppendF(&result, " MAX_VIRT_DISPLAY_DIM=%zu",
+                  getHwComposer().getMaxVirtualDisplayDimension());
     StringAppendF(&result, " RUNNING_WITHOUT_SYNC_FRAMEWORK=%d", !hasSyncFramework);
     StringAppendF(&result, " NUM_FRAMEBUFFER_SURFACE_BUFFERS=%" PRId64,
                   maxFrameBufferAcquiredBuffers);
@@ -5359,8 +5404,8 @@
                 return NO_ERROR;
             }
             case 1021: { // Disable HWC virtual displays
-                n = data.readInt32();
-                mUseHwcVirtualDisplays = !n;
+                const bool enable = data.readInt32() != 0;
+                static_cast<void>(schedule([this, enable] { enableHalVirtualDisplays(enable); }));
                 return NO_ERROR;
             }
             case 1022: { // Set saturation boost
@@ -5508,37 +5553,24 @@
             }
             case 1035: {
                 const int modeId = data.readInt32();
-                mDebugDisplayModeSetByBackdoor = false;
 
-                const auto displayId = [&]() -> std::optional<PhysicalDisplayId> {
-                    uint64_t inputDisplayId = 0;
-                    if (data.readUint64(&inputDisplayId) == NO_ERROR) {
-                        const auto token = getPhysicalDisplayToken(
-                                static_cast<PhysicalDisplayId>(inputDisplayId));
-                        if (!token) {
-                            ALOGE("No display with id: %" PRIu64, inputDisplayId);
-                            return std::nullopt;
-                        }
-
-                        return std::make_optional<PhysicalDisplayId>(inputDisplayId);
+                const auto display = [&]() -> sp<IBinder> {
+                    uint64_t value;
+                    if (data.readUint64(&value) != NO_ERROR) {
+                        return getInternalDisplayToken();
                     }
 
-                    return getInternalDisplayId();
+                    if (const auto id = DisplayId::fromValue<PhysicalDisplayId>(value)) {
+                        return getPhysicalDisplayToken(*id);
+                    }
+
+                    ALOGE("Invalid physical display ID");
+                    return nullptr;
                 }();
 
-                if (!displayId) {
-                    ALOGE("No display found");
-                    return NO_ERROR;
-                }
-
-                status_t result = setActiveMode(getPhysicalDisplayToken(*displayId), modeId);
-                if (result != NO_ERROR) {
-                    return result;
-                }
-
-                mDebugDisplayModeSetByBackdoor = true;
-
-                return NO_ERROR;
+                const status_t result = setActiveMode(display, modeId);
+                mDebugDisplayModeSetByBackdoor = result == NO_ERROR;
+                return result;
             }
             case 1036: {
                 if (data.readInt32() > 0) {
@@ -5560,7 +5592,7 @@
                     Mutex::Autolock lock(mStateLock);
                     hwcId = getHwComposer().getInternalHwcDisplayId();
                 }
-                onHotplugReceived(getBE().mComposerSequenceId, *hwcId, hal::Connection::CONNECTED);
+                onComposerHalHotplug(*hwcId, hal::Connection::CONNECTED);
                 return NO_ERROR;
             }
             // Modify the max number of display frames stored within FrameTimeline
@@ -5601,14 +5633,11 @@
                             std::optional<PhysicalDisplayId> inputId = std::nullopt;
                             if (uint64_t inputDisplayId;
                                 data.readUint64(&inputDisplayId) == NO_ERROR) {
-                                const auto token = getPhysicalDisplayToken(
-                                        static_cast<PhysicalDisplayId>(inputDisplayId));
-                                if (!token) {
+                                inputId = DisplayId::fromValue<PhysicalDisplayId>(inputDisplayId);
+                                if (!inputId || getPhysicalDisplayToken(*inputId)) {
                                     ALOGE("No display with id: %" PRIu64, inputDisplayId);
                                     return NAME_NOT_FOUND;
                                 }
-
-                                inputId = std::make_optional<PhysicalDisplayId>(inputDisplayId);
                             }
                             {
                                 Mutex::Autolock lock(mStateLock);
@@ -5770,34 +5799,6 @@
     return NO_ERROR;
 }
 
-sp<DisplayDevice> SurfaceFlinger::getDisplayByIdOrLayerStack(uint64_t displayOrLayerStack) {
-    if (const sp<IBinder> displayToken =
-                getPhysicalDisplayTokenLocked(PhysicalDisplayId{displayOrLayerStack})) {
-        return getDisplayDeviceLocked(displayToken);
-    }
-    // Couldn't find display by displayId. Try to get display by layerStack since virtual displays
-    // may not have a displayId.
-    return getDisplayByLayerStack(displayOrLayerStack);
-}
-
-sp<DisplayDevice> SurfaceFlinger::getDisplayById(DisplayId displayId) const {
-    for (const auto& [token, display] : mDisplays) {
-        if (display->getId() == displayId) {
-            return display;
-        }
-    }
-    return nullptr;
-}
-
-sp<DisplayDevice> SurfaceFlinger::getDisplayByLayerStack(uint64_t layerStack) {
-    for (const auto& [token, display] : mDisplays) {
-        if (display->getLayerStack() == layerStack) {
-            return display;
-        }
-    }
-    return nullptr;
-}
-
 status_t SurfaceFlinger::captureDisplay(const DisplayCaptureArgs& args,
                                         const sp<IScreenCaptureListener>& captureListener) {
     ATRACE_CALL();
@@ -5809,7 +5810,7 @@
 
     if (!args.displayToken) return BAD_VALUE;
 
-    wp<DisplayDevice> displayWeak;
+    wp<const DisplayDevice> displayWeak;
     ui::LayerStack layerStack;
     ui::Size reqSize(args.width, args.height);
     ui::Dataspace dataspace;
@@ -5850,21 +5851,22 @@
                                captureListener);
 }
 
-status_t SurfaceFlinger::captureDisplay(uint64_t displayOrLayerStack,
+status_t SurfaceFlinger::captureDisplay(DisplayId displayId,
                                         const sp<IScreenCaptureListener>& captureListener) {
     ui::LayerStack layerStack;
-    wp<DisplayDevice> displayWeak;
+    wp<const DisplayDevice> displayWeak;
     ui::Size size;
     ui::Dataspace dataspace;
     {
         Mutex::Autolock lock(mStateLock);
-        sp<DisplayDevice> display = getDisplayByIdOrLayerStack(displayOrLayerStack);
+
+        const auto display = getDisplayDeviceLocked(displayId);
         if (!display) {
             return NAME_NOT_FOUND;
         }
-        layerStack = display->getLayerStack();
-        displayWeak = display;
 
+        displayWeak = display;
+        layerStack = display->getLayerStack();
         size = display->getLayerStackSpaceRect().getSize();
 
         dataspace =
@@ -5949,7 +5951,11 @@
             }
         }
 
-        const auto display = getDisplayByLayerStack(parent->getLayerStack());
+        const auto display =
+                findDisplay([layerStack = parent->getLayerStack()](const auto& display) {
+                    return display.getLayerStack() == layerStack;
+                });
+
         if (!display) {
             return NAME_NOT_FOUND;
         }
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index cb8d312..ee354c6 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -169,11 +169,6 @@
     };
     mutable Mutex mBufferingStatsMutex;
     std::unordered_map<std::string, BufferingStats> mBufferingStats;
-
-    // The composer sequence id is a monotonically increasing integer that we
-    // use to differentiate callbacks from different hardware composer
-    // instances. Each hardware composer instance gets a different sequence id.
-    int32_t mComposerSequenceId = 0;
 };
 
 class SurfaceFlinger : public BnSurfaceComposer,
@@ -228,10 +223,6 @@
     // GL composition.
     static bool useHwcForRgbToYuv;
 
-    // Maximum dimension supported by HWC for virtual display.
-    // Equal to min(max_height, max_width).
-    static uint64_t maxVirtualDisplaySize;
-
     // Controls the number of buffers SurfaceFlinger will allocate for use in
     // FramebufferSurface
     static int64_t maxFrameBufferAcquiredBuffers;
@@ -624,12 +615,10 @@
     sp<IDisplayEventConnection> createDisplayEventConnection(
             ISurfaceComposer::VsyncSource vsyncSource = eVsyncSourceApp,
             ISurfaceComposer::EventRegistrationFlags eventRegistration = {}) override;
-    status_t captureDisplay(const DisplayCaptureArgs& args,
-                            const sp<IScreenCaptureListener>& captureListener) override;
-    status_t captureDisplay(uint64_t displayOrLayerStack,
-                            const sp<IScreenCaptureListener>& captureListener) override;
-    status_t captureLayers(const LayerCaptureArgs& args,
-                           const sp<IScreenCaptureListener>& captureListener) override;
+
+    status_t captureDisplay(const DisplayCaptureArgs&, const sp<IScreenCaptureListener>&) override;
+    status_t captureDisplay(DisplayId, const sp<IScreenCaptureListener>&) override;
+    status_t captureLayers(const LayerCaptureArgs&, const sp<IScreenCaptureListener>&) override;
 
     status_t getDisplayStats(const sp<IBinder>& displayToken, DisplayStatInfo* stats) override;
     status_t getDisplayState(const sp<IBinder>& displayToken, ui::DisplayState*)
@@ -716,18 +705,14 @@
     // Implements RefBase.
     void onFirstRef() override;
 
-    /*
-     * HWC2::ComposerCallback / HWComposer::EventHandler interface
-     */
-    void onVsyncReceived(int32_t sequenceId, hal::HWDisplayId hwcDisplayId, int64_t timestamp,
-                         std::optional<hal::VsyncPeriodNanos> vsyncPeriod) override;
-    void onHotplugReceived(int32_t sequenceId, hal::HWDisplayId hwcDisplayId,
-                           hal::Connection connection) override;
-    void onRefreshReceived(int32_t sequenceId, hal::HWDisplayId hwcDisplayId) override;
-    void onVsyncPeriodTimingChangedReceived(
-            int32_t sequenceId, hal::HWDisplayId display,
-            const hal::VsyncPeriodChangeTimeline& updatedTimeline) override;
-    void onSeamlessPossible(int32_t sequenceId, hal::HWDisplayId display) override;
+    // HWC2::ComposerCallback overrides:
+    void onComposerHalVsync(hal::HWDisplayId, int64_t timestamp,
+                            std::optional<hal::VsyncPeriodNanos>) override;
+    void onComposerHalHotplug(hal::HWDisplayId, hal::Connection) override;
+    void onComposerHalRefresh(hal::HWDisplayId) override;
+    void onComposerHalVsyncPeriodTimingChanged(hal::HWDisplayId,
+                                               const hal::VsyncPeriodChangeTimeline&) override;
+    void onComposerHalSeamlessPossible(hal::HWDisplayId) override;
 
     /*
      * ISchedulerCallback
@@ -918,10 +903,6 @@
                                     bool canCaptureBlackoutContent, bool regionSampling,
                                     bool grayscale, ScreenCaptureResults&);
 
-    sp<DisplayDevice> getDisplayByIdOrLayerStack(uint64_t displayOrLayerStack) REQUIRES(mStateLock);
-    sp<DisplayDevice> getDisplayById(DisplayId displayId) const REQUIRES(mStateLock);
-    sp<DisplayDevice> getDisplayByLayerStack(uint64_t layerStack) REQUIRES(mStateLock);
-
     // If the uid provided is not UNSET_UID, the traverse will skip any layers that don't have a
     // matching ownerUid
     void traverseLayersInLayerStack(ui::LayerStack, const int32_t uid, const LayerVector::Visitor&);
@@ -963,6 +944,20 @@
         return getDefaultDisplayDeviceLocked();
     }
 
+    // Returns the first display that matches a `bool(const DisplayDevice&)` predicate.
+    template <typename Predicate>
+    sp<DisplayDevice> findDisplay(Predicate p) const REQUIRES(mStateLock) {
+        const auto it = std::find_if(mDisplays.begin(), mDisplays.end(),
+                                     [&](const auto& pair) { return p(*pair.second); });
+
+        return it == mDisplays.end() ? nullptr : it->second;
+    }
+
+    sp<const DisplayDevice> getDisplayDeviceLocked(DisplayId id) const REQUIRES(mStateLock) {
+        // TODO(b/182939859): Replace tokens with IDs for display lookup.
+        return findDisplay([id](const auto& display) { return display.getId() == id; });
+    }
+
     // mark a region of a layer stack dirty. this updates the dirty
     // region of all screens presenting this layer stack.
     void invalidateLayerStack(const sp<const Layer>& layer, const Region& dirty);
@@ -1080,6 +1075,14 @@
         return hwcDisplayId ? getHwComposer().toPhysicalDisplayId(*hwcDisplayId) : std::nullopt;
     }
 
+    // Toggles use of HAL/GPU virtual displays.
+    void enableHalVirtualDisplays(bool);
+
+    // Virtual display lifecycle for ID generation and HAL allocation.
+    VirtualDisplayId acquireVirtualDisplay(ui::Size, ui::PixelFormat, ui::LayerStack)
+            REQUIRES(mStateLock);
+    void releaseVirtualDisplay(VirtualDisplayId);
+
     /*
      * Debugging & dumpsys
      */
@@ -1232,7 +1235,10 @@
     std::unordered_map<PhysicalDisplayId, sp<IBinder>> mPhysicalDisplayTokens
             GUARDED_BY(mStateLock);
 
-    RandomDisplayIdGenerator<GpuVirtualDisplayId> mGpuVirtualDisplayIdGenerator;
+    struct {
+        DisplayIdGenerator<GpuVirtualDisplayId> gpu;
+        std::optional<DisplayIdGenerator<HalVirtualDisplayId>> hal;
+    } mVirtualDisplayIdGenerators;
 
     std::unordered_map<BBinder*, wp<Layer>> mLayersByLocalBinderToken GUARDED_BY(mStateLock);
 
@@ -1255,7 +1261,7 @@
     const std::shared_ptr<TimeStats> mTimeStats;
     const std::unique_ptr<FrameTracer> mFrameTracer;
     const std::unique_ptr<frametimeline::FrameTimeline> mFrameTimeline;
-    bool mUseHwcVirtualDisplays = false;
+
     // If blurs should be enabled on this device.
     bool mSupportsBlur = false;
     // Disable blurs, for debugging
diff --git a/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp b/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp
index 162711d..a9e935d 100644
--- a/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp
+++ b/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp
@@ -279,7 +279,7 @@
     }
 
     bool waitForHotplugEvent(Display displayId, bool connected) {
-        return waitForHotplugEvent(PhysicalDisplayId(displayId), connected);
+        return waitForHotplugEvent(physicalIdFromHwcDisplayId(displayId), connected);
     }
 
     bool waitForHotplugEvent(PhysicalDisplayId displayId, bool connected) {
@@ -305,7 +305,7 @@
     }
 
     bool waitForModeChangedEvent(Display display, int32_t modeId) {
-        PhysicalDisplayId displayId(display);
+        PhysicalDisplayId displayId = physicalIdFromHwcDisplayId(display);
         int waitCount = 20;
         while (waitCount--) {
             while (!mReceivedDisplayEvents.empty()) {
diff --git a/services/surfaceflinger/tests/unittests/Android.bp b/services/surfaceflinger/tests/unittests/Android.bp
index b33434e..83575bd 100644
--- a/services/surfaceflinger/tests/unittests/Android.bp
+++ b/services/surfaceflinger/tests/unittests/Android.bp
@@ -68,7 +68,7 @@
         "SurfaceFlinger_GetDisplayNativePrimariesTest.cpp",
         "SurfaceFlinger_HandleTransactionLockedTest.cpp",
         "SurfaceFlinger_NotifyPowerBoostTest.cpp",
-        "SurfaceFlinger_OnHotplugReceivedTest.cpp",
+        "SurfaceFlinger_HotplugTest.cpp",
         "SurfaceFlinger_OnInitializeDisplaysTest.cpp",
         "SurfaceFlinger_SetDisplayStateTest.cpp",
         "SurfaceFlinger_SetPowerModeInternalTest.cpp",
diff --git a/services/surfaceflinger/tests/unittests/CompositionTest.cpp b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
index 3042450..fca3bfc 100644
--- a/services/surfaceflinger/tests/unittests/CompositionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
@@ -77,7 +77,7 @@
 constexpr hal::HWLayerId HWC_LAYER = 5000;
 constexpr Transform DEFAULT_TRANSFORM = static_cast<Transform>(0);
 
-constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID(42);
+constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(42u);
 constexpr int DEFAULT_DISPLAY_WIDTH = 1920;
 constexpr int DEFAULT_DISPLAY_HEIGHT = 1024;
 
@@ -105,7 +105,9 @@
 
         mFlinger.setupRenderEngine(std::unique_ptr<renderengine::RenderEngine>(mRenderEngine));
         mFlinger.setupTimeStats(std::shared_ptr<TimeStats>(mTimeStats));
-        setupComposer(0);
+
+        mComposer = new Hwc2::mock::Composer();
+        mFlinger.setupComposer(std::unique_ptr<Hwc2::Composer>(mComposer));
     }
 
     ~CompositionTest() {
@@ -114,14 +116,6 @@
         ALOGD("**** Tearing down after %s.%s\n", test_info->test_case_name(), test_info->name());
     }
 
-    void setupComposer(int virtualDisplayCount) {
-        mComposer = new Hwc2::mock::Composer();
-        EXPECT_CALL(*mComposer, getMaxVirtualDisplayCount()).WillOnce(Return(virtualDisplayCount));
-        mFlinger.setupComposer(std::unique_ptr<Hwc2::Composer>(mComposer));
-
-        Mock::VerifyAndClear(mComposer);
-    }
-
     void setupScheduler() {
         auto eventThread = std::make_unique<mock::EventThread>();
         auto sfEventThread = std::make_unique<mock::EventThread>();
@@ -289,16 +283,16 @@
         const ::testing::TestInfo* const test_info =
                 ::testing::UnitTest::GetInstance()->current_test_info();
 
-        auto ceDisplayArgs =
-                compositionengine::DisplayCreationArgsBuilder()
-                        .setPhysical({DEFAULT_DISPLAY_ID, ui::DisplayConnectionType::Internal})
-                        .setPixels({DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_HEIGHT})
-                        .setIsSecure(Derived::IS_SECURE)
-                        .setLayerStackId(DEFAULT_LAYER_STACK)
-                        .setPowerAdvisor(&test->mPowerAdvisor)
-                        .setName(std::string("Injected display for ") +
-                                 test_info->test_case_name() + "." + test_info->name())
-                        .build();
+        auto ceDisplayArgs = compositionengine::DisplayCreationArgsBuilder()
+                                     .setId(DEFAULT_DISPLAY_ID)
+                                     .setConnectionType(ui::DisplayConnectionType::Internal)
+                                     .setPixels({DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_HEIGHT})
+                                     .setIsSecure(Derived::IS_SECURE)
+                                     .setLayerStackId(DEFAULT_LAYER_STACK)
+                                     .setPowerAdvisor(&test->mPowerAdvisor)
+                                     .setName(std::string("Injected display for ") +
+                                              test_info->test_case_name() + "." + test_info->name())
+                                     .build();
 
         auto compositionDisplay =
                 compositionengine::impl::createDisplay(test->mFlinger.getCompositionEngine(),
diff --git a/services/surfaceflinger/tests/unittests/DisplayIdGeneratorTest.cpp b/services/surfaceflinger/tests/unittests/DisplayIdGeneratorTest.cpp
index 77a3e14..8d4a023 100644
--- a/services/surfaceflinger/tests/unittests/DisplayIdGeneratorTest.cpp
+++ b/services/surfaceflinger/tests/unittests/DisplayIdGeneratorTest.cpp
@@ -14,76 +14,68 @@
  * limitations under the License.
  */
 
-// TODO(b/129481165): remove the #pragma below and fix conversion issues
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wextra"
-
 #include <gtest/gtest.h>
+#include <ui/DisplayId.h>
 
+#include <algorithm>
+#include <iterator>
 #include <vector>
 
-#include <ui/DisplayId.h>
 #include "DisplayIdGenerator.h"
 
 namespace android {
 
-template <typename T>
-void testNextId(DisplayIdGenerator<T>& generator) {
-    constexpr int kNumIds = 5;
-    std::vector<T> ids;
-    for (int i = 0; i < kNumIds; i++) {
-        const auto id = generator.nextId();
-        ASSERT_TRUE(id);
-        ids.push_back(*id);
-    }
+template <typename Id>
+void testGenerateId() {
+    DisplayIdGenerator<Id> generator;
+
+    std::vector<std::optional<Id>> ids;
+    std::generate_n(std::back_inserter(ids), 10, [&] { return generator.generateId(); });
 
     // All IDs should be different.
-    for (size_t i = 0; i < kNumIds; i++) {
-        for (size_t j = i + 1; j < kNumIds; j++) {
-            EXPECT_NE(ids[i], ids[j]);
+    for (auto it = ids.begin(); it != ids.end(); ++it) {
+        EXPECT_TRUE(*it);
+
+        for (auto dup = it + 1; dup != ids.end(); ++dup) {
+            EXPECT_NE(*it, *dup);
         }
     }
 }
 
-TEST(DisplayIdGeneratorTest, nextIdGpuVirtual) {
-    RandomDisplayIdGenerator<GpuVirtualDisplayId> generator;
-    testNextId(generator);
+TEST(DisplayIdGeneratorTest, generateGpuVirtualDisplayId) {
+    testGenerateId<GpuVirtualDisplayId>();
 }
 
-TEST(DisplayIdGeneratorTest, nextIdHalVirtual) {
-    RandomDisplayIdGenerator<HalVirtualDisplayId> generator;
-    testNextId(generator);
+TEST(DisplayIdGeneratorTest, generateHalVirtualDisplayId) {
+    testGenerateId<HalVirtualDisplayId>();
 }
 
-TEST(DisplayIdGeneratorTest, markUnused) {
+TEST(DisplayIdGeneratorTest, releaseId) {
     constexpr size_t kMaxIdsCount = 5;
-    RandomDisplayIdGenerator<GpuVirtualDisplayId> generator(kMaxIdsCount);
+    DisplayIdGenerator<GpuVirtualDisplayId> generator(kMaxIdsCount);
 
-    const auto id = generator.nextId();
+    const auto id = generator.generateId();
     EXPECT_TRUE(id);
 
-    for (int i = 1; i < kMaxIdsCount; i++) {
-        EXPECT_TRUE(generator.nextId());
+    for (size_t i = 1; i < kMaxIdsCount; i++) {
+        EXPECT_TRUE(generator.generateId());
     }
 
-    EXPECT_FALSE(generator.nextId());
+    EXPECT_FALSE(generator.generateId());
 
-    generator.markUnused(*id);
-    EXPECT_TRUE(generator.nextId());
+    generator.releaseId(*id);
+    EXPECT_TRUE(generator.generateId());
 }
 
 TEST(DisplayIdGeneratorTest, maxIdsCount) {
     constexpr size_t kMaxIdsCount = 5;
-    RandomDisplayIdGenerator<GpuVirtualDisplayId> generator(kMaxIdsCount);
+    DisplayIdGenerator<GpuVirtualDisplayId> generator(kMaxIdsCount);
 
-    for (int i = 0; i < kMaxIdsCount; i++) {
-        EXPECT_TRUE(generator.nextId());
+    for (size_t i = 0; i < kMaxIdsCount; i++) {
+        EXPECT_TRUE(generator.generateId());
     }
 
-    EXPECT_FALSE(generator.nextId());
+    EXPECT_FALSE(generator.generateId());
 }
 
 } // namespace android
-
-// TODO(b/129481165): remove the #pragma below and fix conversion issues
-#pragma clang diagnostic pop // ignored "-Wextra"
\ No newline at end of file
diff --git a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
index a3e8108..60b0f53 100644
--- a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
@@ -41,9 +41,6 @@
     mFlinger.mutableUseColorManagement() = false;
     mFlinger.mutableDisplayColorSetting() = DisplayColorSetting::kUnmanaged;
 
-    // Default to using HWC virtual displays
-    mFlinger.mutableUseHwcVirtualDisplays() = true;
-
     mFlinger.setCreateBufferQueueFunction([](auto, auto, auto) {
         ADD_FAILURE() << "Unexpected request to create a buffer queue.";
     });
@@ -85,10 +82,17 @@
 }
 
 void DisplayTransactionTest::injectMockComposer(int virtualDisplayCount) {
+    if (mComposer) {
+        // If reinjecting, disable first to prevent the enable below from being a no-op.
+        mFlinger.enableHalVirtualDisplays(false);
+    }
+
     mComposer = new Hwc2::mock::Composer();
-    EXPECT_CALL(*mComposer, getMaxVirtualDisplayCount()).WillOnce(Return(virtualDisplayCount));
     mFlinger.setupComposer(std::unique_ptr<Hwc2::Composer>(mComposer));
 
+    EXPECT_CALL(*mComposer, getMaxVirtualDisplayCount()).WillOnce(Return(virtualDisplayCount));
+    mFlinger.enableHalVirtualDisplays(true);
+
     Mock::VerifyAndClear(mComposer);
 }
 
@@ -118,7 +122,7 @@
 
 sp<DisplayDevice> DisplayTransactionTest::injectDefaultInternalDisplay(
         std::function<void(FakeDisplayDeviceInjector&)> injectExtra) {
-    constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID(777);
+    constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(255u);
     constexpr int DEFAULT_DISPLAY_WIDTH = 1080;
     constexpr int DEFAULT_DISPLAY_HEIGHT = 1920;
     constexpr HWDisplayId DEFAULT_DISPLAY_HWC_DISPLAY_ID = 0;
@@ -135,18 +139,21 @@
     EXPECT_CALL(*mNativeWindow, perform(NATIVE_WINDOW_SET_USAGE64));
     EXPECT_CALL(*mNativeWindow, perform(NATIVE_WINDOW_API_DISCONNECT)).Times(AnyNumber());
 
-    auto compositionDisplay = compositionengine::impl::
-            createDisplay(mFlinger.getCompositionEngine(),
-                          compositionengine::DisplayCreationArgsBuilder()
-                                  .setPhysical(
-                                          {DEFAULT_DISPLAY_ID, ui::DisplayConnectionType::Internal})
-                                  .setPixels({DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_HEIGHT})
-                                  .setPowerAdvisor(&mPowerAdvisor)
-                                  .build());
+    constexpr auto kConnectionType = ui::DisplayConnectionType::Internal;
+    constexpr bool kIsPrimary = true;
 
-    auto injector = FakeDisplayDeviceInjector(mFlinger, compositionDisplay,
-                                              ui::DisplayConnectionType::Internal,
-                                              DEFAULT_DISPLAY_HWC_DISPLAY_ID, true /* isPrimary */);
+    auto compositionDisplay =
+            compositionengine::impl::createDisplay(mFlinger.getCompositionEngine(),
+                                                   compositionengine::DisplayCreationArgsBuilder()
+                                                           .setId(DEFAULT_DISPLAY_ID)
+                                                           .setConnectionType(kConnectionType)
+                                                           .setPixels({DEFAULT_DISPLAY_WIDTH,
+                                                                       DEFAULT_DISPLAY_HEIGHT})
+                                                           .setPowerAdvisor(&mPowerAdvisor)
+                                                           .build());
+
+    auto injector = FakeDisplayDeviceInjector(mFlinger, compositionDisplay, kConnectionType,
+                                              DEFAULT_DISPLAY_HWC_DISPLAY_ID, kIsPrimary);
 
     injector.setNativeWindow(mNativeWindow);
     if (injectExtra) {
diff --git a/services/surfaceflinger/tests/unittests/DisplayTransactionTestHelpers.h b/services/surfaceflinger/tests/unittests/DisplayTransactionTestHelpers.h
index d68fff6..6ce281d 100644
--- a/services/surfaceflinger/tests/unittests/DisplayTransactionTestHelpers.h
+++ b/services/surfaceflinger/tests/unittests/DisplayTransactionTestHelpers.h
@@ -263,40 +263,23 @@
 
     static auto makeFakeExistingDisplayInjector(DisplayTransactionTest* test) {
         auto ceDisplayArgs = compositionengine::DisplayCreationArgsBuilder();
-        if (auto displayId = PhysicalDisplayId::tryCast(DISPLAY_ID::get())) {
-            ceDisplayArgs.setPhysical({*displayId, ui::DisplayConnectionType::Internal});
-        } else {
-            // We turn off the use of HwcVirtualDisplays, to prevent Composition Engine
-            // from calling into HWComposer. This way all virtual displays will get
-            // a GpuVirtualDisplayId, even if we are in the HwcVirtualDisplayVariant.
-            // In this case we later override it by calling display.setDisplayIdForTesting().
-            ceDisplayArgs.setUseHwcVirtualDisplays(false);
+        ceDisplayArgs.setId(DISPLAY_ID::get())
+                .setPixels({WIDTH, HEIGHT})
+                .setPowerAdvisor(&test->mPowerAdvisor);
 
-            GpuVirtualDisplayId desiredDisplayId = GpuVirtualDisplayId::tryCast(DISPLAY_ID::get())
-                                                           .value_or(GpuVirtualDisplayId(0));
-
-            ON_CALL(test->mFlinger.gpuVirtualDisplayIdGenerator(), nextId())
-                    .WillByDefault(Return(desiredDisplayId));
-
-            auto& generator = test->mFlinger.gpuVirtualDisplayIdGenerator();
-            ceDisplayArgs.setGpuVirtualDisplayIdGenerator(generator);
+        const auto connectionType = CONNECTION_TYPE::value;
+        if (connectionType) {
+            ceDisplayArgs.setConnectionType(*connectionType);
         }
-        ceDisplayArgs.setPixels({WIDTH, HEIGHT}).setPowerAdvisor(&test->mPowerAdvisor);
 
         auto compositionDisplay =
                 compositionengine::impl::createDisplay(test->mFlinger.getCompositionEngine(),
                                                        ceDisplayArgs.build());
 
-        if (HalVirtualDisplayId::tryCast(DISPLAY_ID::get())) {
-            // CompositionEngine has assigned a placeholder GpuVirtualDisplayId and we need to
-            // override it with the correct HalVirtualDisplayId.
-            compositionDisplay->setDisplayIdForTesting(DISPLAY_ID::get());
-        }
-
         auto injector =
                 TestableSurfaceFlinger::FakeDisplayDeviceInjector(test->mFlinger,
                                                                   compositionDisplay,
-                                                                  CONNECTION_TYPE::value,
+                                                                  connectionType,
                                                                   HWC_DISPLAY_ID_OPT::value,
                                                                   static_cast<bool>(PRIMARY));
 
@@ -404,8 +387,8 @@
                 ::testing::UnitTest::GetInstance()->current_test_info();
 
         auto ceDisplayArgs = compositionengine::DisplayCreationArgsBuilder()
-                                     .setPhysical({DisplayVariant::DISPLAY_ID::get(),
-                                                   PhysicalDisplay::CONNECTION_TYPE})
+                                     .setId(DisplayVariant::DISPLAY_ID::get())
+                                     .setConnectionType(PhysicalDisplay::CONNECTION_TYPE)
                                      .setPixels({DisplayVariant::WIDTH, DisplayVariant::HEIGHT})
                                      .setIsSecure(static_cast<bool>(DisplayVariant::SECURE))
                                      .setPowerAdvisor(&test->mPowerAdvisor)
@@ -558,17 +541,13 @@
         const ::testing::TestInfo* const test_info =
                 ::testing::UnitTest::GetInstance()->current_test_info();
 
-        ON_CALL(test->mFlinger.gpuVirtualDisplayIdGenerator(), nextId())
-                .WillByDefault(Return(Base::DISPLAY_ID::get()));
-
         auto ceDisplayArgs = compositionengine::DisplayCreationArgsBuilder()
+                                     .setId(Base::DISPLAY_ID::get())
                                      .setPixels({Base::WIDTH, Base::HEIGHT})
                                      .setIsSecure(static_cast<bool>(Base::SECURE))
                                      .setPowerAdvisor(&test->mPowerAdvisor)
                                      .setName(std::string("Injected display for ") +
                                               test_info->test_case_name() + "." + test_info->name())
-                                     .setGpuVirtualDisplayIdGenerator(
-                                             test->mFlinger.gpuVirtualDisplayIdGenerator())
                                      .build();
 
         return compositionengine::impl::createDisplay(test->mFlinger.getCompositionEngine(),
@@ -610,35 +589,22 @@
         const ::testing::TestInfo* const test_info =
                 ::testing::UnitTest::GetInstance()->current_test_info();
 
-        // In order to prevent compostition engine calling into HWComposer, we
-        // 1. turn off the use of HWC virtual displays,
-        // 2. provide a GpuVirtualDisplayIdGenerator which always returns some fake ID
-        // 3. override the ID by calling setDisplayIdForTesting()
-
-        ON_CALL(test->mFlinger.gpuVirtualDisplayIdGenerator(), nextId())
-                .WillByDefault(Return(GpuVirtualDisplayId(0)));
-
+        const auto displayId = Base::DISPLAY_ID::get();
         auto ceDisplayArgs = compositionengine::DisplayCreationArgsBuilder()
-                                     .setUseHwcVirtualDisplays(false)
+                                     .setId(displayId)
                                      .setPixels({Base::WIDTH, Base::HEIGHT})
                                      .setIsSecure(static_cast<bool>(Base::SECURE))
                                      .setPowerAdvisor(&test->mPowerAdvisor)
                                      .setName(std::string("Injected display for ") +
                                               test_info->test_case_name() + "." + test_info->name())
-                                     .setGpuVirtualDisplayIdGenerator(
-                                             test->mFlinger.gpuVirtualDisplayIdGenerator())
                                      .build();
 
         auto compositionDisplay =
                 compositionengine::impl::createDisplay(test->mFlinger.getCompositionEngine(),
                                                        ceDisplayArgs);
-        compositionDisplay->setDisplayIdForTesting(Base::DISPLAY_ID::get());
 
         // Insert display data so that the HWC thinks it created the virtual display.
-        if (const auto displayId = Base::DISPLAY_ID::get();
-            HalVirtualDisplayId::tryCast(displayId)) {
-            test->mFlinger.mutableHwcDisplayData().try_emplace(displayId);
-        }
+        test->mFlinger.mutableHwcDisplayData().try_emplace(displayId);
 
         return compositionDisplay;
     }
@@ -649,8 +615,8 @@
     }
 
     static void setupHwcVirtualDisplayCreationCallExpectations(DisplayTransactionTest* test) {
-        EXPECT_CALL(*test->mComposer, createVirtualDisplay(Base::WIDTH, Base::HEIGHT, _, _))
-                .WillOnce(DoAll(SetArgPointee<3>(Self::HWC_DISPLAY_ID), Return(Error::NONE)));
+        EXPECT_CALL(*test->mComposer, createVirtualDisplay(Base::WIDTH, Base::HEIGHT, _, _, _))
+                .WillOnce(DoAll(SetArgPointee<4>(Self::HWC_DISPLAY_ID), Return(Error::NONE)));
         EXPECT_CALL(*test->mComposer, setClientTargetSlotCount(_)).WillOnce(Return(Error::NONE));
     }
 };
diff --git a/services/surfaceflinger/tests/unittests/EventThreadTest.cpp b/services/surfaceflinger/tests/unittests/EventThreadTest.cpp
index b4a1481..62acc6b 100644
--- a/services/surfaceflinger/tests/unittests/EventThreadTest.cpp
+++ b/services/surfaceflinger/tests/unittests/EventThreadTest.cpp
@@ -41,10 +41,13 @@
 
 namespace {
 
-constexpr PhysicalDisplayId INTERNAL_DISPLAY_ID(111);
-constexpr PhysicalDisplayId EXTERNAL_DISPLAY_ID(222);
-constexpr PhysicalDisplayId DISPLAY_ID_64BIT(0xabcd12349876fedcULL);
+constexpr PhysicalDisplayId INTERNAL_DISPLAY_ID = PhysicalDisplayId::fromPort(111u);
+constexpr PhysicalDisplayId EXTERNAL_DISPLAY_ID = PhysicalDisplayId::fromPort(222u);
+constexpr PhysicalDisplayId DISPLAY_ID_64BIT =
+        PhysicalDisplayId::fromEdid(0xffu, 0xffffu, 0xffff'ffffu);
+
 constexpr std::chrono::duration VSYNC_PERIOD(16ms);
+
 class MockVSyncSource : public VSyncSource {
 public:
     const char* getName() const override { return "test"; }
diff --git a/services/surfaceflinger/tests/unittests/FpsReporterTest.cpp b/services/surfaceflinger/tests/unittests/FpsReporterTest.cpp
index dec0ff5..010c675 100644
--- a/services/surfaceflinger/tests/unittests/FpsReporterTest.cpp
+++ b/services/surfaceflinger/tests/unittests/FpsReporterTest.cpp
@@ -76,11 +76,9 @@
     static constexpr int32_t PRIORITY_UNSET = -1;
 
     void setupScheduler();
-    void setupComposer(uint32_t virtualDisplayCount);
     sp<BufferStateLayer> createBufferStateLayer(LayerMetadata metadata);
 
     TestableSurfaceFlinger mFlinger;
-    Hwc2::mock::Composer* mComposer = nullptr;
     mock::FrameTimeline mFrameTimeline =
             mock::FrameTimeline(std::make_shared<impl::TimeStats>(), 0);
 
@@ -103,7 +101,8 @@
     ALOGD("**** Setting up for %s.%s\n", test_info->test_case_name(), test_info->name());
 
     setupScheduler();
-    setupComposer(0);
+    mFlinger.setupComposer(std::make_unique<Hwc2::mock::Composer>());
+
     mFpsListener = new TestableFpsListener();
 }
 
@@ -145,19 +144,11 @@
                             std::move(eventThread), std::move(sfEventThread));
 }
 
-void FpsReporterTest::setupComposer(uint32_t virtualDisplayCount) {
-    mComposer = new Hwc2::mock::Composer();
-    EXPECT_CALL(*mComposer, getMaxVirtualDisplayCount()).WillOnce(Return(virtualDisplayCount));
-    mFlinger.setupComposer(std::unique_ptr<Hwc2::Composer>(mComposer));
-
-    Mock::VerifyAndClear(mComposer);
-}
-
 namespace {
 
 TEST_F(FpsReporterTest, callsListeners) {
     mParent = createBufferStateLayer();
-    const constexpr int32_t kTaskId = 12;
+    constexpr int32_t kTaskId = 12;
     LayerMetadata targetMetadata;
     targetMetadata.setInt32(METADATA_TASK_ID, kTaskId);
     mTarget = createBufferStateLayer(targetMetadata);
diff --git a/services/surfaceflinger/tests/unittests/HWComposerTest.cpp b/services/surfaceflinger/tests/unittests/HWComposerTest.cpp
index cbf8cc2..655baf8 100644
--- a/services/surfaceflinger/tests/unittests/HWComposerTest.cpp
+++ b/services/surfaceflinger/tests/unittests/HWComposerTest.cpp
@@ -58,28 +58,26 @@
 using ::testing::StrictMock;
 
 struct MockHWC2ComposerCallback final : StrictMock<HWC2::ComposerCallback> {
-    MOCK_METHOD3(onHotplugReceived, void(int32_t sequenceId, hal::HWDisplayId, hal::Connection));
-    MOCK_METHOD2(onRefreshReceived, void(int32_t sequenceId, hal::HWDisplayId));
-    MOCK_METHOD4(onVsyncReceived,
-                 void(int32_t sequenceId, hal::HWDisplayId, int64_t timestamp,
-                      std::optional<hal::VsyncPeriodNanos>));
-    MOCK_METHOD3(onVsyncPeriodTimingChangedReceived,
-                 void(int32_t sequenceId, hal::HWDisplayId, const hal::VsyncPeriodChangeTimeline&));
-    MOCK_METHOD2(onSeamlessPossible, void(int32_t sequenceId, hal::HWDisplayId));
+    MOCK_METHOD2(onComposerHalHotplug, void(hal::HWDisplayId, hal::Connection));
+    MOCK_METHOD1(onComposerHalRefresh, void(hal::HWDisplayId));
+    MOCK_METHOD3(onComposerHalVsync,
+                 void(hal::HWDisplayId, int64_t timestamp, std::optional<hal::VsyncPeriodNanos>));
+    MOCK_METHOD2(onComposerHalVsyncPeriodTimingChanged,
+                 void(hal::HWDisplayId, const hal::VsyncPeriodChangeTimeline&));
+    MOCK_METHOD1(onComposerHalSeamlessPossible, void(hal::HWDisplayId));
 };
 
-struct HWComposerSetConfigurationTest : testing::Test {
+struct HWComposerSetCallbackTest : testing::Test {
     Hwc2::mock::Composer* mHal = new StrictMock<Hwc2::mock::Composer>();
     MockHWC2ComposerCallback mCallback;
 };
 
-TEST_F(HWComposerSetConfigurationTest, loadsLayerMetadataSupport) {
+TEST_F(HWComposerSetCallbackTest, loadsLayerMetadataSupport) {
     const std::string kMetadata1Name = "com.example.metadata.1";
     constexpr bool kMetadata1Mandatory = false;
     const std::string kMetadata2Name = "com.example.metadata.2";
     constexpr bool kMetadata2Mandatory = true;
 
-    EXPECT_CALL(*mHal, getMaxVirtualDisplayCount()).WillOnce(Return(0));
     EXPECT_CALL(*mHal, getCapabilities()).WillOnce(Return(std::vector<hal::Capability>{}));
     EXPECT_CALL(*mHal, getLayerGenericMetadataKeys(_))
             .WillOnce(DoAll(SetArgPointee<0>(std::vector<hal::LayerGenericMetadataKey>{
@@ -91,7 +89,7 @@
     EXPECT_CALL(*mHal, isVsyncPeriodSwitchSupported()).WillOnce(Return(false));
 
     impl::HWComposer hwc{std::unique_ptr<Hwc2::Composer>(mHal)};
-    hwc.setConfiguration(&mCallback, 123);
+    hwc.setCallback(&mCallback);
 
     const auto& supported = hwc.getSupportedLayerGenericMetadata();
     EXPECT_EQ(2u, supported.size());
@@ -101,8 +99,7 @@
     EXPECT_EQ(kMetadata2Mandatory, supported.find(kMetadata2Name)->second);
 }
 
-TEST_F(HWComposerSetConfigurationTest, handlesUnsupportedCallToGetLayerGenericMetadataKeys) {
-    EXPECT_CALL(*mHal, getMaxVirtualDisplayCount()).WillOnce(Return(0));
+TEST_F(HWComposerSetCallbackTest, handlesUnsupportedCallToGetLayerGenericMetadataKeys) {
     EXPECT_CALL(*mHal, getCapabilities()).WillOnce(Return(std::vector<hal::Capability>{}));
     EXPECT_CALL(*mHal, getLayerGenericMetadataKeys(_))
             .WillOnce(Return(hardware::graphics::composer::V2_4::Error::UNSUPPORTED));
@@ -110,7 +107,7 @@
     EXPECT_CALL(*mHal, isVsyncPeriodSwitchSupported()).WillOnce(Return(false));
 
     impl::HWComposer hwc{std::unique_ptr<Hwc2::Composer>(mHal)};
-    hwc.setConfiguration(&mCallback, 123);
+    hwc.setCallback(&mCallback);
 
     const auto& supported = hwc.getSupportedLayerGenericMetadata();
     EXPECT_EQ(0u, supported.size());
diff --git a/services/surfaceflinger/tests/unittests/OneShotTimerTest.cpp b/services/surfaceflinger/tests/unittests/OneShotTimerTest.cpp
index 6916764..597e5e7 100644
--- a/services/surfaceflinger/tests/unittests/OneShotTimerTest.cpp
+++ b/services/surfaceflinger/tests/unittests/OneShotTimerTest.cpp
@@ -72,7 +72,8 @@
     mIdleTimer->stop();
 }
 
-TEST_F(OneShotTimerTest, resetTest) {
+// TODO(b/186417847) This test is flaky. Reenable once fixed.
+TEST_F(OneShotTimerTest, DISABLED_resetTest) {
     fake::FakeClock* clock = new fake::FakeClock();
     mIdleTimer = std::make_unique<scheduler::OneShotTimer>("TestTimer", 1ms,
                                                            mResetTimerCallback.getInvocable(),
@@ -94,7 +95,8 @@
     EXPECT_FALSE(mResetTimerCallback.waitForUnexpectedCall().has_value());
 }
 
-TEST_F(OneShotTimerTest, resetBackToBackTest) {
+// TODO(b/186417847) This test is flaky. Reenable once fixed.
+TEST_F(OneShotTimerTest, DISABLED_resetBackToBackTest) {
     fake::FakeClock* clock = new fake::FakeClock();
     mIdleTimer = std::make_unique<scheduler::OneShotTimer>("TestTimer", 1ms,
                                                            mResetTimerCallback.getInvocable(),
@@ -144,7 +146,8 @@
     EXPECT_FALSE(mResetTimerCallback.waitForUnexpectedCall().has_value());
 }
 
-TEST_F(OneShotTimerTest, idleTimerIdlesTest) {
+// TODO(b/186417847) This test is flaky. Reenable once fixed.
+TEST_F(OneShotTimerTest, DISABLED_idleTimerIdlesTest) {
     fake::FakeClock* clock = new fake::FakeClock();
     mIdleTimer = std::make_unique<scheduler::OneShotTimer>("TestTimer", 1ms,
                                                            mResetTimerCallback.getInvocable(),
@@ -169,7 +172,8 @@
     EXPECT_FALSE(mResetTimerCallback.waitForUnexpectedCall().has_value());
 }
 
-TEST_F(OneShotTimerTest, timeoutCallbackExecutionTest) {
+// TODO(b/186417847) This test is flaky. Reenable once fixed.
+TEST_F(OneShotTimerTest, DISABLED_timeoutCallbackExecutionTest) {
     fake::FakeClock* clock = new fake::FakeClock();
     mIdleTimer = std::make_unique<scheduler::OneShotTimer>("TestTimer", 1ms,
                                                            mResetTimerCallback.getInvocable(),
diff --git a/services/surfaceflinger/tests/unittests/RefreshRateSelectionTest.cpp b/services/surfaceflinger/tests/unittests/RefreshRateSelectionTest.cpp
index 9c6ad06..fd3e564 100644
--- a/services/surfaceflinger/tests/unittests/RefreshRateSelectionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/RefreshRateSelectionTest.cpp
@@ -60,7 +60,6 @@
     static constexpr int32_t PRIORITY_UNSET = -1;
 
     void setupScheduler();
-    void setupComposer(uint32_t virtualDisplayCount);
     sp<BufferQueueLayer> createBufferQueueLayer();
     sp<BufferStateLayer> createBufferStateLayer();
     sp<EffectLayer> createEffectLayer();
@@ -69,7 +68,6 @@
     void commitTransaction(Layer* layer);
 
     TestableSurfaceFlinger mFlinger;
-    Hwc2::mock::Composer* mComposer = nullptr;
 
     sp<Client> mClient;
     sp<Layer> mParent;
@@ -83,7 +81,7 @@
     ALOGD("**** Setting up for %s.%s\n", test_info->test_case_name(), test_info->name());
 
     setupScheduler();
-    setupComposer(0);
+    mFlinger.setupComposer(std::make_unique<Hwc2::mock::Composer>());
 }
 
 RefreshRateSelectionTest::~RefreshRateSelectionTest() {
@@ -147,14 +145,6 @@
                             std::move(eventThread), std::move(sfEventThread));
 }
 
-void RefreshRateSelectionTest::setupComposer(uint32_t virtualDisplayCount) {
-    mComposer = new Hwc2::mock::Composer();
-    EXPECT_CALL(*mComposer, getMaxVirtualDisplayCount()).WillOnce(Return(virtualDisplayCount));
-    mFlinger.setupComposer(std::unique_ptr<Hwc2::Composer>(mComposer));
-
-    Mock::VerifyAndClear(mComposer);
-}
-
 namespace {
 /* ------------------------------------------------------------------------
  * Test cases
diff --git a/services/surfaceflinger/tests/unittests/SchedulerTest.cpp b/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
index 38e503f..7a6ae5b 100644
--- a/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
+++ b/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
@@ -34,7 +34,7 @@
 namespace android {
 namespace {
 
-constexpr PhysicalDisplayId PHYSICAL_DISPLAY_ID(999);
+constexpr PhysicalDisplayId PHYSICAL_DISPLAY_ID = PhysicalDisplayId::fromPort(255u);
 
 class SchedulerTest : public testing::Test {
 protected:
diff --git a/services/surfaceflinger/tests/unittests/SetFrameRateTest.cpp b/services/surfaceflinger/tests/unittests/SetFrameRateTest.cpp
index c088ddc..46ef750 100644
--- a/services/surfaceflinger/tests/unittests/SetFrameRateTest.cpp
+++ b/services/surfaceflinger/tests/unittests/SetFrameRateTest.cpp
@@ -118,14 +118,12 @@
     SetFrameRateTest();
 
     void setupScheduler();
-    void setupComposer(uint32_t virtualDisplayCount);
 
     void addChild(sp<Layer> layer, sp<Layer> child);
     void removeChild(sp<Layer> layer, sp<Layer> child);
     void commitTransaction();
 
     TestableSurfaceFlinger mFlinger;
-    Hwc2::mock::Composer* mComposer = nullptr;
     mock::MessageQueue* mMessageQueue = new mock::MessageQueue();
 
     std::vector<sp<Layer>> mLayers;
@@ -139,10 +137,11 @@
     mFlinger.mutableUseFrameRateApi() = true;
 
     setupScheduler();
-    setupComposer(0);
 
+    mFlinger.setupComposer(std::make_unique<Hwc2::mock::Composer>());
     mFlinger.mutableEventQueue().reset(mMessageQueue);
 }
+
 void SetFrameRateTest::addChild(sp<Layer> layer, sp<Layer> child) {
     layer.get()->addChild(child.get());
 }
@@ -184,14 +183,6 @@
                             /*hasMultipleModes*/ true);
 }
 
-void SetFrameRateTest::setupComposer(uint32_t virtualDisplayCount) {
-    mComposer = new Hwc2::mock::Composer();
-    EXPECT_CALL(*mComposer, getMaxVirtualDisplayCount()).WillOnce(Return(virtualDisplayCount));
-    mFlinger.setupComposer(std::unique_ptr<Hwc2::Composer>(mComposer));
-
-    Mock::VerifyAndClear(mComposer);
-}
-
 namespace {
 /* ------------------------------------------------------------------------
  * Test cases
diff --git a/services/surfaceflinger/tests/unittests/SurfaceFlinger_OnHotplugReceivedTest.cpp b/services/surfaceflinger/tests/unittests/SurfaceFlinger_HotplugTest.cpp
similarity index 62%
rename from services/surfaceflinger/tests/unittests/SurfaceFlinger_OnHotplugReceivedTest.cpp
rename to services/surfaceflinger/tests/unittests/SurfaceFlinger_HotplugTest.cpp
index 42f4cf3..bd89397 100644
--- a/services/surfaceflinger/tests/unittests/SurfaceFlinger_OnHotplugReceivedTest.cpp
+++ b/services/surfaceflinger/tests/unittests/SurfaceFlinger_HotplugTest.cpp
@@ -22,19 +22,15 @@
 namespace android {
 namespace {
 
-class OnHotplugReceivedTest : public DisplayTransactionTest {};
+class HotplugTest : public DisplayTransactionTest {};
 
-TEST_F(OnHotplugReceivedTest, hotplugEnqueuesEventsForDisplayTransaction) {
-    constexpr int currentSequenceId = 123;
+TEST_F(HotplugTest, enqueuesEventsForDisplayTransaction) {
     constexpr HWDisplayId hwcDisplayId1 = 456;
     constexpr HWDisplayId hwcDisplayId2 = 654;
 
     // --------------------------------------------------------------------
     // Preconditions
 
-    // Set the current sequence id for accepted events
-    mFlinger.mutableComposerSequenceId() = currentSequenceId;
-
     // Set the main thread id so that the current thread does not appear to be
     // the main thread.
     mFlinger.mutableMainThreadId() = std::thread::id();
@@ -50,8 +46,8 @@
     // Invocation
 
     // Simulate two hotplug events (a connect and a disconnect)
-    mFlinger.onHotplugReceived(currentSequenceId, hwcDisplayId1, Connection::CONNECTED);
-    mFlinger.onHotplugReceived(currentSequenceId, hwcDisplayId2, Connection::DISCONNECTED);
+    mFlinger.onComposerHalHotplug(hwcDisplayId1, Connection::CONNECTED);
+    mFlinger.onComposerHalHotplug(hwcDisplayId2, Connection::DISCONNECTED);
 
     // --------------------------------------------------------------------
     // Postconditions
@@ -68,52 +64,14 @@
     EXPECT_EQ(Connection::DISCONNECTED, pendingEvents[1].connection);
 }
 
-TEST_F(OnHotplugReceivedTest, hotplugDiscardsUnexpectedEvents) {
-    constexpr int currentSequenceId = 123;
-    constexpr int otherSequenceId = 321;
-    constexpr HWDisplayId displayId = 456;
-
-    // --------------------------------------------------------------------
-    // Preconditions
-
-    // Set the current sequence id for accepted events
-    mFlinger.mutableComposerSequenceId() = currentSequenceId;
-
-    // Set the main thread id so that the current thread does not appear to be
-    // the main thread.
-    mFlinger.mutableMainThreadId() = std::thread::id();
-
-    // --------------------------------------------------------------------
-    // Call Expectations
-
-    // We do not expect any calls to invalidate().
-    EXPECT_CALL(*mMessageQueue, invalidate()).Times(0);
-
-    // --------------------------------------------------------------------
-    // Invocation
-
-    // Call with an unexpected sequence id
-    mFlinger.onHotplugReceived(otherSequenceId, displayId, Connection::INVALID);
-
-    // --------------------------------------------------------------------
-    // Postconditions
-
-    // The display transaction needed flag should not be set
-    EXPECT_FALSE(hasTransactionFlagSet(eDisplayTransactionNeeded));
-
-    // There should be no pending events
-    EXPECT_TRUE(mFlinger.mutablePendingHotplugEvents().empty());
-}
-
-TEST_F(OnHotplugReceivedTest, hotplugProcessesEnqueuedEventsIfCalledOnMainThread) {
-    constexpr int currentSequenceId = 123;
+TEST_F(HotplugTest, processesEnqueuedEventsIfCalledOnMainThread) {
     constexpr HWDisplayId displayId1 = 456;
 
     // --------------------------------------------------------------------
     // Note:
     // --------------------------------------------------------------------
     // This test case is a bit tricky. We want to verify that
-    // onHotplugReceived() calls processDisplayHotplugEventsLocked(), but we
+    // onComposerHalHotplug() calls processDisplayHotplugEventsLocked(), but we
     // don't really want to provide coverage for everything the later function
     // does as there are specific tests for it.
     // --------------------------------------------------------------------
@@ -121,9 +79,6 @@
     // --------------------------------------------------------------------
     // Preconditions
 
-    // Set the current sequence id for accepted events
-    mFlinger.mutableComposerSequenceId() = currentSequenceId;
-
     // Set the main thread id so that the current thread does appear to be the
     // main thread.
     mFlinger.mutableMainThreadId() = std::this_thread::get_id();
@@ -139,9 +94,9 @@
     // Invocation
 
     // Simulate a disconnect on a display id that is not connected. This should
-    // be enqueued by onHotplugReceived(), and dequeued by
+    // be enqueued by onComposerHalHotplug(), and dequeued by
     // processDisplayHotplugEventsLocked(), but then ignored as invalid.
-    mFlinger.onHotplugReceived(currentSequenceId, displayId1, Connection::DISCONNECTED);
+    mFlinger.onComposerHalHotplug(displayId1, Connection::DISCONNECTED);
 
     // --------------------------------------------------------------------
     // Postconditions
@@ -155,4 +110,4 @@
 }
 
 } // namespace
-} // namespace android
\ No newline at end of file
+} // namespace android
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index d004b9d..82eb3bf 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -42,7 +42,6 @@
 #include "SurfaceInterceptor.h"
 #include "TestableScheduler.h"
 #include "mock/DisplayHardware/MockComposer.h"
-#include "mock/MockDisplayIdGenerator.h"
 #include "mock/MockFrameTimeline.h"
 #include "mock/MockFrameTracer.h"
 
@@ -185,9 +184,6 @@
 
     SurfaceFlinger* flinger() { return mFlinger.get(); }
     TestableScheduler* scheduler() { return mScheduler; }
-    mock::DisplayIdGenerator<GpuVirtualDisplayId>& gpuVirtualDisplayIdGenerator() {
-        return mGpuVirtualDisplayIdGenerator;
-    }
 
     // Extend this as needed for accessing SurfaceFlinger private (and public)
     // functions.
@@ -308,6 +304,8 @@
         return mFlinger->destroyDisplay(displayToken);
     }
 
+    void enableHalVirtualDisplays(bool enable) { mFlinger->enableHalVirtualDisplays(enable); }
+
     auto setupNewDisplayDeviceInternal(
             const wp<IBinder>& displayToken,
             std::shared_ptr<compositionengine::Display> compositionDisplay,
@@ -323,9 +321,8 @@
         return mFlinger->handleTransactionLocked(transactionFlags);
     }
 
-    auto onHotplugReceived(int32_t sequenceId, hal::HWDisplayId display,
-                           hal::Connection connection) {
-        return mFlinger->onHotplugReceived(sequenceId, display, connection);
+    void onComposerHalHotplug(hal::HWDisplayId hwcDisplayId, hal::Connection connection) {
+        mFlinger->onComposerHalHotplug(hwcDisplayId, connection);
     }
 
     auto setDisplayStateLocked(const DisplayState& s) {
@@ -436,11 +433,9 @@
     auto& mutablePhysicalDisplayTokens() { return mFlinger->mPhysicalDisplayTokens; }
     auto& mutableTexturePool() { return mFlinger->mTexturePool; }
     auto& mutableTransactionFlags() { return mFlinger->mTransactionFlags; }
-    auto& mutableUseHwcVirtualDisplays() { return mFlinger->mUseHwcVirtualDisplays; }
     auto& mutablePowerAdvisor() { return mFlinger->mPowerAdvisor; }
     auto& mutableDebugDisableHWC() { return mFlinger->mDebugDisableHWC; }
 
-    auto& mutableComposerSequenceId() { return mFlinger->getBE().mComposerSequenceId; }
     auto& mutableHwcDisplayData() { return getHwComposer().mDisplayData; }
     auto& mutableHwcPhysicalDisplayIdMap() { return getHwComposer().mPhysicalDisplayIdMap; }
     auto& mutableInternalHwcDisplayId() { return getHwComposer().mInternalHwcDisplayId; }
@@ -775,7 +770,6 @@
     surfaceflinger::test::Factory mFactory;
     sp<SurfaceFlinger> mFlinger = new SurfaceFlinger(mFactory, SurfaceFlinger::SkipInitialization);
     TestableScheduler* mScheduler = nullptr;
-    mock::DisplayIdGenerator<GpuVirtualDisplayId> mGpuVirtualDisplayIdGenerator;
 };
 
 } // namespace android
diff --git a/services/surfaceflinger/tests/unittests/TransactionFrameTracerTest.cpp b/services/surfaceflinger/tests/unittests/TransactionFrameTracerTest.cpp
index 25001d3..546bc4a 100644
--- a/services/surfaceflinger/tests/unittests/TransactionFrameTracerTest.cpp
+++ b/services/surfaceflinger/tests/unittests/TransactionFrameTracerTest.cpp
@@ -45,7 +45,7 @@
                 ::testing::UnitTest::GetInstance()->current_test_info();
         ALOGD("**** Setting up for %s.%s\n", test_info->test_case_name(), test_info->name());
         setupScheduler();
-        setupComposer(0);
+        mFlinger.setupComposer(std::make_unique<Hwc2::mock::Composer>());
     }
 
     ~TransactionFrameTracerTest() {
@@ -91,17 +91,9 @@
                                 std::move(eventThread), std::move(sfEventThread));
     }
 
-    void setupComposer(uint32_t virtualDisplayCount) {
-        mComposer = new Hwc2::mock::Composer();
-        EXPECT_CALL(*mComposer, getMaxVirtualDisplayCount()).WillOnce(Return(virtualDisplayCount));
-        mFlinger.setupComposer(std::unique_ptr<Hwc2::Composer>(mComposer));
-
-        Mock::VerifyAndClear(mComposer);
-    }
-
     TestableSurfaceFlinger mFlinger;
-    Hwc2::mock::Composer* mComposer = nullptr;
     renderengine::mock::RenderEngine mRenderEngine;
+
     FenceToFenceTimeMap fenceFactory;
     client_cache_t mClientCache;
 
diff --git a/services/surfaceflinger/tests/unittests/TransactionSurfaceFrameTest.cpp b/services/surfaceflinger/tests/unittests/TransactionSurfaceFrameTest.cpp
index b7917aa..c1123cd 100644
--- a/services/surfaceflinger/tests/unittests/TransactionSurfaceFrameTest.cpp
+++ b/services/surfaceflinger/tests/unittests/TransactionSurfaceFrameTest.cpp
@@ -45,7 +45,7 @@
                 ::testing::UnitTest::GetInstance()->current_test_info();
         ALOGD("**** Setting up for %s.%s\n", test_info->test_case_name(), test_info->name());
         setupScheduler();
-        setupComposer(0);
+        mFlinger.setupComposer(std::make_unique<Hwc2::mock::Composer>());
     }
 
     ~TransactionSurfaceFrameTest() {
@@ -91,17 +91,9 @@
                                 std::move(eventThread), std::move(sfEventThread));
     }
 
-    void setupComposer(uint32_t virtualDisplayCount) {
-        mComposer = new Hwc2::mock::Composer();
-        EXPECT_CALL(*mComposer, getMaxVirtualDisplayCount()).WillOnce(Return(virtualDisplayCount));
-        mFlinger.setupComposer(std::unique_ptr<Hwc2::Composer>(mComposer));
-
-        Mock::VerifyAndClear(mComposer);
-    }
-
     TestableSurfaceFlinger mFlinger;
-    Hwc2::mock::Composer* mComposer = nullptr;
     renderengine::mock::RenderEngine mRenderEngine;
+
     FenceToFenceTimeMap fenceFactory;
     client_cache_t mClientCache;
 
diff --git a/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.h b/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.h
index 1ba3c0f..cb3bd73 100644
--- a/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.h
+++ b/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.h
@@ -54,7 +54,8 @@
     MOCK_METHOD0(resetCommands, void());
     MOCK_METHOD0(executeCommands, Error());
     MOCK_METHOD0(getMaxVirtualDisplayCount, uint32_t());
-    MOCK_METHOD4(createVirtualDisplay, Error(uint32_t, uint32_t, PixelFormat*, Display*));
+    MOCK_METHOD5(createVirtualDisplay,
+                 Error(uint32_t, uint32_t, PixelFormat*, std::optional<Display>, Display*));
     MOCK_METHOD1(destroyVirtualDisplay, Error(Display));
     MOCK_METHOD1(acceptDisplayChanges, Error(Display));
     MOCK_METHOD2(createLayer, Error(Display, Layer* outLayer));
diff --git a/services/surfaceflinger/tests/unittests/mock/MockDisplayIdGenerator.h b/services/surfaceflinger/tests/unittests/mock/MockDisplayIdGenerator.h
deleted file mode 100644
index cfc37ea..0000000
--- a/services/surfaceflinger/tests/unittests/mock/MockDisplayIdGenerator.h
+++ /dev/null
@@ -1,36 +0,0 @@
-/*
- * Copyright 2020 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#pragma once
-
-#include <gmock/gmock.h>
-
-#include "DisplayIdGenerator.h"
-
-namespace android::mock {
-
-template <typename T>
-class DisplayIdGenerator : public android::DisplayIdGenerator<T> {
-public:
-    // Explicit default instantiation is recommended.
-    DisplayIdGenerator() = default;
-    virtual ~DisplayIdGenerator() = default;
-
-    MOCK_METHOD0(nextId, std::optional<T>());
-    MOCK_METHOD1(markUnused, void(T));
-};
-
-} // namespace android::mock