Bug 1137267 - Enable event-regions automatically when APZ is enabled, and allow the APZ code to assume event-regions are enabled always. r=botond,tn

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -269,14 +269,11 @@ APZCTreeManager::AttachNodeToTree(HitTestingTreeNode* aNode,
 static EventRegions
 GetEventRegions(const LayerMetricsWrapper& aLayer)
 {
-  if (gfxPrefs::LayoutEventRegionsEnabled()) {
-    if (aLayer.IsScrollInfoLayer()) {
-      return EventRegions(nsIntRegion(ParentLayerIntRect::ToUntyped(
-        RoundedToInt(aLayer.Metrics().mCompositionBounds))));
-    }
-    return aLayer.GetEventRegions();
+  if (aLayer.IsScrollInfoLayer()) {
+    return EventRegions(nsIntRegion(ParentLayerIntRect::ToUntyped(
+      RoundedToInt(aLayer.Metrics().mCompositionBounds))));
   }
-  return EventRegions(aLayer.GetVisibleRegion());
+  return aLayer.GetEventRegions();
 }
 
 already_AddRefed<HitTestingTreeNode>
@@ -1361,35 +1358,6 @@ APZCTreeManager::GetAPZCAtPoint(HitTestingTreeNode* aNode,
     }
 
     if (*aOutHitResult != HitNothing) {
-      if (result && !gfxPrefs::LayoutEventRegionsEnabled()) {
-        // When event-regions are disabled, we treat scrollinfo layers as
-        // regular scrollable layers. Unfortunately, their "hit region" (which
-        // we create from the composition bounds) is their full area, and they
-        // sit on top of their non-scrollinfo siblings. This means they will get
-        // a HitTestingTreeNode with a hit region that will aggressively match
-        // any input events that might be directed to sub-APZCs of their non-
-        // scrollinfo siblings. Therefore, we need to keep looping through to
-        // see if there are any other non-scrollinfo siblings that have children
-        // that match this input. If so, they should take priority. With event-
-        // regions enabled we use the actual regions from the layer, which are
-        // empty, and so this is unnecessary.
-        AsyncPanZoomController* prevSiblingApzc = nullptr;
-        for (HitTestingTreeNode* n = node->GetPrevSibling(); n; n = n->GetPrevSibling()) {
-          if (n->GetApzc()) {
-            prevSiblingApzc = n->GetApzc();
-            break;
-          }
-        }
-        if (result == prevSiblingApzc) {
-          APZCTM_LOG("Continuing search past probable scrollinfo info layer\n");
-          // We need to reset aOutHitResult in order to keep searching. This is
-          // ok because we know that we will at least hit prevSiblingApzc
-          // again, which is the same as result.
-          *aOutHitResult = HitNothing;
-          continue;
-        }
-      }
-
       return result;
     }
   }

gfx/layers/apz/src/HitTestingTreeNode.cpp

@@ -197,15 +197,6 @@ HitTestingTreeNode::HitTest(const ParentLayerPoint& aPoint) const
     return HitTestResult::HitNothing;
   }
 
-  // When event regions are disabled and we have an APZC on this node, we are
-  // actually storing the touch-sensitive section of the composition bounds in
-  // the clip region, and we don't need to check against the mEventRegions.
-  // If there's no APZC, then we do need to check against the mEventRegions
-  // (which contains the layer's visible region) for obscuration purposes.
-  if (!gfxPrefs::LayoutEventRegionsEnabled() && GetApzc()) {
-    return HitTestResult::HitLayer;
-  }
-
   // convert into Layer coordinate space
   Maybe<LayerPoint> pointInLayerPixels = Untransform(aPoint);
   if (!pointInLayerPixels) {

gfx/layers/apz/src/InputQueue.cpp

@@ -201,9 +201,6 @@ InputQueue::MaybeRequestContentResponse(const nsRefPtr<AsyncPanZoomController>&
                                         CancelableBlockState* aBlock)
 {
   bool waitForMainThread = !aBlock->IsTargetConfirmed();
-  if (!gfxPrefs::LayoutEventRegionsEnabled()) {
-    waitForMainThread |= aTarget->NeedToWaitForContent();
-  }
   if (aBlock->AsTouchBlock() && aBlock->AsTouchBlock()->IsDuringFastMotion()) {
     aBlock->SetConfirmedTargetApzc(aTarget);
     waitForMainThread = false;

gfx/tests/gtest/TestAsyncPanZoomController.cpp

@@ -2668,8 +2668,6 @@ protected:
 };
 
 TEST_F(APZEventRegionsTester, HitRegionImmediateResponse) {
-  SCOPED_GFX_PREF(LayoutEventRegionsEnabled, bool, true);
-
   CreateEventRegionsLayerTree1();
 
   TestAsyncPanZoomController* root = ApzcOf(layers[0]);
@@ -2723,8 +2721,6 @@ TEST_F(APZEventRegionsTester, HitRegionImmediateResponse) {
 }
 
 TEST_F(APZEventRegionsTester, HitRegionAccumulatesChildren) {
-  SCOPED_GFX_PREF(LayoutEventRegionsEnabled, bool, true);
-
   CreateEventRegionsLayerTree2();
 
   int time = 0;
@@ -2738,8 +2734,6 @@ TEST_F(APZEventRegionsTester, HitRegionAccumulatesChildren) {
 }
 
 TEST_F(APZEventRegionsTester, Obscuration) {
-  SCOPED_GFX_PREF(LayoutEventRegionsEnabled, bool, true);
-
   CreateObscuringLayerTree();
   ScopedLayerTreeRegistration registration(0, root, mcc);
 
@@ -2758,8 +2752,6 @@ TEST_F(APZEventRegionsTester, Obscuration) {
 }
 
 TEST_F(APZEventRegionsTester, Bug1119497) {
-  SCOPED_GFX_PREF(LayoutEventRegionsEnabled, bool, true);
-
   CreateBug1119497LayerTree();
 
   HitTestResult result;
@@ -2771,8 +2763,6 @@ TEST_F(APZEventRegionsTester, Bug1119497) {
 }
 
 TEST_F(APZEventRegionsTester, Bug1117712) {
-  SCOPED_GFX_PREF(LayoutEventRegionsEnabled, bool, true);
-
   CreateBug1117712LayerTree();
 
   TestAsyncPanZoomController* apzc2 = ApzcOf(layers[2]);

layout/base/nsDisplayList.cpp

@@ -4803,17 +4803,14 @@ nsDisplayScrollInfoLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
                                      LayerManager* aManager,
                                      const ContainerLayerParameters& aContainerParameters)
 {
-  // Only build scrollinfo layers if event-regions are disabled, so that the
-  // compositor knows where the inactive scrollframes are. When event-regions
-  // are enabled, the dispatch-to-content regions generally provide this
-  // information to the APZ code. However, in some cases, there might be
-  // content that cannot be layerized, and so needs to scroll synchronously.
-  // To handle those cases (which are indicated by setting mHoisted to true), we
-  // still want to generate scrollinfo layers.
-  if (gfxPrefs::LayoutEventRegionsEnabled() && !mHoisted) {
-    return nullptr;
-  }
-  return nsDisplayScrollLayer::BuildLayer(aBuilder, aManager, aContainerParameters);
+  // In general for APZ with event-regions we no longer have a need for
+  // scrollinfo layers. However, in some cases, there might be content that
+  // cannot be layerized, and so needs to scroll synchronously. To handle those
+  // cases (which are indicated by setting mHoisted to true), we still want to
+  // generate scrollinfo layers.
+  return mHoisted
+    ? nsDisplayScrollLayer::BuildLayer(aBuilder, aManager, aContainerParameters)
+    : nullptr;
 }
 
 LayerState
@@ -4822,10 +4819,9 @@ nsDisplayScrollInfoLayer::GetLayerState(nsDisplayListBuilder* aBuilder,
                                         const ContainerLayerParameters& aParameters)
 {
   // See comment in BuildLayer
-  if (gfxPrefs::LayoutEventRegionsEnabled() && !mHoisted) {
-    return LAYER_NONE;
-  }
-  return LAYER_ACTIVE_EMPTY;
+  return mHoisted
+    ? LAYER_ACTIVE_EMPTY
+    : LAYER_NONE;
 }
 
 bool

layout/base/nsDisplayList.h

@@ -345,7 +345,11 @@ public:
   }
   bool IsBuildingLayerEventRegions()
   {
-    return (gfxPrefs::LayoutEventRegionsEnabled() && mMode == PAINTING);
+    if (mMode == PAINTING) {
+      return (gfxPrefs::LayoutEventRegionsEnabled() ||
+              gfxPrefs::AsyncPanZoomEnabled());
+    }
+    return false;
   }
   bool IsInsidePointerEventsNoneDoc()
   {