Refactoring source image usage in CanvasRenderingContext2D

Source/core/html/HTMLImageElement.cpp

Index: Source/core/html/HTMLImageElement.cpp
diff --git a/Source/core/html/HTMLImageElement.cpp b/Source/core/html/HTMLImageElement.cpp
index bed556d30ffc1e5b8771cdbc2fa1bdd38948d4ff..c41ec94cf84020cdd603b53101043b17e2d226e9 100644
--- a/Source/core/html/HTMLImageElement.cpp
+++ b/Source/core/html/HTMLImageElement.cpp
@@ -31,7 +31,9 @@
 #include "core/events/ThreadLocalEventNames.h"
 #include "core/fetch/ImageResource.h"
 #include "core/html/HTMLAnchorElement.h"
+#include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLFormElement.h"
+#include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/html/parser/HTMLSrcsetParser.h"
 #include "core/rendering/RenderImage.h"
@@ -410,4 +412,61 @@ bool HTMLImageElement::isInteractiveContent() const
     return fastHasAttribute(usemapAttr);
 }
 
+PassRefPtr<Image> HTMLImageElement::getSourceImageForCanvas(HTMLCanvasElement* canvas, ExceptionState& exceptionState, CanvasImageSourceUsage usage, bool* isVolatile) const
+{
+    if (isVolatile)
+        *isVolatile = false;
+    if (cachedImage() && cachedImage()->errorOccurred()) {
+        exceptionState.throwDOMException(InvalidStateError, "The HTMLImageElement provided is in the 'broken' state.");
+        return nullptr;
+    }
+
+    if (!complete()) {
+        return nullptr;
+    }
+
+    if (!cachedImage()) {
+        return usage == DrawCanvasImageSourceUsage ? Image::nullImage() : PassRefPtr<Image>();
+    }
+
+    RefPtr<Image> sourceImage = cachedImage()->imageForRenderer(renderer());
+
+    // We need to synthesize a container size if a renderer is not available to provide one.
+    if (!renderer() && sourceImage->usesContainerSize())
+        sourceImage->setContainerSize(sourceImage->size());
+
+    return sourceImage.release();
+}
+
+bool HTMLImageElement::wouldTaintOrigin(CanvasRenderingContext* dst) const

[Stephen White, 2014/02/27 18:53:41]

It seems unfortunate to add a dependency on CanvasRenderingContext (and
HTMLCanvasElement) here. Could we just pass the security origin, and possibly an
interface for querying back the origin by URL instead? (or move the latter up to
a different common class, as you suggested.)

+{
+    ImageResource* image = cachedImage();
+    if (!image)
+        return false;
+    return !image->isAccessAllowed(dst->canvas()->securityOrigin());
+}
+
+FloatSize HTMLImageElement::sourceSize() const
+{
+    ImageResource* image = cachedImage();
+    if (!image)
+        return FloatSize();
+    LayoutSize size;
+    size = image->imageSizeForRenderer(renderer(), 1.0f); // FIXME: Not sure about this.
+
+    return size;
+}
+
+FloatSize HTMLImageElement::defaultDestinationSize() const
+{
+    ImageResource* image = cachedImage();
+    if (!image)
+        return FloatSize();
+    LayoutSize size;
+    size = image->imageSizeForRenderer(renderer(), 1.0f); // FIXME: Not sure about this.
+    if (renderer() && renderer()->isRenderImage() && image->image() && !image->image()->hasRelativeWidth())
+        size.scale(toRenderImage(renderer())->imageDevicePixelRatio());
+    return size;
+}
+
 }