Don't queue buffer if nothing new to draw in Display

The current logic only checks if dirty is not empty, but doesn't account
for no content changing. Instead use the same logic that's in
beginFrame to compute mustRecompute and use that when determining if the
display should queue a buffer.

This fixes an issue where a Displays first few frames could be black
until the content is loaded.

Bug: 239888440
Test: First frame from screenrecord is no longer black
Change-Id: Ibb568302bf2d50db167a1f9ca76a0f37e2c65bf5

4 files changed, 45 insertions, 8 deletions

diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/Output.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/Output.h
index fc8dd8be94..38a391b114 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/Output.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/Output.h
@@ -152,6 +152,8 @@ protected:
     virtual const compositionengine::CompositionEngine& getCompositionEngine() const = 0;
     virtual void dumpState(std::string& out) const = 0;
 
+    bool mustRecompose() const;
+
 private:
     void dirtyEntireOutput();
     void updateCompositionStateForBorder(const compositionengine::CompositionRefreshArgs&);
@@ -171,6 +173,9 @@ private:
     std::unique_ptr<ClientCompositionRequestCache> mClientCompositionRequestCache;
     std::unique_ptr<planner::Planner> mPlanner;
     std::unique_ptr<HwcAsyncWorker> mHwComposerAsyncWorker;
+
+    // Whether the content must be recomposed this frame.
+    bool mMustRecompose = false;
 };
 
 // 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 09adaed6fc..d359424801 100644
--- a/services/surfaceflinger/CompositionEngine/src/Display.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/Display.cpp
@@ -421,7 +421,7 @@ void Display::finishFrame(const compositionengine::CompositionRefreshArgs& refre
     // 1) It is being handled by hardware composer, which may need this to
     //    keep its virtual display state machine in sync, or
     // 2) There is work to be done (the dirty region isn't empty)
-    if (GpuVirtualDisplayId::tryCast(mId) && getDirtyRegion().isEmpty()) {
+    if (GpuVirtualDisplayId::tryCast(mId) && !mustRecompose()) {
         ALOGV("Skipping display composition");
         return;
     }
diff --git a/services/surfaceflinger/CompositionEngine/src/Output.cpp b/services/surfaceflinger/CompositionEngine/src/Output.cpp
index 6edc00f1e1..993b8ef2a9 100644
--- a/services/surfaceflinger/CompositionEngine/src/Output.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/Output.cpp
@@ -1015,17 +1015,17 @@ void Output::beginFrame() {
     //   frame, then nothing more until we get new layers.
     // - When a display is created with a private layer stack, we won't
     //   emit any black frames until a layer is added to the layer stack.
-    const bool mustRecompose = dirty && !(empty && wasEmpty);
+    mMustRecompose = dirty && !(empty && wasEmpty);
 
     const char flagPrefix[] = {'-', '+'};
     static_cast<void>(flagPrefix);
-    ALOGV_IF("%s: %s composition for %s (%cdirty %cempty %cwasEmpty)", __FUNCTION__,
-             mustRecompose ? "doing" : "skipping", getName().c_str(), flagPrefix[dirty],
-             flagPrefix[empty], flagPrefix[wasEmpty]);
+    ALOGV("%s: %s composition for %s (%cdirty %cempty %cwasEmpty)", __func__,
+          mMustRecompose ? "doing" : "skipping", getName().c_str(), flagPrefix[dirty],
+          flagPrefix[empty], flagPrefix[wasEmpty]);
 
-    mRenderSurface->beginFrame(mustRecompose);
+    mRenderSurface->beginFrame(mMustRecompose);
 
-    if (mustRecompose) {
+    if (mMustRecompose) {
         outputState.lastCompositionHadVisibleLayers = !empty;
     }
 }
@@ -1631,5 +1631,9 @@ void Output::finishPrepareFrame() {
     mRenderSurface->prepareFrame(state.usesClientComposition, state.usesDeviceComposition);
 }
 
+bool Output::mustRecompose() const {
+    return mMustRecompose;
+}
+
 } // namespace impl
 } // namespace android::compositionengine
diff --git a/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp b/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
index 51ca213f52..95459c0499 100644
--- a/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp
@@ -971,16 +971,40 @@ TEST_F(DisplayFinishFrameTest, skipsCompositionIfNotDirty) {
 
     // We expect no calls to queueBuffer if composition was skipped.
     EXPECT_CALL(*renderSurface, queueBuffer(_)).Times(0);
+    EXPECT_CALL(*renderSurface, beginFrame(false));
 
     gpuDisplay->editState().isEnabled = true;
     gpuDisplay->editState().usesClientComposition = false;
     gpuDisplay->editState().layerStackSpace.setContent(Rect(0, 0, 1, 1));
     gpuDisplay->editState().dirtyRegion = Region::INVALID_REGION;
+    gpuDisplay->editState().lastCompositionHadVisibleLayers = true;
 
+    gpuDisplay->beginFrame();
     gpuDisplay->finishFrame({}, std::move(mResultWithoutBuffer));
 }
 
-TEST_F(DisplayFinishFrameTest, performsCompositionIfDirty) {
+TEST_F(DisplayFinishFrameTest, skipsCompositionIfEmpty) {
+    auto args = getDisplayCreationArgsForGpuVirtualDisplay();
+    std::shared_ptr<impl::Display> gpuDisplay = impl::createDisplay(mCompositionEngine, args);
+
+    mock::RenderSurface* renderSurface = new StrictMock<mock::RenderSurface>();
+    gpuDisplay->setRenderSurfaceForTest(std::unique_ptr<RenderSurface>(renderSurface));
+
+    // We expect no calls to queueBuffer if composition was skipped.
+    EXPECT_CALL(*renderSurface, queueBuffer(_)).Times(0);
+    EXPECT_CALL(*renderSurface, beginFrame(false));
+
+    gpuDisplay->editState().isEnabled = true;
+    gpuDisplay->editState().usesClientComposition = false;
+    gpuDisplay->editState().layerStackSpace.setContent(Rect(0, 0, 1, 1));
+    gpuDisplay->editState().dirtyRegion = Region(Rect(0, 0, 1, 1));
+    gpuDisplay->editState().lastCompositionHadVisibleLayers = false;
+
+    gpuDisplay->beginFrame();
+    gpuDisplay->finishFrame({}, std::move(mResultWithoutBuffer));
+}
+
+TEST_F(DisplayFinishFrameTest, performsCompositionIfDirtyAndNotEmpty) {
     auto args = getDisplayCreationArgsForGpuVirtualDisplay();
     std::shared_ptr<impl::Display> gpuDisplay = impl::createDisplay(mCompositionEngine, args);
 
@@ -989,11 +1013,15 @@ TEST_F(DisplayFinishFrameTest, performsCompositionIfDirty) {
 
     // We expect a single call to queueBuffer when composition is not skipped.
     EXPECT_CALL(*renderSurface, queueBuffer(_)).Times(1);
+    EXPECT_CALL(*renderSurface, beginFrame(true));
 
     gpuDisplay->editState().isEnabled = true;
     gpuDisplay->editState().usesClientComposition = false;
     gpuDisplay->editState().layerStackSpace.setContent(Rect(0, 0, 1, 1));
     gpuDisplay->editState().dirtyRegion = Region(Rect(0, 0, 1, 1));
+    gpuDisplay->editState().lastCompositionHadVisibleLayers = true;
+
+    gpuDisplay->beginFrame();
     gpuDisplay->finishFrame({}, std::move(mResultWithBuffer));
 }