Ensure that a single composition happens for each acc canvas or WebGL frame.

Rendering a new WebGL or accelerated canvas frame can request two compositions,
one due to the layerFlush and another one because of the new buffer pushed to
the proxies. This can cause problems to apps relying on rAF. This commit disables
the composition request that comes from pushing a new buffer from WebGL or the
acc canvas, and ensures that the only composition request comes from the layerFlush.

Author: magomez

Source/WebCore/platform/graphics/cairo/ImageBufferCairoGLSurfaceBackend.cpp

@@ -223,10 +223,8 @@ void ImageBufferCairoGLSurfaceBackend::swapBuffersIfNeeded()
         auto& proxy = downcast<Nicosia::ContentLayerTextureMapperImpl>(m_nicosiaLayer->impl()).proxy();
         ASSERT(is<TextureMapperPlatformLayerProxyGL>(proxy));
 
-        if (proxy.isEmpty()) {
-            Locker locker { proxy.lock() };
-            downcast<TextureMapperPlatformLayerProxyGL>(proxy).pushNextBuffer(makeUnique<TextureMapperPlatformLayerBuffer>(m_textures[1], backendSize, TextureMapperGL::ShouldBlend, GL_RGBA));
-        }
+        Locker locker { proxy.lock() };
+        downcast<TextureMapperPlatformLayerProxyGL>(proxy).pushNextBuffer(makeUnique<TextureMapperPlatformLayerBuffer>(m_textures[1], backendSize, TextureMapperGL::ShouldBlend, GL_RGBA), false);
     }
 
     if (previousActiveContext)

Source/WebCore/platform/graphics/nicosia/texmap/NicosiaGCGLLayer.cpp

@@ -132,7 +132,7 @@ void GCGLLayer::swapBuffersIfNeeded()
         auto& proxy = downcast<Nicosia::ContentLayerTextureMapperImpl>(m_contentLayer->impl()).proxy();
         Locker locker { proxy.lock() };
         ASSERT(is<TextureMapperPlatformLayerProxyGL>(proxy));
-        downcast<TextureMapperPlatformLayerProxyGL>(proxy).pushNextBuffer(makeUnique<TextureMapperPlatformLayerBuffer>(m_context.m_compositorTexture, textureSize, flags, m_context.m_internalColorFormat));
+        downcast<TextureMapperPlatformLayerProxyGL>(proxy).pushNextBuffer(makeUnique<TextureMapperPlatformLayerBuffer>(m_context.m_compositorTexture, textureSize, flags, m_context.m_internalColorFormat), false);
     }
 
     m_context.markLayerComposited();

Source/WebCore/platform/graphics/texmap/TextureMapperPlatformLayerProxyGL.cpp

@@ -124,7 +124,7 @@ void TextureMapperPlatformLayerProxyGL::invalidate()
     updateFunction();
 }
 
-void TextureMapperPlatformLayerProxyGL::pushNextBuffer(std::unique_ptr<TextureMapperPlatformLayerBuffer>&& newBuffer)
+void TextureMapperPlatformLayerProxyGL::pushNextBuffer(std::unique_ptr<TextureMapperPlatformLayerBuffer>&& newBuffer, bool requestComposition)
 {
     ASSERT(m_lock.isHeld());
 #if USE(ANGLE)
@@ -136,7 +136,7 @@ void TextureMapperPlatformLayerProxyGL::pushNextBuffer(std::unique_ptr<TextureMa
     m_pendingBuffer = WTFMove(newBuffer);
     m_wasBufferDropped = false;
 
-    if (m_compositor)
+    if (m_compositor && requestComposition)
         m_compositor->onNewBufferAvailable();
 }
 

Source/WebCore/platform/graphics/texmap/TextureMapperPlatformLayerProxyGL.h

@@ -55,7 +55,7 @@ class TextureMapperPlatformLayerProxyGL final : public TextureMapperPlatformLaye
     WEBCORE_EXPORT void swapBuffer() override;
 
     std::unique_ptr<TextureMapperPlatformLayerBuffer> getAvailableBuffer(const IntSize&, GLint internalFormat);
-    void pushNextBuffer(std::unique_ptr<TextureMapperPlatformLayerBuffer>&&);
+    void pushNextBuffer(std::unique_ptr<TextureMapperPlatformLayerBuffer>&&, bool = true);
 
     void dropCurrentBufferWhilePreservingTexture(bool shouldWait = false);
 

Source/WebCore/platform/graphics/texmap/coordinated/CoordinatedGraphicsLayer.cpp

@@ -754,8 +754,13 @@ void CoordinatedGraphicsLayer::updatePlatformLayer()
 
     m_shouldUpdatePlatformLayer = false;
 #if USE(COORDINATED_GRAPHICS) && USE(NICOSIA)
-    if (m_nicosia.contentLayer)
+    if (m_nicosia.contentLayer) {
+        // The call to swapBuffersIfNeeded will cause that WebGL and acc canvas push a new buffer to their proxy.
+        // They won't request a composition with this new buffer, so we need to ensure that the composition is
+        // triggered in case no other component does it.
         downcast<Nicosia::ContentLayerTextureMapperImpl>(m_nicosia.contentLayer->impl()).swapBuffersIfNeeded();
+        // m_nicosia.performLayerSync |= true;
+    }
 #endif
 }