Bug 1610731 - Remove GetIsStickyPosition and clean up some TODOs. r=botond

The GetIsStickyPosition function isn't really needed since we can distinguish
whether or not a layer is sticky via NULL_SCROLL_ID as the container id. Also
ensure we have proper AtBottomLayer checks where needed for fixed and sticky
data.

Differential Revision: https://phabricator.services.mozilla.com/D69554

--HG--
extra : moz-landing-system : lando

gfx/layers/LayerMetricsWrapper.h

@@ -409,38 +409,50 @@ class MOZ_STACK_CLASS LayerMetricsWrapper final {
   ScrollableLayerGuid::ViewID GetFixedPositionScrollContainerId() const {
     MOZ_ASSERT(IsValid());
 
-    // TODO: Restrict this only for AtBottomLayer.
-    return mLayer->GetFixedPositionScrollContainerId();
+    if (AtBottomLayer()) {
+      return mLayer->GetFixedPositionScrollContainerId();
+    }
+    return ScrollableLayerGuid::NULL_SCROLL_ID;
   }
 
   SideBits GetFixedPositionSides() const {
     MOZ_ASSERT(IsValid());
 
-    return mLayer->GetFixedPositionSides();
-  }
-
-  bool GetIsStickyPosition() const {
-    MOZ_ASSERT(IsValid());
-
-    return mLayer->GetIsStickyPosition();
+    if (AtBottomLayer()) {
+      return mLayer->GetFixedPositionSides();
+    }
+    return SideBits::eNone;
   }
 
   ScrollableLayerGuid::ViewID GetStickyScrollContainerId() const {
     MOZ_ASSERT(IsValid());
 
-    // TODO: Restrict this only for AtBottomLayer.
-    return mLayer->GetStickyScrollContainerId();
+    if (AtBottomLayer() && mLayer->GetIsStickyPosition()) {
+      return mLayer->GetStickyScrollContainerId();
+    }
+    return ScrollableLayerGuid::NULL_SCROLL_ID;
   }
 
   const LayerRectAbsolute& GetStickyScrollRangeOuter() const {
     MOZ_ASSERT(IsValid());
 
-    return mLayer->GetStickyScrollRangeOuter();
+    if (AtBottomLayer() && mLayer->GetIsStickyPosition()) {
+      return mLayer->GetStickyScrollRangeOuter();
+    }
+
+    static const LayerRectAbsolute empty;
+    return empty;
   }
+
   const LayerRectAbsolute& GetStickyScrollRangeInner() const {
     MOZ_ASSERT(IsValid());
 
-    return mLayer->GetStickyScrollRangeInner();
+    if (AtBottomLayer() && mLayer->GetIsStickyPosition()) {
+      return mLayer->GetStickyScrollRangeInner();
+    }
+
+    static const LayerRectAbsolute empty;
+    return empty;
   }
 
   Maybe<uint64_t> GetZoomAnimationId() const {

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -1174,14 +1174,9 @@ HitTestingTreeNode* APZCTreeManager::PrepareNodeForLayer(
     node->SetFixedPosData(aLayer.GetFixedPositionScrollContainerId(),
                           aLayer.GetFixedPositionSides(),
                           aLayer.GetFixedPositionAnimationId());
-    if (aLayer.GetIsStickyPosition()) {
-      node->SetStickyPosData(aLayer.GetStickyScrollContainerId(),
-                             aLayer.GetStickyScrollRangeOuter(),
-                             aLayer.GetStickyScrollRangeInner());
-    } else {
-      node->SetStickyPosData(ScrollableLayerGuid::NULL_SCROLL_ID,
-                             LayerRectAbsolute(), LayerRectAbsolute());
-    }
+    node->SetStickyPosData(aLayer.GetStickyScrollContainerId(),
+                           aLayer.GetStickyScrollRangeOuter(),
+                           aLayer.GetStickyScrollRangeInner());
     return node;
   }
 
@@ -1408,14 +1403,9 @@ HitTestingTreeNode* APZCTreeManager::PrepareNodeForLayer(
   node->SetFixedPosData(aLayer.GetFixedPositionScrollContainerId(),
                         aLayer.GetFixedPositionSides(),
                         aLayer.GetFixedPositionAnimationId());
-  if (aLayer.GetIsStickyPosition()) {
-    node->SetStickyPosData(aLayer.GetStickyScrollContainerId(),
-                           aLayer.GetStickyScrollRangeOuter(),
-                           aLayer.GetStickyScrollRangeInner());
-  } else {
-    node->SetStickyPosData(ScrollableLayerGuid::NULL_SCROLL_ID,
-                           LayerRectAbsolute(), LayerRectAbsolute());
-  }
+  node->SetStickyPosData(aLayer.GetStickyScrollContainerId(),
+                         aLayer.GetStickyScrollRangeOuter(),
+                         aLayer.GetStickyScrollRangeInner());
   return node;
 }
 

gfx/layers/wr/WebRenderScrollDataWrapper.h

@@ -304,24 +304,29 @@ class MOZ_STACK_CLASS WebRenderScrollDataWrapper final {
 
   Maybe<uint64_t> GetFixedPositionAnimationId() const {
     MOZ_ASSERT(IsValid());
-    return mLayer->GetFixedPositionAnimationId();
+
+    if (AtBottomLayer()) {
+      return mLayer->GetFixedPositionAnimationId();
+    }
+    return Nothing();
   }
 
   ScrollableLayerGuid::ViewID GetFixedPositionScrollContainerId() const {
     MOZ_ASSERT(IsValid());
-    return mLayer->GetFixedPositionScrollContainerId();
+
+    if (AtBottomLayer()) {
+      return mLayer->GetFixedPositionScrollContainerId();
+    }
+    return ScrollableLayerGuid::NULL_SCROLL_ID;
   }
 
   SideBits GetFixedPositionSides() const {
     MOZ_ASSERT(IsValid());
-    return mLayer->GetFixedPositionSides();
-  }
 
-  bool GetIsStickyPosition() const {
-    MOZ_ASSERT(IsValid());
-
-    // TODO: Bug 1610731 Implement this for WebRender.
-    return false;
+    if (AtBottomLayer()) {
+      return mLayer->GetFixedPositionSides();
+    }
+    return SideBits::eNone;
   }
 
   ScrollableLayerGuid::ViewID GetStickyScrollContainerId() const {