Bug 966591 - Part 1: Put very basic hit region interface in + add runtime flag. r=roc

content/canvas/src/CanvasRenderingContext2D.cpp

@@ -2355,6 +2355,13 @@ CanvasRenderingContext2D::MeasureText(const nsAString& rawText,
   return new TextMetrics(width);
 }
 
+void CanvasRenderingContext2D::AddHitRegion(const HitRegionOptions& )
+{}
+
+void CanvasRenderingContext2D::RemoveHitRegion(const nsAString&)
+{}
+
+
 /**
  * Used for nsBidiPresUtils::ProcessText
  */

content/canvas/src/CanvasRenderingContext2D.h

@@ -186,6 +186,9 @@ public:
   TextMetrics*
     MeasureText(const nsAString& rawText, mozilla::ErrorResult& error);
 
+  void AddHitRegion(const HitRegionOptions& options);
+  void RemoveHitRegion(const nsAString& id);
+
   void DrawImage(const HTMLImageOrCanvasOrVideoElement& image,
                  double dx, double dy, mozilla::ErrorResult& error)
   {

dom/webidl/CanvasRenderingContext2D.webidl

@@ -11,8 +11,6 @@
  * and create derivative works of this document.
  */
 
-interface HitRegionOptions;
-
 enum CanvasWindingRule { "nonzero", "evenodd" };
 
 dictionary ContextAttributes2D {
@@ -20,6 +18,11 @@ dictionary ContextAttributes2D {
   boolean willReadFrequently = false;
 };
 
+dictionary HitRegionOptions {
+  DOMString id = "";
+  Element? control = null;
+};
+
 interface CanvasRenderingContext2D {
 
   // back-reference to the canvas.  Might be null if we're not
@@ -113,7 +116,8 @@ interface CanvasRenderingContext2D {
   void drawImage((HTMLImageElement or HTMLCanvasElement or HTMLVideoElement) image, double sx, double sy, double sw, double sh, double dx, double dy, double dw, double dh);
 
   // hit regions
-// NOT IMPLEMENTED  void addHitRegion(HitRegionOptions options);
+  [Pref="canvas.hitregions.enabled"] void addHitRegion(optional HitRegionOptions options);
+  [Pref="canvas.hitregions.enabled"] void removeHitRegion(DOMString id);
 
   // pixel manipulation
   [NewObject, Throws]

modules/libpref/src/init/all.js

@@ -432,6 +432,7 @@ pref("accessibility.tabfocus_applies_to_xul", true);
 // provide ability to turn on support for canvas focus rings
 pref("canvas.focusring.enabled", false);
 pref("canvas.customfocusring.enabled", false);
+pref("canvas.hitregions.enabled", false);
 
 // We want the ability to forcibly disable platform a11y, because
 // some non-a11y-related components attempt to bring it up.  See bug