Bug 1441796 - Part 3: Reuse the results in nsIFrame::BuildDisplayListForStackingContext() for ChildrenHavePerspective(), IsTransformed(), and Combines3DTransformWithAncestors() r=mattwoodrow

MozReview-Commit-ID: J2PtZDMbHh2

--HG--
extra : rebase_source : be988df9ed220fea143aa35e463c2d3a85a2d799

layout/generic/nsFrame.cpp

@@ -2826,9 +2826,15 @@ nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
   nsRect visibleRect = aBuilder->GetVisibleRect();
   nsRect dirtyRect = aBuilder->GetDirtyRect();
 
-  bool extend3DContext = Extend3DContext(disp, effectSet);
+  const bool isTransformed = IsTransformed(disp);
+  const bool hasPerspective = isTransformed && HasPerspective(disp);
+  const bool extend3DContext = Extend3DContext(disp, effectSet);
+  const bool combines3DTransformWithAncestors =
+    (extend3DContext || isTransformed) && Combines3DTransformWithAncestors(disp);
+  const bool childrenHavePerspective = ChildrenHavePerspective(disp);
+
   Maybe<nsDisplayListBuilder::AutoPreserves3DContext> autoPreserves3DContext;
-  if (extend3DContext && !Combines3DTransformWithAncestors(disp)) {
+  if (extend3DContext && !combines3DTransformWithAncestors) {
     // Start a new preserves3d context to keep informations on
     // nsDisplayListBuilder.
     autoPreserves3DContext.emplace(aBuilder);
@@ -2848,15 +2854,11 @@ nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
   // We need to make sure we build all of them for them to be consistent, so
   // rebuild all items if we have perspective. Bug 1431249 should remove
   // this requirement.
-  if (aBuilder->IsRetainingDisplayList() &&
-      ChildrenHavePerspective(disp)) {
+  if (aBuilder->IsRetainingDisplayList() && childrenHavePerspective) {
     dirtyRect = visibleRect;
     aBuilder->MarkFrameModifiedDuringBuilding(this);
   }
 
-  bool inTransform = aBuilder->IsInTransform();
-  bool isTransformed = IsTransformed(disp);
-  bool hasPerspective = HasPerspective(disp);
   // reset blend mode so we can keep track if this stacking context needs have
   // a nsDisplayBlendContainer. Set the blend mode back when the routine exits
   // so we keep track if the parent stacking context needs a container too.
@@ -2865,6 +2867,7 @@ nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
 
   nsRect visibleRectOutsideTransform = visibleRect;
   bool allowAsyncAnimation = false;
+  bool inTransform = aBuilder->IsInTransform();
   if (isTransformed) {
     const nsRect overflow = GetVisualOverflowRectRelativeToSelf();
     nsDisplayTransform::PrerenderDecision decision =
@@ -2886,7 +2889,7 @@ nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
 
       // If we're in preserve-3d then grab the dirty rect that was given to the root
       // and transform using the combined transform.
-      if (Combines3DTransformWithAncestors(disp)) {
+      if (combines3DTransformWithAncestors) {
         visibleRect = dirtyRect = aBuilder->GetPreserves3DRect();
       }
 
@@ -3025,7 +3028,7 @@ nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
     nsDisplayListBuilder::AutoInTransformSetter
       inTransformSetter(aBuilder, inTransform);
     nsDisplayListBuilder::AutoSaveRestorePerspectiveIndex
-      perspectiveIndex(aBuilder, this);
+      perspectiveIndex(aBuilder, childrenHavePerspective);
     nsDisplayListBuilder::AutoFilterASRSetter
       filterASRSetter(aBuilder, usingFilter);
 

layout/painting/nsDisplayList.h

@@ -1182,10 +1182,11 @@ public:
 
   class AutoSaveRestorePerspectiveIndex {
   public:
-    AutoSaveRestorePerspectiveIndex(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame)
+    AutoSaveRestorePerspectiveIndex(nsDisplayListBuilder* aBuilder,
+                                    const bool aChildrenHavePerspective)
       : mBuilder(nullptr)
     {
-      if (aFrame->ChildrenHavePerspective()) {
+      if (aChildrenHavePerspective) {
         mBuilder = aBuilder;
         mCachedItemIndex = aBuilder->mPerspectiveItemIndex;
         aBuilder->mPerspectiveItemIndex = 0;