Bug 1802142 - Remove layer="" attribute support from XUL elements. r=tnikkel,layout-reviewers

No remaining users.

Depends on D162851

Differential Revision: https://phabricator.services.mozilla.com/D162852

layout/generic/nsIFrame.cpp

@@ -3766,15 +3766,6 @@ void nsIFrame::BuildDisplayListForStackingContext(
     createdContainer = true;
   }
 
-  bool createdOwnLayer = false;
-  CreateOwnLayerIfNeeded(aBuilder, &resultList,
-                         nsDisplayOwnLayer::OwnLayerForStackingContext,
-                         &createdOwnLayer);
-
-  if (createdOwnLayer) {
-    createdContainer = true;
-  }
-
   if (aBuilder->IsReusingStackingContextItems()) {
     if (resultList.IsEmpty()) {
       return;
@@ -11113,21 +11104,6 @@ void nsIFrame::SetParent(nsContainerFrame* aParent) {
   }
 }
 
-void nsIFrame::CreateOwnLayerIfNeeded(nsDisplayListBuilder* aBuilder,
-                                      nsDisplayList* aList, uint16_t aType,
-                                      bool* aCreatedContainerItem) {
-  if (GetContent() && GetContent()->IsXULElement() &&
-      GetContent()->AsElement()->HasAttr(kNameSpaceID_None, nsGkAtoms::layer)) {
-    aList->AppendNewToTopWithIndex<nsDisplayOwnLayer>(
-        aBuilder, this, /* aIndex = */ aType, aList,
-        aBuilder->CurrentActiveScrolledRoot(), nsDisplayOwnLayerFlags::None,
-        ScrollbarData{}, true, false);
-    if (aCreatedContainerItem) {
-      *aCreatedContainerItem = true;
-    }
-  }
-}
-
 bool nsIFrame::IsStackingContext(const nsStyleDisplay* aStyleDisplay,
                                  const nsStyleEffects* aStyleEffects) {
   // Properties that influence the output of this function should be handled in

layout/generic/nsIFrame.h

@@ -4591,10 +4591,6 @@ class nsIFrame : public nsQueryFrame {
    */
   Maybe<mozilla::StyleVerticalAlignKeyword> VerticalAlignEnum() const;
 
-  void CreateOwnLayerIfNeeded(nsDisplayListBuilder* aBuilder,
-                              nsDisplayList* aList, uint16_t aType,
-                              bool* aCreatedContainerItem = nullptr);
-
   /**
    * Adds the NS_FRAME_IN_POPUP state bit to aFrame, and
    * all descendant frames (including cross-doc ones).

layout/xul/nsBoxFrame.cpp

@@ -843,52 +843,13 @@ nsresult nsBoxFrame::AttributeChanged(int32_t aNameSpaceID, nsAtom* aAttribute,
 
 void nsBoxFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
                                   const nsDisplayListSet& aLists) {
-  bool forceLayer = false;
-
-  if (GetContent()->IsXULElement()) {
-    // forcelayer is only supported on XUL elements with box layout
-    if (GetContent()->AsElement()->HasAttr(kNameSpaceID_None,
-                                           nsGkAtoms::layer)) {
-      forceLayer = true;
-    }
-  }
-
   nsDisplayListCollection tempLists(aBuilder);
-  const nsDisplayListSet& destination = (forceLayer) ? tempLists : aLists;
+  DisplayBorderBackgroundOutline(aBuilder, aLists);
 
-  DisplayBorderBackgroundOutline(aBuilder, destination);
-
-  Maybe<nsDisplayListBuilder::AutoContainerASRTracker> contASRTracker;
-  if (forceLayer) {
-    contASRTracker.emplace(aBuilder);
-  }
-
-  BuildDisplayListForChildren(aBuilder, destination);
+  BuildDisplayListForChildren(aBuilder, aLists);
 
   // see if we have to draw a selection frame around this container
-  DisplaySelectionOverlay(aBuilder, destination.Content());
-
-  if (forceLayer) {
-    // This is a bit of a hack. Collect up all descendant display items
-    // and merge them into a single Content() list. This can cause us
-    // to violate CSS stacking order, but forceLayer is a magic
-    // XUL-only extension anyway.
-    nsDisplayList masterList(aBuilder);
-    masterList.AppendToTop(tempLists.BorderBackground());
-    masterList.AppendToTop(tempLists.BlockBorderBackgrounds());
-    masterList.AppendToTop(tempLists.Floats());
-    masterList.AppendToTop(tempLists.Content());
-    masterList.AppendToTop(tempLists.PositionedDescendants());
-    masterList.AppendToTop(tempLists.Outlines());
-    const ActiveScrolledRoot* ownLayerASR = contASRTracker->GetContainerASR();
-    DisplayListClipState::AutoSaveRestore ownLayerClipState(aBuilder);
-
-    // Wrap the list to make it its own layer
-    aLists.Content()->AppendNewToTopWithIndex<nsDisplayOwnLayer>(
-        aBuilder, this, /* aIndex = */ nsDisplayOwnLayer::OwnLayerForBoxFrame,
-        &masterList, ownLayerASR, mozilla::nsDisplayOwnLayerFlags::None,
-        mozilla::layers::ScrollbarData{}, true, true);
-  }
+  DisplaySelectionOverlay(aBuilder, aLists.Content());
 }
 
 void nsBoxFrame::BuildDisplayListForChildren(nsDisplayListBuilder* aBuilder,

layout/xul/nsImageBoxFrame.cpp

@@ -316,13 +316,7 @@ void nsImageBoxFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
   DisplayListClipState::AutoClipContainingBlockDescendantsToContentBox clip(
       aBuilder, this, clipFlags);
 
-  nsDisplayList list(aBuilder);
-  list.AppendNewToTop<nsDisplayXULImage>(aBuilder, this);
-
-  CreateOwnLayerIfNeeded(aBuilder, &list,
-                         nsDisplayOwnLayer::OwnLayerForImageBoxFrame);
-
-  aLists.Content()->AppendToTop(&list);
+  aLists.Content()->AppendNewToTop<nsDisplayXULImage>(aBuilder, this);
 }
 
 already_AddRefed<imgIContainer> nsImageBoxFrame::GetImageContainerForPainting(