Bug 1090398 - Use EventRegions objects instead of nsIntRegions for tracking APZ hit-test areas. r=botond

This simply swaps out the existing nsIntRegion used in APZ hit-testing for
an EventRegion object. The dispatch-to-content region inside the EventRegions
is kept empty, and there are no functional changes here.

gfx/layers/LayersTypes.h

@@ -162,6 +162,15 @@ struct EventRegions {
   nsIntRegion mHitRegion;
   nsIntRegion mDispatchToContentHitRegion;
 
+  EventRegions()
+  {
+  }
+
+  explicit EventRegions(nsIntRegion aHitRegion)
+    : mHitRegion(aHitRegion)
+  {
+  }
+
   bool operator==(const EventRegions& aRegions) const
   {
     return mHitRegion == aRegions.mHitRegion &&
@@ -172,6 +181,12 @@ struct EventRegions {
     return !(*this == aRegions);
   }
 
+  void OrWith(const EventRegions& aOther)
+  {
+    mHitRegion.OrWith(aOther.mHitRegion);
+    mDispatchToContentHitRegion.OrWith(aOther.mDispatchToContentHitRegion);
+  }
+
   nsCString ToString() const
   {
     nsCString result = mHitRegion.ToString();

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -327,7 +327,7 @@ APZCTreeManager::PrepareAPZCForLayer(const LayerMetricsWrapper& aLayer,
         aState.mIsFirstPaint && (aLayersId == aState.mOriginatingLayersId));
 
     nsIntRegion unobscured = ComputeTouchSensitiveRegion(state->mController, aMetrics, aObscured);
-    apzc->SetLayerHitTestData(unobscured, aAncestorTransform);
+    apzc->SetLayerHitTestData(EventRegions(unobscured), aAncestorTransform);
     APZCTM_LOG("Setting region %s as visible region for APZC %p\n",
         Stringify(unobscured).c_str(), apzc);
 
@@ -391,7 +391,7 @@ APZCTreeManager::PrepareAPZCForLayer(const LayerMetricsWrapper& aLayer,
     // on top of B. Fixing this doesn't appear to be very easy so I'm leaving it for
     // now in the hopes that we won't run into this problem a lot.
     nsIntRegion unobscured = ComputeTouchSensitiveRegion(state->mController, aMetrics, aObscured);
-    apzc->AddHitTestRegion(unobscured);
+    apzc->AddHitTestRegions(EventRegions(unobscured));
     APZCTM_LOG("Adding region %s to visible region of APZC %p\n", Stringify(unobscured).c_str(), apzc);
   }
 
@@ -1225,7 +1225,7 @@ APZCTreeManager::GetAPZCAtPoint(AsyncPanZoomController* aApzc,
     }
   }
   if (!result && hitTestPointForThisLayer.HasPositiveWCoord() &&
-      aApzc->VisibleRegionContains(ParentLayerPoint::FromUnknownPoint(hitTestPointForThisLayer.As2DPoint()))) {
+      aApzc->HitRegionContains(ParentLayerPoint::FromUnknownPoint(hitTestPointForThisLayer.As2DPoint()))) {
     APZCTM_LOG("Successfully matched untransformed point %f %f to visible region for APZC %p\n",
              hitTestPointForThisLayer.x, hitTestPointForThisLayer.y, aApzc);
     result = aApzc;

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -20,6 +20,7 @@
 #include "InputData.h"
 #include "Axis.h"
 #include "InputQueue.h"
+#include "LayersTypes.h"
 #include "TaskThrottler.h"
 #include "mozilla/gfx/Matrix.h"
 #include "nsRegion.h"
@@ -997,22 +998,22 @@ private:
    * hit-testing to see which APZC instance should handle touch events.
    */
 public:
-  void SetLayerHitTestData(const nsIntRegion& aRegion, const Matrix4x4& aTransformToLayer) {
-    mVisibleRegion = aRegion;
+  void SetLayerHitTestData(const EventRegions& aRegions, const Matrix4x4& aTransformToLayer) {
+    mEventRegions = aRegions;
     mAncestorTransform = aTransformToLayer;
   }
 
-  void AddHitTestRegion(const nsIntRegion& aRegion) {
-    mVisibleRegion.OrWith(aRegion);
+  void AddHitTestRegions(const EventRegions& aRegions) {
+    mEventRegions.OrWith(aRegions);
   }
 
   Matrix4x4 GetAncestorTransform() const {
     return mAncestorTransform;
   }
 
-  bool VisibleRegionContains(const ParentLayerPoint& aPoint) const {
+  bool HitRegionContains(const ParentLayerPoint& aPoint) const {
     ParentLayerIntPoint point = RoundedToInt(aPoint);
-    return mVisibleRegion.Contains(point.x, point.y);
+    return mEventRegions.mHitRegion.Contains(point.x, point.y);
   }
 
   bool IsOverscrolled() const {
@@ -1020,11 +1021,11 @@ public:
   }
 
 private:
-  /* This is the union of the visible regions of the layers that this APZC
-   * corresponds to, in the screen pixels of those layers. (This is the same
-   * coordinate system in which this APZC receives events in
+  /* This is the union of the hit regions of the layers that this APZC
+   * corresponds to, in the local screen pixels of those layers. (This is the
+   * same coordinate system in which this APZC receives events in
    * ReceiveInputEvent()). */
-  nsIntRegion mVisibleRegion;
+  EventRegions mEventRegions;
   /* This is the cumulative CSS transform for all the layers from (and including)
    * the parent APZC down to (but excluding) this one. */
   Matrix4x4 mAncestorTransform;