[HTMLCanvasElement.toBlob] Default callback version without scheduler

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index b56dbd2a6b1fec36a8a9a8c2af421e51850300b2..5a52557d6d76a34092f65c5ca34f652833bc934a 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -34,6 +34,7 @@
 #include "core/HTMLNames.h"
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
+#include "core/fileapi/File.h"

[Justin Novosad, 2015/08/13 21:03:40]

File is in core.  I think FileCallback should be as well then. That would
resolve the layering violation.  Forget what I said about making a partial
interface. Just move FileCallback to core/fileapi.  I think moving it to a
module was a mistake.

[xlai (Olivia), 2015/08/20 19:46:44]

Acknowledged. Great! This sounds a simpler solution. Based on what I observed in
the code search, FileCallback was not used by anyone else.

 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/ImageData.h"
@@ -45,6 +46,7 @@
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "platform/MIMETypeRegistry.h"
 #include "platform/RuntimeEnabledFeatures.h"
+#include "platform/ThreadSafeFunctional.h"
 #include "platform/graphics/Canvas2DImageBufferSurface.h"
 #include "platform/graphics/ExpensiveCanvasHeuristicParameters.h"
 #include "platform/graphics/ImageBuffer.h"
@@ -54,6 +56,7 @@
 #include "platform/graphics/gpu/AcceleratedImageBufferSurface.h"
 #include "platform/transforms/AffineTransform.h"
 #include "public/platform/Platform.h"
+#include "public/platform/WebTraceLocation.h"
 #include <math.h>
 #include <v8.h>
 
@@ -508,6 +511,11 @@ String HTMLCanvasElement::toDataURLInternal(const String& mimeType, const double
     return ImageDataBuffer(imageData->size(), imageData->data()->data()).toDataURL(encodingMimeType, quality);
 }
 
+static void invokeFileCallbackWithBlob(FileCallback* callback, File* blob) 
+{
+    callback->handleEvent(blob);
+}
+
 String HTMLCanvasElement::toDataURL(const String& mimeType, const ScriptValue& qualityArgument, ExceptionState& exceptionState) const
 {
     if (!originClean()) {
@@ -526,6 +534,41 @@ String HTMLCanvasElement::toDataURL(const String& mimeType, const ScriptValue& q
     return toDataURLInternal(mimeType, qualityPtr, BackBuffer);
 }
 
+void HTMLCanvasElement::toBlob(FileCallback* callback, const String& mimeType, const ScriptValue& qualityArgument, ExceptionState& exceptionState) const
+{
+    if (!originClean()) {
+        exceptionState.throwSecurityError("Tainted canvases may not be exported.");

[Justin Novosad, 2015/08/13 21:03:40]

Excellent. But this need to be covered by a test.

[xlai (Olivia), 2015/08/20 19:46:44]

Acknowledged. One more layout test in my to-do list.

+        return;
+    }
+
+    File* resultBlob;

[Justin Novosad, 2015/08/13 21:03:40]

Code is less fragile if you initialize to nullptr here.

+    if (!isPaintable()) {
+        // If the canvas element's bitmap has no pixels
+        resultBlob = nullptr;
+        return;
+    }
+
+    double quality;
+    if (!qualityArgument.isEmpty()) {
+        v8::Local<v8::Value> v8Value = qualityArgument.v8Value();
+        if (v8Value->IsNumber()) {
+            quality = v8Value.As<v8::Number>()->Value();
+        }
+    }
+
+    String encodingMimeType = toEncodingMimeType(mimeType);
+
+    ImageData* imageData = toImageData(BackBuffer);
+    ScopedDisposal<ImageData> disposer(imageData);
+
+    // Perform image encoding
+    Vector<char> encodedImage;
+    ImageDataBuffer(imageData->size(), imageData->data()->data()).toDataVector(encodingMimeType, &quality, encodedImage);
+    resultBlob = File::create(&encodedImage, encodingMimeType);
+
+    Platform::current()->mainThread()->postDelayedTask(FROM_HERE, threadSafeBind(&invokeFileCallbackWithBlob, callback, resultBlob), 1);

[Justin Novosad, 2015/08/13 21:03:40]

Why delayed?

[xlai (Olivia), 2015/08/20 19:46:44]

Done. Changed back to postTask. It was my layout test's problem.

+}
+
 SecurityOrigin* HTMLCanvasElement::securityOrigin() const
 {
     return document().securityOrigin();