Bug 1418387 - Add CompositorHitTestInfo bits for scrollbars. r=mstange

MozReview-Commit-ID: KTfpXoESOxF

--HG--
extra : rebase_source : d1db8909b1b075f885b08c86ebca7ef51fd250e0

gfx/src/CompositorHitTestInfo.h

@@ -34,6 +34,17 @@ enum class CompositorHitTestInfo : uint16_t {
   eTouchActionDoubleTapZoomDisabled = 1 << 5,
   // Mask to check for all the touch-action flags at once
   eTouchActionMask = (1 << 2) | (1 << 3) | (1 << 4) | (1 << 5),
+
+  // The frame is a scrollbar or a subframe inside a scrollbar (including
+  // scroll thumbs)
+  eScrollbar = 1 << 6,
+  // The frame is a scrollthumb. If this is set then eScrollbar will also be
+  // set, unless gecko somehow generates a scroll thumb without a containing
+  // scrollbar.
+  eScrollbarThumb = 1 << 7,
+  // If eScrollbar is set, this flag indicates if the scrollbar is a vertical
+  // one (if set) or a horizontal one (if not set)
+  eScrollbarVertical = 1 << 8,
 };
 
 MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(CompositorHitTestInfo)

layout/generic/nsFrame.cpp

@@ -11286,6 +11286,23 @@ nsIFrame::GetCompositorHitTestInfo(nsDisplayListBuilder* aBuilder)
     }
   }
 
+  nsDisplayOwnLayerFlags flags = aBuilder->GetCurrentScrollbarFlags();
+  if (flags != nsDisplayOwnLayerFlags::eNone) {
+    if (GetContent()->IsXULElement(nsGkAtoms::thumb)) {
+      result |= CompositorHitTestInfo::eScrollbarThumb;
+    }
+    // The only flags that get set in nsDisplayListBuilder::mCurrentScrollbarFlags
+    // are the scrollbar direction flags
+    if (flags == nsDisplayOwnLayerFlags::eVerticalScrollbar) {
+      result |= CompositorHitTestInfo::eScrollbarVertical;
+    } else {
+      MOZ_ASSERT(flags == nsDisplayOwnLayerFlags::eHorizontalScrollbar);
+    }
+    // includes the ScrollbarFrame, SliderFrame, anything else that
+    // might be inside the xul:scrollbar
+    result |= CompositorHitTestInfo::eScrollbar;
+  }
+
   return result;
 }
 

layout/generic/nsIFrame.h

@@ -4146,6 +4146,13 @@ public:
   bool BuiltBlendContainer() { return mBuiltBlendContainer; }
   void SetBuiltBlendContainer(bool aBuilt) { mBuiltBlendContainer = aBuilt; }
 
+  /**
+   * Returns the set of flags indicating the properties of the frame that the
+   * compositor might care about for hit-testing purposes. Note that this function
+   * must be called during Gecko display list construction time (i.e while the
+   * frame tree is being traversed) because that is when the display list builder
+   * has the necessary state set up correctly.
+   */
   mozilla::gfx::CompositorHitTestInfo GetCompositorHitTestInfo(nsDisplayListBuilder* aBuilder);
 
 protected:

layout/painting/nsDisplayList.cpp

@@ -4868,6 +4868,27 @@ nsDisplayEventReceiver::CreateWebRenderCommands(mozilla::wr::DisplayListBuilder&
   return true;
 }
 
+nsDisplayCompositorHitTestInfo::nsDisplayCompositorHitTestInfo(nsDisplayListBuilder* aBuilder,
+                                                               nsIFrame* aFrame,
+                                                               mozilla::gfx::CompositorHitTestInfo aHitTestInfo)
+  : nsDisplayEventReceiver(aBuilder, aFrame)
+  , mHitTestInfo(aHitTestInfo)
+{
+  MOZ_COUNT_CTOR(nsDisplayCompositorHitTestInfo);
+  // We should never even create this display item if we're not building
+  // compositor hit-test info or if the computed hit info indicated the
+  // frame is invisible to hit-testing
+  MOZ_ASSERT(aBuilder->BuildCompositorHitTestInfo());
+  MOZ_ASSERT(mHitTestInfo != mozilla::gfx::CompositorHitTestInfo::eInvisibleToHitTest);
+
+  if (aBuilder->GetCurrentScrollbarFlags() != nsDisplayOwnLayerFlags::eNone) {
+    // In the case of scrollbar frames, we use the scrollbar's target scrollframe
+    // instead of the scrollframe with which the scrollbar actually moves.
+    MOZ_ASSERT(mHitTestInfo & CompositorHitTestInfo::eScrollbar);
+    mScrollTarget = Some(aBuilder->GetCurrentScrollbarTarget());
+  }
+}
+
 bool
 nsDisplayCompositorHitTestInfo::CreateWebRenderCommands(mozilla::wr::DisplayListBuilder& aBuilder,
                                                         mozilla::wr::IpcResourceUpdateQueue& aResources,
@@ -4902,10 +4923,13 @@ nsDisplayCompositorHitTestInfo::CreateWebRenderCommands(mozilla::wr::DisplayList
   // we don't need to do it as often, and so that we can do it for other
   // display item types as well (reducing the need for as many instances of
   // this display item).
-  FrameMetrics::ViewID scrollId = FrameMetrics::NULL_SCROLL_ID;
-  if (const ActiveScrolledRoot* asr = GetActiveScrolledRoot()) {
-    scrollId = asr->GetViewId();
-  }
+  FrameMetrics::ViewID scrollId = mScrollTarget.valueOrFrom(
+      [&]() -> FrameMetrics::ViewID {
+          if (const ActiveScrolledRoot* asr = GetActiveScrolledRoot()) {
+            return asr->GetViewId();
+          }
+          return FrameMetrics::NULL_SCROLL_ID;
+      });
 
   // Insert a transparent rectangle with the hit-test info
   aBuilder.SetHitTestInfo(scrollId, mHitTestInfo);
@@ -6934,6 +6958,12 @@ nsDisplayOwnLayer::UpdateScrollData(mozilla::layers::WebRenderScrollData* aData,
   return ret;
 }
 
+void
+nsDisplayOwnLayer::WriteDebugInfo(std::stringstream& aStream)
+{
+  aStream << nsPrintfCString(" (flags 0x%x) (scrolltarget %" PRIu64 ")", (int)mFlags, mScrollTarget).get();
+}
+
 nsDisplaySubDocument::nsDisplaySubDocument(nsDisplayListBuilder* aBuilder,
                                            nsIFrame* aFrame,
                                            nsSubDocumentFrame* aSubDocFrame,

layout/painting/nsDisplayList.h

@@ -4343,17 +4343,7 @@ public:
 class nsDisplayCompositorHitTestInfo : public nsDisplayEventReceiver {
 public:
   nsDisplayCompositorHitTestInfo(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
-                                 mozilla::gfx::CompositorHitTestInfo aHitTestInfo)
-    : nsDisplayEventReceiver(aBuilder, aFrame)
-    , mHitTestInfo(aHitTestInfo)
-  {
-    MOZ_COUNT_CTOR(nsDisplayCompositorHitTestInfo);
-    // We should never even create this display item if we're not building
-    // compositor hit-test info or if the computed hit info indicated the
-    // frame is invisible to hit-testing
-    MOZ_ASSERT(aBuilder->BuildCompositorHitTestInfo());
-    MOZ_ASSERT(mHitTestInfo != mozilla::gfx::CompositorHitTestInfo::eInvisibleToHitTest);
-  }
+                                 mozilla::gfx::CompositorHitTestInfo aHitTestInfo);
 
 #ifdef NS_BUILD_REFCNT_LOGGING
   virtual ~nsDisplayCompositorHitTestInfo()
@@ -4375,6 +4365,7 @@ public:
 
 private:
   mozilla::gfx::CompositorHitTestInfo mHitTestInfo;
+  mozilla::Maybe<mozilla::layers::FrameMetrics::ViewID> mScrollTarget;
 };
 
 /**
@@ -5156,6 +5147,8 @@ public:
     return false;
   }
 
+  void WriteDebugInfo(std::stringstream& aStream) override;
+
   nsDisplayOwnLayerFlags GetFlags() { return mFlags; }
   bool IsScrollThumbLayer() const;
   NS_DISPLAY_DECL_NAME("OwnLayer", TYPE_OWN_LAYER)