Add animation support for WebP images

Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 116 matching lines @@
         m_reader->frameContext(index)->isHeaderDefined()) ?
         m_reader->frameContext(index)->delayTime : 0;
 }
 
 bool GIFImageDecoder::setFailed()
 {
     m_reader.clear();
     return ImageDecoder::setFailed();
 }
 
+// FIXME: Can the intermediate |rowBuffer| be avoided?
 bool GIFImageDecoder::haveDecodedRow(size_t frameIndex, const Vector<unsigned char>& rowBuffer, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
 {
     const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
     // The pixel data and coordinates supplied to us are relative to the frame's
     // origin within the entire image size, i.e.
     // (frameContext->xOffset, frameContext->yOffset). There is no guarantee
     // that width == (size().width() - frameContext->xOffset), so
     // we must ensure we don't run off the end of either the source data or the
     // row's X-coordinates.
     int xBegin = frameContext->xOffset;
@@ skipping 88 matching lines @@
             // it had no alpha, and its rect is contained in the current frame's
             // rect, we know the current frame has no alpha.
             if ((prevBuffer->disposalMethod() == ImageFrame::DisposeOverwriteBgcolor) && !prevBuffer->hasAlpha() && buffer.originalFrameRect().contains(prevBuffer->originalFrameRect()))
                 buffer.setHasAlpha(false);
         }
     }
 
     return true;
 }
 
+size_t GIFImageDecoder::clearCacheExceptFrame(size_t clearExceptFrame)
+{
+    // We need to preserve frames such that:
+    //  1. We don't clear |clearExceptFrame|;
+    //  2. We don't clear any frame from which a future initFrameBuffer() call
+    //     will copy bitmap data.
+    // All other frames can be cleared.
+    while ((clearExceptFrame < m_frameBufferCache.size()) && (m_frameBufferCache[clearExceptFrame].status() == ImageFrame::FrameEmpty))
+        clearExceptFrame = m_frameBufferCache[clearExceptFrame].requiredPreviousFrameIndex();
+
+    return ImageDecoder::clearCacheExceptFrame(clearExceptFrame);
+}
+
 void GIFImageDecoder::clearFrameBuffer(size_t frameIndex)
 {
     if (m_reader && m_frameBufferCache[frameIndex].status() == ImageFrame::FramePartial) {
         // Reset the state of the partial frame in the reader so that the frame
         // can be decoded again when requested.
         m_reader->clearDecodeState(frameIndex);
     }
     ImageDecoder::clearFrameBuffer(frameIndex);
 }
 
@@ skipping 85 matching lines @@
 
         // Preserve the last frame as the starting state for this frame.
         if (!buffer->copyBitmapData(*prevBuffer))
             return setFailed();
 
         if (prevBuffer->disposalMethod() == ImageFrame::DisposeOverwriteBgcolor) {
             // We want to clear the previous frame to transparent, without
             // affecting pixels in the image outside of the frame.
             const IntRect& prevRect = prevBuffer->originalFrameRect();
             ASSERT(!prevRect.contains(IntRect(IntPoint(), size())));
-            for (int y = prevRect.y(); y < prevRect.maxY(); ++y) {
-                for (int x = prevRect.x(); x < prevRect.maxX(); ++x)
-                    buffer->setRGBA(x, y, 0, 0, 0, 0);
-            }
-            if ((prevRect.width() > 0) && (prevRect.height() > 0))
-                buffer->setHasAlpha(true);
+            buffer->zeroFillFrameRect(prevRect);
         }
     }
 
     // Update our status to be partially complete.
     buffer->setStatus(ImageFrame::FramePartial);
 
     // Reset the alpha pixel tracker for this frame.
     m_currentBufferSawAlpha = false;
     return true;
 }
 
 } // namespace WebCore