--- a/layout/painting/RetainedDisplayListBuilder.cpp
+++ b/layout/painting/RetainedDisplayListBuilder.cpp
@@ -413,125 +413,125 @@ RetainedDisplayListBuilder::MergeDisplay
UseItem(aItem);
aItem->SetReused(true);
if (aItem->GetType() == DisplayItemType::TYPE_SUBDOCUMENT) {
IncrementSubDocPresShellPaintCount(aItem);
}
};
- // Build a hashtable of items in the old list so we can look for them quickly.
- // We have similar data in the nsIFrame DisplayItems() property, but it doesn't
- // know which display list items are in, and we only want to match items in
- // this list.
- nsDataHashtable<DisplayItemHashEntry, nsDisplayItem*> oldListLookup(aOldList->Count());
+ const bool newListIsEmpty = aNewList->IsEmpty();
+ if (!newListIsEmpty) {
+ // Build a hashtable of items in the old list so we can look for them quickly.
+ // We have similar data in the nsIFrame DisplayItems() property, but it doesn't
+ // know which display list items are in, and we only want to match items in
+ // this list.
+ nsDataHashtable<DisplayItemHashEntry, nsDisplayItem*> oldListLookup(aOldList->Count());
- for (nsDisplayItem* i = aOldList->GetBottom(); i != nullptr; i = i->GetAbove()) {
- i->SetReused(false);
-
- if (!aNewList->IsEmpty()) {
+ for (nsDisplayItem* i = aOldList->GetBottom(); i != nullptr; i = i->GetAbove()) {
+ i->SetReused(false);
oldListLookup.Put({ i->Frame(), i->GetPerFrameKey() }, i);
}
- }
- nsDataHashtable<DisplayItemHashEntry, nsDisplayItem*> newListLookup(aNewList->Count());
- for (nsDisplayItem* i = aNewList->GetBottom(); i != nullptr; i = i->GetAbove()) {
+ nsDataHashtable<DisplayItemHashEntry, nsDisplayItem*> newListLookup(aNewList->Count());
+ for (nsDisplayItem* i = aNewList->GetBottom(); i != nullptr; i = i->GetAbove()) {
#ifdef DEBUG
- if (newListLookup.Get({ i->Frame(), i->GetPerFrameKey() }, nullptr)) {
- MOZ_CRASH_UNSAFE_PRINTF("Duplicate display items detected!: %s(0x%p) type=%d key=%d",
- i->Name(), i->Frame(),
- static_cast<int>(i->GetType()), i->GetPerFrameKey());
+ if (newListLookup.Get({ i->Frame(), i->GetPerFrameKey() }, nullptr)) {
+ MOZ_CRASH_UNSAFE_PRINTF("Duplicate display items detected!: %s(0x%p) type=%d key=%d",
+ i->Name(), i->Frame(),
+ static_cast<int>(i->GetType()), i->GetPerFrameKey());
+ }
+#endif
+ newListLookup.Put({ i->Frame(), i->GetPerFrameKey() }, i);
}
-#endif
- newListLookup.Put({ i->Frame(), i->GetPerFrameKey() }, i);
- }
- while (nsDisplayItem* newItem = aNewList->RemoveBottom()) {
- if (nsDisplayItem* oldItem = oldListLookup.Get({ newItem->Frame(), newItem->GetPerFrameKey() })) {
- // The new item has a matching counterpart in the old list that we haven't yet reached,
- // so copy all valid items from the old list into the merged list until we get to the
- // matched item.
- nsDisplayItem* old = nullptr;
- while ((old = aOldList->GetBottom()) && old != oldItem) {
- if (IsAnyAncestorModified(old->FrameForInvalidation())) {
- // The old item is invalid, discard it.
- oldListLookup.Remove({ old->Frame(), old->GetPerFrameKey() });
+ while (nsDisplayItem* newItem = aNewList->RemoveBottom()) {
+ if (nsDisplayItem* oldItem = oldListLookup.Get({ newItem->Frame(), newItem->GetPerFrameKey() })) {
+ // The new item has a matching counterpart in the old list that we haven't yet reached,
+ // so copy all valid items from the old list into the merged list until we get to the
+ // matched item.
+ nsDisplayItem* old = nullptr;
+ while ((old = aOldList->GetBottom()) && old != oldItem) {
+ if (IsAnyAncestorModified(old->FrameForInvalidation())) {
+ // The old item is invalid, discard it.
+ oldListLookup.Remove({ old->Frame(), old->GetPerFrameKey() });
+ aOldList->RemoveBottom();
+ old->Destroy(&mBuilder);
+ } else if (newListLookup.Get({ old->Frame(), old->GetPerFrameKey() })) {
+ // This old item is also in the new list, but we haven't got to it yet.
+ // Stop now, and we'll deal with it when we get to the new entry.
+ break;
+ } else {
+ // Recurse into the child list (without a matching new list) to
+ // ensure that we find and remove any invalidated items.
+ if (old->GetChildren()) {
+ nsDisplayList empty;
+ Maybe<const ActiveScrolledRoot*> containerASRForChildren;
+ MergeDisplayLists(&empty, old->GetChildren(),
+ old->GetChildren(), containerASRForChildren);
+ UpdateASR(old, containerASRForChildren);
+ old->UpdateBounds(&mBuilder);
+ }
+ aOldList->RemoveBottom();
+ ReuseItem(old);
+ }
+ }
+ bool destroy = false;
+ if (old == oldItem) {
+ // If we advanced the old list until the matching item then we can pop
+ // the matching item off the old list and make sure we clean it up.
aOldList->RemoveBottom();
- old->Destroy(&mBuilder);
- } else if (newListLookup.Get({ old->Frame(), old->GetPerFrameKey() })) {
- // This old item is also in the new list, but we haven't got to it yet.
- // Stop now, and we'll deal with it when we get to the new entry.
- break;
+ destroy = true;
} else {
- // Recurse into the child list (without a matching new list) to
- // ensure that we find and remove any invalidated items.
- if (old->GetChildren()) {
- nsDisplayList empty;
- Maybe<const ActiveScrolledRoot*> containerASRForChildren;
- MergeDisplayLists(&empty, old->GetChildren(),
- old->GetChildren(), containerASRForChildren);
- UpdateASR(old, containerASRForChildren);
- old->UpdateBounds(&mBuilder);
- }
- aOldList->RemoveBottom();
- ReuseItem(old);
- }
- }
- bool destroy = false;
- if (old == oldItem) {
- // If we advanced the old list until the matching item then we can pop
- // the matching item off the old list and make sure we clean it up.
- aOldList->RemoveBottom();
- destroy = true;
- } else {
- // If we didn't get to the matching item, then mark the old item
- // as being reused (since we're adding the new version to the new
- // list now) so that we don't add it twice at the end.
- oldItem->SetReused(true);
- }
-
- // Recursively merge any child lists, destroy the old item and add
- // the new one to the list.
- if (destroy &&
- oldItem->GetType() == DisplayItemType::TYPE_LAYER_EVENT_REGIONS &&
- !IsAnyAncestorModified(oldItem->FrameForInvalidation())) {
- // Event regions items don't have anything interesting other than
- // the lists of regions and frames, so we have no need to use the
- // newer item. Always use the old item instead since we assume it's
- // likely to have the bigger lists and merging will be quicker.
- MergeLayerEventRegions(oldItem, newItem);
- ReuseItem(oldItem);
- newItem->Destroy(&mBuilder);
- } else {
- if (!IsAnyAncestorModified(oldItem->FrameForInvalidation()) &&
- oldItem->GetChildren()) {
- MOZ_ASSERT(newItem->GetChildren());
- Maybe<const ActiveScrolledRoot*> containerASRForChildren;
- MergeDisplayLists(newItem->GetChildren(), oldItem->GetChildren(),
- newItem->GetChildren(), containerASRForChildren);
- UpdateASR(newItem, containerASRForChildren);
- newItem->UpdateBounds(&mBuilder);
+ // If we didn't get to the matching item, then mark the old item
+ // as being reused (since we're adding the new version to the new
+ // list now) so that we don't add it twice at the end.
+ oldItem->SetReused(true);
}
- if (destroy) {
- oldItem->Destroy(&mBuilder);
+ // Recursively merge any child lists, destroy the old item and add
+ // the new one to the list.
+ if (destroy &&
+ oldItem->GetType() == DisplayItemType::TYPE_LAYER_EVENT_REGIONS &&
+ !IsAnyAncestorModified(oldItem->FrameForInvalidation())) {
+ // Event regions items don't have anything interesting other than
+ // the lists of regions and frames, so we have no need to use the
+ // newer item. Always use the old item instead since we assume it's
+ // likely to have the bigger lists and merging will be quicker.
+ MergeLayerEventRegions(oldItem, newItem);
+ ReuseItem(oldItem);
+ newItem->Destroy(&mBuilder);
+ } else {
+ if (!IsAnyAncestorModified(oldItem->FrameForInvalidation()) &&
+ oldItem->GetChildren()) {
+ MOZ_ASSERT(newItem->GetChildren());
+ Maybe<const ActiveScrolledRoot*> containerASRForChildren;
+ MergeDisplayLists(newItem->GetChildren(), oldItem->GetChildren(),
+ newItem->GetChildren(), containerASRForChildren);
+ UpdateASR(newItem, containerASRForChildren);
+ newItem->UpdateBounds(&mBuilder);
+ }
+
+ if (destroy) {
+ oldItem->Destroy(&mBuilder);
+ }
+ UseItem(newItem);
}
+ } else {
+ // If there was no matching item in the old list, then we only need to
+ // add the new item to the merged list.
UseItem(newItem);
}
- } else {
- // If there was no matching item in the old list, then we only need to
- // add the new item to the merged list.
- UseItem(newItem);
}
}
// Reuse the remaining valid items from the old display list.
while (nsDisplayItem* old = aOldList->RemoveBottom()) {
if (!IsAnyAncestorModified(old->FrameForInvalidation()) &&
- !old->IsReused()) {
+ (!old->IsReused() || newListIsEmpty)) {
if (old->GetChildren()) {
// We are calling MergeDisplayLists() to ensure that the display items
// with modified or deleted children will be correctly handled.
// Passing an empty new display list as an argument skips the merging
// loop above and jumps back here.
nsDisplayList empty;
Maybe<const ActiveScrolledRoot*> containerASRForChildren;
