diff --git a/libs/gui/LayerState.cpp b/libs/gui/LayerState.cpp
index 7742503..725d3cd 100644
--- a/libs/gui/LayerState.cpp
+++ b/libs/gui/LayerState.cpp
@@ -61,7 +61,7 @@
     output.writeUint32(transform);
     output.writeBool(transformToDisplayInverse);
     output.write(crop);
-    output.write(frame);
+    output.write(orientedDisplaySpaceRect);
     if (buffer) {
         output.writeBool(true);
         output.write(*buffer);
@@ -159,7 +159,7 @@
     transform = input.readUint32();
     transformToDisplayInverse = input.readBool();
     input.read(crop);
-    input.read(frame);
+    input.read(orientedDisplaySpaceRect);
     buffer = new GraphicBuffer();
     if (input.readBool()) {
         input.read(*buffer);
@@ -216,15 +216,13 @@
     return state.read(input);
 }
 
-
-DisplayState::DisplayState() :
-    what(0),
-    layerStack(0),
-    viewport(Rect::EMPTY_RECT),
-    frame(Rect::EMPTY_RECT),
-    width(0),
-    height(0) {
-}
+DisplayState::DisplayState()
+      : what(0),
+        layerStack(0),
+        layerStackSpaceRect(Rect::EMPTY_RECT),
+        orientedDisplaySpaceRect(Rect::EMPTY_RECT),
+        width(0),
+        height(0) {}
 
 status_t DisplayState::write(Parcel& output) const {
     output.writeStrongBinder(token);
@@ -232,8 +230,8 @@
     output.writeUint32(what);
     output.writeUint32(layerStack);
     output.writeUint32(toRotationInt(orientation));
-    output.write(viewport);
-    output.write(frame);
+    output.write(layerStackSpaceRect);
+    output.write(orientedDisplaySpaceRect);
     output.writeUint32(width);
     output.writeUint32(height);
     return NO_ERROR;
@@ -245,8 +243,8 @@
     what = input.readUint32();
     layerStack = input.readUint32();
     orientation = ui::toRotation(input.readUint32());
-    input.read(viewport);
-    input.read(frame);
+    input.read(layerStackSpaceRect);
+    input.read(orientedDisplaySpaceRect);
     width = input.readUint32();
     height = input.readUint32();
     return NO_ERROR;
@@ -264,8 +262,8 @@
     if (other.what & eDisplayProjectionChanged) {
         what |= eDisplayProjectionChanged;
         orientation = other.orientation;
-        viewport = other.viewport;
-        frame = other.frame;
+        layerStackSpaceRect = other.layerStackSpaceRect;
+        orientedDisplaySpaceRect = other.orientedDisplaySpaceRect;
     }
     if (other.what & eDisplaySizeChanged) {
         what |= eDisplaySizeChanged;
@@ -368,7 +366,7 @@
     }
     if (other.what & eFrameChanged) {
         what |= eFrameChanged;
-        frame = other.frame;
+        orientedDisplaySpaceRect = other.orientedDisplaySpaceRect;
     }
     if (other.what & eBufferChanged) {
         what |= eBufferChanged;
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index b51bf1f..62a3c45 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -1137,7 +1137,7 @@
         return *this;
     }
     s->what |= layer_state_t::eFrameChanged;
-    s->frame = frame;
+    s->orientedDisplaySpaceRect = frame;
 
     registerSurfaceControlForCallback(sc);
     return *this;
@@ -1545,8 +1545,8 @@
                                                               const Rect& displayRect) {
     DisplayState& s(getDisplayState(token));
     s.orientation = orientation;
-    s.viewport = layerStackRect;
-    s.frame = displayRect;
+    s.layerStackSpaceRect = layerStackRect;
+    s.orientedDisplaySpaceRect = displayRect;
     s.what |= DisplayState::eDisplayProjectionChanged;
     mForceSynchronous = true; // TODO: do we actually still need this?
 }
diff --git a/libs/gui/include/gui/LayerState.h b/libs/gui/include/gui/LayerState.h
index 6a304ef..187e478 100644
--- a/libs/gui/include/gui/LayerState.h
+++ b/libs/gui/include/gui/LayerState.h
@@ -129,7 +129,7 @@
             transform(0),
             transformToDisplayInverse(false),
             crop(Rect::INVALID_RECT),
-            frame(Rect::INVALID_RECT),
+            orientedDisplaySpaceRect(Rect::INVALID_RECT),
             dataspace(ui::Dataspace::UNKNOWN),
             surfaceDamageRegion(),
             api(-1),
@@ -192,7 +192,7 @@
     uint32_t transform;
     bool transformToDisplayInverse;
     Rect crop;
-    Rect frame;
+    Rect orientedDisplaySpaceRect;
     sp<GraphicBuffer> buffer;
     sp<Fence> acquireFence;
     ui::Dataspace dataspace;
@@ -265,18 +265,18 @@
 
     // These states define how layers are projected onto the physical display.
     //
-    // Layers are first clipped to `viewport'.  They are then translated and
-    // scaled from `viewport' to `frame'.  Finally, they are rotated according
-    // to `orientation', `width', and `height'.
+    // Layers are first clipped to `layerStackSpaceRect'.  They are then translated and
+    // scaled from `layerStackSpaceRect' to `orientedDisplaySpaceRect'.  Finally, they are rotated
+    // according to `orientation', `width', and `height'.
     //
-    // For example, assume viewport is Rect(0, 0, 200, 100), frame is Rect(20,
-    // 10, 420, 210), and the size of the display is WxH.  When orientation is
-    // 0, layers will be scaled by a factor of 2 and translated by (20, 10).
-    // When orientation is 1, layers will be additionally rotated by 90
-    // degrees around the origin clockwise and translated by (W, 0).
+    // For example, assume layerStackSpaceRect is Rect(0, 0, 200, 100), orientedDisplaySpaceRect is
+    // Rect(20, 10, 420, 210), and the size of the display is WxH.  When orientation is 0, layers
+    // will be scaled by a factor of 2 and translated by (20, 10). When orientation is 1, layers
+    // will be additionally rotated by 90 degrees around the origin clockwise and translated by (W,
+    // 0).
     ui::Rotation orientation = ui::ROTATION_0;
-    Rect viewport;
-    Rect frame;
+    Rect layerStackSpaceRect;
+    Rect orientedDisplaySpaceRect;
 
     uint32_t width, height;
 
diff --git a/libs/ui/DebugUtils.cpp b/libs/ui/DebugUtils.cpp
index f394635..1f006ce 100644
--- a/libs/ui/DebugUtils.cpp
+++ b/libs/ui/DebugUtils.cpp
@@ -321,10 +321,6 @@
     return std::string("Unknown RenderIntent");
 }
 
-std::string to_string(const android::Rect& rect) {
-    return StringPrintf("(%4d,%4d,%4d,%4d)", rect.left, rect.top, rect.right, rect.bottom);
-}
-
 std::string toString(const android::DeviceProductInfo::ManufactureOrModelDate& date) {
     using ModelYear = android::DeviceProductInfo::ModelYear;
     using ManufactureYear = android::DeviceProductInfo::ManufactureYear;
diff --git a/libs/ui/Rect.cpp b/libs/ui/Rect.cpp
index 13fed3a..a8d6285 100644
--- a/libs/ui/Rect.cpp
+++ b/libs/ui/Rect.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include <android-base/stringprintf.h>
 #include <system/graphics.h>
 #include <ui/Rect.h>
 
@@ -149,4 +150,13 @@
     return result;
 }
 
+std::string to_string(const android::Rect& rect) {
+    return android::base::StringPrintf("Rect(%d, %d, %d, %d)", rect.left, rect.top, rect.right,
+                                       rect.bottom);
+}
+
+void PrintTo(const Rect& rect, ::std::ostream* os) {
+    *os << to_string(rect);
+}
+
 }; // namespace android
diff --git a/libs/ui/include/ui/DebugUtils.h b/libs/ui/include/ui/DebugUtils.h
index 4685575..18cd487 100644
--- a/libs/ui/include/ui/DebugUtils.h
+++ b/libs/ui/include/ui/DebugUtils.h
@@ -34,5 +34,4 @@
 std::string decodeColorTransform(android_color_transform colorTransform);
 std::string decodePixelFormat(android::PixelFormat format);
 std::string decodeRenderIntent(android::ui::RenderIntent renderIntent);
-std::string to_string(const android::Rect& rect);
 std::string toString(const android::DeviceProductInfo&);
diff --git a/libs/ui/include/ui/DisplayState.h b/libs/ui/include/ui/DisplayState.h
index 64efc84..70a0d50 100644
--- a/libs/ui/include/ui/DisplayState.h
+++ b/libs/ui/include/ui/DisplayState.h
@@ -32,7 +32,7 @@
 struct DisplayState {
     LayerStack layerStack = NO_LAYER_STACK;
     Rotation orientation = ROTATION_0;
-    Size viewport;
+    Size layerStackSpaceRect;
 };
 
 static_assert(std::is_trivially_copyable_v<DisplayState>);
diff --git a/libs/ui/include/ui/Rect.h b/libs/ui/include/ui/Rect.h
index 2f2229e..6670dc0 100644
--- a/libs/ui/include/ui/Rect.h
+++ b/libs/ui/include/ui/Rect.h
@@ -19,10 +19,10 @@
 
 #include <ostream>
 
+#include <log/log.h>
 #include <utils/Flattenable.h>
 #include <utils/Log.h>
 #include <utils/TypeHelpers.h>
-#include <log/log.h>
 
 #include <ui/FloatRect.h>
 #include <ui/Point.h>
@@ -216,11 +216,10 @@
     }
 };
 
+std::string to_string(const android::Rect& rect);
+
 // Defining PrintTo helps with Google Tests.
-static inline void PrintTo(const Rect& rect, ::std::ostream* os) {
-    *os << "Rect(" << rect.left << ", " << rect.top << ", " << rect.right << ", " << rect.bottom
-        << ")";
-}
+void PrintTo(const Rect& rect, ::std::ostream* os);
 
 ANDROID_BASIC_TYPES_TRAITS(Rect)
 
diff --git a/libs/ui/include/ui/Rotation.h b/libs/ui/include/ui/Rotation.h
index 89008f6..83d431d 100644
--- a/libs/ui/include/ui/Rotation.h
+++ b/libs/ui/include/ui/Rotation.h
@@ -41,6 +41,15 @@
     return toRotation((toRotationInt(lhs) + toRotationInt(rhs)) % N);
 }
 
+constexpr Rotation operator-(Rotation lhs, Rotation rhs) {
+    constexpr auto N = toRotationInt(ROTATION_270) + 1;
+    return toRotation((N + toRotationInt(lhs) - toRotationInt(rhs)) % N);
+}
+
+constexpr Rotation operator-(Rotation rotation) {
+    return ROTATION_0 - rotation;
+}
+
 constexpr const char* toCString(Rotation rotation) {
     switch (rotation) {
         case ROTATION_0: