Bug 979692 - Calculate hit detection and fill in region parameter to mouse events. r=roc

content/canvas/src/CanvasRenderingContext2D.cpp

@@ -1110,6 +1110,17 @@ CanvasRenderingContext2D::GetImageBuffer(uint8_t** aImageBuffer,
   *aFormat = imgIEncoder::INPUT_FORMAT_HOSTARGB;
 }
 
+nsString CanvasRenderingContext2D::GetHitRegion(const mozilla::gfx::Point& aPoint)
+{
+  for (unsigned int x = 0 ; x < mHitRegionsOptions.Length(); x++) {
+    RegionInfo& info = mHitRegionsOptions[x];
+    if (info.mPath->ContainsPoint(aPoint, Matrix())) {
+      return info.mId;
+    }
+  }
+  return nsString();
+}
+
 NS_IMETHODIMP
 CanvasRenderingContext2D::GetInputStream(const char *aMimeType,
                                          const char16_t *aEncoderOptions,

content/canvas/src/CanvasRenderingContext2D.h

@@ -537,6 +537,11 @@ public:
 
   virtual void GetImageBuffer(uint8_t** aImageBuffer, int32_t* aFormat);
 
+
+  // Given a point, return hit region ID if it exists
+  nsString GetHitRegion(const mozilla::gfx::Point& aPoint);
+
+
   // return true and fills in the bound rect if element has a hit region.
   bool GetHitRegionRect(Element* aElement, nsRect& aRect);
 

content/html/content/public/HTMLCanvasElement.h

@@ -185,6 +185,8 @@ public:
   virtual nsresult Clone(nsINodeInfo *aNodeInfo, nsINode **aResult) const MOZ_OVERRIDE;
   nsresult CopyInnerTo(mozilla::dom::Element* aDest);
 
+  virtual nsresult PreHandleEvent(mozilla::EventChainPreVisitor& aVisitor) MOZ_OVERRIDE;
+
   /*
    * Helpers called by various users of Canvas
    */

content/html/content/src/HTMLCanvasElement.cpp

@@ -1,4 +1,4 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+   /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
@@ -14,7 +14,10 @@
 #include "mozilla/dom/CanvasRenderingContext2D.h"
 #include "mozilla/dom/HTMLCanvasElementBinding.h"
 #include "mozilla/dom/UnionTypes.h"
+#include "mozilla/dom/MouseEvent.h"
+#include "mozilla/EventDispatcher.h"
 #include "mozilla/gfx/Rect.h"
+#include "mozilla/MouseEvents.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/Telemetry.h"
 #include "nsAttrValueInlines.h"
@@ -28,6 +31,7 @@
 #include "nsIWritablePropertyBag2.h"
 #include "nsIXPConnect.h"
 #include "nsJSUtils.h"
+#include "nsLayoutUtils.h"
 #include "nsMathUtils.h"
 #include "nsNetUtil.h"
 #include "nsStreamUtils.h"
@@ -288,6 +292,34 @@ HTMLCanvasElement::CopyInnerTo(Element* aDest)
   return rv;
 }
 
+nsresult HTMLCanvasElement::PreHandleEvent(EventChainPreVisitor& aVisitor)
+{
+  if (aVisitor.mEvent->eventStructType == NS_MOUSE_EVENT) {
+    WidgetMouseEventBase* evt = (WidgetMouseEventBase*)aVisitor.mEvent;
+    if (evt) {
+      nsCOMPtr<nsISupports> cxt;
+      GetContext(NS_LITERAL_STRING("2d"), getter_AddRefs(cxt));
+      nsRefPtr<CanvasRenderingContext2D> context2d =
+        static_cast<CanvasRenderingContext2D*>(cxt.get());
+
+      if (context2d) {
+        nsIFrame *frame = GetPrimaryFrame();
+        if (!frame)
+          return NS_OK;
+        nsPoint ptInRoot = nsLayoutUtils::GetEventCoordinatesRelativeTo(evt, frame);
+        nsRect paddingRect = frame->GetContentRectRelativeToSelf();
+        Point hitpoint;
+        hitpoint.x = (ptInRoot.x - paddingRect.x) / AppUnitsPerCSSPixel();
+        hitpoint.y = (ptInRoot.y - paddingRect.y) / AppUnitsPerCSSPixel();
+
+        evt->region = context2d->GetHitRegion(hitpoint);
+        aVisitor.mCanHandle = true;
+      }
+    }
+  }
+  return nsGenericHTMLElement::PreHandleEvent(aVisitor);
+}
+
 nsChangeHint
 HTMLCanvasElement::GetAttributeChangeHint(const nsIAtom* aAttribute,
                                           int32_t aModType) const

dom/events/MouseEvent.cpp

@@ -299,6 +299,10 @@ void
 MouseEvent::GetRegion(nsAString& aRegion)
 {
   SetDOMStringToNull(aRegion);
+  WidgetMouseEventBase* mouseEventBase = mEvent->AsMouseEventBase();
+  if (mouseEventBase) {
+    aRegion = mouseEventBase->region;
+  }
 }
 
 NS_IMETHODIMP

widget/MouseEvents.h

@@ -126,6 +126,9 @@ public:
   // Possible values at nsIDOMMouseEvent
   uint16_t inputSource;
 
+  // ID of the canvas HitRegion
+  nsString region;
+
   void AssignMouseEventBaseData(const WidgetMouseEventBase& aEvent,
                                 bool aCopyTargets)
   {