Initial implementation of display list backed 2D canvases

Source/platform/graphics/RecordingImageBufferSurface.cpp

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+
+#include "platform/graphics/RecordingImageBufferSurface.h"
+
+#include "platform/graphics/GraphicsContext.h"
+#include "platform/graphics/ImageBuffer.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkPictureRecorder.h"
+#include "wtf/PassOwnPtr.h"
+#include "wtf/PassRefPtr.h"
+
+namespace WebCore {
+
+RecordingImageBufferSurface::RecordingImageBufferSurface(const IntSize& size, OpacityMode opacityMode)
+    : ImageBufferSurface(size, opacityMode)
+    , m_graphicsContext(0)
+    , m_frameWasCleared(true)
+{
+    initializeCurrentFrame();
+}
+
+RecordingImageBufferSurface::~RecordingImageBufferSurface()
+{ }
+
+void RecordingImageBufferSurface::initializeCurrentFrame()
+{
+    static SkRTreeFactory rTreeFactory;
+    m_currentFrame = adoptPtr(new SkPictureRecorder);
+    m_currentFrame->beginRecording(size().width(), size().height(), &rTreeFactory);
+    if (m_graphicsContext) {
+        m_graphicsContext->resetCanvas(m_currentFrame->getRecordingCanvas());
+        m_graphicsContext->setTrackOpaqueRegion(true);
+    }
+}
+
+void RecordingImageBufferSurface::setImageBuffer(ImageBuffer* imageBuffer)
+{
+    m_graphicsContext = imageBuffer ? imageBuffer->context() : 0;
+    if (m_currentFrame) {
+        m_graphicsContext->setTrackOpaqueRegion(true);

[Stephen White, 2014/07/17 18:55:48]

Either the ": 0" clause above can never happen (and should assert instead), or
this indirection needs a NULL ptr check as well. Pick one. :)

[Justin Novosad, 2014/07/17 19:19:09]

Done.

+        m_graphicsContext->resetCanvas(m_currentFrame->getRecordingCanvas());
+    }
+}
+
+void RecordingImageBufferSurface::willReadback()
+{
+    fallBackToRasterCanvas();
+}
+
+void RecordingImageBufferSurface::fallBackToRasterCanvas()
+{
+    if (m_rasterCanvas) {
+        ASSERT(!m_currentFrame);
+        return;
+    }
+
+    m_rasterCanvas = adoptPtr(SkCanvas::NewRasterN32(size().width(), size().height()));
+
+    if (m_previousFrame) {
+        m_previousFrame->draw(m_rasterCanvas.get());
+        m_previousFrame.clear();
+    }
+    if (m_currentFrame) {
+        RefPtr<SkPicture> currentPicture = adoptRef(m_currentFrame->endRecording());
+        currentPicture->draw(m_rasterCanvas.get());
+        m_currentFrame.clear();
+    }
+
+    if (m_graphicsContext) {
+        m_graphicsContext->setTrackOpaqueRegion(false);
+        m_graphicsContext->resetCanvas(m_rasterCanvas.get());
+    }
+}
+
+SkCanvas* RecordingImageBufferSurface::canvas() const
+{
+    if (m_rasterCanvas)
+        return m_rasterCanvas.get();
+
+    ASSERT(m_currentFrame->getRecordingCanvas());
+    return m_currentFrame->getRecordingCanvas();
+}
+
+PassRefPtr<SkPicture> RecordingImageBufferSurface::getPicture()
+{
+    if (handleOpaqueFrame())
+        return m_previousFrame;
+
+    if (!m_rasterCanvas)
+        fallBackToRasterCanvas();
+    return nullptr;
+}
+
+void RecordingImageBufferSurface::didClearCanvas()
+{
+    m_frameWasCleared = true;
+}
+
+bool RecordingImageBufferSurface::handleOpaqueFrame()
+{
+    if (!m_currentFrame)
+        return false;
+    IntRect canvasRect(IntPoint(0, 0), size());
+    if (!m_frameWasCleared && !m_graphicsContext->opaqueRegion().asRect().contains(canvasRect))
+        return false;
+
+    SkCanvas* oldCanvas = m_currentFrame->getRecordingCanvas(); // Could be raster or picture
+
+    // FIXME(crbug.com/392614): handle transferring complex state from the current picture to the new one.
+    if (oldCanvas->getSaveCount())
+        return false;
+    if (!oldCanvas->isClipRect())
+        return false;
+
+    SkMatrix ctm = oldCanvas->getTotalMatrix();
+    SkRect clip;
+    oldCanvas->getClipBounds(&clip);
+
+    m_previousFrame = adoptRef(m_currentFrame->endRecording());
+    initializeCurrentFrame();
+
+    SkCanvas* newCanvas = m_currentFrame->getRecordingCanvas();
+    newCanvas->concat(ctm);
+    newCanvas->clipRect(clip);
+
+    m_frameWasCleared = false;
+    return true;
+}
+
+} // namespace WebCore