Attachment 416416 Details for Bug 219946 – Patch

[patch] Patch

bug-219946-20201217142852.patch (text/plain), 62.47 KB, created by Kimmo Kinnunen on 2020-12-17 04:28:54 PST

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Creator: Kimmo Kinnunen

Created: 2020-12-17 04:28:54 PST

Size: 62.47 KB

patch

obsolete

>Subversion Revision: 270765
>diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
>index 8300cb39856524fc01ef87b9d91ad85dcfe7a69e..7b2e3867fb45ee23272da76d2c5fb9a599984ca3 100644
>--- a/Source/WebCore/ChangeLog
>+++ b/Source/WebCore/ChangeLog
>@@ -1,3 +1,186 @@
>+2020-12-17  Kimmo Kinnunen  <kkinnunen@apple.com>
>+
>+        REGRESSION (r268386): Snapshots of WebGL content in the tab picker don't work (black map on Google Maps)
>+        https://bugs.webkit.org/show_bug.cgi?id=219946
>+        <rdar://problem/72013784>
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Fix case where WebGL would first be displayed with hardware code path
>+        and then displayed with software code path (painting from the paint
>+        tree). Former happens when user looks at the page and latter happens
>+        when printing or when Safari takes a snapshot.
>+
>+        This is not a real regression of r268386. Prior to that, the software
>+        display would have used uninitialized IOSurface contents or contents of
>+        1-2 frames prior and would leave the hardware display buffer not
>+        updated.
>+
>+        CanvasRenderingContext::paintRenderingResultsToCanvas() is used for two
>+        purposes:
>+          1) Image extraction uses, such as toData() or
>+             constructing an Image out of the contents.
>+          2) Painting the rendering to the document during software display.
>+
>+        The 1) case uses always the drawing buffer.
>+
>+        The 2) case presents the drawing buffer as the new display buffer if
>+        there are changes to the drawing buffer and uses the potentially new
>+        display buffer to display.
>+
>+        For 2D canvas, these two cases are the same case. For WebGL they are
>+        different.
>+
>+        The display is destructive for WebGL drawing buffer when
>+        preserveDrawingBuffer == false. This means that if hardware display has
>+        happened, we must read the display buffer during case 2. This code was
>+        missing, so the scenario could not have ever worked.
>+
>+        The previous code tried to workaround this by the
>+        WebGLGraphicsContextBase to detect what the owner intended with the
>+        paintRenderingResultsToCanvas, then skip the potential drawing buffer
>+        clear, read the drawing buffer and put that data to the "presentation
>+        copy" of the HTMLElement. This is not ok, as the uncleared drawing
>+        buffer has non-deterministic contents in case the context has displayed
>+        and the client has not drawn new content to the drawing buffer.
>+
>+        Fix by removing the "presentation copy" of the HTMLCanvas. The
>+        presentation image can always be drawn to the CanvasBase::buffer():
>+         - The current contents of the buffer is the presentation image if the
>+           context has not changed since updating the buffer with either drawing
>+           buffer or previous display buffer.
>+         - If the context has changed, we must present and put the new display
>+           buffer to the CanvasBase::buffer()
>+         - This is also correct contents for the potential next image extraction
>+           uses, up to a point when context changes.
>+         - If the context changes before an image extraction use, CanvasBase::buffer() is
>+           updated with the normal logic, the same as what happens when CanvasBase::buffer()
>+           is updated between two image extraction uses.
>+
>+        Prior to this, there was an unneeded and incorrectly implemented
>+        GPUCanvasContext::markLayerComposited(). The sequence would be:
>+
>+        HTMLCanvasElement::paint():
>+           canvasContext().paintRenderingResultsToCanvas(buffer());
>+           context().drawImageBuffer(buffer());
>+           canvasContext().markLayerComposited();
>+
>+        The markLayerComposited() would incorrectly mark the WebGL context compositing
>+        being done, but there was no compositing actually happening. The GPU-side
>+        display buffer would be incorrect. Also, there is nothing to be done at
>+        this stage, as the compositing of WebGL context itself is already
>+        finished at WebGL context paintRenderingResultsToCanvas() return.
>+
>+        Instead, add CanvasRenderingContext::prepareForDisplayWithPaint() which signals that next
>+        paintRenderingResultsToCanvas() is a display operation. This can be used to to detect the
>+        paintRenderingResultsToCanvas() in which we must present the drawing buffer as
>+        display buffer.
>+
>+        Implement the display buffer read with OpenGL.
>+
>+        Refactor the drawing buffer read code to be able to reuse the read code
>+        for the display buffer read. The refactored code reduces redundant the
>+        allocations of full-screen malloc buffers and ensures allocation results are
>+        checked instead of crashing with nullptr derefs when OOM happens. Fixes
>+        errors such as rdar://67553531 (CrashTracer: com.apple.WebKit.WebContent at
>+        WebCore: WebCore::GraphicsContextGLOpenGL::paintRenderingResultsToCanvas).
>+        Removes RGBA->BGRA->RGBA conversions from
>+        GraphicsContextGLOpenGL::paintRenderingResultsToImageData().
>+        Removes manual alpha premultiplication and makes CG draw with unpremultiplied
>+        alpha.
>+        Changes Cairo variant of GraphicsContextGLOpenGL to convert manually RGBA->BGRA
>+        instead of (big) OpenGL driver doing it in case of non-NVIDIA platforms.
>+
>+        No new tests, the snapshot / sw+hw drawing is not testable at the moment.
>+
>+        * Modules/webgpu/GPUCanvasContext.cpp:
>+        (WebCore::GPUCanvasContext::configureSwapChain):
>+        (WebCore::GPUCanvasContext::prepareForDisplayWithPaint):
>+        (WebCore::GPUCanvasContext::paintRenderingResultsToCanvas):
>+        * Modules/webgpu/GPUCanvasContext.h:
>+        * html/HTMLCanvasElement.cpp:
>+        (WebCore::HTMLCanvasElement::paint):
>+        * html/HTMLCanvasElement.h:
>+        * html/canvas/CanvasRenderingContext.h:
>+        (WebCore::CanvasRenderingContext::prepareForDisplayWithPaint):
>+        * html/canvas/GPUBasedCanvasRenderingContext.h:
>+        * html/canvas/WebGLRenderingContextBase.cpp:
>+        (WebCore::WebGLRenderingContextBase::initializeNewContext):
>+        (WebCore::WebGLRenderingContextBase::prepareForDisplayWithPaint):
>+        (WebCore::WebGLRenderingContextBase::paintRenderingResultsToCanvas):
>+        (WebCore::WebGLRenderingContextBase::validateElementArraySize):
>+        (WebCore::WebGLRenderingContextBase::validateIndexArrayPrecise):
>+        (WebCore::WebGLRenderingContextBase::validateDrawElements):
>+        (WebCore::WebGLRenderingContextBase::vertexAttribfvImpl):
>+        (WebCore::WebGLRenderingContextBase::initVertexAttrib0):
>+        * html/canvas/WebGLRenderingContextBase.h:
>+        * platform/graphics/GraphicsContextGL.h:
>+        * platform/graphics/RemoteGraphicsContextGLProxyBase.cpp:
>+        * platform/graphics/RemoteGraphicsContextGLProxyBase.h:
>+        * platform/graphics/angle/GraphicsContextGLANGLE.cpp:
>+        (WebCore::GraphicsContextGLOpenGL::readPixelsForPaintResults):
>+        (WebCore::GraphicsContextGLOpenGL::readRenderingResults):
>+        (WebCore::GraphicsContextGLOpenGL::reshape):
>+        (WebCore::GraphicsContextGLOpenGL::getProgramInfoLog):
>+        (WebCore::GraphicsContextGLOpenGL::getShaderInfoLog):
>+        * platform/graphics/angle/GraphicsContextGLANGLEUtilities.h:
>+        (WebCore::ScopedRestoreTextureBinding::ScopedRestoreTextureBinding):
>+        (WebCore::ScopedBufferBinding::ScopedBufferBinding):
>+        (WebCore::ScopedBufferBinding::~ScopedBufferBinding):
>+        (WebCore::ScopedBufferBinding::query):
>+        (WebCore::ScopedRestoreReadFramebufferBinding::ScopedRestoreReadFramebufferBinding):
>+        (WebCore::ScopedRestoreReadFramebufferBinding::markBindingChanged):
>+        (WebCore::ScopedRestoreReadFramebufferBinding::bindFramebuffer):
>+        (WebCore::ScopedRestoreReadFramebufferBinding::~ScopedRestoreReadFramebufferBinding):
>+        (WebCore::ScopedPixelStorageMode::ScopedPixelStorageMode):
>+        (WebCore::ScopedPixelStorageMode::~ScopedPixelStorageMode):
>+        (WebCore::ScopedPixelStorageMode::pixelStore):
>+        (WebCore::ScopedPixelStorageMode::operator GLint const):
>+        (WebCore::ScopedTexture::ScopedTexture):
>+        (WebCore::ScopedTexture::~ScopedTexture):
>+        (WebCore::ScopedTexture::operator GLuint const):
>+        (WebCore::ScopedFramebuffer::ScopedFramebuffer):
>+        (WebCore::ScopedFramebuffer::~ScopedFramebuffer):
>+        (WebCore::ScopedFramebuffer::operator GLuint const):
>+        * platform/graphics/cairo/GraphicsContextGLCairo.cpp:
>+        (WebCore::GraphicsContextGLOpenGL::paintToCanvas):
>+        * platform/graphics/cg/GraphicsContextGLCG.cpp:
>+        (WebCore::releaseImageData):
>+        (WebCore::GraphicsContextGLOpenGL::paintToCanvas):
>+        * platform/graphics/cocoa/GraphicsContextGLIOSurfaceSwapChain.h:
>+        * platform/graphics/cocoa/GraphicsContextGLOpenGLCocoa.mm:
>+        (WebCore::GraphicsContextGLOpenGL::allowOfflineRenderers const):
>+        (WebCore::GraphicsContextGLOpenGL::readCompositedResults):
>+        * platform/graphics/cocoa/WebGLLayer.mm:
>+        * platform/graphics/opengl/GraphicsContextGLOpenGL.cpp:
>+        (WebCore::GraphicsContextGLOpenGL::paintRenderingResultsToCanvas):
>+        (WebCore::GraphicsContextGLOpenGL::paintCompositedResultsToCanvas):
>+        (WebCore::GraphicsContextGLOpenGL::paintRenderingResultsToImageData):
>+        (WebCore::GraphicsContextGLOpenGL::readCompositedResults):
>+        * platform/graphics/opengl/GraphicsContextGLOpenGL.h:
>+        * platform/graphics/opengl/GraphicsContextGLOpenGLBase.cpp:
>+        (WebCore::GraphicsContextGLOpenGL::readPixelsForPaintResults):
>+        * platform/graphics/opengl/GraphicsContextGLOpenGLCommon.cpp:
>+        (WebCore::GraphicsContextGLOpenGL::readRenderingResults):
>+        (WebCore::GraphicsContextGLOpenGL::reshape):
>+        (WebCore::GraphicsContextGLOpenGL::blendFunc):
>+        (WebCore::GraphicsContextGLOpenGL::compileShader):
>+        (WebCore::GraphicsContextGLOpenGL::getActiveAttribImpl):
>+        (WebCore::GraphicsContextGLOpenGL::getActiveAttrib):
>+        (WebCore::GraphicsContextGLOpenGL::getActiveUniformImpl):
>+        (WebCore::GraphicsContextGLOpenGL::getActiveUniform):
>+        (WebCore::GraphicsContextGLOpenGL::originalSymbolName):
>+        (WebCore::GraphicsContextGLOpenGL::mappedSymbolName):
>+        (WebCore::GraphicsContextGLOpenGL::deleteVertexArray):
>+        (WebCore::GraphicsContextGLOpenGL::isVertexArray):
>+        (WebCore::GraphicsContextGLOpenGL::getNonBuiltInActiveSymbolCount):
>+        (WebCore::GraphicsContextGLOpenGL::getUnmangledInfoLog):
>+        (WebCore::GraphicsContextGLOpenGL::getShaderi):
>+        (WebCore::GraphicsContextGLOpenGL::getShaderInfoLog):
>+        (WebCore::GraphicsContextGLOpenGL::getShaderSource):
>+        * platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp:
>+        (WebCore::GraphicsContextGLOpenGL::readPixelsForPaintResults):
>+
> 2020-12-14  Lauro Moura  <lmoura@igalia.com>
> 
>         REGRESSSION(270435) [GStreamer] Many media source tests failing and timing out
>diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
>index 30328cf6e845f753e642b453b86311817d4c06c9..e0899a92bc20c359ba807b2810b0dd89eb22dc9e 100644
>--- a/Source/WebKit/ChangeLog
>+++ b/Source/WebKit/ChangeLog
>@@ -1,3 +1,20 @@
>+2020-12-17  Kimmo Kinnunen  <kkinnunen@apple.com>
>+
>+        REGRESSION (r268386): Snapshots of WebGL content in the tab picker don't work (black map on Google Maps)
>+        https://bugs.webkit.org/show_bug.cgi?id=219946
>+        <rdar://problem/72013784>
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Add dummy implementations of GraphicsContextGL::paintCompositedResultsToCanvas.
>+        Painting to canvas is not implemented yet for the remote GraphicsContextGL implementation.
>+
>+        * GPUProcess/graphics/RemoteGraphicsContextGLCocoa.cpp:
>+        (WebKit::RemoteGraphicsContextGLCocoa::displayBuffer const):
>+        * WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.cpp:
>+        (WebKit::RemoteGraphicsContextGLProxy::paintCompositedResultsToCanvas):
>+        * WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.h:
>+
> 2020-12-13  Yusuke Suzuki  <ysuzuki@apple.com>
> 
>         [JSC] Introduce vmEntryCustomAccessor and vmEntryHostFunction for JITCage
>diff --git a/Source/WebCore/Modules/webgpu/GPUCanvasContext.cpp b/Source/WebCore/Modules/webgpu/GPUCanvasContext.cpp
>index e30350b462a0fed44668bf896029293e1178e887..38b1528ffc3a9525850a94d65ed2794a4d804c35 100644
>--- a/Source/WebCore/Modules/webgpu/GPUCanvasContext.cpp
>+++ b/Source/WebCore/Modules/webgpu/GPUCanvasContext.cpp
>@@ -90,10 +90,18 @@ void GPUCanvasContext::reshape(int width, int height)
>     notifyCanvasContentChanged();
> }
> 
>-void GPUCanvasContext::markLayerComposited()
>+void GPUCanvasContext::prepareForDisplayWithPaint()
> {
>-    if (m_swapChain && m_swapChain->swapChain())
>+    m_isDisplayingWithPaint = true;
>+}
>+
>+void GPUCanvasContext::paintRenderingResultsToCanvas()
>+{
>+    // FIXME: Unimplemented.
>+    if (m_isDisplayingWithPaint && m_swapChain && m_swapChain->swapChain()) {
>         m_swapChain->swapChain()->present();
>+        m_isDisplayingWithPaint = false;
>+    }
> }
> 
> } // namespace WebCore
>diff --git a/Source/WebCore/Modules/webgpu/GPUCanvasContext.h b/Source/WebCore/Modules/webgpu/GPUCanvasContext.h
>index 6df20b4a647f6a1878b38156c2d0710765432a8d..9b0fe7b0d08ce93c7eca8694a00d1632e13d0c98 100644
>--- a/Source/WebCore/Modules/webgpu/GPUCanvasContext.h
>+++ b/Source/WebCore/Modules/webgpu/GPUCanvasContext.h
>@@ -53,13 +53,15 @@ private:
>     bool isWebGPU() const final { return true; }
>     PlatformLayer* platformLayer() const final;
>     void reshape(int width, int height) final;
>-    void markLayerComposited() final;
>+    void prepareForDisplayWithPaint() final;
>+    void paintRenderingResultsToCanvas() final;
> 
>     // ActiveDOMObject.
>     const char* activeDOMObjectName() const final { return "GPUCanvasContext"; }
>     // FIXME: Stubs.
>     void stop() final { }
> 
>+    bool m_isDisplayingWithPaint { false };
>     RefPtr<WebGPUSwapChain> m_swapChain;
> };
> 
>diff --git a/Source/WebCore/html/HTMLCanvasElement.cpp b/Source/WebCore/html/HTMLCanvasElement.cpp
>index 169caa90024d26772305062f598d12ccddbab3ff..54b3401de90f22a89b69627fb401d8555d567e70 100644
>--- a/Source/WebCore/html/HTMLCanvasElement.cpp
>+++ b/Source/WebCore/html/HTMLCanvasElement.cpp
>@@ -642,20 +642,17 @@ void HTMLCanvasElement::paint(GraphicsContext& context, const LayoutRect& r)
> 
>         if (m_context) {
>             shouldPaint = paintsIntoCanvasBuffer() || document().printing() || m_isSnapshotting;
>-            if (shouldPaint)
>+            if (shouldPaint) {
>+                m_context->prepareForDisplayWithPaint();
>                 m_context->paintRenderingResultsToCanvas();
>+            }
>         }
> 
>         if (shouldPaint) {
>             if (hasCreatedImageBuffer()) {
>-                if (m_presentedImage)
>-                    context.drawImage(*m_presentedImage, snappedIntRect(r), renderer()->imageOrientation());
>-                else if (ImageBuffer* imageBuffer = buffer())
>+                if (ImageBuffer* imageBuffer = buffer())
>                     context.drawImageBuffer(*imageBuffer, snappedIntRect(r));
>             }
>-
>-            if (isGPUBased())
>-                downcast<GPUBasedCanvasRenderingContext>(*m_context).markLayerComposited();
>         }
>     }
> 
>@@ -668,19 +665,6 @@ bool HTMLCanvasElement::isGPUBased() const
>     return m_context && m_context->isGPUBased();
> }
> 
>-void HTMLCanvasElement::makePresentationCopy()
>-{
>-    if (!m_presentedImage) {
>-        // The buffer contains the last presented data, so save a copy of it.
>-        m_presentedImage = buffer()->copyImage(CopyBackingStore, PreserveResolution::Yes);
>-    }
>-}
>-
>-void HTMLCanvasElement::clearPresentationCopy()
>-{
>-    m_presentedImage = nullptr;
>-}
>-
> void HTMLCanvasElement::setSurfaceSize(const IntSize& size)
> {
>     CanvasBase::setSize(size);
>diff --git a/Source/WebCore/html/HTMLCanvasElement.h b/Source/WebCore/html/HTMLCanvasElement.h
>index aeb0189749b58333748404c95bafed04528f9cef..9c9230f5fbb7e6de4b69fd5c86beee4064b442b8 100644
>--- a/Source/WebCore/html/HTMLCanvasElement.h
>+++ b/Source/WebCore/html/HTMLCanvasElement.h
>@@ -115,8 +115,6 @@ public:
>     Image* copiedImage() const final;
>     void clearCopiedImage() const final;
>     RefPtr<ImageData> getImageData();
>-    void makePresentationCopy();
>-    void clearPresentationCopy();
> 
>     SecurityOrigin* securityOrigin() const final;
> 
>@@ -199,7 +197,6 @@ private:
> 
>     bool m_isSnapshotting { false };
> 
>-    mutable RefPtr<Image> m_presentedImage;
>     mutable RefPtr<Image> m_copiedImage; // FIXME: This is temporary for platforms that have to copy the image buffer to render (and for CSSCanvasValue).
> };
> 
>@@ -216,4 +213,3 @@ private:
>     static bool checkTagName(const WebCore::EventTarget& target) { return is<WebCore::Node>(target) && checkTagName(downcast<WebCore::Node>(target)); }
> };
> }
>-
>diff --git a/Source/WebCore/html/canvas/CanvasRenderingContext.h b/Source/WebCore/html/canvas/CanvasRenderingContext.h
>index acf83bb72dca701c0fcc6738c1d86ca1178fd494..f38863f78fee3ff89929c74c47ca2e5341990055 100644
>--- a/Source/WebCore/html/canvas/CanvasRenderingContext.h
>+++ b/Source/WebCore/html/canvas/CanvasRenderingContext.h
>@@ -71,6 +71,9 @@ public:
>     virtual bool isOffscreen2d() const { return false; }
>     virtual bool isPaint() const { return false; }
> 
>+    // Called before paintRenderingResultsToCanvas if paintRenderingResultsToCanvas is
>+    // used for compositing purposes.
>+    virtual void prepareForDisplayWithPaint() { }
>     virtual void paintRenderingResultsToCanvas() {}
>     virtual PlatformLayer* platformLayer() const { return 0; }
> 
>diff --git a/Source/WebCore/html/canvas/GPUBasedCanvasRenderingContext.h b/Source/WebCore/html/canvas/GPUBasedCanvasRenderingContext.h
>index 47a02eb706ce45d88f19754bb7d8beff9b1f942c..890cd723501e04e28e82f77a0b69dbed59a48595 100644
>--- a/Source/WebCore/html/canvas/GPUBasedCanvasRenderingContext.h
>+++ b/Source/WebCore/html/canvas/GPUBasedCanvasRenderingContext.h
>@@ -50,8 +50,6 @@ public:
>     }
> 
>     virtual void reshape(int width, int height) = 0;
>-    virtual void markLayerComposited() = 0;
>-
> protected:
>     explicit GPUBasedCanvasRenderingContext(CanvasBase&);
> 
>diff --git a/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp b/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp
>index 013b89af4888b87c0f648e52cb561cdb91c54973..30d9e7e91a43c39e812f7bb52b51068bc9367559 100644
>--- a/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp
>+++ b/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp
>@@ -1199,11 +1199,10 @@ void WebGLRenderingContextBase::restoreStateAfterClear()
>     m_context->depthMask(m_depthMask);
> }
> 
>-void WebGLRenderingContextBase::markLayerComposited()
>+
>+void WebGLRenderingContextBase::prepareForDisplayWithPaint()
> {
>-    if (isContextLostOrPending())
>-        return;
>-    m_context->markLayerComposited();
>+    m_isDisplayingWithPaint = true;
> }
> 
> void WebGLRenderingContextBase::paintRenderingResultsToCanvas()
>@@ -1211,18 +1210,17 @@ void WebGLRenderingContextBase::paintRenderingResultsToCanvas()
>     if (isContextLostOrPending())
>         return;
> 
>-    if (auto* canvas = htmlCanvas()) {
>-        if (canvas->document().printing() || (canvas->isSnapshotting() && canvas->document().page()->isVisible()))
>-            canvas->clearPresentationCopy();
>-
>-        // Until the canvas is written to by the application, the clear that
>-        // happened after it was composited should be ignored by the compositor.
>-        if (m_context->layerComposited() && !m_attributes.preserveDrawingBuffer) {
>-            m_context->paintRenderingResultsToCanvas(canvas->buffer());
>-
>-            canvas->makePresentationCopy();
>-        } else
>-            canvas->clearPresentationCopy();
>+    if (m_isDisplayingWithPaint) {
>+        bool canvasContainsDisplayBuffer = !m_markedCanvasDirty;
>+        prepareForDisplay();
>+        m_isDisplayingWithPaint = false;
>+        if (!canvasContainsDisplayBuffer) {
>+            auto& base = canvasBase();
>+            base.clearCopiedImage();
>+            m_markedCanvasDirty = false;
>+            m_context->paintCompositedResultsToCanvas(base.buffer());
>+        }
>+        return;
>     }
> 
>     clearIfComposited(ClearCallerOther);
>diff --git a/Source/WebCore/html/canvas/WebGLRenderingContextBase.h b/Source/WebCore/html/canvas/WebGLRenderingContextBase.h
>index 30a8557d8688e2ea495db716f08be609ec3b4e8a..e8e90cfba16b14dd148c98e069e500ecde2b550f 100644
>--- a/Source/WebCore/html/canvas/WebGLRenderingContextBase.h
>+++ b/Source/WebCore/html/canvas/WebGLRenderingContextBase.h
>@@ -384,8 +384,8 @@ public:
> 
>     void reshape(int width, int height) override;
> 
>-    void markLayerComposited() final;
>-    void paintRenderingResultsToCanvas() override;
>+    void prepareForDisplayWithPaint() final;
>+    void paintRenderingResultsToCanvas() final;
>     RefPtr<ImageData> paintRenderingResultsToImageData();
> 
>     void removeSharedObject(WebGLSharedObject&);
>@@ -668,6 +668,7 @@ protected:
>     bool isContextLostOrPending();
> 
>     bool m_compositingResultsNeedUpdating { false };
>+    bool m_isDisplayingWithPaint { false };
> 
>     // Enabled extension objects.
>     // FIXME: Move some of these to WebGLRenderingContext, the ones not needed for WebGL2
>diff --git a/Source/WebCore/platform/graphics/GraphicsContextGL.h b/Source/WebCore/platform/graphics/GraphicsContextGL.h
>index 223a5c9bf1697f25f112dbcc186f819b7ce1de45..aa8ff2368dffd89ceab6a443330db4516a18f9f5 100644
>--- a/Source/WebCore/platform/graphics/GraphicsContextGL.h
>+++ b/Source/WebCore/platform/graphics/GraphicsContextGL.h
>@@ -1292,7 +1292,7 @@ public:
>     // the context.
>     virtual void paintRenderingResultsToCanvas(ImageBuffer*) = 0;
>     virtual RefPtr<ImageData> paintRenderingResultsToImageData() = 0;
>-    virtual bool paintCompositedResultsToCanvas(ImageBuffer*) = 0;
>+    virtual void paintCompositedResultsToCanvas(ImageBuffer*) = 0;
> 
>     // FIXME: this should be removed. The layer should be marked composited by
>     // preparing for display, so that canvas image buffer and the layer agree
>diff --git a/Source/WebCore/platform/graphics/RemoteGraphicsContextGLProxyBase.cpp b/Source/WebCore/platform/graphics/RemoteGraphicsContextGLProxyBase.cpp
>index 60f7a947efcbb37156c098e0b5ee33c3b62b849b..36faaa7e46622baf3a123fbe95ee94be6409d54c 100644
>--- a/Source/WebCore/platform/graphics/RemoteGraphicsContextGLProxyBase.cpp
>+++ b/Source/WebCore/platform/graphics/RemoteGraphicsContextGLProxyBase.cpp
>@@ -99,11 +99,6 @@ GCGLbitfield RemoteGraphicsContextGLProxyBase::getBuffersToAutoClear() const
>     return m_buffersToAutoClear;
> }
> 
>-bool RemoteGraphicsContextGLProxyBase::paintCompositedResultsToCanvas(ImageBuffer*)
>-{
>-    return false;
>-}
>-
> void RemoteGraphicsContextGLProxyBase::enablePreserveDrawingBuffer()
> {
>     // Redeclared for export reasons.
>diff --git a/Source/WebCore/platform/graphics/RemoteGraphicsContextGLProxyBase.h b/Source/WebCore/platform/graphics/RemoteGraphicsContextGLProxyBase.h
>index 726aaf6c6a0f62ff282e5b8d202a1294e1de8571..2471d4e25c9aa200ec743b1fe0c6468b0c9a5083 100644
>--- a/Source/WebCore/platform/graphics/RemoteGraphicsContextGLProxyBase.h
>+++ b/Source/WebCore/platform/graphics/RemoteGraphicsContextGLProxyBase.h
>@@ -67,7 +67,6 @@ public:
>     bool layerComposited() const final;
>     void setBuffersToAutoClear(GCGLbitfield) final;
>     GCGLbitfield getBuffersToAutoClear() const final;
>-    bool paintCompositedResultsToCanvas(ImageBuffer*) final;
>     void markLayerComposited() final;
>     void enablePreserveDrawingBuffer() final;
> 
>diff --git a/Source/WebCore/platform/graphics/angle/GraphicsContextGLANGLE.cpp b/Source/WebCore/platform/graphics/angle/GraphicsContextGLANGLE.cpp
>index 309a5309b640a3d6a28141ca7b1a75db46e9f951..b5043b74636f7885c5d80c0773555d71200023d5 100644
>--- a/Source/WebCore/platform/graphics/angle/GraphicsContextGLANGLE.cpp
>+++ b/Source/WebCore/platform/graphics/angle/GraphicsContextGLANGLE.cpp
>@@ -31,6 +31,7 @@
> 
> #include "ANGLEHeaders.h"
> #include "ExtensionsGLANGLE.h"
>+#include "GraphicsContextGLANGLEUtilities.h"
> #include "ImageBuffer.h"
> #include "ImageData.h"
> #include "IntRect.h"
>@@ -46,9 +47,6 @@
> #include <wtf/text/CString.h>
> #include <wtf/text/StringBuilder.h>
> 
>-#if USE(ACCELERATE)
>-#include <Accelerate/Accelerate.h>
>-#endif
> 
> #if ENABLE(VIDEO) && USE(AVFOUNDATION)
> #include "GraphicsContextGLCVANGLE.h"
>@@ -64,30 +62,6 @@ static const char* packedDepthStencilExtensionName = "GL_OES_packed_depth_stenci
> 
> namespace {
> 
>-class ScopedResetBufferBinding {
>-    WTF_MAKE_NONCOPYABLE(ScopedResetBufferBinding);
>-public:
>-    ScopedResetBufferBinding(bool shouldDoWork, GLenum bindingPointQuery, GLenum bindingPoint)
>-        : m_bindingPointQuery(bindingPointQuery)
>-        , m_bindingPoint(bindingPoint)
>-    {
>-        if (shouldDoWork)
>-            gl::GetIntegerv(m_bindingPointQuery, &m_bindingValue);
>-        if (m_bindingValue)
>-            gl::BindBuffer(m_bindingPoint, 0);
>-    }
>-
>-    ~ScopedResetBufferBinding()
>-    {
>-        if (m_bindingValue)
>-            gl::BindBuffer(m_bindingPoint, m_bindingValue);
>-    }
>-
>-private:
>-    GLint m_bindingPointQuery { 0 };
>-    GLint m_bindingPoint { 0 };
>-    GLint m_bindingValue { 0 };
>-};
> 
> } // namespace anonymous
> 
>@@ -102,36 +76,29 @@ static void wipeAlphaChannelFromPixels(int width, int height, unsigned char* pix
> }
> #endif
> 
>-void GraphicsContextGLOpenGL::readPixelsAndConvertToBGRAIfNecessary(int x, int y, int width, int height, unsigned char* pixels)
>-{
>-    // NVIDIA drivers have a bug where calling readPixels in BGRA can return the wrong values for the alpha channel when the alpha is off for the context.
>-    gl::ReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
>-#if USE(ACCELERATE)
>-    vImage_Buffer src;
>-    src.height = height;
>-    src.width = width;
>-    src.rowBytes = width * 4;
>-    src.data = pixels;
>-
>-    vImage_Buffer dest;
>-    dest.height = height;
>-    dest.width = width;
>-    dest.rowBytes = width * 4;
>-    dest.data = pixels;
>-
>-    // Swap pixel channels from RGBA to BGRA.
>-    const uint8_t map[4] = { 2, 1, 0, 3 };
>-    vImagePermuteChannels_ARGB8888(&src, &dest, map, kvImageNoFlags);
>-#else
>-    int totalBytes = width * height * 4;
>-    for (int i = 0; i < totalBytes; i += 4)
>-        std::swap(pixels[i], pixels[i + 2]);
>-#endif
>-
>+RefPtr<ImageData> GraphicsContextGLOpenGL::readPixelsForPaintResults()
>+{
>+    auto imageData = ImageData::create(getInternalFramebufferSize());
>+    if (!imageData)
>+        return nullptr;
>+    ScopedPixelStorageMode packAlignment(GL_PACK_ALIGNMENT);
>+    if (packAlignment > 4)
>+        packAlignment.pixelStore(4);
>+    ScopedPixelStorageMode packRowLength(GL_PACK_ROW_LENGTH, 0, m_isForWebGL2);
>+    ScopedPixelStorageMode packSkipRows(GL_PACK_SKIP_ROWS, 0, m_isForWebGL2);
>+    ScopedPixelStorageMode packSkipPixels(GL_PACK_SKIP_PIXELS, 0, m_isForWebGL2);
>+    ScopedBufferBinding scopedPixelPackBufferReset(GL_PIXEL_PACK_BUFFER, 0, m_isForWebGL2);
>+
>+    gl::ReadnPixelsRobustANGLE(0, 0, imageData->width(), imageData->height(), GL_RGBA, GL_UNSIGNED_BYTE, imageData->data()->byteLength(), nullptr, nullptr, nullptr, imageData->data()->data());
>+    // FIXME: Rendering to GL_RGB textures with a IOSurface bound to the texture image leaves
>+    // the alpha in the IOSurface in incorrect state. Also ANGLE gl::ReadPixels will in some
>+    // cases expose the non-255 values.
>+    // https://bugs.webkit.org/show_bug.cgi?id=215804
> #if PLATFORM(MAC) || PLATFORM(IOS_FAMILY)
>     if (!contextAttributes().alpha)
>-        wipeAlphaChannelFromPixels(width, height, pixels);
>+        wipeAlphaChannelFromPixels(imageData->width(), imageData->height(), imageData->data()->data());
> #endif
>+    return imageData;
> }
> 
> void GraphicsContextGLOpenGL::validateAttributes()
>@@ -510,64 +477,6 @@ void GraphicsContextGLOpenGL::validateDepthStencil(const char* packedDepthStenci
>     }
> }
> 
>-void GraphicsContextGLOpenGL::paintRenderingResultsToCanvas(ImageBuffer* imageBuffer)
>-{
>-    Checked<int, RecordOverflow> rowBytes = Checked<int, RecordOverflow>(m_currentWidth) * 4;
>-    if (rowBytes.hasOverflowed())
>-        return;
>-
>-    Checked<int, RecordOverflow> totalBytesChecked = rowBytes * m_currentHeight;
>-    if (totalBytesChecked.hasOverflowed())
>-        return;
>-    int totalBytes = totalBytesChecked.unsafeGet();
>-
>-    auto pixels = makeUniqueArray<unsigned char>(totalBytes);
>-    if (!pixels)
>-        return;
>-
>-    readRenderingResults(pixels.get(), totalBytes);
>-
>-    if (!contextAttributes().premultipliedAlpha) {
>-        for (int i = 0; i < totalBytes; i += 4) {
>-            // Premultiply alpha.
>-            pixels[i + 0] = std::min(255, pixels[i + 0] * pixels[i + 3] / 255);
>-            pixels[i + 1] = std::min(255, pixels[i + 1] * pixels[i + 3] / 255);
>-            pixels[i + 2] = std::min(255, pixels[i + 2] * pixels[i + 3] / 255);
>-        }
>-    }
>-
>-    paintToCanvas(pixels.get(), IntSize(m_currentWidth, m_currentHeight), imageBuffer->backendSize(), imageBuffer->context());
>-}
>-
>-bool GraphicsContextGLOpenGL::paintCompositedResultsToCanvas(ImageBuffer*)
>-{
>-    // Not needed at the moment, so return that nothing was done.
>-    return false;
>-}
>-
>-RefPtr<ImageData> GraphicsContextGLOpenGL::paintRenderingResultsToImageData()
>-{
>-    // Reading premultiplied alpha would involve unpremultiplying, which is
>-    // lossy.
>-    if (contextAttributes().premultipliedAlpha)
>-        return nullptr;
>-
>-    auto imageData = ImageData::create(IntSize(m_currentWidth, m_currentHeight));
>-    unsigned char* pixels = imageData->data()->data();
>-    Checked<int, RecordOverflow> totalBytesChecked = 4 * Checked<int, RecordOverflow>(m_currentWidth) * Checked<int, RecordOverflow>(m_currentHeight);
>-    if (totalBytesChecked.hasOverflowed())
>-        return imageData;
>-    int totalBytes = totalBytesChecked.unsafeGet();
>-
>-    readRenderingResults(pixels, totalBytes);
>-
>-    // Convert to RGBA.
>-    for (int i = 0; i < totalBytes; i += 4)
>-        std::swap(pixels[i], pixels[i + 2]);
>-
>-    return imageData;
>-}
>-
> void GraphicsContextGLOpenGL::prepareTexture()
> {
>     if (m_layerComposited)
>@@ -620,65 +529,15 @@ void GraphicsContextGLOpenGL::prepareTextureImpl()
> #endif
> }
> 
>-void GraphicsContextGLOpenGL::readRenderingResults(unsigned char *pixels, int pixelsSize)
>+RefPtr<ImageData> GraphicsContextGLOpenGL::readRenderingResults()
> {
>-    if (pixelsSize < m_currentWidth * m_currentHeight * 4)
>-        return;
>-
>-    if (!makeContextCurrent())
>-        return;
>-
>-
>-    GCGLenum framebufferTarget = m_isForWebGL2 ? GraphicsContextGL::READ_FRAMEBUFFER : GraphicsContextGL::FRAMEBUFFER;
>-
>-    bool mustRestoreFBO = false;
>+    ScopedRestoreReadFramebufferBinding fboBinding(m_isForWebGL2, m_state.boundReadFBO);
>     if (contextAttributes().antialias) {
>         resolveMultisamplingIfNecessary();
>-        gl::BindFramebuffer(framebufferTarget, m_fbo);
>-        mustRestoreFBO = true;
>-    } else {
>-        if (m_state.boundReadFBO != m_fbo) {
>-            mustRestoreFBO = true;
>-            gl::BindFramebuffer(framebufferTarget, m_fbo);
>-        }
>+        fboBinding.markBindingChanged();
>     }
>-
>-    GLint packAlignment = 4;
>-    bool mustRestorePackAlignment = false;
>-    gl::GetIntegerv(GL_PACK_ALIGNMENT, &packAlignment);
>-    if (packAlignment > 4) {
>-        gl::PixelStorei(GL_PACK_ALIGNMENT, 4);
>-        mustRestorePackAlignment = true;
>-    }
>-    GLint packRowLength = 0;
>-    GLint packSkipRows = 0;
>-    GLint packSkipPixels = 0;
>-    ScopedResetBufferBinding scopedPixelPackBufferReset(m_isForWebGL2, GL_PIXEL_PACK_BUFFER_BINDING, GL_PIXEL_PACK_BUFFER);
>-    if (m_isForWebGL2) {
>-        gl::GetIntegerv(GL_PACK_ROW_LENGTH, &packRowLength);
>-        if (packRowLength > 0)
>-            gl::PixelStorei(GL_PACK_ROW_LENGTH, 0);
>-        gl::GetIntegerv(GL_PACK_SKIP_ROWS, &packSkipRows);
>-        if (packSkipRows > 0)
>-            gl::PixelStorei(GL_PACK_SKIP_ROWS, 0);
>-        gl::GetIntegerv(GL_PACK_SKIP_PIXELS, &packSkipPixels);
>-        if (packSkipPixels > 0)
>-            gl::PixelStorei(GL_PACK_SKIP_PIXELS, 0);
>-    }
>-
>-    readPixelsAndConvertToBGRAIfNecessary(0, 0, m_currentWidth, m_currentHeight, pixels);
>-
>-    if (mustRestorePackAlignment)
>-        gl::PixelStorei(GL_PACK_ALIGNMENT, packAlignment);
>-    if (packRowLength > 0)
>-        gl::PixelStorei(GL_PACK_ROW_LENGTH, packRowLength);
>-    if (packSkipRows > 0)
>-        gl::PixelStorei(GL_PACK_SKIP_ROWS, packSkipRows);
>-    if (packSkipPixels > 0)
>-        gl::PixelStorei(GL_PACK_SKIP_PIXELS, packSkipPixels);
>-
>-    if (mustRestoreFBO)
>-        gl::BindFramebuffer(framebufferTarget, m_state.boundReadFBO);
>+    fboBinding.bindFramebuffer(m_fbo);
>+    return readPixelsForPaintResults();
> }
> 
> void GraphicsContextGLOpenGL::reshape(int width, int height)
>@@ -704,7 +563,7 @@ void GraphicsContextGLOpenGL::reshape(int width, int height)
> 
>     TemporaryANGLESetting scopedScissor(GL_SCISSOR_TEST, GL_FALSE);
>     TemporaryANGLESetting scopedDither(GL_DITHER, GL_FALSE);
>-    ScopedResetBufferBinding scopedPixelUnpackBufferReset(m_isForWebGL2, GL_PIXEL_UNPACK_BUFFER_BINDING, GL_PIXEL_UNPACK_BUFFER);
>+    ScopedBufferBinding scopedPixelUnpackBufferReset(GL_PIXEL_UNPACK_BUFFER, 0, m_isForWebGL2);
> 
>     bool mustRestoreFBO = reshapeFBOs(IntSize(width, height));
>     auto attrs = contextAttributes();
>diff --git a/Source/WebCore/platform/graphics/angle/GraphicsContextGLANGLEUtilities.h b/Source/WebCore/platform/graphics/angle/GraphicsContextGLANGLEUtilities.h
>index 21327ddafc3db5fed2e81326b1fa22c52869f151..4942a955456bf9448401c2e26b57fdb821cd4c51 100644
>--- a/Source/WebCore/platform/graphics/angle/GraphicsContextGLANGLEUtilities.h
>+++ b/Source/WebCore/platform/graphics/angle/GraphicsContextGLANGLEUtilities.h
>@@ -36,9 +36,9 @@ namespace WebCore {
> class ScopedRestoreTextureBinding {
>     WTF_MAKE_NONCOPYABLE(ScopedRestoreTextureBinding);
> public:
>-    ScopedRestoreTextureBinding(GCGLenum bindingPointQuery, GCGLenum bindingPoint, bool condition = true)
>+    ScopedRestoreTextureBinding(GLenum bindingPointQuery, GLenum bindingPoint, bool condition = true)
>     {
>-        ASSERT(bindingPoint != static_cast<GCGLenum>(0u));
>+        ASSERT(bindingPoint != static_cast<GLenum>(0u));
>         if (condition) {
>             m_bindingPoint = bindingPoint;
>             gl::GetIntegerv(bindingPointQuery, reinterpret_cast<GLint*>(&m_bindingValue));
>@@ -56,6 +56,153 @@ private:
>     GLuint m_bindingValue { 0u };
> };
> 
>+
>+class ScopedBufferBinding {
>+    WTF_MAKE_NONCOPYABLE(ScopedBufferBinding);
>+public:
>+    ScopedBufferBinding(GLenum bindingPoint, GLuint bindingValue, bool condition = true)
>+    {
>+        if (!condition)
>+            return;
>+        gl::GetIntegerv(query(bindingPoint), reinterpret_cast<GLint*>(&m_bindingValue));
>+        if (bindingValue == m_bindingValue)
>+            return;
>+        m_bindingPoint = bindingPoint;
>+        gl::BindBuffer(m_bindingPoint, bindingValue);
>+    }
>+
>+    ~ScopedBufferBinding()
>+    {
>+        if (m_bindingPoint)
>+            gl::BindBuffer(m_bindingPoint, m_bindingValue);
>+    }
>+
>+private:
>+    static constexpr GLenum query(GLenum bindingPoint)
>+    {
>+        if (bindingPoint == GL_PIXEL_PACK_BUFFER)
>+            return GL_PIXEL_PACK_BUFFER_BINDING;
>+        ASSERT(bindingPoint == GL_PIXEL_UNPACK_BUFFER);
>+        return GL_PIXEL_UNPACK_BUFFER_BINDING;
>+    }
>+    GLint m_bindingPoint { 0 };
>+    GLuint m_bindingValue { 0u };
>+};
>+class ScopedRestoreReadFramebufferBinding {
>+    WTF_MAKE_NONCOPYABLE(ScopedRestoreReadFramebufferBinding);
>+public:
>+    ScopedRestoreReadFramebufferBinding(bool isForWebGL2, GLuint restoreValue)
>+        : m_framebufferTarget(isForWebGL2 ? GL_READ_FRAMEBUFFER : GL_FRAMEBUFFER)
>+        , m_bindingValue(restoreValue)
>+    {
>+    }
>+    ScopedRestoreReadFramebufferBinding(bool isForWebGL2, GLuint restoreValue, GLuint value)
>+        : m_framebufferTarget(isForWebGL2 ? GL_READ_FRAMEBUFFER : GL_FRAMEBUFFER)
>+        , m_bindingValue(restoreValue)
>+    {
>+        bindFramebuffer(value);
>+    }
>+    void markBindingChanged()
>+    {
>+        m_bindingChanged = true;
>+    }
>+    void bindFramebuffer(GLuint bindingValue)
>+    {
>+        if (!m_bindingChanged && m_bindingValue == bindingValue)
>+            return;
>+        gl::BindFramebuffer(m_framebufferTarget, bindingValue);
>+        m_bindingChanged = m_bindingValue != bindingValue;
>+    }
>+    ~ScopedRestoreReadFramebufferBinding()
>+    {
>+        if (m_bindingChanged)
>+            gl::BindFramebuffer(m_framebufferTarget, m_bindingValue);
>+    }
>+private:
>+    const GLenum m_framebufferTarget;
>+    GLuint m_bindingValue { 0u };
>+    bool m_bindingChanged { false };
>+};
>+
>+class ScopedPixelStorageMode {
>+    WTF_MAKE_NONCOPYABLE(ScopedPixelStorageMode);
>+public:
>+    explicit ScopedPixelStorageMode(GLenum name, bool condition = true)
>+        : m_name(condition ? name : 0)
>+    {
>+        if (m_name)
>+            gl::GetIntegerv(m_name, &m_originalValue);
>+    }
>+    ScopedPixelStorageMode(GLenum name, GLint value, bool condition = true)
>+        : m_name(condition ? name : 0)
>+    {
>+        if (m_name) {
>+            gl::GetIntegerv(m_name, &m_originalValue);
>+            pixelStore(value);
>+        }
>+    }
>+    ~ScopedPixelStorageMode()
>+    {
>+        if (m_name && m_valueChanged)
>+            gl::PixelStorei(m_name, m_originalValue);
>+    }
>+    void pixelStore(GLint value)
>+    {
>+        ASSERT(m_name);
>+        if (!m_valueChanged && m_originalValue == value)
>+            return;
>+        gl::PixelStorei(m_name, value);
>+        m_valueChanged = m_originalValue != value;
>+    }
>+    operator GLint() const
>+    {
>+        ASSERT(m_name && !m_valueChanged);
>+        return m_originalValue;
>+    }
>+private:
>+    const GLenum m_name;
>+    bool m_valueChanged { false };
>+    GLint m_originalValue { 0 };
>+};
>+
>+class ScopedTexture {
>+    WTF_MAKE_NONCOPYABLE(ScopedTexture);
>+public:
>+    ScopedTexture()
>+    {
>+        gl::GenTextures(1, &m_object);
>+    }
>+    ~ScopedTexture()
>+    {
>+        gl::DeleteTextures(1, &m_object);
>+    }
>+    operator GLuint() const
>+    {
>+        return m_object;
>+    }
>+private:
>+    GLuint m_object { 0u };
>+};
>+
>+class ScopedFramebuffer {
>+    WTF_MAKE_NONCOPYABLE(ScopedFramebuffer);
>+public:
>+    ScopedFramebuffer()
>+    {
>+        gl::GenFramebuffers(1, &m_object);
>+    }
>+    ~ScopedFramebuffer()
>+    {
>+        gl::DeleteFramebuffers(1, &m_object);
>+    }
>+    operator GLuint() const
>+    {
>+        return m_object;
>+    }
>+private:
>+    GLuint m_object { 0 };
>+};
>+
> }
> 
> #endif
>diff --git a/Source/WebCore/platform/graphics/cairo/GraphicsContextGLCairo.cpp b/Source/WebCore/platform/graphics/cairo/GraphicsContextGLCairo.cpp
>index 43cdac8b01cda0df062186f15003ea308fa20cd6..56f6b1a701b200c9868d282f07c376da110ce25e 100644
>--- a/Source/WebCore/platform/graphics/cairo/GraphicsContextGLCairo.cpp
>+++ b/Source/WebCore/platform/graphics/cairo/GraphicsContextGLCairo.cpp
>@@ -33,6 +33,7 @@
> #include "CairoUtilities.h"
> #include "GraphicsContextGLImageExtractor.h"
> #include "Image.h"
>+#include "ImageData.h"
> #include "ImageSource.h"
> #include "PlatformContextCairo.h"
> #include "RefPtrCairo.h"
>@@ -105,15 +106,30 @@ bool GraphicsContextGLImageExtractor::extractImage(bool premultiplyAlpha, bool i
>     return true;
> }
> 
>-void GraphicsContextGLOpenGL::paintToCanvas(const unsigned char* imagePixels, const IntSize& imageSize, const IntSize& canvasSize, GraphicsContext& context)
>+void GraphicsContextGLOpenGL::paintToCanvas(Ref<ImageData>&& imageData, const IntSize& canvasSize, GraphicsContext& context)
> {
>-    if (!imagePixels || imageSize.isEmpty() || canvasSize.isEmpty())
>+    ASSERT(!imageData->size().isEmpty());
>+    if (canvasSize.isEmpty())
>         return;
> 
>     PlatformContextCairo* platformContext = context.platformContext();
>     if (!platformContext)
>         return;
> 
>+    // Convert RGBA to BGRA. BGRA is CAIRO_FORMAT_ARGB32 on little-endian architectures.
>+    size_t totalBytes = imageData->data()->byteLength();
>+    uint8_t* pixels = imageData->data()->data();
>+    for (size_t i = 0; i < totalBytes; i += 4)
>+        std::swap(pixels[i], pixels[i + 2]);
>+
>+    if (!contextAttributes().premultipliedAlpha) {
>+        for (size_t i = 0; i < totalBytes; i += 4) {
>+            pixels[i + 0] = std::min(255, pixels[i + 0] * pixels[i + 3] / 255);
>+            pixels[i + 1] = std::min(255, pixels[i + 1] * pixels[i + 3] / 255);
>+            pixels[i + 2] = std::min(255, pixels[i + 2] * pixels[i + 3] / 255);
>+        }
>+    }
>+
>     cairo_t* cr = platformContext->cr();
>     platformContext->save();
> 
>@@ -122,10 +138,10 @@ void GraphicsContextGLOpenGL::paintToCanvas(const unsigned char* imagePixels, co
>     cairo_paint(cr);
> 
>     RefPtr<cairo_surface_t> imageSurface = adoptRef(cairo_image_surface_create_for_data(
>-        const_cast<unsigned char*>(imagePixels), CAIRO_FORMAT_ARGB32, imageSize.width(), imageSize.height(), imageSize.width() * 4));
>+        imageData->data()->data(), CAIRO_FORMAT_ARGB32, imageData->width(), imageData->height(), imageData->width() * 4));
> 
>     // OpenGL keeps the pixels stored bottom up, so we need to flip the image here.
>-    cairo_translate(cr, 0, imageSize.height());
>+    cairo_translate(cr, 0, imageData->height());
>     cairo_scale(cr, 1, -1);
> 
>     cairo_set_operator(cr, CAIRO_OPERATOR_OVER);
>diff --git a/Source/WebCore/platform/graphics/cg/GraphicsContextGLCG.cpp b/Source/WebCore/platform/graphics/cg/GraphicsContextGLCG.cpp
>index 68d5ac83d912e86efebff4239dfa06466300f1b4..e2e51fd0a060dad21b2d21a5285d40d473bc526a 100644
>--- a/Source/WebCore/platform/graphics/cg/GraphicsContextGLCG.cpp
>+++ b/Source/WebCore/platform/graphics/cg/GraphicsContextGLCG.cpp
>@@ -505,36 +505,35 @@ bool GraphicsContextGLImageExtractor::extractImage(bool premultiplyAlpha, bool i
>     return true;
> }
> 
>-static void releaseImageData(void*, const void* data, size_t)
>+static void releaseImageData(void* imageData, const void*, size_t)
> {
>-    fastFree(const_cast<void*>(data));
>+    reinterpret_cast<ImageData*>(imageData)->deref();
> }
> 
>-void GraphicsContextGLOpenGL::paintToCanvas(const unsigned char* imagePixels, const IntSize& imageSize, const IntSize& canvasSize, GraphicsContext& context)
>+void GraphicsContextGLOpenGL::paintToCanvas(Ref<ImageData>&& imageData, const IntSize& canvasSize, GraphicsContext& context)
> {
>-    if (!imagePixels || imageSize.isEmpty() || canvasSize.isEmpty())
>+    ASSERT(!imageData->size().isEmpty());
>+    if (canvasSize.isEmpty())
>         return;
>+    auto attrs = contextAttributes();
>+    // Input is GL_RGBA == kCGBitmapByteOrder32Big | kCGImageAlpha*Last.
>+    // GL_BGRA would be kCGBitmapByteOrder32Little | kCGImageAlpha*First.
>+    CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Big;
>+    if (!attrs.alpha)
>+        bitmapInfo |= kCGImageAlphaNoneSkipLast;
>+    else if (attrs.premultipliedAlpha)
>+        bitmapInfo |= kCGImageAlphaPremultipliedLast;
>+    else
>+        bitmapInfo |= kCGImageAlphaLast;
>+
>+    auto imageSize = imageData->size();
>     int rowBytes = imageSize.width() * 4;
>-    RetainPtr<CGDataProviderRef> dataProvider;
>-
>-    if (context.isAcceleratedContext()) {
>-        unsigned char* copiedPixels;
>-
>-        if (!tryFastCalloc(imageSize.height(), rowBytes).getValue(copiedPixels))
>-            return;
>-
>-        memcpy(copiedPixels, imagePixels, rowBytes * imageSize.height());
>-
>-        size_t dataSize = rowBytes * imageSize.height();
>-        verifyImageBufferIsBigEnough(copiedPixels, dataSize);
>-        dataProvider = adoptCF(CGDataProviderCreateWithData(0, copiedPixels, dataSize, releaseImageData));
>-    } else {
>         size_t dataSize = rowBytes * imageSize.height();
>+    uint8_t* imagePixels = imageData->data()->data();
>         verifyImageBufferIsBigEnough(imagePixels, dataSize);
>-        dataProvider = adoptCF(CGDataProviderCreateWithData(0, imagePixels, dataSize, 0));
>-    }
>+    RetainPtr<CGDataProviderRef> dataProvider = adoptCF(CGDataProviderCreateWithData(&imageData.leakRef(), imagePixels, dataSize, releaseImageData));
> 
>-    auto image = NativeImage::create(adoptCF(CGImageCreate(imageSize.width(), imageSize.height(), 8, 32, rowBytes, sRGBColorSpaceRef(), kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host,
>+    auto image = NativeImage::create(adoptCF(CGImageCreate(imageSize.width(), imageSize.height(), 8, 32, rowBytes, sRGBColorSpaceRef(), bitmapInfo,
>         dataProvider.get(), 0, false, kCGRenderingIntentDefault)));
> 
>     // CSS styling may cause the canvas's content to be resized on
>diff --git a/Source/WebCore/platform/graphics/cocoa/GraphicsContextGLIOSurfaceSwapChain.h b/Source/WebCore/platform/graphics/cocoa/GraphicsContextGLIOSurfaceSwapChain.h
>index d5e4168e31beb8f2bb774cf7de1e95f8d0b99619..4ded8e5f94982671746c9e7f533aac6b18ac6b0a 100644
>--- a/Source/WebCore/platform/graphics/cocoa/GraphicsContextGLIOSurfaceSwapChain.h
>+++ b/Source/WebCore/platform/graphics/cocoa/GraphicsContextGLIOSurfaceSwapChain.h
>@@ -63,6 +63,10 @@ public:
>     // Prepares the target for display with a contents buffer.
>     virtual void present(Buffer) = 0;
> 
>+    // Returns the most recent presented display buffer. The reference is valid until
>+    // next present, recycleBuffer or detachClient call.
>+    virtual const Buffer& displayBuffer() const = 0;
>+
>     // Detaches the client and returns the current contents buffer metadata handle.
>     // The if multiple buffers have been submitted, recycleBuffer must have been called before calling
>     // this.
>diff --git a/Source/WebCore/platform/graphics/cocoa/GraphicsContextGLOpenGLCocoa.mm b/Source/WebCore/platform/graphics/cocoa/GraphicsContextGLOpenGLCocoa.mm
>index 891e9783e25fd4784e36863b3e6e682c295cb424..dbe9c05d328b65c275ec9512046024f3da40c84a 100644
>--- a/Source/WebCore/platform/graphics/cocoa/GraphicsContextGLOpenGLCocoa.mm
>+++ b/Source/WebCore/platform/graphics/cocoa/GraphicsContextGLOpenGLCocoa.mm
>@@ -730,6 +730,37 @@ void GraphicsContextGLOpenGL::prepareForDisplay()
>     markLayerComposited();
> }
> 
>+RefPtr<ImageData> GraphicsContextGLOpenGL::readCompositedResults()
>+{
>+    auto& displayBuffer = m_swapChain->displayBuffer();
>+    if (!displayBuffer.surface || !displayBuffer.handle)
>+        return nullptr;
>+    if (displayBuffer.surface->size() != getInternalFramebufferSize())
>+        return nullptr;
>+    // Note: We are using GL to read the IOSurface. At the time of writing, there are no convinient
>+    // functions to convert the IOSurface pixel data to ImageData. The image data ends up being
>+    // drawn to a ImageBuffer, but at the time there's no functions to construct a NativeImage
>+    // out of an IOSurface in such a way that drawing the NativeImage would be guaranteed leave
>+    // the IOSurface be unrefenced after the draw call finishes.
>+    ScopedTexture texture;
>+    GCGLenum textureTarget = drawingBufferTextureTarget();
>+    ScopedRestoreTextureBinding restoreBinding(drawingBufferTextureTargetQuery(), textureTarget, textureTarget != TEXTURE_RECTANGLE_ARB);
>+    gl::BindTexture(textureTarget, texture);
>+    if (!EGL_BindTexImage(m_displayObj, displayBuffer.handle, EGL_BACK_BUFFER))
>+        return nullptr;
>+    gl::TexParameteri(textureTarget, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
>+    ScopedFramebuffer fbo;
>+    ScopedRestoreReadFramebufferBinding fboBinding(m_isForWebGL2, m_state.boundReadFBO, fbo);
>+    gl::FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, textureTarget, texture, 0);
>+    ASSERT(gl::CheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);
>+
>+    auto result = readPixelsForPaintResults();
>+
>+    EGLBoolean releaseOk = EGL_ReleaseTexImage(m_displayObj, displayBuffer.handle, EGL_BACK_BUFFER);
>+    ASSERT_UNUSED(releaseOk, releaseOk);
>+    return result;
>+}
>+
> }
> 
> #endif // ENABLE(WEBGL)
>diff --git a/Source/WebCore/platform/graphics/cocoa/WebGLLayer.mm b/Source/WebCore/platform/graphics/cocoa/WebGLLayer.mm
>index 38597e4a8f633a5ee5db74933022dc237fe7e47c..03138ef1430988d715a98b7777d3a5388a3299aa 100644
>--- a/Source/WebCore/platform/graphics/cocoa/WebGLLayer.mm
>+++ b/Source/WebCore/platform/graphics/cocoa/WebGLLayer.mm
>@@ -39,6 +39,10 @@ public:
>     explicit WebGLLayerSwapChain(WebGLLayer* layer)  : m_layer(layer) { };
>     ~WebGLLayerSwapChain() override = default;
>     void present(Buffer) override;
>+    const Buffer& displayBuffer() const override
>+    {
>+        return m_displayBuffer;
>+    }
>     Buffer recycleBuffer() override
>     {
>         if (m_spareBuffer.surface) {
>diff --git a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.cpp b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.cpp
>index 069d286ce4eba4829e0c7383e2f3e8bee72fe292..2feb74c2fad1b2a62ff60c6125d1b8fccf5db56a 100644
>--- a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.cpp
>+++ b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.cpp
>@@ -31,6 +31,8 @@
> #if ENABLE(WEBGL)
> 
> #include "ExtensionsGL.h"
>+#include "ImageBuffer.h"
>+#include "ImageData.h"
> #include <wtf/UniqueArray.h>
> 
> namespace WebCore {
>@@ -194,6 +196,50 @@ void GraphicsContextGLOpenGL::prepareForDisplay()
> }
> #endif
> 
>+void GraphicsContextGLOpenGL::paintRenderingResultsToCanvas(ImageBuffer* imageBuffer)
>+{
>+    if (!makeContextCurrent())
>+        return;
>+    if (getInternalFramebufferSize().isEmpty())
>+        return;
>+    auto imageData = readRenderingResults();
>+    if (!imageData)
>+        return;
>+    paintToCanvas(imageData.releaseNonNull(), imageBuffer->backendSize(), imageBuffer->context());
>+}
>+
>+void GraphicsContextGLOpenGL::paintCompositedResultsToCanvas(ImageBuffer* imageBuffer)
>+{
>+    if (!makeContextCurrent())
>+        return;
>+    if (getInternalFramebufferSize().isEmpty())
>+        return;
>+    auto imageData = readCompositedResults();
>+    if (!imageData)
>+        return;
>+    paintToCanvas(imageData.releaseNonNull(), imageBuffer->backendSize(), imageBuffer->context());
>+}
>+
>+RefPtr<ImageData> GraphicsContextGLOpenGL::paintRenderingResultsToImageData()
>+{
>+    if (!makeContextCurrent())
>+        return nullptr;
>+    if (getInternalFramebufferSize().isEmpty())
>+        return nullptr;
>+    // Reading premultiplied alpha would involve unpremultiplying, which is
>+    // lossy.
>+    if (contextAttributes().premultipliedAlpha)
>+        return nullptr;
>+    return readRenderingResults();
>+}
>+
>+#if !PLATFORM(COCOA)
>+RefPtr<ImageData> GraphicsContextGLOpenGL::readCompositedResults()
>+{
>+    return nullptr;
>+}
>+#endif
>+
> } // namespace WebCore
> 
> #endif // ENABLE(WEBGL)
>diff --git a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.h b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.h
>index f524de92dcd9a598b0fbef8d33b9c4409b8cd1b0..78096e2eb0876f9527c854790d1afa735120c8a9 100644
>--- a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.h
>+++ b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.h
>@@ -428,9 +428,6 @@ public:
>     void getActiveUniformBlockiv(GCGLuint program, GCGLuint uniformBlockIndex, GCGLenum pname, GCGLSpan<GCGLint> params) final;
> 
>     // Helper methods.
>-
>-    void paintToCanvas(const unsigned char* imagePixels, const IntSize& imageSize, const IntSize& canvasSize, GraphicsContext&);
>-
>     void markContextChanged() final;
>     void markLayerComposited() final;
>     bool layerComposited() const final;
>@@ -450,7 +447,7 @@ public:
> 
>     void paintRenderingResultsToCanvas(ImageBuffer*) final;
>     RefPtr<ImageData> paintRenderingResultsToImageData() final;
>-    bool paintCompositedResultsToCanvas(ImageBuffer*) final;
>+    void paintCompositedResultsToCanvas(ImageBuffer*) final;
> 
> #if USE(OPENGL) && ENABLE(WEBGL2)
>     void primitiveRestartIndex(GCGLuint);
>@@ -530,10 +527,11 @@ private:
>     // Did the most recent drawing operation leave the GPU in an acceptable state?
>     void checkGPUStatus();
> 
>-    // Read rendering results into a pixel array with the same format as the
>-    // backbuffer.
>-    void readRenderingResults(unsigned char* pixels, int pixelsSize);
>-    void readPixelsAndConvertToBGRAIfNecessary(int x, int y, int width, int height, unsigned char* pixels);
>+
>+    RefPtr<ImageData> readRenderingResults();
>+    RefPtr<ImageData> readCompositedResults();
>+    RefPtr<ImageData> readPixelsForPaintResults();
>+    void paintToCanvas(Ref<ImageData>&&, const IntSize& canvasSize, GraphicsContext&);
> 
>     bool reshapeFBOs(const IntSize&);
>     void prepareTextureImpl();
>diff --git a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLBase.cpp b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLBase.cpp
>index f414f9c9634d61b8d9015d5a6afa527cc342be8f..29df7c9013cb915934abab894fab26c9d7fe770f 100644
>--- a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLBase.cpp
>+++ b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLBase.cpp
>@@ -30,6 +30,7 @@
> #if ENABLE(WEBGL) && USE(OPENGL)
> 
> #include "ExtensionsGLOpenGL.h"
>+#include "ImageData.h"
> #include "IntRect.h"
> #include "IntSize.h"
> #include "Logging.h"
>@@ -61,37 +62,26 @@
> namespace WebCore {
> 
> 
>-void GraphicsContextGLOpenGL::readPixelsAndConvertToBGRAIfNecessary(int x, int y, int width, int height, unsigned char* pixels)
>+RefPtr<ImageData> GraphicsContextGLOpenGL::readPixelsForPaintResults()
> {
>-    auto attrs = contextAttributes();
>+    auto imageData = ImageData::create(getInternalFramebufferSize());
>+    if (!imageData)
>+        return nullptr;
>+
>+    GLint packAlignment = 4;
>+    bool mustRestorePackAlignment = false;
>+    ::glGetIntegerv(GL_PACK_ALIGNMENT, &packAlignment);
>+    if (packAlignment > 4) {
>+        ::glPixelStorei(GL_PACK_ALIGNMENT, 4);
>+        mustRestorePackAlignment = true;
>+    }
> 
>-    // NVIDIA drivers have a bug where calling readPixels in BGRA can return the wrong values for the alpha channel when the alpha is off for the context.
>-    if (!attrs.alpha && getExtensions().isNVIDIA()) {
>-        ::glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
>-#if USE(ACCELERATE)
>-        vImage_Buffer src;
>-        src.height = height;
>-        src.width = width;
>-        src.rowBytes = width * 4;
>-        src.data = pixels;
>-
>-        vImage_Buffer dest;
>-        dest.height = height;
>-        dest.width = width;
>-        dest.rowBytes = width * 4;
>-        dest.data = pixels;
>-
>-        // Swap pixel channels from RGBA to BGRA.
>-        const uint8_t map[4] = { 2, 1, 0, 3 };
>-        vImagePermuteChannels_ARGB8888(&src, &dest, map, kvImageNoFlags);
>-#else
>-        int totalBytes = width * height * 4;
>-        for (int i = 0; i < totalBytes; i += 4)
>-            std::swap(pixels[i], pixels[i + 2]);
>-#endif
>-    } else
>-        ::glReadPixels(x, y, width, height, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, pixels);
>+    ::glReadPixels(0, 0, imageData->width(), imageData->height(), GL_RGBA, GL_UNSIGNED_BYTE, imageData->data()->data());
>+
>+    if (mustRestorePackAlignment)
>+        ::glPixelStorei(GL_PACK_ALIGNMENT, packAlignment);
> 
>+    return imageData;
> }
> 
> void GraphicsContextGLOpenGL::validateAttributes()
>diff --git a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLCommon.cpp b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLCommon.cpp
>index 2de185a668130a362c12767f383f57f1349dd481..fcdb711a6f8cb059e00b74cd0ccb7c9ace90da60 100644
>--- a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLCommon.cpp
>+++ b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLCommon.cpp
>@@ -137,64 +137,6 @@ void GraphicsContextGLOpenGL::validateDepthStencil(const char* packedDepthStenci
>     }
> }
> 
>-void GraphicsContextGLOpenGL::paintRenderingResultsToCanvas(ImageBuffer* imageBuffer)
>-{
>-    Checked<int, RecordOverflow> rowBytes = Checked<int, RecordOverflow>(m_currentWidth) * 4;
>-    if (rowBytes.hasOverflowed())
>-        return;
>-
>-    Checked<int, RecordOverflow> totalBytesChecked = rowBytes * m_currentHeight;
>-    if (totalBytesChecked.hasOverflowed())
>-        return;
>-    int totalBytes = totalBytesChecked.unsafeGet();
>-
>-    auto pixels = makeUniqueArray<unsigned char>(totalBytes);
>-    if (!pixels)
>-        return;
>-
>-    readRenderingResults(pixels.get(), totalBytes);
>-
>-    if (!contextAttributes().premultipliedAlpha) {
>-        for (int i = 0; i < totalBytes; i += 4) {
>-            // Premultiply alpha.
>-            pixels[i + 0] = std::min(255, pixels[i + 0] * pixels[i + 3] / 255);
>-            pixels[i + 1] = std::min(255, pixels[i + 1] * pixels[i + 3] / 255);
>-            pixels[i + 2] = std::min(255, pixels[i + 2] * pixels[i + 3] / 255);
>-        }
>-    }
>-
>-    paintToCanvas(pixels.get(), IntSize(m_currentWidth, m_currentHeight), imageBuffer->backendSize(), imageBuffer->context());
>-}
>-
>-bool GraphicsContextGLOpenGL::paintCompositedResultsToCanvas(ImageBuffer*)
>-{
>-    // Not needed at the moment, so return that nothing was done.
>-    return false;
>-}
>-
>-RefPtr<ImageData> GraphicsContextGLOpenGL::paintRenderingResultsToImageData()
>-{
>-    // Reading premultiplied alpha would involve unpremultiplying, which is
>-    // lossy.
>-    if (contextAttributes().premultipliedAlpha)
>-        return nullptr;
>-
>-    auto imageData = ImageData::create(IntSize(m_currentWidth, m_currentHeight));
>-    unsigned char* pixels = imageData->data()->data();
>-    Checked<int, RecordOverflow> totalBytesChecked = 4 * Checked<int, RecordOverflow>(m_currentWidth) * Checked<int, RecordOverflow>(m_currentHeight);
>-    if (totalBytesChecked.hasOverflowed())
>-        return imageData;
>-    int totalBytes = totalBytesChecked.unsafeGet();
>-
>-    readRenderingResults(pixels, totalBytes);
>-
>-    // Convert to RGBA.
>-    for (int i = 0; i < totalBytes; i += 4)
>-        std::swap(pixels[i], pixels[i + 2]);
>-
>-    return imageData;
>-}
>-
> void GraphicsContextGLOpenGL::prepareTexture()
> {
>     if (m_layerComposited)
>@@ -236,15 +178,8 @@ void GraphicsContextGLOpenGL::prepareTexture()
>     ::glFlush();
> }
> 
>-void GraphicsContextGLOpenGL::readRenderingResults(unsigned char *pixels, int pixelsSize)
>+RefPtr<ImageData> GraphicsContextGLOpenGL::readRenderingResults()
> {
>-    if (pixelsSize < m_currentWidth * m_currentHeight * 4)
>-        return;
>-
>-    if (!makeContextCurrent())
>-        return;
>-
>-
>     bool mustRestoreFBO = false;
>     if (contextAttributes().antialias) {
>         resolveMultisamplingIfNecessary();
>@@ -257,22 +192,10 @@ void GraphicsContextGLOpenGL::readRenderingResults(unsigned char *pixels, int pi
>             ::glBindFramebufferEXT(GraphicsContextGL::FRAMEBUFFER, m_fbo);
>         }
>     }
>-
>-    GLint packAlignment = 4;
>-    bool mustRestorePackAlignment = false;
>-    ::glGetIntegerv(GL_PACK_ALIGNMENT, &packAlignment);
>-    if (packAlignment > 4) {
>-        ::glPixelStorei(GL_PACK_ALIGNMENT, 4);
>-        mustRestorePackAlignment = true;
>-    }
>-
>-    readPixelsAndConvertToBGRAIfNecessary(0, 0, m_currentWidth, m_currentHeight, pixels);
>-
>-    if (mustRestorePackAlignment)
>-        ::glPixelStorei(GL_PACK_ALIGNMENT, packAlignment);
>-
>+    auto result = readPixelsForPaintResults();
>     if (mustRestoreFBO)
>         ::glBindFramebufferEXT(GraphicsContextGL::FRAMEBUFFER, m_state.boundDrawFBO);
>+    return result;
> }
> 
> void GraphicsContextGLOpenGL::reshape(int width, int height)
>diff --git a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp
>index 0d476c229d6f6ee96ccf993d81d5c3dd65215e48..939fb93e1c213449d07e03e5cbe80aa81e18ef64 100644
>--- a/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp
>+++ b/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGLES.cpp
>@@ -64,14 +64,26 @@ void GraphicsContextGLOpenGL::readnPixels(GCGLint x, GCGLint y, GCGLsizei width,
>         ::glBindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
> }
> 
>-void GraphicsContextGLOpenGL::readPixelsAndConvertToBGRAIfNecessary(int x, int y, int width, int height, unsigned char* pixels)
>+RefPtr<ImageData> GraphicsContextGLOpenGL::readPixelsForPaintResults()
> {
>-    ::glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
>-    int totalBytes = width * height * 4;
>-    if (isGLES2Compliant()) {
>-        for (int i = 0; i < totalBytes; i += 4)
>-            std::swap(pixels[i], pixels[i + 2]); // Convert to BGRA.
>+    auto imageData = ImageData::create(getInternalFramebufferSize());
>+    if (!imageData)
>+        return nullptr;
>+
>+    GLint packAlignment = 4;
>+    bool mustRestorePackAlignment = false;
>+    ::glGetIntegerv(GL_PACK_ALIGNMENT, &packAlignment);
>+    if (packAlignment > 4) {
>+        ::glPixelStorei(GL_PACK_ALIGNMENT, 4);
>+        mustRestorePackAlignment = true;
>     }
>+
>+    ::glReadPixels(0, 0, imageData->width(), imageData->height(), GL_RGBA, GL_UNSIGNED_BYTE, imageData->data()->data());
>+
>+    if (mustRestorePackAlignment)
>+        ::glPixelStorei(GL_PACK_ALIGNMENT, packAlignment);
>+
>+    return imageData;
> }
> 
> bool GraphicsContextGLOpenGL::reshapeFBOs(const IntSize& size)
>diff --git a/Source/WebKit/GPUProcess/graphics/RemoteGraphicsContextGLCocoa.cpp b/Source/WebKit/GPUProcess/graphics/RemoteGraphicsContextGLCocoa.cpp
>index e7c40c985cb7d2722869a5dff9691947077af46c..8e2d1fc6518628395e9741c44e7ac851b08ef627 100644
>--- a/Source/WebKit/GPUProcess/graphics/RemoteGraphicsContextGLCocoa.cpp
>+++ b/Source/WebKit/GPUProcess/graphics/RemoteGraphicsContextGLCocoa.cpp
>@@ -48,6 +48,7 @@ public:
>     // GraphicsContextGLIOSurfaceSwapChain overrides.
>     Buffer recycleBuffer() final;
>     void present(Buffer) final;
>+    const Buffer& displayBuffer() const final;
>     void* detachClient() final;
> private:
>     GraphicsContextGLIOSurfaceSwapChain::Buffer m_displayBuffer;
>@@ -76,6 +77,11 @@ void RemoteGraphicsContextGLCocoa::present(Buffer buffer)
>     m_displayBuffer = WTFMove(buffer);
> }
> 
>+const GraphicsContextGLIOSurfaceSwapChain::Buffer& RemoteGraphicsContextGLCocoa::displayBuffer() const
>+{
>+    return m_displayBuffer;
>+}
>+
> void* RemoteGraphicsContextGLCocoa::detachClient()
> {
>     return std::exchange(m_displayBuffer.handle, nullptr);
>diff --git a/Source/WebKit/WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.cpp b/Source/WebKit/WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.cpp
>index 34a06fb0076acd3fd32b3a4b6b09d68d027bb588..53db6150c1d8ec825e23abef651e5b3b9799245e 100644
>--- a/Source/WebKit/WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.cpp
>+++ b/Source/WebKit/WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.cpp
>@@ -121,6 +121,11 @@ void RemoteGraphicsContextGLProxy::paintRenderingResultsToCanvas(ImageBuffer*)
>     notImplemented();
> }
> 
>+void RemoteGraphicsContextGLProxy::paintCompositedResultsToCanvas(ImageBuffer*)
>+{
>+    notImplemented();
>+}
>+
> RefPtr<ImageData> RemoteGraphicsContextGLProxy::paintRenderingResultsToImageData()
> {
>     notImplemented();
>diff --git a/Source/WebKit/WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.h b/Source/WebKit/WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.h
>index d99eda29f6db5e1819713178f2aa531b4f5dd6e0..a1439347d89e0adbf08a42a42591bbb3dbeb21e7 100644
>--- a/Source/WebKit/WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.h
>+++ b/Source/WebKit/WebProcess/GPU/graphics/RemoteGraphicsContextGLProxy.h
>@@ -71,6 +71,7 @@ public:
>     void simulateContextChanged() final;
>     void paintRenderingResultsToCanvas(WebCore::ImageBuffer*) final;
>     RefPtr<WebCore::ImageData> paintRenderingResultsToImageData() final;
>+    void paintCompositedResultsToCanvas(WebCore::ImageBuffer*) final;
> 
>     // Functions with a generated implementation. This list is used by generate-gpup-webgl script.
>     void setFailNextGPUStatusCheck() final;

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Attachments on bug 219946: 416405 | 416406 | 416408 | 416411 | 416412 | 416413 | 416414 | 416415 | 416416