Streamline the presentation of ImageBitmapRenderingContext

third_party/WebKit/Source/platform/graphics/gpu/ImageLayerBridge.cpp

+// Copyright 2017 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 "platform/graphics/gpu/ImageLayerBridge.h"
+
+#include "cc/resources/shared_bitmap.h"
+#include "cc/resources/texture_mailbox.h"
+#include "gpu/command_buffer/client/gles2_interface.h"
+#include "platform/graphics/ColorBehavior.h"
+#include "platform/graphics/GraphicsLayer.h"
+#include "public/platform/Platform.h"
+#include "public/platform/WebCompositorSupport.h"
+#include "public/platform/WebExternalTextureLayer.h"
+
+namespace blink {
+
+ImageLayerBridge::ImageLayerBridge(OpacityMode opacityMode)
+    : m_weakPtrFactory(this), m_opacityMode(opacityMode) {}
+
+ImageLayerBridge::~ImageLayerBridge() {
+  if (!m_disposed)
+    dispose();
+}
+
+void ImageLayerBridge::setImage(PassRefPtr<StaticBitmapImage> image) {
+  if (!m_layer) {
+    m_layer =
+        Platform::current()->compositorSupport()->createExternalTextureLayer(
+            this);
+    GraphicsLayer::registerContentsLayer(m_layer->layer());
+    m_layer->setNearestNeighbor(m_filterQuality == kNone_SkFilterQuality);
+    if (m_opacityMode == Opaque) {
+      m_layer->setOpaque(true);
+      m_layer->setBlendBackgroundColor(false);

[xlai (Olivia), 2017/03/09 21:57:27]

Do you need to consider the "premultiplied alpha" attribute of the layer?

[Justin Novosad, 2017/03/10 21:09:59]

Turns out I don't. Premul is assumed here.  FWIW, we already have layout tests
with semi-transparent ImageBitmapRenderingContexts and they still pass with this
change.

+    }
+  }
+  m_image = std::move(image);
+  if (m_image) {
+    if (m_opacityMode == NonOpaque) {
+      m_layer->setOpaque(m_image->currentFrameKnownToBeOpaque());
+      m_layer->setBlendBackgroundColor(!m_image->currentFrameKnownToBeOpaque());
+    }
+  }
+  m_layer->layer()->invalidate();
+  if (!m_hasPresentedSinceLastSetImage && m_image &&
+      m_image->isTextureBacked()) {
+    // If the layer bridge is not presenting, the GrContext may not be getting
+    // flushed regularly.  The flush is normally triggered inside the
+    // m_image->ensureMailbox() call of
+    // ImageLayerBridge::PrepareTextureMailbox. To prevent a potential memory
+    // leak we must flush the GrContext here.
+    m_image->imageForCurrentFrame(ColorBehavior::tag())
+        ->getTextureHandle(true);  // triggers a GrContext flush if needed.
+  }
+  m_hasPresentedSinceLastSetImage = false;
+}
+
+void ImageLayerBridge::dispose() {
+  if (m_layer) {
+    GraphicsLayer::unregisterContentsLayer(m_layer->layer());
+    m_layer->clearTexture();
+    m_layer.reset();
+  }
+  m_image = nullptr;
+  m_disposed = true;
+}
+
+bool ImageLayerBridge::PrepareTextureMailbox(
+    cc::TextureMailbox* outMailbox,
+    std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback) {
+  if (m_disposed)
+    return false;
+
+  if (!m_image)
+    return false;
+
+  m_hasPresentedSinceLastSetImage = true;
+
+  if (m_image->isAccelerated()) {
+    m_image->ensureMailbox();
+    *outMailbox = cc::TextureMailbox(m_image->mailbox(), m_image->syncToken(),
+                                     GL_TEXTURE_2D);
+    auto func = WTF::bind(&ImageLayerBridge::mailboxReleasedGpu,
+                          m_weakPtrFactory.createWeakPtr(), m_image);
+    *outReleaseCallback = cc::SingleReleaseCallback::Create(
+        convertToBaseCallback(std::move(func)));
+  } else {
+    std::unique_ptr<cc::SharedBitmap> bitmap = createOrRecycleBitmap();
+    if (!bitmap)
+      return false;
+
+    sk_sp<SkImage> skImage =
+        m_image->imageForCurrentFrame(ColorBehavior::tag());
+    if (!skImage)
+      return false;
+
+    SkImageInfo dstInfo = SkImageInfo::MakeN32Premul(m_image->width(), 1);
+    size_t rowBytes = m_image->width() * 4;
+
+    // loop to flip Y
+    for (int row = 0; row < m_image->height(); row++) {

[xlai (Olivia), 2017/03/09 21:57:27]

Why do you do this loop? The source (x, y) seems to be fixed, is that what you
intent to do? Do you have an existing test that covers this?

[Justin Novosad, 2017/03/10 21:09:59]

This is to do a y-flip on the image data.  For some reason Skia and SharedBitmpa
don't use the same orientation.  And skia has no option for flipping vertically
with readPixels.

+      if (!skImage->readPixels(
+              dstInfo,
+              bitmap->pixels() + rowBytes * (m_image->height() - 1 - row),
+              rowBytes, 0, row))
+        return false;
+    }
+
+    *outMailbox = cc::TextureMailbox(
+        bitmap.get(), gfx::Size(m_image->width(), m_image->height()));
+    auto func = WTF::bind(&ImageLayerBridge::mailboxReleasedSoftware,
+                          m_weakPtrFactory.createWeakPtr(),
+                          base::Passed(&bitmap), m_image->size());
+    *outReleaseCallback = cc::SingleReleaseCallback::Create(
+        convertToBaseCallback(std::move(func)));
+  }
+
+  outMailbox->set_nearest_neighbor(m_filterQuality == kNone_SkFilterQuality);
+  // TODO(junov): Figure out how to get the color space info.
+  // outMailbox->set_color_space();
+
+  return true;
+}
+
+std::unique_ptr<cc::SharedBitmap> ImageLayerBridge::createOrRecycleBitmap() {
+  auto it = std::remove_if(m_recycledBitmaps.begin(), m_recycledBitmaps.end(),
+                           [this](const RecycledBitmap& bitmap) {
+                             return bitmap.size != m_image->size();
+                           });
+  m_recycledBitmaps.shrink(it - m_recycledBitmaps.begin());
+
+  if (!m_recycledBitmaps.isEmpty()) {
+    RecycledBitmap recycled = std::move(m_recycledBitmaps.back());
+    m_recycledBitmaps.pop_back();
+    DCHECK(recycled.size == m_image->size());
+    return std::move(recycled.bitmap);
+  }
+  return Platform::current()->allocateSharedBitmap(m_image->size());
+}
+
+void ImageLayerBridge::mailboxReleasedGpu(RefPtr<StaticBitmapImage> image,
+                                          const gpu::SyncToken& token,
+                                          bool lostResource) {
+  if (image) {
+    DCHECK(image->isAccelerated());
+    DCHECK(image->hasMailbox());
+    if (token.HasData()) {
+      image->updateSyncToken(token);
+    }
+  }
+  // let 'image' go out of scope to finalize the release. The
+  // destructor will wait on sync token before deleting resource.
+}
+
+void ImageLayerBridge::mailboxReleasedSoftware(
+    std::unique_ptr<cc::SharedBitmap> bitmap,
+    const IntSize& size,
+    const gpu::SyncToken& syncToken,
+    bool lostResource) {
+  DCHECK(!syncToken.HasData());  // No sync tokens for software resources.
+  if (!m_disposed && !lostResource) {
+    RecycledBitmap recycled = {std::move(bitmap), size};
+    m_recycledBitmaps.push_back(std::move(recycled));
+  }
+}
+
+WebLayer* ImageLayerBridge::platformLayer() const {
+  return m_layer->layer();
+}
+
+}  // namespace blink