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

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

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
index 2b554b54362aa1de55080ff79e61bf09aad4937e..286ab619aaa9a134ba1bee6d63f2b3843dbd07a4 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -33,6 +33,9 @@
 #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/events/MouseEvent.h"
 #include "core/fileapi/File.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/frame/LocalFrame.h"
@@ -1022,4 +1025,23 @@ bool HTMLCanvasElement::isOpaque() const
     return m_context && !m_context->hasAlpha();
 }
 
+bool HTMLCanvasElement::dispatchEventInternal(PassRefPtrWillBeRawPtr<Event> event)
+{
+    if (event->isMouseEvent() && event->isTrusted()) {
+        MouseEvent* mouseEvent = toMouseEvent(event);
+        std::pair<Element*, String> regionInfo = getControlAndIDIfHitRegionExists(mouseEvent->absoluteLocation());
+        mouseEvent->setRegion(regionInfo.second);
+        if (regionInfo.first)
+            return EventDispatcher::dispatchEvent(*regionInfo.first, event->createMediator());
+    }
+    return HTMLElement::dispatchEventInternal(event);
+}
+
+std::pair<Element*, String> HTMLCanvasElement::getControlAndIDIfHitRegionExists(const LayoutPoint& location)

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

Should probably be Id (not ID) for consistency. I defer to canvas owners,
though.

[zino, 2016/02/12 15:26:18]

I think it's better to "Id" than "ID".

Done.

+{
+    if (m_context && m_context->is2d() && m_context->hitRegionsCount() > 0)

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

It's a bit odd to both have an is2d() test and a virtual call, is this a
necessary optimization or could the m_context check be moved out to
dispatchEventInternal and the gitRegionsCount() check into the implementation,
so that this helper vanishes?

+        return m_context->getControlAndIDIfHitRegionExists(location);
+    return std::make_pair(nullptr, String());
+}
+
 } // namespace blink