Bug 1125422 - Populate the ContainerLayer flag to force events to be dispatched to content. r=roc

layout/base/nsDisplayList.cpp

@@ -1629,6 +1629,9 @@ already_AddRefed<LayerManager> nsDisplayList::PaintRoot(nsDisplayListBuilder* aB
                      1.0f/containerParameters.mYScale);
   root->SetScaleToResolution(presShell->ScaleToResolution(),
       containerParameters.mXScale);
+  root->SetForceDispatchToContentRegion(
+      aBuilder->IsBuildingLayerEventRegions() &&
+      nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(presShell));
 
   if (gfxPrefs::LayoutUseContainersForRootFrames()) {
     bool isRoot = presContext->IsRootContentDocument();
@@ -4061,6 +4064,9 @@ nsDisplaySubDocument::nsDisplaySubDocument(nsDisplayListBuilder* aBuilder,
     , mScrollParentId(aBuilder->GetCurrentScrollParentId())
 {
   MOZ_COUNT_CTOR(nsDisplaySubDocument);
+  mForceDispatchToContentRegion =
+    aBuilder->IsBuildingLayerEventRegions() &&
+    nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(aFrame->PresContext()->PresShell());
 }
 
 #ifdef NS_BUILD_REFCNT_LOGGING
@@ -4082,7 +4088,9 @@ nsDisplaySubDocument::BuildLayer(nsDisplayListBuilder* aBuilder,
     params.mInLowPrecisionDisplayPort = true; 
   }
 
-  return nsDisplayOwnLayer::BuildLayer(aBuilder, aManager, params);
+  nsRefPtr<Layer> layer = nsDisplayOwnLayer::BuildLayer(aBuilder, aManager, params);
+  layer->AsContainerLayer()->SetForceDispatchToContentRegion(mForceDispatchToContentRegion);
+  return layer.forget();
 }
 
 UniquePtr<FrameMetrics>

layout/base/nsDisplayList.h

@@ -3036,6 +3036,7 @@ public:
 
 protected:
   ViewID mScrollParentId;
+  bool mForceDispatchToContentRegion;
 };
 
 /**

layout/base/nsLayoutUtils.cpp

@@ -20,6 +20,7 @@
 #include "nsIDOMHTMLElement.h"
 #include "nsFrameList.h"
 #include "nsGkAtoms.h"
+#include "nsHtml5Atoms.h"
 #include "nsIAtom.h"
 #include "nsCSSPseudoElements.h"
 #include "nsCSSAnonBoxes.h"
@@ -7851,3 +7852,21 @@ nsLayoutUtils::HasApzAwareListeners(EventListenerManager* aElm)
          aElm->HasListenersFor(nsGkAtoms::onDOMMouseScroll) ||
          aElm->HasListenersFor(nsHtml5Atoms::onmousewheel);
 }
+
+/* static */ bool
+nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(nsIPresShell* aShell)
+{
+  if (nsIDocument* doc = aShell->GetDocument()) {
+    WidgetEvent event(true, NS_EVENT_NULL);
+    nsTArray<EventTarget*> targets;
+    nsresult rv = EventDispatcher::Dispatch(doc, nullptr, &event, nullptr,
+        nullptr, nullptr, &targets);
+    NS_ENSURE_SUCCESS(rv, false);
+    for (size_t i = 0; i < targets.Length(); i++) {
+      if (HasApzAwareListeners(targets[i]->GetExistingListenerManager())) {
+        return true;
+      }
+    }
+  }
+  return false;
+}

layout/base/nsLayoutUtils.h

@@ -2553,6 +2553,7 @@ public:
                                       mozilla::WritingMode aFrameWM);
 
   static bool HasApzAwareListeners(mozilla::EventListenerManager* aElm);
+  static bool HasDocumentLevelListenersForApzAwareEvents(nsIPresShell* aShell);
 
 private:
   static uint32_t sFontSizeInflationEmPerLine;

layout/ipc/RenderFrameParent.cpp

@@ -615,6 +615,17 @@ RenderFrameParent::TakeFocusForClick()
 }  // namespace layout
 }  // namespace mozilla
 
+nsDisplayRemote::nsDisplayRemote(nsDisplayListBuilder* aBuilder,
+                                 nsIFrame* aFrame,
+                                 RenderFrameParent* aRemoteFrame)
+  : nsDisplayItem(aBuilder, aFrame)
+  , mRemoteFrame(aRemoteFrame)
+{
+  mForceDispatchToContentRegion =
+    aBuilder->IsBuildingLayerEventRegions() &&
+    nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(aFrame->PresContext()->PresShell());
+}
+
 already_AddRefed<Layer>
 nsDisplayRemote::BuildLayer(nsDisplayListBuilder* aBuilder,
                             LayerManager* aManager,
@@ -624,6 +635,9 @@ nsDisplayRemote::BuildLayer(nsDisplayListBuilder* aBuilder,
   nsIntRect visibleRect = GetVisibleRect().ToNearestPixels(appUnitsPerDevPixel);
   visibleRect += aContainerParameters.mOffset;
   nsRefPtr<Layer> layer = mRemoteFrame->BuildLayer(aBuilder, mFrame, aManager, visibleRect, this, aContainerParameters);
+  if (layer && layer->AsContainerLayer()) {
+    layer->AsContainerLayer()->SetForceDispatchToContentRegion(mForceDispatchToContentRegion);
+  }
   return layer.forget();
 }
 

layout/ipc/RenderFrameParent.h

@@ -166,10 +166,7 @@ class nsDisplayRemote : public nsDisplayItem
 
 public:
   nsDisplayRemote(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
-                  RenderFrameParent* aRemoteFrame)
-    : nsDisplayItem(aBuilder, aFrame)
-    , mRemoteFrame(aRemoteFrame)
-  {}
+                  RenderFrameParent* aRemoteFrame);
 
   virtual LayerState GetLayerState(nsDisplayListBuilder* aBuilder,
                                    LayerManager* aManager,
@@ -187,6 +184,7 @@ public:
 
 private:
   RenderFrameParent* mRemoteFrame;
+  bool mForceDispatchToContentRegion;
 };