Bug 1714584 - Part 2: Remove nsDisplayList::RemoveBottom() r=mstange

Differential Revision: https://phabricator.services.mozilla.com/D138153

layout/base/PresShell.cpp

@@ -4692,12 +4692,10 @@ nsRect PresShell::ClipListToRange(nsDisplayListBuilder* aBuilder,
   // part of the selection. Then, append the wrapper to the top of the list.
   // Otherwise, just delete the item and don't append it.
   nsRect surfaceRect;
-  nsDisplayList tmpList;
 
-  nsDisplayItem* i;
-  while ((i = aList->RemoveBottom())) {
+  for (nsDisplayItem* i : aList->TakeItems()) {
     if (i->GetType() == DisplayItemType::TYPE_CONTAINER) {
-      tmpList.AppendToTop(i);
+      aList->AppendToTop(i);
       surfaceRect.UnionRect(
           surfaceRect, ClipListToRange(aBuilder, i->GetChildren(), aRange));
       continue;
@@ -4778,7 +4776,7 @@ nsRect PresShell::ClipListToRange(nsDisplayListBuilder* aBuilder,
     // list, insert that as well
     nsDisplayList* sublist = i->GetSameCoordinateSystemChildren();
     if (itemToInsert || sublist) {
-      tmpList.AppendToTop(itemToInsert ? itemToInsert : i);
+      aList->AppendToTop(itemToInsert ? itemToInsert : i);
       // if the item is a list, iterate over it as well
       if (sublist)
         surfaceRect.UnionRect(surfaceRect,
@@ -4789,9 +4787,6 @@ nsRect PresShell::ClipListToRange(nsDisplayListBuilder* aBuilder,
     }
   }
 
-  // now add all the items back onto the original list again
-  aList->AppendToTop(&tmpList);
-
   return surfaceRect;
 }
 

layout/generic/TextOverflow.cpp

@@ -766,9 +766,7 @@ void TextOverflow::ProcessLine(const nsDisplayListSet& aLists, nsLineBox* aLine,
 void TextOverflow::PruneDisplayListContents(
     nsDisplayList* aList, const FrameHashtable& aFramesToHide,
     const LogicalRect& aInsideMarkersArea) {
-  nsDisplayList saved;
-  nsDisplayItem* item;
-  while ((item = aList->RemoveBottom())) {
+  for (nsDisplayItem* item : aList->TakeItems()) {
     nsIFrame* itemFrame = item->Frame();
     if (IsFrameDescendantOfAny(itemFrame, aFramesToHide, mBlock)) {
       item->Destroy(mBuilder);
@@ -804,9 +802,8 @@ void TextOverflow::PruneDisplayListContents(
       }
     }
 
-    saved.AppendToTop(item);
+    aList->AppendToTop(item);
   }
-  aList->AppendToTop(&saved);
 }
 
 /* static */

layout/generic/nsIFrame.cpp

@@ -3702,7 +3702,8 @@ void nsIFrame::BuildDisplayListForStackingContext(
 
     nsDisplayItem* separator = nullptr;
 
-    while (nsDisplayItem* item = resultList.RemoveBottom()) {
+    // TODO: This can be simplified: |participants| is just |resultList|.
+    for (nsDisplayItem* item : resultList.TakeItems()) {
       if (ItemParticipatesIn3DContext(this, item) &&
           !item->GetClip().HasClip()) {
         // The frame of this item participates the same 3D context.
@@ -3883,7 +3884,8 @@ void nsIFrame::BuildDisplayListForStackingContext(
       container = MakeDisplayItem<nsDisplayContainer>(
           aBuilder, this, containerItemASR, &resultList);
     } else {
-      container = resultList.RemoveBottom();
+      MOZ_ASSERT(resultList.Length() == 1);
+      resultList.Clear();
     }
 
     // Mark the outermost display item as reusable. These display items and
@@ -3923,7 +3925,8 @@ static nsDisplayItem* WrapInWrapList(nsDisplayListBuilder* aBuilder,
   // invalidation) or we're doing a full build and don't need a wrap list, then
   // we can skip adding one.
   if (aBuiltContainerItem || (!aBuilder->IsPartialUpdate() && !needsWrapList)) {
-    aList->RemoveBottom();
+    MOZ_ASSERT(aList->Length() == 1);
+    aList->Clear();
     return item;
   }
 
@@ -3940,7 +3943,8 @@ static nsDisplayItem* WrapInWrapList(nsDisplayListBuilder* aBuilder,
     if (needsWrapList) {
       DiscardOldItems(aFrame);
     } else {
-      aList->RemoveBottom();
+      MOZ_ASSERT(aList->Length() == 1);
+      aList->Clear();
       return item;
     }
   }

layout/generic/nsPageContentFrame.cpp

@@ -267,10 +267,7 @@ static void BuildPreviousPageOverflow(nsDisplayListBuilder* aBuilder,
 static void PruneDisplayListForExtraPage(nsDisplayListBuilder* aBuilder,
                                          nsPageFrame* aPage,
                                          nsDisplayList* aList) {
-  nsDisplayList newList;
-
-  while (true) {
-    nsDisplayItem* i = aList->RemoveBottom();
+  for (nsDisplayItem* i : aList->TakeItems()) {
     if (!i) break;
     nsDisplayList* subList = i->GetSameCoordinateSystemChildren();
     if (subList) {
@@ -285,9 +282,8 @@ static void PruneDisplayListForExtraPage(nsDisplayListBuilder* aBuilder,
         continue;
       }
     }
-    newList.AppendToTop(i);
+    aList->AppendToTop(i);
   }
-  aList->AppendToTop(&newList);
 }
 
 static void BuildDisplayListForExtraPage(nsDisplayListBuilder* aBuilder,

layout/generic/nsSubDocumentFrame.cpp

@@ -306,9 +306,7 @@ ScreenIntSize nsSubDocumentFrame::GetSubdocumentSize() {
 static void WrapBackgroundColorInOwnLayer(nsDisplayListBuilder* aBuilder,
                                           nsIFrame* aFrame,
                                           nsDisplayList* aList) {
-  nsDisplayList tempItems;
-  nsDisplayItem* item;
-  while ((item = aList->RemoveBottom()) != nullptr) {
+  for (nsDisplayItem* item : aList->TakeItems()) {
     if (item->GetType() == DisplayItemType::TYPE_BACKGROUND_COLOR) {
       nsDisplayList tmpList(aBuilder);
       tmpList.AppendToTop(item);
@@ -317,11 +315,8 @@ static void WrapBackgroundColorInOwnLayer(nsDisplayListBuilder* aBuilder,
           &tmpList, aBuilder->CurrentActiveScrolledRoot(),
           nsDisplayOwnLayerFlags::None, ScrollbarData{}, true, false);
     }
-    if (item) {
-      tempItems.AppendToTop(item);
-    }
+    aList->AppendToTop(item);
   }
-  aList->AppendToTop(&tempItems);
 }
 
 void nsSubDocumentFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,

layout/painting/RetainedDisplayListBuilder.cpp

@@ -203,10 +203,8 @@ bool RetainedDisplayListBuilder::PreProcessDisplayList(
       aList->mDAG.Length() ==
           (initializeOldItems ? aList->Length() : aList->mOldItems.Length()));
 
-  nsDisplayList out;
-
   size_t i = 0;
-  while (nsDisplayItem* item = aList->RemoveBottom()) {
+  for (nsDisplayItem* item : aList->TakeItems()) {
 #ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
     item->SetMergedPreProcessed(false, true);
 #endif
@@ -343,16 +341,13 @@ bool RetainedDisplayListBuilder::PreProcessDisplayList(
       if (item->GetType() == DisplayItemType::TYPE_SUBDOCUMENT) {
         IncrementSubDocPresShellPaintCount(item);
       }
-      out.AppendToTop(item);
+      aList->AppendToTop(item);
     }
     i++;
   }
 
   MOZ_RELEASE_ASSERT(aList->mOldItems.Length() == aList->mDAG.Length());
 
-  if (aKeepLinked) {
-    aList->AppendToTop(&out);
-  }
   return true;
 }
 
@@ -856,7 +851,7 @@ bool RetainedDisplayListBuilder::MergeDisplayLists(
   MergeState merge(this, *aOldList, aOuterItem);
 
   Maybe<MergedListIndex> previousItemIndex;
-  while (nsDisplayItem* item = aNewList->RemoveBottom()) {
+  for (nsDisplayItem* item : aNewList->TakeItems()) {
     Metrics()->mNewItems++;
     previousItemIndex = merge.ProcessItemFromNewList(item, previousItemIndex);
   }
@@ -1561,9 +1556,7 @@ bool IsReuseableStackingContextItem(nsDisplayItem* aItem) {
 void CollectStackingContextItems(nsDisplayListBuilder* aBuilder,
                                  nsDisplayList* aList, nsIFrame* aOuterFrame,
                                  int aDepth = 0, bool aParentReused = false) {
-  nsDisplayList out;
-
-  for (nsDisplayItem* item : *aList) {
+  for (nsDisplayItem* item : aList->TakeItems()) {
     if (DL_LOG_TEST(LogLevel::Debug)) {
       DL_LOGD(
           "%*s Preprocessing item %p (%s) (frame: %p) "
@@ -1600,7 +1593,7 @@ void CollectStackingContextItems(nsDisplayListBuilder* aBuilder,
     if (aParentReused) {
       // Keep the contents of the current container item linked.
       RDLUtils::AssertDisplayItemUnmodified(item);
-      out.AppendToTop(item);
+      aList->AppendToTop(item);
     } else if (isStackingContextItem) {
       // |item| is a stacking context item that can be reused.
       ReuseStackingContextItem(aBuilder, item);
@@ -1615,9 +1608,6 @@ void CollectStackingContextItems(nsDisplayListBuilder* aBuilder,
       IncrementPresShellPaintCount(aBuilder, item);
     }
   }
-
-  aList->Clear();
-  aList->AppendToTop(&out);
 }
 
 }  // namespace RDL

layout/painting/nsDisplayList.cpp

@@ -2326,8 +2326,7 @@ void nsDisplayList::PaintRoot(nsDisplayListBuilder* aBuilder, gfxContext* aCtx,
 }
 
 void nsDisplayList::DeleteAll(nsDisplayListBuilder* aBuilder) {
-  nsDisplayItem* item;
-  while ((item = RemoveBottom()) != nullptr) {
+  for (auto* item : TakeItems()) {
     item->Destroy(aBuilder);
   }
 }
@@ -4674,17 +4673,14 @@ static nsresult WrapDisplayList(nsDisplayListBuilder* aBuilder,
 static nsresult WrapEachDisplayItem(nsDisplayListBuilder* aBuilder,
                                     nsDisplayList* aList,
                                     nsDisplayItemWrapper* aWrapper) {
-  nsDisplayList newList;
-  nsDisplayItem* item;
-  while ((item = aList->RemoveBottom())) {
+  for (nsDisplayItem* item : aList->TakeItems()) {
     item = aWrapper->WrapItem(aBuilder, item);
     if (!item) {
       return NS_ERROR_OUT_OF_MEMORY;
     }
-    newList.AppendToTop(item);
+    aList->AppendToTop(item);
   }
   // aList was emptied
-  aList->AppendToTop(&newList);
   return NS_OK;
 }
 
@@ -8543,15 +8539,14 @@ void nsDisplayListCollection::SerializeWithCorrectZOrder(
   // 1,2: backgrounds and borders
   aOutResultList->AppendToTop(BorderBackground());
   // 3: negative z-index children.
-  for (;;) {
-    nsDisplayItem* item = PositionedDescendants()->GetBottom();
-    if (item && item->ZIndex() < 0) {
-      PositionedDescendants()->RemoveBottom();
+  for (auto* item : PositionedDescendants()->TakeItems()) {
+    if (item->ZIndex() < 0) {
       aOutResultList->AppendToTop(item);
-      continue;
+    } else {
+      PositionedDescendants()->AppendToTop(item);
     }
-    break;
   }
+
   // 4: block backgrounds
   aOutResultList->AppendToTop(BlockBorderBackgrounds());
   // 5: floats