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

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp

Index: third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
diff --git a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
index a7155d9eea21952d09be79e81fd6ccc9a465ae25..2c332677b0a1c3539e6f9cce0ca491418c9a0ef1 100644
--- a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
+++ b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
@@ -42,6 +42,7 @@
 #include "core/dom/AXObjectCache.h"
 #include "core/dom/StyleEngine.h"
 #include "core/events/Event.h"
+#include "core/events/MouseEvent.h"
 #include "core/frame/ImageBitmap.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLVideoElement.h"
@@ -1796,6 +1797,34 @@ void CanvasRenderingContext2D::styleDidChange(const ComputedStyle* oldStyle, con
     pruneLocalFontCache(0);
 }
 
+Node* CanvasRenderingContext2D::getControlAndUpdateEvent(Event& event)
+{
+    if (!event.isMouseEvent())
+        return nullptr;
+
+    MouseEvent& e = toMouseEvent(event);

[philipj_slow, 2016/02/01 04:05:20]

https://www.chromium.org/blink/coding-style#TOC-Names asks for full names in
general.

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

Done.

+
+    Document& document = canvas()->document();
+    document.updateLayoutTreeForNodeIfNeeded(canvas());

[Justin Novosad, 2016/02/01 16:51:43]

Don't forget write a test that requires this update.

+
+    LayoutBox* box = canvas()->layoutBox();
+    FloatPoint localPos = box->absoluteToLocal(FloatPoint(e.absoluteLocation()), UseTransforms);
+    if (box->hasBorderOrPadding())
+        localPos.move(-box->contentBoxOffset());
+    localPos.scale(canvas()->width() / box->contentWidth(), canvas()->height() / box->contentHeight());

[Justin Novosad, 2016/02/01 16:51:42]

don't forget test cases that cover CSS zooming and hidpi (use
testRunner.setBackingScaleFactor)

+
+    HitRegion* hitRegion = hitRegionAtPoint(localPos);
+    if (hitRegion) {
+        e.setRegion(hitRegion->id());
+        if (hitRegion->control()) {
+            e.preventDefault();
+            e.setCancelBubble(true);
+            return hitRegion->control();
+        }
+    }
+    return nullptr;
+}
+
 String CanvasRenderingContext2D::textAlign() const
 {
     return textAlignName(state().textAlign());