Save a bitmap copy when advancing to dependent GIF and WebP animation frames

third_party/WebKit/Source/platform/image-decoders/ImageFrame.cpp

 /*
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 #include "platform/image-decoders/ImageFrame.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
+#include "platform/graphics/skia/SkiaUtils.h"
 #include "platform/image-decoders/ImageDecoder.h"
 
 namespace blink {
 
 ImageFrame::ImageFrame()
     : m_allocator(0)
     , m_hasAlpha(true)
     , m_status(FrameEmpty)
     , m_duration(0)
     , m_disposalMethod(DisposeNotSpecified)
@@ skipping 41 matching lines @@
 }
 
 void ImageFrame::zeroFillPixelData()
 {
     m_bitmap.eraseARGB(0, 0, 0, 0);
     m_hasAlpha = true;
 }
 
 bool ImageFrame::copyBitmapData(const ImageFrame& other)
 {
-    if (this == &other)
-        return true;
-
+    DCHECK_NE(this, &other);
     m_hasAlpha = other.m_hasAlpha;
     m_bitmap.reset();
     return other.m_bitmap.copyTo(&m_bitmap, other.m_bitmap.colorType());
 }
 
+bool ImageFrame::takeBitmapDataIfWritable(ImageFrame* other)
+{
+    DCHECK(other);
+    DCHECK_NE(this, other);
+    if (other->m_bitmap.isImmutable())
+        return false;
+    m_hasAlpha = other->m_hasAlpha;
+    m_bitmap.reset();
+    m_bitmap.swap(other->m_bitmap);
+    other->m_status = FrameEmpty;

[Ken Russell (switch to Gerrit), 2016/09/29 00:40:04]

What about all of the other fields of this ImageFrame, like m_status? Are you
sure this ImageFrame object will be in a consistent state after swapping
m_bitmap with other->m_bitmap?

Or, if the invariant is that m_status on both sides must be FrameComplete for
this to run, what about either DCHECKs for that, or explicit tests and returning
false if not?

[aleksandar.stojiljkovic, 2016/09/29 08:03:53]

For both clients, GIF and WebP right after this call (or copyBitmapData variant)
m_status is set to FramePartial (m_status before this call is FrameEmpty).
Added DCHECKs: other is always in FrameComplete status, this frame m_status is
FrameEmpty - both of the conditions are ensured on client side  before the call
but adding them here too should help clarifying and avoid misuse later. Thanks.

+    return true;
+}
+
 bool ImageFrame::setSizeAndColorProfile(int newWidth, int newHeight, const ICCProfile& newIccProfile)
 {
     // setSizeAndColorProfile() should only be called once, it leaks memory otherwise.
     ASSERT(!width() && !height());
 
     sk_sp<SkColorSpace> colorSpace;
     if (RuntimeEnabledFeatures::colorCorrectRenderingEnabled()) {
         if (newIccProfile.isEmpty())
             colorSpace = SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named);
         else
             colorSpace = SkColorSpace::NewICC(newIccProfile.data(), newIccProfile.size());
         DCHECK(colorSpace);
     }
 
     m_bitmap.setInfo(SkImageInfo::MakeN32(newWidth, newHeight,
         m_premultiplyAlpha ? kPremul_SkAlphaType : kUnpremul_SkAlphaType, colorSpace));
     if (!m_bitmap.tryAllocPixels(m_allocator, 0))
         return false;
 
     zeroFillPixelData();
     return true;
 }
 
 bool ImageFrame::hasAlpha() const
 {
     return m_hasAlpha;
 }
 
+sk_sp<SkImage> ImageFrame::finalizePixelsAndGetImage()
+{
+    DCHECK_EQ(FrameComplete, m_status);
+    m_bitmap.setImmutable();
+    return SkImage::MakeFromBitmap(m_bitmap);
+}
+
 void ImageFrame::setHasAlpha(bool alpha)
 {
     m_hasAlpha = alpha;
 
     m_bitmap.setAlphaType(computeAlphaType());
 }
 
 void ImageFrame::setStatus(Status status)
 {
     m_status = status;
     if (m_status == FrameComplete) {
         m_bitmap.setAlphaType(computeAlphaType());
-        // Send pending pixels changed notifications now, because we can't do this after
-        // the bitmap has been marked immutable.
+        // Send pending pixels changed notifications now, because we can't do
+        // this after the bitmap has been marked immutable.  We don't set the
+        // bitmap immutable here because it would defeat
+        // takeBitmapDataIfWritable().  Instead we let the bitmap stay mutable
+        // until someone calls finalizePixelsAndGetImage() to actually get the
+        // SkImage.
         notifyBitmapIfPixelsChanged();
-        m_bitmap.setImmutable(); // Tell the bitmap it's done.
     }
 }
 
 void ImageFrame::zeroFillFrameRect(const IntRect& rect)
 {
     if (rect.isEmpty())
         return;
 
     m_bitmap.eraseArea(rect, SkColorSetARGB(0, 0, 0, 0));
     setHasAlpha(true);
 }
 
 SkAlphaType ImageFrame::computeAlphaType() const
 {
     // If the frame is not fully loaded, there will be transparent pixels,
     // so we can't tell skia we're opaque, even for image types that logically
     // always are (e.g. jpeg).
     if (!m_hasAlpha && m_status == FrameComplete)
         return kOpaque_SkAlphaType;
 
     return m_premultiplyAlpha ? kPremul_SkAlphaType : kUnpremul_SkAlphaType;
 }
 
 } // namespace blink