Canvas2d: Implement rerouting event by hit region's control.

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 15 matching lines @@
  */
 
 #include "core/html/HTMLCanvasElement.h"
 
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptController.h"
 #include "core/HTMLNames.h"
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
+#include "core/events/Event.h"
+#include "core/events/EventDispatcher.h"
 #include "core/fileapi/File.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/ImageData.h"
 #include "core/html/canvas/CanvasAsyncBlobCreator.h"
 #include "core/html/canvas/CanvasContextCreationAttributes.h"
 #include "core/html/canvas/CanvasFontCache.h"
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/html/canvas/CanvasRenderingContextFactory.h"
@@ skipping 965 matching lines @@
         return ScriptPromise();
     }
     return ImageBitmapSource::fulfillImageBitmap(scriptState, isPaintable() ? ImageBitmap::create(this, IntRect(sx, sy, sw, sh), options) : nullptr);
 }
 
 bool HTMLCanvasElement::isOpaque() const
 {
     return m_context && !m_context->hasAlpha();
 }
 
+bool HTMLCanvasElement::dispatchEventInternal(PassRefPtrWillBeRawPtr<Event> event)

[philipj_slow, 2016/02/01 04:05:19]

Will this happen for both UA-created and script-created events? I'm trying to
understand how this will be expressed in the spec, and if this will really
correspond to patching hit testing, or if we're now inside DOM's
dispatchEvent().

[zino, 2016/02/05 06:59:48]

In the new patch set, I filtered script-created events out.
I think we avoid hit-testing in case of script-created events. (It can be
initialized from MouseEventInit dictionary).

+{
+    Node* target = nullptr;
+    if (m_context && m_context->is2d() && m_context->hitRegionsCount() > 0)
+        target = m_context->getControlAndUpdateEvent(*event);

[philipj_slow, 2016/02/01 04:05:19]

Might it be more clear to just return the target here and modify the event
outside of getControlAndUpdateEvent? I think so :)

[zino, 2016/02/05 06:59:48]

I agree with you but performance is also important.
So, I thought it is better to avoid to get hit-region if possible.
If we split the function into two parts(getControl and updateEvent), we will
have to get hit-region twice.
So, Instead, I introduced getControlAndIDIfHitRegionExists() in the new patch
set.

[philipj_slow, 2016/02/05 07:30:06]

Ack, std::pair looks like a nice fit.

+    if (!target)
+        target = this;

[philipj_slow, 2016/02/01 04:05:19]

Shouldn't this fall back to the parent class's dispatchEventInternal? Seems like
the easiest way to guarantee no change in behavior if there is no region.

[zino, 2016/02/05 06:59:48]

Sure!

Thank you.

Done.

+    return EventDispatcher::dispatchEvent(*target, event->createMediator());
+}
+
 } // namespace blink