Merge "SF: Introduce a configure stage"
diff --git a/services/surfaceflinger/BufferStateLayer.cpp b/services/surfaceflinger/BufferStateLayer.cpp
index 51a5445..cce6ad7 100644
--- a/services/surfaceflinger/BufferStateLayer.cpp
+++ b/services/surfaceflinger/BufferStateLayer.cpp
@@ -1109,7 +1109,29 @@
 }
 
 std::optional<compositionengine::LayerFE::LayerSettings> BufferStateLayer::prepareClientComposition(
-        compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) {
+        compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) const {
+    std::optional<compositionengine::LayerFE::LayerSettings> layerSettings =
+            prepareClientCompositionInternal(targetSettings);
+    // Nothing to render.
+    if (!layerSettings) {
+        return {};
+    }
+
+    // HWC requests to clear this layer.
+    if (targetSettings.clearContent) {
+        prepareClearClientComposition(*layerSettings, false /* blackout */);
+        return *layerSettings;
+    }
+
+    // set the shadow for the layer if needed
+    prepareShadowClientComposition(*layerSettings, targetSettings.viewport);
+
+    return *layerSettings;
+}
+
+std::optional<compositionengine::LayerFE::LayerSettings>
+BufferStateLayer::prepareClientCompositionInternal(
+        compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) const {
     ATRACE_CALL();
 
     std::optional<compositionengine::LayerFE::LayerSettings> result =
@@ -1559,7 +1581,7 @@
     return mBufferInfo.mBuffer ? mBufferInfo.mBuffer->getBuffer() : nullptr;
 }
 
-void BufferStateLayer::getDrawingTransformMatrix(bool filteringEnabled, float outMatrix[16]) {
+void BufferStateLayer::getDrawingTransformMatrix(bool filteringEnabled, float outMatrix[16]) const {
     sp<GraphicBuffer> buffer = getBuffer();
     if (!buffer) {
         ALOGE("Buffer should not be null!");
diff --git a/services/surfaceflinger/BufferStateLayer.h b/services/surfaceflinger/BufferStateLayer.h
index 8bad3d2..a0f13e2 100644
--- a/services/surfaceflinger/BufferStateLayer.h
+++ b/services/surfaceflinger/BufferStateLayer.h
@@ -159,6 +159,9 @@
     std::atomic<int32_t>* getPendingBufferCounter() override { return &mPendingBufferTransactions; }
     std::string getPendingBufferCounterName() override { return mBlastTransactionName; }
 
+    std::optional<compositionengine::LayerFE::LayerSettings> prepareClientComposition(
+            compositionengine::LayerFE::ClientCompositionTargetSettings&) const override;
+
 protected:
     void gatherBufferInfo();
     void onSurfaceFrameCreated(const std::shared_ptr<frametimeline::SurfaceFrame>& surfaceFrame);
@@ -188,9 +191,6 @@
 
     BufferInfo mBufferInfo;
 
-    std::optional<compositionengine::LayerFE::LayerSettings> prepareClientComposition(
-            compositionengine::LayerFE::ClientCompositionTargetSettings&) override;
-
     /*
      * compositionengine::LayerFE overrides
      */
@@ -236,7 +236,7 @@
 
     // Computes the transform matrix using the setFilteringEnabled to determine whether the
     // transform matrix should be computed for use with bilinear filtering.
-    void getDrawingTransformMatrix(bool filteringEnabled, float outMatrix[16]);
+    void getDrawingTransformMatrix(bool filteringEnabled, float outMatrix[16]) const;
 
     std::unique_ptr<compositionengine::LayerFECompositionState> mCompositionState;
 
@@ -270,6 +270,9 @@
                                    const sp<Fence>& releaseFence,
                                    uint32_t currentMaxAcquiredBufferCount);
 
+    std::optional<compositionengine::LayerFE::LayerSettings> prepareClientCompositionInternal(
+            compositionengine::LayerFE::ClientCompositionTargetSettings&) const;
+
     ReleaseCallbackId mPreviousReleaseCallbackId = ReleaseCallbackId::INVALID_ID;
     uint64_t mPreviousReleasedFrameNumber = 0;
 
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/LayerFE.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/LayerFE.h
index ec610c1..f93fd99 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/LayerFE.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/LayerFE.h
@@ -150,11 +150,11 @@
         uint64_t frameNumber = 0;
     };
 
-    // Returns the z-ordered list of LayerSettings to pass to RenderEngine::drawLayers. The list
-    // may contain shadows casted by the layer or the content of the layer itself.  If the layer
-    // does not render then an empty list will be returned.
-    virtual std::vector<LayerSettings> prepareClientCompositionList(
-            ClientCompositionTargetSettings&) = 0;
+    // Returns the LayerSettings to pass to RenderEngine::drawLayers. The state may contain shadows
+    // casted by the layer or the content of the layer itself. If the layer does not render then an
+    // empty optional will be returned.
+    virtual std::optional<LayerSettings> prepareClientComposition(
+            ClientCompositionTargetSettings&) const = 0;
 
     // Called after the layer is displayed to update the presentation fence
     virtual void onLayerDisplayed(ftl::SharedFuture<FenceResult>) = 0;
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/OutputLayer.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/OutputLayer.h
index bf5184e..6d0c395 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/OutputLayer.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/OutputLayer.h
@@ -126,9 +126,9 @@
     // Returns true if the composition settings scale pixels
     virtual bool needsFiltering() const = 0;
 
-    // Returns a composition list to be used by RenderEngine if the layer has been overridden
+    // Returns LayerSettings to be used by RenderEngine if the layer has been overridden
     // during the composition process
-    virtual std::vector<LayerFE::LayerSettings> getOverrideCompositionList() const = 0;
+    virtual std::optional<LayerFE::LayerSettings> getOverrideCompositionSettings() const = 0;
 
     // Debugging
     virtual void dump(std::string& result) const = 0;
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayer.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayer.h
index ecd432f..6d4abf9 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayer.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayer.h
@@ -18,6 +18,7 @@
 
 #include <cstdint>
 #include <memory>
+#include <optional>
 #include <string>
 
 #include <compositionengine/LayerFE.h>
@@ -57,7 +58,7 @@
     void prepareForDeviceLayerRequests() override;
     void applyDeviceLayerRequest(Hwc2::IComposerClient::LayerRequest request) override;
     bool needsFiltering() const override;
-    std::vector<LayerFE::LayerSettings> getOverrideCompositionList() const override;
+    std::optional<LayerFE::LayerSettings> getOverrideCompositionSettings() const override;
 
     void dump(std::string&) const override;
     virtual FloatRect calculateOutputSourceCrop(uint32_t internalDisplayRotationFlags) const;
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h
index 1c5c10f..2b704e6 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h
@@ -45,9 +45,9 @@
     MOCK_METHOD1(onPreComposition, bool(nsecs_t));
 
     MOCK_METHOD1(prepareCompositionState, void(compositionengine::LayerFE::StateSubset));
-    MOCK_METHOD1(prepareClientCompositionList,
-                 std::vector<compositionengine::LayerFE::LayerSettings>(
-                         compositionengine::LayerFE::ClientCompositionTargetSettings&));
+    MOCK_CONST_METHOD1(prepareClientComposition,
+                       std::optional<compositionengine::LayerFE::LayerSettings>(
+                               compositionengine::LayerFE::ClientCompositionTargetSettings&));
 
     MOCK_METHOD(void, onLayerDisplayed, (ftl::SharedFuture<FenceResult>), (override));
 
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/OutputLayer.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/OutputLayer.h
index a6cb811..c22f1bf 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/OutputLayer.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/OutputLayer.h
@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include <optional>
+
 #include <compositionengine/CompositionEngine.h>
 #include <compositionengine/LayerFE.h>
 #include <compositionengine/Output.h>
@@ -51,7 +53,7 @@
     MOCK_METHOD0(prepareForDeviceLayerRequests, void());
     MOCK_METHOD1(applyDeviceLayerRequest, void(Hwc2::IComposerClient::LayerRequest request));
     MOCK_CONST_METHOD0(needsFiltering, bool());
-    MOCK_CONST_METHOD0(getOverrideCompositionList, std::vector<LayerFE::LayerSettings>());
+    MOCK_CONST_METHOD0(getOverrideCompositionSettings, std::optional<LayerFE::LayerSettings>());
 
     MOCK_CONST_METHOD1(dump, void(std::string&));
 };
diff --git a/services/surfaceflinger/CompositionEngine/src/Output.cpp b/services/surfaceflinger/CompositionEngine/src/Output.cpp
index 8ebc5b1..6edc00f 100644
--- a/services/surfaceflinger/CompositionEngine/src/Output.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/Output.cpp
@@ -1366,7 +1366,7 @@
     bool firstLayer = true;
 
     bool disableBlurs = false;
-    sp<GraphicBuffer> previousOverrideBuffer = nullptr;
+    uint64_t previousOverrideBufferId = 0;
 
     for (auto* layer : getOutputLayersOrderedByZ()) {
         const auto& layerState = layer->getState();
@@ -1402,11 +1402,10 @@
                 !layerState.visibleRegion.subtract(layerState.shadowRegion).isEmpty();
 
         if (clientComposition || clearClientComposition) {
-            std::vector<LayerFE::LayerSettings> results;
-            if (layer->getState().overrideInfo.buffer != nullptr) {
-                if (layer->getState().overrideInfo.buffer->getBuffer() != previousOverrideBuffer) {
-                    results = layer->getOverrideCompositionList();
-                    previousOverrideBuffer = layer->getState().overrideInfo.buffer->getBuffer();
+            if (auto overrideSettings = layer->getOverrideCompositionSettings()) {
+                if (overrideSettings->bufferId != previousOverrideBufferId) {
+                    previousOverrideBufferId = overrideSettings->bufferId;
+                    clientCompositionLayers.push_back(std::move(*overrideSettings));
                     ALOGV("Replacing [%s] with override in RE", layer->getLayerFE().getDebugName());
                 } else {
                     ALOGV("Skipping redundant override buffer for [%s] in RE",
@@ -1432,20 +1431,18 @@
                                        .clearContent = !clientComposition,
                                        .blurSetting = blurSetting,
                                        .whitePointNits = layerState.whitePointNits};
-                results = layerFE.prepareClientCompositionList(targetSettings);
-                if (realContentIsVisible && !results.empty()) {
-                    layer->editState().clientCompositionTimestamp = systemTime();
+                if (auto clientCompositionSettings =
+                            layerFE.prepareClientComposition(targetSettings)) {
+                    clientCompositionLayers.push_back(std::move(*clientCompositionSettings));
+                    if (realContentIsVisible) {
+                        layer->editState().clientCompositionTimestamp = systemTime();
+                    }
                 }
             }
 
             if (clientComposition) {
                 outLayerFEs.push_back(&layerFE);
             }
-
-            clientCompositionLayers.insert(clientCompositionLayers.end(),
-                                           std::make_move_iterator(results.begin()),
-                                           std::make_move_iterator(results.end()));
-            results.clear();
         }
 
         firstLayer = false;
diff --git a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
index 1bb9d0eb..a39c527 100644
--- a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
@@ -787,7 +787,7 @@
             sourceCrop.getWidth() != displayFrame.getWidth();
 }
 
-std::vector<LayerFE::LayerSettings> OutputLayer::getOverrideCompositionList() const {
+std::optional<LayerFE::LayerSettings> OutputLayer::getOverrideCompositionSettings() const {
     if (getState().overrideInfo.buffer == nullptr) {
         return {};
     }
@@ -816,7 +816,7 @@
     settings.alpha = 1.0f;
     settings.whitePointNits = getOutput().getState().sdrWhitePointNits;
 
-    return {static_cast<LayerFE::LayerSettings>(settings)};
+    return settings;
 }
 
 void OutputLayer::dump(std::string& out) const {
diff --git a/services/surfaceflinger/CompositionEngine/src/planner/CachedSet.cpp b/services/surfaceflinger/CompositionEngine/src/planner/CachedSet.cpp
index 641b806..9058f67 100644
--- a/services/surfaceflinger/CompositionEngine/src/planner/CachedSet.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/planner/CachedSet.cpp
@@ -190,11 +190,11 @@
     std::vector<renderengine::LayerSettings> layerSettings;
     renderengine::LayerSettings highlight;
     for (const auto& layer : mLayers) {
-        const auto clientCompositionList =
-                layer.getState()->getOutputLayer()->getLayerFE().prepareClientCompositionList(
-                        targetSettings);
-        layerSettings.insert(layerSettings.end(), clientCompositionList.cbegin(),
-                             clientCompositionList.cend());
+        if (auto clientCompositionSettings =
+                    layer.getState()->getOutputLayer()->getLayerFE().prepareClientComposition(
+                            targetSettings)) {
+            layerSettings.push_back(std::move(*clientCompositionSettings));
+        }
     }
 
     renderengine::LayerSettings blurLayerSettings;
@@ -202,43 +202,40 @@
         auto blurSettings = targetSettings;
         blurSettings.blurSetting =
                 LayerFE::ClientCompositionTargetSettings::BlurSetting::BackgroundBlurOnly;
-        auto clientCompositionList =
-                mBlurLayer->getOutputLayer()->getLayerFE().prepareClientCompositionList(
-                        blurSettings);
-        blurLayerSettings = clientCompositionList.back();
+
+        auto blurLayerSettings =
+                mBlurLayer->getOutputLayer()->getLayerFE().prepareClientComposition(blurSettings);
         // This mimics Layer::prepareClearClientComposition
-        blurLayerSettings.skipContentDraw = true;
-        blurLayerSettings.name = std::string("blur layer");
+        blurLayerSettings->skipContentDraw = true;
+        blurLayerSettings->name = std::string("blur layer");
         // Clear out the shadow settings
-        blurLayerSettings.shadow = {};
-        layerSettings.push_back(blurLayerSettings);
+        blurLayerSettings->shadow = {};
+        layerSettings.push_back(std::move(*blurLayerSettings));
     }
 
-    renderengine::LayerSettings holePunchSettings;
-    renderengine::LayerSettings holePunchBackgroundSettings;
     if (mHolePunchLayer) {
         auto& layerFE = mHolePunchLayer->getOutputLayer()->getLayerFE();
-        auto clientCompositionList = layerFE.prepareClientCompositionList(targetSettings);
-        // Assume that the final layer contains the buffer that we want to
-        // replace with a hole punch.
-        holePunchSettings = clientCompositionList.back();
+
+        auto holePunchSettings = layerFE.prepareClientComposition(targetSettings);
         // This mimics Layer::prepareClearClientComposition
-        holePunchSettings.source.buffer.buffer = nullptr;
-        holePunchSettings.source.solidColor = half3(0.0f, 0.0f, 0.0f);
-        holePunchSettings.disableBlending = true;
-        holePunchSettings.alpha = 0.0f;
-        holePunchSettings.name =
+        holePunchSettings->source.buffer.buffer = nullptr;
+        holePunchSettings->source.solidColor = half3(0.0f, 0.0f, 0.0f);
+        holePunchSettings->disableBlending = true;
+        holePunchSettings->alpha = 0.0f;
+        holePunchSettings->name =
                 android::base::StringPrintf("hole punch layer for %s", layerFE.getDebugName());
-        layerSettings.push_back(holePunchSettings);
 
         // Add a solid background as the first layer in case there is no opaque
         // buffer behind the punch hole
+        renderengine::LayerSettings holePunchBackgroundSettings;
         holePunchBackgroundSettings.alpha = 1.0f;
         holePunchBackgroundSettings.name = std::string("holePunchBackground");
-        holePunchBackgroundSettings.geometry.boundaries = holePunchSettings.geometry.boundaries;
+        holePunchBackgroundSettings.geometry.boundaries = holePunchSettings->geometry.boundaries;
         holePunchBackgroundSettings.geometry.positionTransform =
-                holePunchSettings.geometry.positionTransform;
-        layerSettings.emplace(layerSettings.begin(), holePunchBackgroundSettings);
+                holePunchSettings->geometry.positionTransform;
+        layerSettings.emplace(layerSettings.begin(), std::move(holePunchBackgroundSettings));
+
+        layerSettings.push_back(std::move(*holePunchSettings));
     }
 
     if (sDebugHighlighLayers) {
diff --git a/services/surfaceflinger/CompositionEngine/tests/OutputTest.cpp b/services/surfaceflinger/CompositionEngine/tests/OutputTest.cpp
index ad0fb9d..163a11c 100644
--- a/services/surfaceflinger/CompositionEngine/tests/OutputTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/OutputTest.cpp
@@ -4308,6 +4308,8 @@
 
     struct Layer {
         Layer() {
+            EXPECT_CALL(mOutputLayer, getOverrideCompositionSettings())
+                    .WillRepeatedly(Return(std::nullopt));
             EXPECT_CALL(mOutputLayer, getState()).WillRepeatedly(ReturnRef(mOutputLayerState));
             EXPECT_CALL(mOutputLayer, editState()).WillRepeatedly(ReturnRef(mOutputLayerState));
             EXPECT_CALL(mOutputLayer, getLayerFE()).WillRepeatedly(ReturnRef(*mLayerFE));
@@ -4405,23 +4407,18 @@
 }
 
 TEST_F(GenerateClientCompositionRequestsTest_ThreeLayers, gathersClientCompositionRequests) {
-    LayerFE::LayerSettings mShadowSettings;
-    mShadowSettings.source.solidColor = {0.1f, 0.1f, 0.1f};
-
-    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({mLayers[1].mLayerSettings})));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>(
-                    {mShadowSettings, mLayers[2].mLayerSettings})));
+    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientComposition(_))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientComposition(_))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mLayers[1].mLayerSettings)));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(_))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mLayers[2].mLayerSettings)));
 
     auto requests = mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
                                                               kDisplayDataspace);
-    ASSERT_EQ(3u, requests.size());
+    ASSERT_EQ(2u, requests.size());
     EXPECT_EQ(mLayers[1].mLayerSettings, requests[0]);
-    EXPECT_EQ(mShadowSettings, requests[1]);
-    EXPECT_EQ(mLayers[2].mLayerSettings, requests[2]);
+    EXPECT_EQ(mLayers[2].mLayerSettings, requests[1]);
 
     // Check that a timestamp was set for the layers that generated requests
     EXPECT_TRUE(0 == mLayers[0].mOutputLayerState.clientCompositionTimestamp);
@@ -4438,27 +4435,21 @@
 }
 
 TEST_F(GenerateClientCompositionRequestsTest_ThreeLayers, overridesBlur) {
-    LayerFE::LayerSettings mShadowSettings;
-    mShadowSettings.source.solidColor = {0.1f, 0.1f, 0.1f};
-
     mLayers[2].mOutputLayerState.overrideInfo.disableBackgroundBlur = true;
 
-    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({mLayers[1].mLayerSettings})));
+    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientComposition(_))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientComposition(_))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mLayers[1].mLayerSettings)));
     EXPECT_CALL(*mLayers[2].mLayerFE,
-                prepareClientCompositionList(ClientCompositionTargetSettingsBlurSettingsEq(
+                prepareClientComposition(ClientCompositionTargetSettingsBlurSettingsEq(
                         LayerFE::ClientCompositionTargetSettings::BlurSetting::BlurRegionsOnly)))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>(
-                    {mShadowSettings, mLayers[2].mLayerSettings})));
-
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mLayers[2].mLayerSettings)));
     auto requests = mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
                                                               kDisplayDataspace);
-    ASSERT_EQ(3u, requests.size());
+    ASSERT_EQ(2u, requests.size());
     EXPECT_EQ(mLayers[1].mLayerSettings, requests[0]);
-    EXPECT_EQ(mShadowSettings, requests[1]);
-    EXPECT_EQ(mLayers[2].mLayerSettings, requests[2]);
+    EXPECT_EQ(mLayers[2].mLayerSettings, requests[1]);
 
     // Check that a timestamp was set for the layers that generated requests
     EXPECT_TRUE(0 == mLayers[0].mOutputLayerState.clientCompositionTimestamp);
@@ -4480,8 +4471,8 @@
     mLayers[1].mLayerFEState.isOpaque = true;
     mLayers[2].mLayerFEState.isOpaque = true;
 
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({mLayers[2].mLayerSettings})));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(_))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mLayers[2].mLayerSettings)));
 
     auto requests = mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
                                                               kDisplayDataspace);
@@ -4503,8 +4494,8 @@
     mLayers[1].mLayerFEState.isOpaque = false;
     mLayers[2].mLayerFEState.isOpaque = false;
 
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({mLayers[2].mLayerSettings})));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(_))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mLayers[2].mLayerSettings)));
 
     auto requests = mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
                                                               kDisplayDataspace);
@@ -4562,10 +4553,10 @@
     mBlackoutSettings.alpha = 0.f;
     mBlackoutSettings.disableBlending = true;
 
-    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer1TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({mBlackoutSettings})));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer2TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({mLayers[2].mLayerSettings})));
+    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientComposition(Eq(ByRef(layer1TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mBlackoutSettings)));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(Eq(ByRef(layer2TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mLayers[2].mLayerSettings)));
 
     auto requests = mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
                                                               kDisplayDataspace);
@@ -4620,12 +4611,12 @@
             kLayerWhitePointNits,
     };
 
-    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer0TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer1TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer2TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientComposition(Eq(ByRef(layer0TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientComposition(Eq(ByRef(layer1TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(Eq(ByRef(layer2TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
 
     static_cast<void>(
             mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
@@ -4674,12 +4665,12 @@
             kLayerWhitePointNits,
     };
 
-    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer0TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer1TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer2TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientComposition(Eq(ByRef(layer0TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientComposition(Eq(ByRef(layer1TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(Eq(ByRef(layer2TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
 
     static_cast<void>(
             mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
@@ -4728,12 +4719,12 @@
             kLayerWhitePointNits,
     };
 
-    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer0TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer1TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer2TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientComposition(Eq(ByRef(layer0TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientComposition(Eq(ByRef(layer1TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(Eq(ByRef(layer2TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
 
     static_cast<void>(
             mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
@@ -4781,12 +4772,12 @@
             kLayerWhitePointNits,
     };
 
-    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer0TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer1TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer2TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientComposition(Eq(ByRef(layer0TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientComposition(Eq(ByRef(layer1TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(Eq(ByRef(layer2TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
 
     static_cast<void>(
             mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
@@ -4832,12 +4823,12 @@
             kLayerWhitePointNits,
     };
 
-    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer0TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer1TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer2TargetSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[0].mLayerFE, prepareClientComposition(Eq(ByRef(layer0TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[1].mLayerFE, prepareClientComposition(Eq(ByRef(layer1TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(Eq(ByRef(layer2TargetSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>()));
 
     static_cast<void>(mOutput.generateClientCompositionRequestsHelper(true /* supportsProtectedContent */,
                                                                 kDisplayDataspace));
@@ -5018,8 +5009,8 @@
 
     EXPECT_CALL(leftLayer.mOutputLayer, requiresClientComposition()).WillRepeatedly(Return(true));
     EXPECT_CALL(leftLayer.mOutputLayer, needsFiltering()).WillRepeatedly(Return(false));
-    EXPECT_CALL(*leftLayer.mLayerFE, prepareClientCompositionList(Eq(ByRef(leftLayerSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({leftLayer.mLayerSettings})));
+    EXPECT_CALL(*leftLayer.mLayerFE, prepareClientComposition(Eq(ByRef(leftLayerSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(leftLayer.mLayerSettings)));
 
     compositionengine::LayerFE::ClientCompositionTargetSettings rightLayerSettings{
             Region(Rect(1000, 0, 2000, 1000)),
@@ -5036,8 +5027,8 @@
 
     EXPECT_CALL(rightLayer.mOutputLayer, requiresClientComposition()).WillRepeatedly(Return(true));
     EXPECT_CALL(rightLayer.mOutputLayer, needsFiltering()).WillRepeatedly(Return(false));
-    EXPECT_CALL(*rightLayer.mLayerFE, prepareClientCompositionList(Eq(ByRef(rightLayerSettings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({rightLayer.mLayerSettings})));
+    EXPECT_CALL(*rightLayer.mLayerFE, prepareClientComposition(Eq(ByRef(rightLayerSettings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(rightLayer.mLayerSettings)));
 
     constexpr bool supportsProtectedContent = true;
     auto requests =
@@ -5075,8 +5066,8 @@
 
     EXPECT_CALL(mLayers[0].mOutputLayer, requiresClientComposition()).WillOnce(Return(false));
     EXPECT_CALL(mLayers[1].mOutputLayer, requiresClientComposition()).WillOnce(Return(false));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer2Settings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>({mShadowSettings})));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(Eq(ByRef(layer2Settings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mShadowSettings)));
 
     auto requests = mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
                                                               kDisplayDataspace);
@@ -5093,9 +5084,6 @@
     const Region kPartialContentWithPartialShadowRegion =
             Region(kContentWithShadow).subtract(Rect(40, 40, 50, 80));
 
-    LayerFE::LayerSettings mShadowSettings;
-    mShadowSettings.source.solidColor = {0.1f, 0.1f, 0.1f};
-
     mLayers[2].mOutputLayerState.visibleRegion = kPartialContentWithPartialShadowRegion;
     mLayers[2].mOutputLayerState.shadowRegion = kShadowRegion;
 
@@ -5114,16 +5102,14 @@
 
     EXPECT_CALL(mLayers[0].mOutputLayer, requiresClientComposition()).WillOnce(Return(false));
     EXPECT_CALL(mLayers[1].mOutputLayer, requiresClientComposition()).WillOnce(Return(false));
-    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientCompositionList(Eq(ByRef(layer2Settings))))
-            .WillOnce(Return(std::vector<LayerFE::LayerSettings>(
-                    {mShadowSettings, mLayers[2].mLayerSettings})));
+    EXPECT_CALL(*mLayers[2].mLayerFE, prepareClientComposition(Eq(ByRef(layer2Settings))))
+            .WillOnce(Return(std::optional<LayerFE::LayerSettings>(mLayers[2].mLayerSettings)));
 
     auto requests = mOutput.generateClientCompositionRequestsHelper(false /* supportsProtectedContent */,
                                                               kDisplayDataspace);
-    ASSERT_EQ(2u, requests.size());
+    ASSERT_EQ(1u, requests.size());
 
-    EXPECT_EQ(mShadowSettings, requests[0]);
-    EXPECT_EQ(mLayers[2].mLayerSettings, requests[1]);
+    EXPECT_EQ(mLayers[2].mLayerSettings, requests[0]);
 }
 
 } // namespace
diff --git a/services/surfaceflinger/CompositionEngine/tests/planner/CachedSetTest.cpp b/services/surfaceflinger/CompositionEngine/tests/planner/CachedSetTest.cpp
index 8a99e4e..cb4c4e2 100644
--- a/services/surfaceflinger/CompositionEngine/tests/planner/CachedSetTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/planner/CachedSetTest.cpp
@@ -345,13 +345,13 @@
     CachedSet cachedSet(layer1);
     cachedSet.append(CachedSet(layer2));
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList1;
-    clientCompList1.push_back({});
-    clientCompList1[0].alpha = 0.5f;
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp1;
+    clientComp1.emplace();
+    clientComp1->alpha = 0.5f;
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList2;
-    clientCompList2.push_back({});
-    clientCompList2[0].alpha = 0.75f;
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp2;
+    clientComp2.emplace();
+    clientComp2->alpha = 0.75f;
 
     const auto drawLayers =
             [&](const renderengine::DisplaySettings& displaySettings,
@@ -368,12 +368,10 @@
         return futureOf<renderengine::RenderEngineResult>({NO_ERROR, base::unique_fd()});
     };
 
-    EXPECT_CALL(*layerFE1,
-                prepareClientCompositionList(ClientCompositionTargetSettingsSecureEq(false)))
-            .WillOnce(Return(clientCompList1));
-    EXPECT_CALL(*layerFE2,
-                prepareClientCompositionList(ClientCompositionTargetSettingsSecureEq(false)))
-            .WillOnce(Return(clientCompList2));
+    EXPECT_CALL(*layerFE1, prepareClientComposition(ClientCompositionTargetSettingsSecureEq(false)))
+            .WillOnce(Return(clientComp1));
+    EXPECT_CALL(*layerFE2, prepareClientComposition(ClientCompositionTargetSettingsSecureEq(false)))
+            .WillOnce(Return(clientComp2));
     EXPECT_CALL(mRenderEngine, drawLayers(_, _, _, _, _)).WillOnce(Invoke(drawLayers));
     mOutputState.isSecure = false;
     cachedSet.render(mRenderEngine, mTexturePool, mOutputState);
@@ -397,13 +395,13 @@
     CachedSet cachedSet(layer1);
     cachedSet.append(CachedSet(layer2));
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList1;
-    clientCompList1.push_back({});
-    clientCompList1[0].alpha = 0.5f;
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp1;
+    clientComp1.emplace();
+    clientComp1->alpha = 0.5f;
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList2;
-    clientCompList2.push_back({});
-    clientCompList2[0].alpha = 0.75f;
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp2;
+    clientComp2.emplace();
+    clientComp2->alpha = 0.75f;
 
     const auto drawLayers =
             [&](const renderengine::DisplaySettings& displaySettings,
@@ -421,12 +419,10 @@
         return futureOf<renderengine::RenderEngineResult>({NO_ERROR, base::unique_fd()});
     };
 
-    EXPECT_CALL(*layerFE1,
-                prepareClientCompositionList(ClientCompositionTargetSettingsSecureEq(true)))
-            .WillOnce(Return(clientCompList1));
-    EXPECT_CALL(*layerFE2,
-                prepareClientCompositionList(ClientCompositionTargetSettingsSecureEq(true)))
-            .WillOnce(Return(clientCompList2));
+    EXPECT_CALL(*layerFE1, prepareClientComposition(ClientCompositionTargetSettingsSecureEq(true)))
+            .WillOnce(Return(clientComp1));
+    EXPECT_CALL(*layerFE2, prepareClientComposition(ClientCompositionTargetSettingsSecureEq(true)))
+            .WillOnce(Return(clientComp2));
     EXPECT_CALL(mRenderEngine, drawLayers(_, _, _, _, _)).WillOnce(Invoke(drawLayers));
     mOutputState.isSecure = true;
     cachedSet.render(mRenderEngine, mTexturePool, mOutputState);
@@ -450,11 +446,11 @@
     CachedSet cachedSet(layer1);
     cachedSet.append(CachedSet(layer2));
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList1;
-    clientCompList1.push_back({});
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp1;
+    clientComp1.emplace();
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList2;
-    clientCompList2.push_back({});
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp2;
+    clientComp2.emplace();
 
     mOutputState.displayBrightnessNits = 400.f;
 
@@ -468,13 +464,13 @@
     };
 
     EXPECT_CALL(*layerFE1,
-                prepareClientCompositionList(ClientCompositionTargetSettingsWhitePointEq(
+                prepareClientComposition(ClientCompositionTargetSettingsWhitePointEq(
                         mOutputState.displayBrightnessNits)))
-            .WillOnce(Return(clientCompList1));
+            .WillOnce(Return(clientComp1));
     EXPECT_CALL(*layerFE2,
-                prepareClientCompositionList(ClientCompositionTargetSettingsWhitePointEq(
+                prepareClientComposition(ClientCompositionTargetSettingsWhitePointEq(
                         mOutputState.displayBrightnessNits)))
-            .WillOnce(Return(clientCompList2));
+            .WillOnce(Return(clientComp2));
     EXPECT_CALL(mRenderEngine, drawLayers(_, _, _, _, _)).WillOnce(Invoke(drawLayers));
     mOutputState.isSecure = true;
     cachedSet.render(mRenderEngine, mTexturePool, mOutputState);
@@ -498,13 +494,13 @@
     CachedSet cachedSet(layer1);
     cachedSet.append(CachedSet(layer2));
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList1;
-    clientCompList1.push_back({});
-    clientCompList1[0].alpha = 0.5f;
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp1;
+    clientComp1.emplace();
+    clientComp1->alpha = 0.5f;
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList2;
-    clientCompList2.push_back({});
-    clientCompList2[0].alpha = 0.75f;
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp2;
+    clientComp2.emplace();
+    clientComp2->alpha = 0.75f;
 
     mOutputState.framebufferSpace = ProjectionSpace(ui::Size(10, 20), Rect(2, 3, 10, 5));
 
@@ -524,8 +520,8 @@
         return futureOf<renderengine::RenderEngineResult>({NO_ERROR, base::unique_fd()});
     };
 
-    EXPECT_CALL(*layerFE1, prepareClientCompositionList(_)).WillOnce(Return(clientCompList1));
-    EXPECT_CALL(*layerFE2, prepareClientCompositionList(_)).WillOnce(Return(clientCompList2));
+    EXPECT_CALL(*layerFE1, prepareClientComposition(_)).WillOnce(Return(clientComp1));
+    EXPECT_CALL(*layerFE2, prepareClientComposition(_)).WillOnce(Return(clientComp2));
     EXPECT_CALL(mRenderEngine, drawLayers(_, _, _, _, _)).WillOnce(Invoke(drawLayers));
     cachedSet.render(mRenderEngine, mTexturePool, mOutputState);
     expectReadyBuffer(cachedSet);
@@ -722,22 +718,22 @@
 
     cachedSet.addHolePunchLayerIfFeasible(layer3, true);
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList1;
-    clientCompList1.push_back({});
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList2;
-    clientCompList2.push_back({});
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList3;
-    clientCompList3.push_back({});
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp1;
+    clientComp1.emplace();
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp2;
+    clientComp2.emplace();
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp3;
+    clientComp3.emplace();
 
-    clientCompList3[0].source.buffer.buffer =
+    clientComp3->source.buffer.buffer =
             std::make_shared<renderengine::mock::FakeExternalTexture>(1U /*width*/, 1U /*height*/,
                                                                       1ULL /* bufferId */,
                                                                       HAL_PIXEL_FORMAT_RGBA_8888,
                                                                       0ULL /*usage*/);
 
-    EXPECT_CALL(*layerFE1, prepareClientCompositionList(_)).WillOnce(Return(clientCompList1));
-    EXPECT_CALL(*layerFE2, prepareClientCompositionList(_)).WillOnce(Return(clientCompList2));
-    EXPECT_CALL(*layerFE3, prepareClientCompositionList(_)).WillOnce(Return(clientCompList3));
+    EXPECT_CALL(*layerFE1, prepareClientComposition(_)).WillOnce(Return(clientComp1));
+    EXPECT_CALL(*layerFE2, prepareClientComposition(_)).WillOnce(Return(clientComp2));
+    EXPECT_CALL(*layerFE3, prepareClientComposition(_)).WillOnce(Return(clientComp3));
 
     const auto drawLayers =
             [&](const renderengine::DisplaySettings&,
@@ -771,7 +767,7 @@
 }
 
 TEST_F(CachedSetTest, addHolePunch_noBuffer) {
-    // Same as addHolePunch, except that clientCompList3 does not contain a
+    // Same as addHolePunch, except that clientComp3 does not contain a
     // buffer. This imitates the case where the buffer had protected content, so
     // BufferLayer did not add it to the LayerSettings. This should not assert.
     mTestLayers[0]->outputLayerCompositionState.displayFrame = Rect(0, 0, 5, 5);
@@ -789,16 +785,16 @@
 
     cachedSet.addHolePunchLayerIfFeasible(layer3, true);
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList1;
-    clientCompList1.push_back({});
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList2;
-    clientCompList2.push_back({});
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList3;
-    clientCompList3.push_back({});
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp1;
+    clientComp1.emplace();
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp2;
+    clientComp2.emplace();
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp3;
+    clientComp3.emplace();
 
-    EXPECT_CALL(*layerFE1, prepareClientCompositionList(_)).WillOnce(Return(clientCompList1));
-    EXPECT_CALL(*layerFE2, prepareClientCompositionList(_)).WillOnce(Return(clientCompList2));
-    EXPECT_CALL(*layerFE3, prepareClientCompositionList(_)).WillOnce(Return(clientCompList3));
+    EXPECT_CALL(*layerFE1, prepareClientComposition(_)).WillOnce(Return(clientComp1));
+    EXPECT_CALL(*layerFE2, prepareClientComposition(_)).WillOnce(Return(clientComp2));
+    EXPECT_CALL(*layerFE3, prepareClientComposition(_)).WillOnce(Return(clientComp3));
 
     const auto drawLayers =
             [&](const renderengine::DisplaySettings&,
@@ -923,34 +919,34 @@
 
     cachedSet.addBackgroundBlurLayer(layer3);
 
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList1;
-    clientCompList1.push_back({});
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList2;
-    clientCompList2.push_back({});
-    std::vector<compositionengine::LayerFE::LayerSettings> clientCompList3;
-    clientCompList3.push_back({});
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp1;
+    clientComp1.emplace();
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp2;
+    clientComp2.emplace();
+    std::optional<compositionengine::LayerFE::LayerSettings> clientComp3;
+    clientComp3.emplace();
 
-    clientCompList3[0].source.buffer.buffer =
+    clientComp3->source.buffer.buffer =
             std::make_shared<renderengine::mock::FakeExternalTexture>(1U /*width*/, 1U /*height*/,
                                                                       1ULL /* bufferId */,
                                                                       HAL_PIXEL_FORMAT_RGBA_8888,
                                                                       0ULL /*usage*/);
 
     EXPECT_CALL(*layerFE1,
-                prepareClientCompositionList(ClientCompositionTargetSettingsBlurSettingsEq(
+                prepareClientComposition(ClientCompositionTargetSettingsBlurSettingsEq(
                         compositionengine::LayerFE::ClientCompositionTargetSettings::BlurSetting::
                                 Enabled)))
-            .WillOnce(Return(clientCompList1));
+            .WillOnce(Return(clientComp1));
     EXPECT_CALL(*layerFE2,
-                prepareClientCompositionList(ClientCompositionTargetSettingsBlurSettingsEq(
+                prepareClientComposition(ClientCompositionTargetSettingsBlurSettingsEq(
                         compositionengine::LayerFE::ClientCompositionTargetSettings::BlurSetting::
                                 Enabled)))
-            .WillOnce(Return(clientCompList2));
+            .WillOnce(Return(clientComp2));
     EXPECT_CALL(*layerFE3,
-                prepareClientCompositionList(ClientCompositionTargetSettingsBlurSettingsEq(
+                prepareClientComposition(ClientCompositionTargetSettingsBlurSettingsEq(
                         compositionengine::LayerFE::ClientCompositionTargetSettings::BlurSetting::
                                 BackgroundBlurOnly)))
-            .WillOnce(Return(clientCompList3));
+            .WillOnce(Return(clientComp3));
 
     const auto drawLayers =
             [&](const renderengine::DisplaySettings&,
diff --git a/services/surfaceflinger/CompositionEngine/tests/planner/FlattenerTest.cpp b/services/surfaceflinger/CompositionEngine/tests/planner/FlattenerTest.cpp
index 200278c..b624d1a 100644
--- a/services/surfaceflinger/CompositionEngine/tests/planner/FlattenerTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/planner/FlattenerTest.cpp
@@ -124,12 +124,11 @@
         EXPECT_CALL(*testLayer->layerFE, getCompositionState)
                 .WillRepeatedly(Return(&testLayer->layerFECompositionState));
 
-        std::vector<LayerFE::LayerSettings> clientCompositionList = {
-                LayerFE::LayerSettings{},
-        };
+        std::optional<LayerFE::LayerSettings> clientComposition;
+        clientComposition.emplace();
 
-        EXPECT_CALL(*testLayer->layerFE, prepareClientCompositionList)
-                .WillRepeatedly(Return(clientCompositionList));
+        EXPECT_CALL(*testLayer->layerFE, prepareClientComposition)
+                .WillRepeatedly(Return(clientComposition));
         EXPECT_CALL(testLayer->outputLayer, getLayerFE)
                 .WillRepeatedly(ReturnRef(*testLayer->layerFE));
         EXPECT_CALL(testLayer->outputLayer, getState)
@@ -638,16 +637,15 @@
 
     EXPECT_CALL(*mTestLayers[2]->layerFE, hasRoundedCorners()).WillRepeatedly(Return(true));
 
-    std::vector<LayerFE::LayerSettings> clientCompositionList = {
-            LayerFE::LayerSettings{},
-    };
-    clientCompositionList[0].source.buffer.buffer = std::make_shared<
+    std::optional<LayerFE::LayerSettings> clientComposition;
+    clientComposition.emplace();
+    clientComposition->source.buffer.buffer = std::make_shared<
             renderengine::impl::ExternalTexture>(mTestLayers[2]->layerFECompositionState.buffer,
                                                  mRenderEngine,
                                                  renderengine::impl::ExternalTexture::Usage::
                                                          READABLE);
-    EXPECT_CALL(*mTestLayers[2]->layerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(clientCompositionList));
+    EXPECT_CALL(*mTestLayers[2]->layerFE, prepareClientComposition(_))
+            .WillOnce(Return(clientComposition));
 
     const std::vector<const LayerState*> layers = {
             layerState1.get(),
@@ -712,16 +710,15 @@
 
     EXPECT_CALL(*mTestLayers[1]->layerFE, hasRoundedCorners()).WillRepeatedly(Return(true));
 
-    std::vector<LayerFE::LayerSettings> clientCompositionList = {
-            LayerFE::LayerSettings{},
-    };
-    clientCompositionList[0].source.buffer.buffer = std::make_shared<
+    std::optional<LayerFE::LayerSettings> clientComposition;
+    clientComposition.emplace();
+    clientComposition->source.buffer.buffer = std::make_shared<
             renderengine::impl::ExternalTexture>(mTestLayers[1]->layerFECompositionState.buffer,
                                                  mRenderEngine,
                                                  renderengine::impl::ExternalTexture::Usage::
                                                          READABLE);
-    EXPECT_CALL(*mTestLayers[1]->layerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(clientCompositionList));
+    EXPECT_CALL(*mTestLayers[1]->layerFE, prepareClientComposition(_))
+            .WillOnce(Return(clientComposition));
 
     const std::vector<const LayerState*> layers = {
             layerState0.get(),
@@ -784,16 +781,15 @@
 
     EXPECT_CALL(*mTestLayers[1]->layerFE, hasRoundedCorners()).WillRepeatedly(Return(true));
 
-    std::vector<LayerFE::LayerSettings> clientCompositionList = {
-            LayerFE::LayerSettings{},
-    };
-    clientCompositionList[0].source.buffer.buffer = std::make_shared<
+    std::optional<LayerFE::LayerSettings> clientComposition;
+    clientComposition.emplace();
+    clientComposition->source.buffer.buffer = std::make_shared<
             renderengine::impl::ExternalTexture>(mTestLayers[1]->layerFECompositionState.buffer,
                                                  mRenderEngine,
                                                  renderengine::impl::ExternalTexture::Usage::
                                                          READABLE);
-    EXPECT_CALL(*mTestLayers[1]->layerFE, prepareClientCompositionList(_))
-            .WillOnce(Return(clientCompositionList));
+    EXPECT_CALL(*mTestLayers[1]->layerFE, prepareClientComposition(_))
+            .WillOnce(Return(clientComposition));
 
     const std::vector<const LayerState*> layers = {
             layerState0.get(),
diff --git a/services/surfaceflinger/EffectLayer.cpp b/services/surfaceflinger/EffectLayer.cpp
index d8bbc30..d161c51 100644
--- a/services/surfaceflinger/EffectLayer.cpp
+++ b/services/surfaceflinger/EffectLayer.cpp
@@ -47,11 +47,10 @@
 
 EffectLayer::~EffectLayer() = default;
 
-std::vector<compositionengine::LayerFE::LayerSettings> EffectLayer::prepareClientCompositionList(
-        compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) {
-    std::vector<compositionengine::LayerFE::LayerSettings> results;
+std::optional<compositionengine::LayerFE::LayerSettings> EffectLayer::prepareClientComposition(
+        compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) const {
     std::optional<compositionengine::LayerFE::LayerSettings> layerSettings =
-            prepareClientComposition(targetSettings);
+            Layer::prepareClientComposition(targetSettings);
     // Nothing to render.
     if (!layerSettings) {
         return {};
@@ -64,13 +63,13 @@
     if (targetSettings.realContentIsVisible && fillsColor()) {
         // Set color for color fill settings.
         layerSettings->source.solidColor = getColor().rgb;
-        results.push_back(*layerSettings);
+        return layerSettings;
     } else if (hasBlur() || drawShadows()) {
         layerSettings->skipContentDraw = true;
-        results.push_back(*layerSettings);
+        return layerSettings;
     }
 
-    return results;
+    return {};
 }
 
 bool EffectLayer::isVisible() const {
diff --git a/services/surfaceflinger/EffectLayer.h b/services/surfaceflinger/EffectLayer.h
index 1dcb633..747b0bf 100644
--- a/services/surfaceflinger/EffectLayer.h
+++ b/services/surfaceflinger/EffectLayer.h
@@ -52,8 +52,9 @@
      */
     const compositionengine::LayerFECompositionState* getCompositionState() const override;
     void preparePerFrameCompositionState() override;
-    std::vector<compositionengine::LayerFE::LayerSettings> prepareClientCompositionList(
-            compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) override;
+    std::optional<compositionengine::LayerFE::LayerSettings> prepareClientComposition(
+            compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings)
+            const override;
 
     std::unique_ptr<compositionengine::LayerFECompositionState> mCompositionState;
 
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 5e1a858..dfff8fe 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -575,7 +575,7 @@
 // ---------------------------------------------------------------------------
 
 std::optional<compositionengine::LayerFE::LayerSettings> Layer::prepareClientComposition(
-        compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) {
+        compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) const {
     if (!getCompositionState()) {
         return {};
     }
@@ -653,30 +653,6 @@
     layerSettings.name = getName();
 }
 
-// TODO(b/188891810): This method now only ever returns 0 or 1 layers so we should return
-// std::optional instead of a vector.  Additionally, we should consider removing
-// this method entirely in favor of calling prepareClientComposition directly.
-std::vector<compositionengine::LayerFE::LayerSettings> Layer::prepareClientCompositionList(
-        compositionengine::LayerFE::ClientCompositionTargetSettings& targetSettings) {
-    std::optional<compositionengine::LayerFE::LayerSettings> layerSettings =
-            prepareClientComposition(targetSettings);
-    // Nothing to render.
-    if (!layerSettings) {
-        return {};
-    }
-
-    // HWC requests to clear this layer.
-    if (targetSettings.clearContent) {
-        prepareClearClientComposition(*layerSettings, false /* blackout */);
-        return {*layerSettings};
-    }
-
-    // set the shadow for the layer if needed
-    prepareShadowClientComposition(*layerSettings, targetSettings.viewport);
-
-    return {*layerSettings};
-}
-
 aidl::android::hardware::graphics::composer3::Composition Layer::getCompositionType(
         const DisplayDevice& display) const {
     const auto outputLayer = findOutputLayerForDisplay(&display);
@@ -2006,7 +1982,7 @@
 }
 
 void Layer::prepareShadowClientComposition(LayerFE::LayerSettings& caster,
-                                           const Rect& layerStackRect) {
+                                           const Rect& layerStackRect) const {
     renderengine::ShadowSettings state = mFlinger->mDrawingState.globalShadowSettings;
 
     // Note: this preserves existing behavior of shadowing the entire layer and not cropping it if
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 22bb866..6e83b23 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -618,8 +618,9 @@
     const compositionengine::LayerFECompositionState* getCompositionState() const override;
     bool onPreComposition(nsecs_t) override;
     void prepareCompositionState(compositionengine::LayerFE::StateSubset subset) override;
-    std::vector<compositionengine::LayerFE::LayerSettings> prepareClientCompositionList(
-            compositionengine::LayerFE::ClientCompositionTargetSettings&) override;
+
+    std::optional<compositionengine::LayerFE::LayerSettings> prepareClientComposition(
+            compositionengine::LayerFE::ClientCompositionTargetSettings&) const override;
     void onLayerDisplayed(ftl::SharedFuture<FenceResult>) override;
 
     void setWasClientComposed(const sp<Fence>& fence) override {
@@ -918,8 +919,6 @@
     friend class TransactionSurfaceFrameTest;
 
     virtual void setInitialValuesForClone(const sp<Layer>& clonedFrom);
-    virtual std::optional<compositionengine::LayerFE::LayerSettings> prepareClientComposition(
-            compositionengine::LayerFE::ClientCompositionTargetSettings&);
     virtual void preparePerFrameCompositionState();
     virtual void commitTransaction(State& stateToCommit);
     virtual void onSurfaceFrameCreated(const std::shared_ptr<frametimeline::SurfaceFrame>&) {}
@@ -940,7 +939,8 @@
     // Modifies the passed in layer settings to clear the contents. If the blackout flag is set,
     // the settings clears the content with a solid black fill.
     void prepareClearClientComposition(LayerFE::LayerSettings&, bool blackout) const;
-    void prepareShadowClientComposition(LayerFE::LayerSettings& caster, const Rect& layerStackRect);
+    void prepareShadowClientComposition(LayerFE::LayerSettings& caster,
+                                        const Rect& layerStackRect) const;
 
     void prepareBasicGeometryCompositionState();
     void prepareGeometryCompositionState();
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 85c003a..6b4cfa1 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -6584,27 +6584,24 @@
                 isHdrLayer(layer) ? displayBrightnessNits : sdrWhitePointNits,
 
         };
-        std::vector<compositionengine::LayerFE::LayerSettings> results =
-                layer->prepareClientCompositionList(targetSettings);
-        if (results.size() > 0) {
-            for (auto& settings : results) {
-                settings.geometry.positionTransform =
-                        transform.asMatrix4() * settings.geometry.positionTransform;
-                // There's no need to process blurs when we're executing region sampling,
-                // we're just trying to understand what we're drawing, and doing so without
-                // blurs is already a pretty good approximation.
-                if (regionSampling) {
-                    settings.backgroundBlurRadius = 0;
-                }
-                captureResults.capturedHdrLayers |= isHdrLayer(layer);
-            }
-
-            clientCompositionLayers.insert(clientCompositionLayers.end(),
-                                           std::make_move_iterator(results.begin()),
-                                           std::make_move_iterator(results.end()));
-            renderedLayers.push_back(layer);
+        std::optional<compositionengine::LayerFE::LayerSettings> settings =
+                layer->prepareClientComposition(targetSettings);
+        if (!settings) {
+            return;
         }
 
+        settings->geometry.positionTransform =
+                transform.asMatrix4() * settings->geometry.positionTransform;
+        // There's no need to process blurs when we're executing region sampling,
+        // we're just trying to understand what we're drawing, and doing so without
+        // blurs is already a pretty good approximation.
+        if (regionSampling) {
+            settings->backgroundBlurRadius = 0;
+        }
+        captureResults.capturedHdrLayers |= isHdrLayer(layer);
+
+        clientCompositionLayers.push_back(std::move(*settings));
+        renderedLayers.push_back(layer);
     });
 
     std::vector<renderengine::LayerSettings> clientRenderEngineLayers;