Deferred image decoding to support animated GIFs

Source/core/platform/graphics/chromium/DeferredImageDecoder.cpp

Index: Source/core/platform/graphics/chromium/DeferredImageDecoder.cpp
diff --git a/Source/core/platform/graphics/chromium/DeferredImageDecoder.cpp b/Source/core/platform/graphics/chromium/DeferredImageDecoder.cpp
index 1bd684cc979688e2136762adc0594ed8153477ed..717d38d38c62be01a4ef8d9cccfaa5964b0f8303 100644
--- a/Source/core/platform/graphics/chromium/DeferredImageDecoder.cpp
+++ b/Source/core/platform/graphics/chromium/DeferredImageDecoder.cpp
@@ -46,6 +46,7 @@ DeferredImageDecoder::DeferredImageDecoder(PassOwnPtr<ImageDecoder> actualDecode
     : m_allDataReceived(false)
     , m_actualDecoder(actualDecoder)
     , m_orientation(DefaultImageOrientation)
+    , m_repetitionCount(cAnimationNone)
 {
 }
 
@@ -84,7 +85,7 @@ SkBitmap DeferredImageDecoder::createResizedLazyDecodingBitmap(const SkBitmap& b
     // FIXME: This code has the potential problem that multiple
     // LazyDecodingPixelRefs are created even though they share the same
     // scaled size and ImageFrameGenerator.
-    resizedBitmap.setPixelRef(new LazyDecodingPixelRef(pixelRef->frameGenerator(), scaledSize, scaledSubset))->unref();
+    resizedBitmap.setPixelRef(new LazyDecodingPixelRef(pixelRef->frameGenerator(), scaledSize, pixelRef->frameIndex(), scaledSubset))->unref();
 
     // See comments in createLazyDecodingBitmap().
     resizedBitmap.setImmutable();
@@ -98,44 +99,25 @@ void DeferredImageDecoder::setEnabled(bool enabled)
 
 ImageFrame* DeferredImageDecoder::frameBufferAtIndex(size_t index)
 {
-    // Only defer image decoding if this is a single frame image. The reason is
-    // because a multiframe is usually animated GIF. Animation is handled by
-    // BitmapImage which uses some metadata functions that do synchronous image
-    // decoding.
-    if (s_enabled
-        && m_actualDecoder
-        && m_actualDecoder->repetitionCount() == cAnimationNone
-        && m_actualDecoder->isSizeAvailable()
-        && m_actualDecoder->frameCount() == 1) {
-
-        m_size = m_actualDecoder->size();
-        m_orientation = m_actualDecoder->orientation();
-
-        SkBitmap lazyDecodedSkBitmap = createLazyDecodingBitmap();
-        m_lazyDecodedFrame.setSkBitmap(lazyDecodedSkBitmap);
-
-        // Don't mark the frame as completely decoded until the underlying
-        // decoder has really decoded it. Until then, our data and metadata may
-        // be incorrect, so callers can't rely on them.
-        m_lazyDecodedFrame.setStatus(ImageFrame::FramePartial);
-    }
-
-    return m_actualDecoder ? m_actualDecoder->frameBufferAtIndex(index) : &m_lazyDecodedFrame;
+    prepareLazyDecodedFrames();
+    if (index < m_lazyDecodedFrames.size())
+        return m_lazyDecodedFrames[index].get();
+    if (m_actualDecoder)
+        return m_actualDecoder->frameBufferAtIndex(index);
+    return 0;
 }
 
 void DeferredImageDecoder::setData(SharedBuffer* data, bool allDataReceived)
 {
     if (m_actualDecoder) {
-        // Keep a reference to data until image decoding is deferred.
-        // When image decoding is deferred then ownership of m_data is
-        // transferred to ImageDecodingStore.
         m_data = data;
         m_allDataReceived = allDataReceived;
         m_actualDecoder->setData(data, allDataReceived);
-    } else {
-        ASSERT(!m_data);
-        m_frameGenerator->setData(data, allDataReceived);
+        prepareLazyDecodedFrames();
     }
+
+    if (m_frameGenerator)
+        m_frameGenerator->setData(data, allDataReceived);
 }
 
 bool DeferredImageDecoder::isSizeAvailable()
@@ -152,17 +134,19 @@ IntSize DeferredImageDecoder::size() const
 
 IntSize DeferredImageDecoder::frameSizeAtIndex(size_t index) const
 {
+    // FIXME: Frame size is assumed to be uniform. This might not be true for
+    // future supported codecs.
     return m_actualDecoder ? m_actualDecoder->frameSizeAtIndex(index) : m_size;
 }
 
 size_t DeferredImageDecoder::frameCount()
 {
-    return m_actualDecoder ? m_actualDecoder->frameCount() : 1;
+    return m_actualDecoder ? m_actualDecoder->frameCount() : m_lazyDecodedFrames.size();
 }
 
 int DeferredImageDecoder::repetitionCount() const
 {
-    return m_actualDecoder ? m_actualDecoder->repetitionCount() : cAnimationNone;
+    return m_actualDecoder ? m_actualDecoder->repetitionCount() : m_repetitionCount;
 }
 
 size_t DeferredImageDecoder::clearCacheExceptFrame(size_t clearExceptFrame)
@@ -174,26 +158,37 @@ size_t DeferredImageDecoder::clearCacheExceptFrame(size_t clearExceptFrame)
 
 bool DeferredImageDecoder::frameHasAlphaAtIndex(size_t index) const
 {
-    return m_actualDecoder ? m_actualDecoder->frameHasAlphaAtIndex(index) : m_frameGenerator->hasAlpha();
+    // FIXME: Report this for multi-frame image.
+    if (m_actualDecoder)
+        return m_actualDecoder->frameHasAlphaAtIndex(index);
+    if (!m_frameGenerator->isMultiFrame())
+        return m_frameGenerator->hasAlpha();
+    return true;
 }
 
 bool DeferredImageDecoder::frameIsCompleteAtIndex(size_t index) const
 {
-    // TODO: Implement this for deferred decoding.
-    return m_actualDecoder && m_actualDecoder->frameIsCompleteAtIndex(index);
+    if (m_actualDecoder)
+        return m_actualDecoder->frameIsCompleteAtIndex(index);
+    if (index < m_lazyDecodedFrames.size())
+        return m_lazyDecodedFrames[index]->status() == ImageFrame::FrameComplete;
+    return false;
 }
 
 float DeferredImageDecoder::frameDurationAtIndex(size_t index) const
 {
-    // TODO: Implement this for deferred decoding.
-    return m_actualDecoder ? m_actualDecoder->frameDurationAtIndex(index) : 0;
+    if (m_actualDecoder)
+        return m_actualDecoder->frameDurationAtIndex(index);
+    if (index < m_lazyDecodedFrames.size())
+        return m_lazyDecodedFrames[index]->duration();
+    return 0;
 }
 
 unsigned DeferredImageDecoder::frameBytesAtIndex(size_t index) const
 {
     // If frame decoding is deferred then it is not managed by MemoryCache
     // so return 0 here.
-    return m_actualDecoder ? m_actualDecoder->frameBytesAtIndex(index) : 0;
+    return m_frameGenerator ? 0 : m_actualDecoder->frameBytesAtIndex(index);
 }
 
 ImageOrientation DeferredImageDecoder::orientation() const
@@ -201,7 +196,48 @@ ImageOrientation DeferredImageDecoder::orientation() const
     return m_actualDecoder ? m_actualDecoder->orientation() : m_orientation;
 }
 
-SkBitmap DeferredImageDecoder::createLazyDecodingBitmap()
+void DeferredImageDecoder::activateLazyDecoding()
+{
+    if (m_frameGenerator)
+        return;
+    m_size = m_actualDecoder->size();
+    m_orientation = m_actualDecoder->orientation();
+    const bool isSingleFrame = m_actualDecoder->repetitionCount() == cAnimationNone || (m_allDataReceived && m_actualDecoder->frameCount() == 1u);
+    m_frameGenerator = ImageFrameGenerator::create(SkISize::Make(m_size.width(), m_size.height()), m_data, m_allDataReceived, !isSingleFrame);
+}
+
+void DeferredImageDecoder::prepareLazyDecodedFrames()
+{
+    if (!s_enabled
+        || !m_actualDecoder
+        || !m_actualDecoder->isSizeAvailable())
+        return;
+
+    activateLazyDecoding();
+
+    const size_t previousSize = m_lazyDecodedFrames.size();
+    m_lazyDecodedFrames.resize(m_actualDecoder->frameCount());
+    for (size_t i = previousSize; i < m_lazyDecodedFrames.size(); ++i) {
+        OwnPtr<ImageFrame> frame(adoptPtr(new ImageFrame()));
+        frame->setSkBitmap(createLazyDecodingBitmap(i));
+        frame->setDuration(m_actualDecoder->frameDurationAtIndex(i));
+        frame->setStatus(m_actualDecoder->frameIsCompleteAtIndex(i) ? ImageFrame::FrameComplete : ImageFrame::FramePartial);
+        m_lazyDecodedFrames[i] = frame.release();
+    }
+
+    // The last lazy decoded frame created from previous call might be
+    // incomplete so update its state.
+    if (previousSize)
+        m_lazyDecodedFrames[previousSize - 1]->setStatus(m_actualDecoder->frameIsCompleteAtIndex(previousSize - 1) ? ImageFrame::FrameComplete : ImageFrame::FramePartial);
+
+    if (m_allDataReceived) {
+        m_repetitionCount = m_actualDecoder->repetitionCount();
+        m_actualDecoder.clear();
+        m_data = nullptr;
+    }
+}
+
+SkBitmap DeferredImageDecoder::createLazyDecodingBitmap(size_t index)
 {
     SkISize fullSize = SkISize::Make(m_actualDecoder->size().width(), m_actualDecoder->size().height());
     ASSERT(!fullSize.isEmpty());
@@ -211,11 +247,7 @@ SkBitmap DeferredImageDecoder::createLazyDecodingBitmap()
     // Creates a lazily decoded SkPixelRef that references the entire image without scaling.
     SkBitmap bitmap;
     bitmap.setConfig(SkBitmap::kARGB_8888_Config, fullSize.width(), fullSize.height());
-
-    m_frameGenerator = ImageFrameGenerator::create(fullSize, m_data.release(), m_allDataReceived);
-    m_actualDecoder.clear();
-
-    bitmap.setPixelRef(new LazyDecodingPixelRef(m_frameGenerator, fullSize, fullRect))->unref();
+    bitmap.setPixelRef(new LazyDecodingPixelRef(m_frameGenerator, fullSize, index, fullRect))->unref();
 
     // Use the URI to identify this as a lazily decoded SkPixelRef of type LazyDecodingPixelRef.
     // FIXME: It would be more useful to give the actual image URI.
@@ -234,6 +266,7 @@ SkBitmap DeferredImageDecoder::createLazyDecodingBitmap()
 
 bool DeferredImageDecoder::hotSpot(IntPoint& hotSpot) const
 {
+    // TODO: Implement.
     return m_actualDecoder ? m_actualDecoder->hotSpot(hotSpot) : false;
 }