Determine if OffscreenCanvas is paintable in different rendering contexts

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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.
@@ skipping 68 matching lines @@
 namespace blink {
 
 using namespace HTMLNames;
 
 namespace {
 
 // These values come from the WhatWG spec.
 const int DefaultWidth = 300;
 const int DefaultHeight = 150;
 
-// Firefox limits width/height to 32767 pixels, but slows down dramatically before it
-// reaches that limit. We limit by area instead, giving us larger maximum dimensions,
-// in exchange for a smaller maximum canvas size.
-const int MaxCanvasArea = 32768 * 8192; // Maximum canvas area in CSS pixels
-
-// In Skia, we will also limit width/height to 32767.
-const int MaxSkiaDim = 32767; // Maximum width/height in CSS pixels.
-
 #if OS(ANDROID)
 // We estimate that the max limit for android phones is a quarter of that for
 // desktops based on local experimental results on Android One.
 const int MaxGlobalAcceleratedImageBufferCount = 25;
 #else
 const int MaxGlobalAcceleratedImageBufferCount = 100;
 #endif
 
 // We estimate the max limit of GPU allocated memory for canvases before Chrome
 // becomes laggy by setting the total allocated memory for accelerated canvases
 // to be equivalent to memory used by 100 accelerated canvases, each has a size
 // of 1000*500 and 2d context.
 // Each such canvas occupies 4000000 = 1000 * 500 * 2 * 4 bytes, where 2 is the
 // gpuBufferCount in ImageBuffer::updateGPUMemoryUsage() and 4 means four bytes
 // per pixel per buffer.
 const int MaxGlobalGPUMemoryUsage = 4000000 * MaxGlobalAcceleratedImageBufferCount;
 
 // A default value of quality argument for toDataURL and toBlob
 // It is in an invalid range (outside 0.0 - 1.0) so that it will not be
 // misinterpreted as a user-input value
 const int UndefinedQualityValue = -1.0;
 
 // Default image mime type for toDataURL and toBlob functions
 const char DefaultMimeType[] = "image/png";
 
-bool canCreateImageBuffer(const IntSize& size)
-{
-    if (size.isEmpty())
-        return false;
-    CheckedNumeric<int> area = size.width();
-    area *= size.height();
-    if (!area.IsValid() || area.ValueOrDie() > MaxCanvasArea)
-        return false;
-    if (size.width() > MaxSkiaDim || size.height() > MaxSkiaDim)
-        return false;
-    return true;
-}
-
 PassRefPtr<Image> createTransparentImage(const IntSize& size)
 {
-    DCHECK(canCreateImageBuffer(size));
+    DCHECK(ImageBuffer::canCreateImageBuffer(size));
     sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(size.width(), size.height());
     return StaticBitmapImage::create(fromSkSp(surface->makeImageSnapshot()));
 }
 
 } // namespace
 
 inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     : HTMLElement(canvasTag, document)
     , ContextLifecycleObserver(&document)
     , PageVisibilityObserver(document.page())
@@ skipping 121 matching lines @@
 }
 
 bool HTMLCanvasElement::shouldBeDirectComposited() const
 {
     return (m_context && m_context->isAccelerated()) || (hasImageBuffer() && buffer()->isExpensiveToPaint()) || (!!m_surfaceLayerBridge);
 }
 
 bool HTMLCanvasElement::isPaintable() const
 {
     if (!m_context)
-        return canCreateImageBuffer(size());
+        return ImageBuffer::canCreateImageBuffer(size());
     return buffer();
 }
 
 void HTMLCanvasElement::didDraw(const FloatRect& rect)
 {
     if (rect.isEmpty())
         return;
     m_imageBufferIsClear = false;
     clearCopiedImage();
     if (layoutObject())
@@ skipping 598 matching lines @@
         m_context->loseContext(CanvasRenderingContext::SyntheticLostContext);
 }
 
 void HTMLCanvasElement::createImageBufferInternal(std::unique_ptr<ImageBufferSurface> externalSurface)
 {
     DCHECK(!m_imageBuffer);
 
     m_didFailToCreateImageBuffer = true;
     m_imageBufferIsClear = true;
 
-    if (!canCreateImageBuffer(size()))
+    if (!ImageBuffer::canCreateImageBuffer(size()))
         return;
 
     int msaaSampleCount = 0;
     std::unique_ptr<ImageBufferSurface> surface;
     if (externalSurface) {
         surface = std::move(externalSurface);
     } else {
         surface = createImageBufferSurface(size(), &msaaSampleCount);
     }
     m_imageBuffer = ImageBuffer::create(std::move(surface));
@@ skipping 327 matching lines @@
 
 bool HTMLCanvasElement::createSurfaceLayer()
 {
     DCHECK(!m_surfaceLayerBridge);
     std::unique_ptr<CanvasSurfaceLayerBridgeClient> bridgeClient = wrapUnique(new CanvasSurfaceLayerBridgeClientImpl());
     m_surfaceLayerBridge = wrapUnique(new CanvasSurfaceLayerBridge(std::move(bridgeClient)));
     return m_surfaceLayerBridge->createSurfaceLayer(this->width(), this->height());
 }
 
 } // namespace blink