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gecko-dev/layout/painting/RetainedDisplayListBuilder.cpp

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
#include "RetainedDisplayListBuilder.h"
#include "DisplayListChecker.h"
#include "gfxPrefs.h"
#include "nsPlaceholderFrame.h"
#include "nsSubDocumentFrame.h"
#include "nsViewManager.h"
#include "nsCanvasFrame.h"
#include "mozilla/AutoRestore.h"
/**
* Code for doing display list building for a modified subset of the window,
* and then merging it into the existing display list (for the full window).
*
* The approach primarily hinges on the observation that the 'true' ordering
* of display items is represented by a DAG (only items that intersect in 2d
* space have a defined ordering). Our display list is just one of a many
* possible linear representations of this ordering.
*
* Each time a frame changes (gets a new ComputedStyle, or has a size/position
* change), we schedule a paint (as we do currently), but also reord the frame
* that changed.
*
* When the next paint occurs we union the overflow areas (in screen space) of
* the changed frames, and compute a rect/region that contains all changed
* items. We then build a display list just for this subset of the screen and
* merge it into the display list from last paint.
*
* Any items that exist in one list and not the other must not have a defined
* ordering in the DAG, since they need to intersect to have an ordering and
* we would have built both in the new list if they intersected. Given that, we
* can align items that appear in both lists, and any items that appear between
* matched items can be inserted into the merged list in any order.
*/
using namespace mozilla;
using mozilla::dom::Document;
void RetainedDisplayListData::AddModifiedFrame(nsIFrame* aFrame) {
MOZ_ASSERT(!aFrame->IsFrameModified());
Flags(aFrame) |= RetainedDisplayListData::FrameFlags::Modified;
mModifiedFramesCount++;
}
RetainedDisplayListData* GetRetainedDisplayListData(nsIFrame* aRootFrame) {
RetainedDisplayListData* data =
aRootFrame->GetProperty(RetainedDisplayListData::DisplayListData());
return data;
}
RetainedDisplayListData* GetOrSetRetainedDisplayListData(nsIFrame* aRootFrame) {
RetainedDisplayListData* data = GetRetainedDisplayListData(aRootFrame);
if (!data) {
data = new RetainedDisplayListData();
aRootFrame->SetProperty(RetainedDisplayListData::DisplayListData(), data);
}
MOZ_ASSERT(data);
return data;
}
static void MarkFramesWithItemsAndImagesModified(nsDisplayList* aList) {
for (nsDisplayItem* i = aList->GetBottom(); i != nullptr; i = i->GetAbove()) {
if (!i->HasDeletedFrame() && i->CanBeReused() &&
!i->Frame()->IsFrameModified()) {
// If we have existing cached geometry for this item, then check that for
// whether we need to invalidate for a sync decode. If we don't, then
// use the item's flags.
DisplayItemData* data = FrameLayerBuilder::GetOldDataFor(i);
// XXX: handle webrender case
bool invalidate = false;
if (data && data->GetGeometry()) {
invalidate = data->GetGeometry()->InvalidateForSyncDecodeImages();
} else if (!(i->GetFlags() & TYPE_RENDERS_NO_IMAGES)) {
invalidate = true;
}
if (invalidate) {
i->FrameForInvalidation()->MarkNeedsDisplayItemRebuild();
if (i->GetDependentFrame()) {
i->GetDependentFrame()->MarkNeedsDisplayItemRebuild();
}
}
}
if (i->GetChildren()) {
MarkFramesWithItemsAndImagesModified(i->GetChildren());
}
}
}
static AnimatedGeometryRoot* SelectAGRForFrame(
nsIFrame* aFrame, AnimatedGeometryRoot* aParentAGR) {
if (!aFrame->IsStackingContext() || !aFrame->IsFixedPosContainingBlock()) {
return aParentAGR;
}
if (!aFrame->HasOverrideDirtyRegion()) {
return nullptr;
}
nsDisplayListBuilder::DisplayListBuildingData* data =
aFrame->GetProperty(nsDisplayListBuilder::DisplayListBuildingRect());
return data && data->mModifiedAGR ? data->mModifiedAGR.get() : nullptr;
}
// Removes any display items that belonged to a frame that was deleted,
// and mark frames that belong to a different AGR so that get their
// items built again.
// TODO: We currently descend into all children even if we don't have an AGR
// to mark, as child stacking contexts might. It would be nice if we could
// jump into those immediately rather than walking the entire thing.
bool RetainedDisplayListBuilder::PreProcessDisplayList(
RetainedDisplayList* aList, AnimatedGeometryRoot* aAGR, uint32_t aCallerKey,
uint32_t aNestingDepth) {
// The DAG merging algorithm does not have strong mechanisms in place to keep
// the complexity of the resulting DAG under control. In some cases we can
// build up edges very quickly. Detect those cases and force a full display
// list build if we hit them.
static const uint32_t kMaxEdgeRatio = 5;
bool initializeDAG = !aList->mDAG.Length();
if (!initializeDAG && aList->mDAG.mDirectPredecessorList.Length() >
(aList->mDAG.mNodesInfo.Length() * kMaxEdgeRatio)) {
return false;
}
MOZ_RELEASE_ASSERT(initializeDAG || aList->mDAG.Length() == aList->Count());
nsDisplayList saved;
aList->mOldItems.SetCapacity(aList->Count());
MOZ_RELEASE_ASSERT(aList->mOldItems.IsEmpty());
while (nsDisplayItem* item = aList->RemoveBottom()) {
#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
item->mMergedItem = false;
item->mPreProcessedItem = true;
#endif
if (item->HasDeletedFrame() || !item->CanBeReused()) {
size_t i = aList->mOldItems.Length();
aList->mOldItems.AppendElement(OldItemInfo(nullptr));
item->Destroy(&mBuilder);
if (initializeDAG) {
if (i == 0) {
aList->mDAG.AddNode(Span<const MergedListIndex>());
} else {
MergedListIndex previous(i - 1);
aList->mDAG.AddNode(Span<const MergedListIndex>(&previous, 1));
}
}
continue;
}
size_t i = aList->mOldItems.Length();
aList->mOldItems.AppendElement(OldItemInfo(item));
item->SetOldListIndex(aList, OldListIndex(i), aCallerKey, aNestingDepth);
if (initializeDAG) {
if (i == 0) {
aList->mDAG.AddNode(Span<const MergedListIndex>());
} else {
MergedListIndex previous(i - 1);
aList->mDAG.AddNode(Span<const MergedListIndex>(&previous, 1));
}
}
nsIFrame* f = item->Frame();
if (item->GetChildren()) {
if (!PreProcessDisplayList(item->GetChildren(),
SelectAGRForFrame(f, aAGR),
item->GetPerFrameKey(), aNestingDepth + 1)) {
return false;
}
}
// TODO: We should be able to check the clipped bounds relative
// to the common AGR (of both the existing item and the invalidated
// frame) and determine if they can ever intersect.
if (aAGR && item->GetAnimatedGeometryRoot()->GetAsyncAGR() != aAGR) {
mBuilder.MarkFrameForDisplayIfVisible(f, mBuilder.RootReferenceFrame());
}
// TODO: This is here because we sometimes reuse the previous display list
// completely. For optimization, we could only restore the state for reused
// display items.
item->RestoreState();
}
MOZ_RELEASE_ASSERT(aList->mOldItems.Length() == aList->mDAG.Length());
aList->RestoreState();
return true;
}
void RetainedDisplayListBuilder::IncrementSubDocPresShellPaintCount(
nsDisplayItem* aItem) {
MOZ_ASSERT(aItem->GetType() == DisplayItemType::TYPE_SUBDOCUMENT);
nsSubDocumentFrame* subDocFrame =
static_cast<nsDisplaySubDocument*>(aItem)->SubDocumentFrame();
MOZ_ASSERT(subDocFrame);
nsIPresShell* presShell = subDocFrame->GetSubdocumentPresShellForPainting(0);
MOZ_ASSERT(presShell);
mBuilder.IncrementPresShellPaintCount(presShell);
}
static bool AnyContentAncestorModified(nsIFrame* aFrame,
nsIFrame* aStopAtFrame = nullptr) {
for (nsIFrame* f = aFrame; f;
f = nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(f)) {
if (f->IsFrameModified()) {
return true;
}
if (aStopAtFrame && f == aStopAtFrame) {
break;
}
}
return false;
}
static Maybe<const ActiveScrolledRoot*> SelectContainerASR(
const DisplayItemClipChain* aClipChain, const ActiveScrolledRoot* aItemASR,
Maybe<const ActiveScrolledRoot*>& aContainerASR) {
const ActiveScrolledRoot* itemClipASR =
aClipChain ? aClipChain->mASR : nullptr;
const ActiveScrolledRoot* finiteBoundsASR =
ActiveScrolledRoot::PickDescendant(itemClipASR, aItemASR);
if (!aContainerASR) {
return Some(finiteBoundsASR);
}
return Some(
ActiveScrolledRoot::PickAncestor(*aContainerASR, finiteBoundsASR));
}
static void UpdateASR(nsDisplayItem* aItem,
Maybe<const ActiveScrolledRoot*>& aContainerASR) {
Maybe<const ActiveScrolledRoot*> asr;
if (aItem->HasHitTestInfo()) {
const HitTestInfo& info =
static_cast<nsDisplayHitTestInfoItem*>(aItem)->GetHitTestInfo();
asr = SelectContainerASR(info.mClipChain, info.mASR, aContainerASR);
} else {
asr = aContainerASR;
}
if (!asr) {
return;
}
nsDisplayWrapList* wrapList = aItem->AsDisplayWrapList();
if (!wrapList) {
aItem->SetActiveScrolledRoot(*asr);
return;
}
wrapList->SetActiveScrolledRoot(ActiveScrolledRoot::PickAncestor(
wrapList->GetFrameActiveScrolledRoot(), *asr));
wrapList->UpdateHitTestInfoActiveScrolledRoot(*asr);
}
void OldItemInfo::AddedMatchToMergedList(RetainedDisplayListBuilder* aBuilder,
MergedListIndex aIndex) {
AddedToMergedList(aIndex);
}
void OldItemInfo::Discard(RetainedDisplayListBuilder* aBuilder,
nsTArray<MergedListIndex>&& aDirectPredecessors) {
MOZ_ASSERT(!IsUsed());
mUsed = mDiscarded = true;
mDirectPredecessors = std::move(aDirectPredecessors);
if (mItem) {
mItem->Destroy(aBuilder->Builder());
}
mItem = nullptr;
}
bool OldItemInfo::IsChanged() {
return !mItem || mItem->HasDeletedFrame() || !mItem->CanBeReused();
}
/**
* A C++ implementation of Markus Stange's merge-dags algorithm.
* https://github.com/mstange/merge-dags
*
* MergeState handles combining a new list of display items into an existing
* DAG and computes the new DAG in a single pass.
* Each time we add a new item, we resolve all dependencies for it, so that the
* resulting list and DAG are built in topological ordering.
*/
class MergeState {
public:
MergeState(RetainedDisplayListBuilder* aBuilder,
RetainedDisplayList& aOldList, uint32_t aOuterKey)
: mBuilder(aBuilder),
mOldList(&aOldList),
mOldItems(std::move(aOldList.mOldItems)),
mOldDAG(
std::move(*reinterpret_cast<DirectedAcyclicGraph<OldListUnits>*>(
&aOldList.mDAG))),
mOuterKey(aOuterKey),
mResultIsModified(false) {
mMergedDAG.EnsureCapacityFor(mOldDAG);
MOZ_RELEASE_ASSERT(mOldItems.Length() == mOldDAG.Length());
}
// Items within an opacity:0 container (excluding plugins and hit test info)
// aren't needed, so we can strip them out from both the old and new lists.
// Do this silently, so that these changes don't result in us reporting that
// the display list changed. Both FrameLayerBuilder and
// WebRenderCommandBuilder also do this removal, so it's functionally correct
// to report that the display list is identical.
bool ShouldSilentlyDiscardItem(nsDisplayItem* aItem) {
return aItem && mBuilder->mCurrentSubtreeIsForEventsAndPluginsOnly &&
(aItem->GetType() != DisplayItemType::TYPE_COMPOSITOR_HITTEST_INFO &&
aItem->GetType() != DisplayItemType::TYPE_PLUGIN);
}
Maybe<MergedListIndex> ProcessItemFromNewList(
nsDisplayItem* aNewItem, const Maybe<MergedListIndex>& aPreviousItem) {
if (ShouldSilentlyDiscardItem(aNewItem)) {
aNewItem->Destroy(mBuilder->Builder());
return aPreviousItem;
}
OldListIndex oldIndex;
if (!HasModifiedFrame(aNewItem) &&
HasMatchingItemInOldList(aNewItem, &oldIndex)) {
nsDisplayItem* oldItem = mOldItems[oldIndex.val].mItem;
MOZ_DIAGNOSTIC_ASSERT(oldItem->GetPerFrameKey() ==
aNewItem->GetPerFrameKey() &&
oldItem->Frame() == aNewItem->Frame());
if (!mOldItems[oldIndex.val].IsChanged()) {
MOZ_DIAGNOSTIC_ASSERT(!mOldItems[oldIndex.val].IsUsed());
nsDisplayItem* destItem;
if (ShouldUseNewItem(aNewItem)) {
destItem = aNewItem;
} else {
destItem = oldItem;
// The building rect can depend on the overflow rect (when the parent
// frame is position:fixed), which can change without invalidating
// the frame/items. If we're using the old item, copy the building
// rect across from the new item.
oldItem->SetBuildingRect(aNewItem->GetBuildingRect());
}
if (aNewItem->GetChildren()) {
Maybe<const ActiveScrolledRoot*> containerASRForChildren;
if (mBuilder->MergeDisplayLists(
aNewItem->GetChildren(), oldItem->GetChildren(),
destItem->GetChildren(), containerASRForChildren, aNewItem)) {
destItem->InvalidateCachedChildInfo();
mResultIsModified = true;
}
UpdateASR(destItem, containerASRForChildren);
destItem->UpdateBounds(mBuilder->Builder());
}
AutoTArray<MergedListIndex, 2> directPredecessors =
ProcessPredecessorsOfOldNode(oldIndex);
MergedListIndex newIndex = AddNewNode(
destItem, Some(oldIndex), directPredecessors, aPreviousItem);
mOldItems[oldIndex.val].AddedMatchToMergedList(mBuilder, newIndex);
if (destItem == aNewItem) {
oldItem->Destroy(mBuilder->Builder());
} else {
aNewItem->Destroy(mBuilder->Builder());
}
return Some(newIndex);
}
}
mResultIsModified = true;
return Some(AddNewNode(aNewItem, Nothing(), Span<MergedListIndex>(),
aPreviousItem));
}
bool ShouldUseNewItem(nsDisplayItem* aNewItem) {
// Generally we want to use the old item when the frame isn't marked as
// modified so that any cached information on the item (or referencing the
// item) gets retained. Quite a few FrameLayerBuilder performance
// improvements benefit by this. Sometimes, however, we can end up where the
// new item paints something different from the old item, even though we
// haven't modified the frame, and it's hard to fix. In these cases we just
// always use the new item to be safe.
DisplayItemType type = aNewItem->GetType();
if (type == DisplayItemType::TYPE_CANVAS_BACKGROUND_COLOR ||
type == DisplayItemType::TYPE_SOLID_COLOR) {
// The canvas background color item can paint the color from another
// frame, and even though we schedule a paint, we don't mark the canvas
// frame as invalid.
return true;
}
if (type == DisplayItemType::TYPE_TABLE_BORDER_COLLAPSE) {
// We intentionally don't mark the root table frame as modified when a
// subframe changes, even though the border collapse item for the root
// frame is what paints the changed border. Marking the root frame as
// modified would rebuild display items for the whole table area, and we
// don't want that.
return true;
}
if (type == DisplayItemType::TYPE_TEXT_OVERFLOW) {
// Text overflow marker items are created with the wrapping block as their
// frame, and have an index value to note which line they are created for.
// Their rendering can change if the items on that line change, which may
// not mark the block as modified. We rebuild them if we build any item on
// the line, so we should always get new items if they might have changed
// rendering, and it's easier to just use the new items rather than
// computing if we actually need them.
return true;
}
if (type == DisplayItemType::TYPE_SUBDOCUMENT) {
// nsDisplaySubDocument::mShouldFlatten can change without an invalidation
// (and is the reason we unconditionally build the subdocument item), so
// always use the new one to make sure we get the right value.
return true;
}
if (type == DisplayItemType::TYPE_CARET) {
// The caret can change position while still being owned by the same frame
// and we don't invalidate in that case. Use the new version since the
// changed bounds are needed for DLBI.
return true;
}
if (type == DisplayItemType::TYPE_MASK ||
type == DisplayItemType::TYPE_FILTER ||
type == DisplayItemType::TYPE_SVG_WRAPPER) {
// SVG items have some invalidation issues, see bugs 1494110 and 1494663.
return true;
}
return false;
}
RetainedDisplayList Finalize() {
for (size_t i = 0; i < mOldDAG.Length(); i++) {
if (mOldItems[i].IsUsed()) {
continue;
}
AutoTArray<MergedListIndex, 2> directPredecessors =
ResolveNodeIndexesOldToMerged(
mOldDAG.GetDirectPredecessors(OldListIndex(i)));
ProcessOldNode(OldListIndex(i), std::move(directPredecessors));
}
RetainedDisplayList result;
result.AppendToTop(&mMergedItems);
result.mDAG = std::move(mMergedDAG);
MOZ_RELEASE_ASSERT(result.mDAG.Length() == result.Count());
return result;
}
bool HasMatchingItemInOldList(nsDisplayItem* aItem, OldListIndex* aOutIndex) {
nsIFrame::DisplayItemArray* items =
aItem->Frame()->GetProperty(nsIFrame::DisplayItems());
// Look for an item that matches aItem's frame and per-frame-key, but isn't
// the same item.
for (nsDisplayItem* i : *items) {
if (i != aItem && i->Frame() == aItem->Frame() &&
i->GetPerFrameKey() == aItem->GetPerFrameKey()) {
if (i->GetOldListIndex(mOldList, mOuterKey, aOutIndex)) {
return true;
}
}
}
return false;
}
bool HasModifiedFrame(nsDisplayItem* aItem) {
return AnyContentAncestorModified(aItem->FrameForInvalidation());
}
void UpdateContainerASR(nsDisplayItem* aItem) {
mContainerASR = SelectContainerASR(
aItem->GetClipChain(), aItem->GetActiveScrolledRoot(), mContainerASR);
}
MergedListIndex AddNewNode(
nsDisplayItem* aItem, const Maybe<OldListIndex>& aOldIndex,
Span<const MergedListIndex> aDirectPredecessors,
const Maybe<MergedListIndex>& aExtraDirectPredecessor) {
UpdateContainerASR(aItem);
#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
nsIFrame::DisplayItemArray* items =
aItem->Frame()->GetProperty(nsIFrame::DisplayItems());
for (nsDisplayItem* i : *items) {
if (i->Frame() == aItem->Frame() &&
i->GetPerFrameKey() == aItem->GetPerFrameKey()) {
MOZ_DIAGNOSTIC_ASSERT(!i->mMergedItem);
}
}
aItem->mMergedItem = true;
aItem->mPreProcessedItem = false;
#endif
mMergedItems.AppendToTop(aItem);
MergedListIndex newIndex =
mMergedDAG.AddNode(aDirectPredecessors, aExtraDirectPredecessor);
return newIndex;
}
void ProcessOldNode(OldListIndex aNode,
nsTArray<MergedListIndex>&& aDirectPredecessors) {
nsDisplayItem* item = mOldItems[aNode.val].mItem;
if (ShouldSilentlyDiscardItem(item)) {
// If the item should be discarded, then just silently drop it and
// don't mark the display list as being modified.
mOldItems[aNode.val].Discard(mBuilder, std::move(aDirectPredecessors));
} else if (mOldItems[aNode.val].IsChanged() || HasModifiedFrame(item)) {
mOldItems[aNode.val].Discard(mBuilder, std::move(aDirectPredecessors));
mResultIsModified = true;
} else {
if (item->GetChildren()) {
Maybe<const ActiveScrolledRoot*> containerASRForChildren;
nsDisplayList empty;
if (mBuilder->MergeDisplayLists(&empty, item->GetChildren(),
item->GetChildren(),
containerASRForChildren, item)) {
item->InvalidateCachedChildInfo();
mResultIsModified = true;
}
UpdateASR(item, containerASRForChildren);
item->UpdateBounds(mBuilder->Builder());
}
if (item->GetType() == DisplayItemType::TYPE_SUBDOCUMENT) {
mBuilder->IncrementSubDocPresShellPaintCount(item);
}
item->SetReused(true);
mOldItems[aNode.val].AddedToMergedList(
AddNewNode(item, Some(aNode), aDirectPredecessors, Nothing()));
}
}
struct PredecessorStackItem {
PredecessorStackItem(OldListIndex aNode, Span<OldListIndex> aPredecessors)
: mNode(aNode),
mDirectPredecessors(aPredecessors),
mCurrentPredecessorIndex(0) {}
bool IsFinished() {
return mCurrentPredecessorIndex == mDirectPredecessors.Length();
}
OldListIndex GetAndIncrementCurrentPredecessor() {
return mDirectPredecessors[mCurrentPredecessorIndex++];
}
OldListIndex mNode;
Span<OldListIndex> mDirectPredecessors;
size_t mCurrentPredecessorIndex;
};
AutoTArray<MergedListIndex, 2> ProcessPredecessorsOfOldNode(
OldListIndex aNode) {
AutoTArray<PredecessorStackItem, 256> mStack;
mStack.AppendElement(
PredecessorStackItem(aNode, mOldDAG.GetDirectPredecessors(aNode)));
while (true) {
if (mStack.LastElement().IsFinished()) {
// If we've finished processing all the entries in the current set, then
// pop it off the processing stack and process it.
PredecessorStackItem item = mStack.PopLastElement();
AutoTArray<MergedListIndex, 2> result =
ResolveNodeIndexesOldToMerged(item.mDirectPredecessors);
if (mStack.IsEmpty()) {
return result;
}
ProcessOldNode(item.mNode, std::move(result));
} else {
// Grab the current predecessor, push predecessors of that onto the
// processing stack (if it hasn't already been processed), and then
// advance to the next entry.
OldListIndex currentIndex =
mStack.LastElement().GetAndIncrementCurrentPredecessor();
if (!mOldItems[currentIndex.val].IsUsed()) {
mStack.AppendElement(PredecessorStackItem(
currentIndex, mOldDAG.GetDirectPredecessors(currentIndex)));
}
}
}
}
AutoTArray<MergedListIndex, 2> ResolveNodeIndexesOldToMerged(
Span<OldListIndex> aDirectPredecessors) {
AutoTArray<MergedListIndex, 2> result;
result.SetCapacity(aDirectPredecessors.Length());
for (OldListIndex index : aDirectPredecessors) {
OldItemInfo& oldItem = mOldItems[index.val];
if (oldItem.IsDiscarded()) {
for (MergedListIndex inner : oldItem.mDirectPredecessors) {
if (!result.Contains(inner)) {
result.AppendElement(inner);
}
}
} else {
result.AppendElement(oldItem.mIndex);
}
}
return result;
}
RetainedDisplayListBuilder* mBuilder;
RetainedDisplayList* mOldList;
Maybe<const ActiveScrolledRoot*> mContainerASR;
nsTArray<OldItemInfo> mOldItems;
DirectedAcyclicGraph<OldListUnits> mOldDAG;
// Unfortunately we can't use strong typing for the hashtables
// since they internally encode the type with the mOps pointer,
// and assert when we try swap the contents
nsDisplayList mMergedItems;
DirectedAcyclicGraph<MergedListUnits> mMergedDAG;
uint32_t mOuterKey;
bool mResultIsModified;
};
/**
* Takes two display lists and merges them into an output list.
*
* Display lists wthout an explicit DAG are interpreted as linear DAGs (with a
* maximum of one direct predecessor and one direct successor per node). We add
* the two DAGs together, and then output the topological sorted ordering as the
* final display list.
*
* Once we've merged a list, we then retain the DAG (as part of the
* RetainedDisplayList object) to use for future merges.
*/
bool RetainedDisplayListBuilder::MergeDisplayLists(
nsDisplayList* aNewList, RetainedDisplayList* aOldList,
RetainedDisplayList* aOutList,
mozilla::Maybe<const mozilla::ActiveScrolledRoot*>& aOutContainerASR,
nsDisplayItem* aOuterItem) {
MergeState merge(this, *aOldList,
aOuterItem ? aOuterItem->GetPerFrameKey() : 0);
AutoRestore<bool> restoreForEventAndPluginsOnly(
mCurrentSubtreeIsForEventsAndPluginsOnly);
if (aOuterItem && aOuterItem->GetType() == DisplayItemType::TYPE_OPACITY &&
static_cast<nsDisplayOpacity*>(aOuterItem)->ForEventsAndPluginsOnly()) {
mCurrentSubtreeIsForEventsAndPluginsOnly = true;
}
Maybe<MergedListIndex> previousItemIndex;
while (nsDisplayItem* item = aNewList->RemoveBottom()) {
previousItemIndex = merge.ProcessItemFromNewList(item, previousItemIndex);
}
*aOutList = merge.Finalize();
aOutContainerASR = merge.mContainerASR;
return merge.mResultIsModified;
}
static void TakeAndAddModifiedAndFramesWithPropsFromRootFrame(
nsDisplayListBuilder* aBuilder, nsTArray<nsIFrame*>* aModifiedFrames,
nsTArray<nsIFrame*>* aFramesWithProps, nsIFrame* aRootFrame) {
MOZ_ASSERT(aRootFrame);
RetainedDisplayListData* data = GetRetainedDisplayListData(aRootFrame);
if (!data) {
return;
}
for (auto it = data->Iterator(); !it.Done(); it.Next()) {
nsIFrame* frame = it.Key();
const RetainedDisplayListData::FrameFlags& flags = it.Data();
if (flags & RetainedDisplayListData::FrameFlags::Modified) {
aModifiedFrames->AppendElement(frame);
}
if (flags & RetainedDisplayListData::FrameFlags::HasProps) {
aFramesWithProps->AppendElement(frame);
}
if (flags & RetainedDisplayListData::FrameFlags::HadWillChange) {
aBuilder->RemoveFromWillChangeBudget(frame);
}
}
data->Clear();
}
struct CbData {
nsDisplayListBuilder* builder;
nsTArray<nsIFrame*>* modifiedFrames;
nsTArray<nsIFrame*>* framesWithProps;
};
static nsIFrame* GetRootFrameForPainting(nsDisplayListBuilder* aBuilder,
Document* aDocument) {
// Although this is the actual subdocument, it might not be
// what painting uses. Walk up to the nsSubDocumentFrame owning
// us, and then ask that which subdoc it's going to paint.
nsIPresShell* presShell = aDocument->GetShell();
if (!presShell) {
return nullptr;
}
nsView* rootView = presShell->GetViewManager()->GetRootView();
if (!rootView) {
return nullptr;
}
// There should be an anonymous inner view between the root view
// of the subdoc, and the view for the nsSubDocumentFrame.
nsView* innerView = rootView->GetParent();
if (!innerView) {
return nullptr;
}
nsView* subDocView = innerView->GetParent();
if (!subDocView) {
return nullptr;
}
nsIFrame* subDocFrame = subDocView->GetFrame();
if (!subDocFrame) {
return nullptr;
}
nsSubDocumentFrame* subdocumentFrame = do_QueryFrame(subDocFrame);
MOZ_ASSERT(subdocumentFrame);
presShell = subdocumentFrame->GetSubdocumentPresShellForPainting(
aBuilder->IsIgnoringPaintSuppression()
? nsSubDocumentFrame::IGNORE_PAINT_SUPPRESSION
: 0);
return presShell ? presShell->GetRootFrame() : nullptr;
}
static bool SubDocEnumCb(Document* aDocument, void* aData) {
MOZ_ASSERT(aDocument);
MOZ_ASSERT(aData);
CbData* data = static_cast<CbData*>(aData);
nsIFrame* rootFrame = GetRootFrameForPainting(data->builder, aDocument);
if (rootFrame) {
TakeAndAddModifiedAndFramesWithPropsFromRootFrame(
data->builder, data->modifiedFrames, data->framesWithProps, rootFrame);
Document* innerDoc = rootFrame->PresShell()->GetDocument();
if (innerDoc) {
innerDoc->EnumerateSubDocuments(SubDocEnumCb, aData);
}
}
return true;
}
static void GetModifiedAndFramesWithProps(
nsDisplayListBuilder* aBuilder, nsTArray<nsIFrame*>* aOutModifiedFrames,
nsTArray<nsIFrame*>* aOutFramesWithProps) {
nsIFrame* rootFrame = aBuilder->RootReferenceFrame();
MOZ_ASSERT(rootFrame);
TakeAndAddModifiedAndFramesWithPropsFromRootFrame(
aBuilder, aOutModifiedFrames, aOutFramesWithProps, rootFrame);
Document* rootdoc = rootFrame->PresContext()->Document();
if (rootdoc) {
CbData data = {aBuilder, aOutModifiedFrames, aOutFramesWithProps};
rootdoc->EnumerateSubDocuments(SubDocEnumCb, &data);
}
}
// ComputeRebuildRegion debugging
// #define CRR_DEBUG 1
#if CRR_DEBUG
# define CRR_LOG(...) printf_stderr(__VA_ARGS__)
#else
# define CRR_LOG(...)
#endif
static nsDisplayItem* GetFirstDisplayItemWithChildren(nsIFrame* aFrame) {
nsIFrame::DisplayItemArray* items =
aFrame->GetProperty(nsIFrame::DisplayItems());
if (!items) {
return nullptr;
}
for (nsDisplayItem* i : *items) {
if (i->GetChildren()) {
return i;
}
}
return nullptr;
}
static bool IsInPreserve3DContext(const nsIFrame* aFrame) {
return aFrame->Extend3DContext() ||
aFrame->Combines3DTransformWithAncestors();
}
static bool ProcessFrameInternal(nsIFrame* aFrame,
nsDisplayListBuilder& aBuilder,
AnimatedGeometryRoot** aAGR, nsRect& aOverflow,
nsIFrame* aStopAtFrame,
nsTArray<nsIFrame*>& aOutFramesWithProps,
const bool aStopAtStackingContext) {
nsIFrame* currentFrame = aFrame;
while (currentFrame != aStopAtFrame) {
CRR_LOG("currentFrame: %p (placeholder=%d), aOverflow: %d %d %d %d\n",
currentFrame, !aStopAtStackingContext, aOverflow.x, aOverflow.y,
aOverflow.width, aOverflow.height);
// If the current frame is an OOF frame, DisplayListBuildingData needs to be
// set on all the ancestor stacking contexts of the placeholder frame, up
// to the containing block of the OOF frame. This is done to ensure that the
// content that might be behind the OOF frame is built for merging.
nsIFrame* placeholder = currentFrame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW)
? currentFrame->GetPlaceholderFrame()
: nullptr;
if (placeholder) {
// The rect aOverflow is in the coordinate space of the containing block.
// Convert it to a coordinate space of the placeholder frame.
nsRect placeholderOverflow =
aOverflow + currentFrame->GetOffsetTo(placeholder);
CRR_LOG("Processing placeholder %p for OOF frame %p\n", placeholder,
currentFrame);
CRR_LOG("OOF frame draw area: %d %d %d %d\n", placeholderOverflow.x,
placeholderOverflow.y, placeholderOverflow.width,
placeholderOverflow.height);
// Tracking AGRs for the placeholder processing is not necessary, as the
// goal is to only modify the DisplayListBuildingData rect.
AnimatedGeometryRoot* dummyAGR = nullptr;
// Find a common ancestor frame to handle frame continuations.
// TODO: It might be possible to write a more specific and efficient
// function for this.
nsIFrame* ancestor = nsLayoutUtils::FindNearestCommonAncestorFrame(
currentFrame->GetParent(), placeholder->GetParent());
if (!ProcessFrameInternal(placeholder, aBuilder, &dummyAGR,
placeholderOverflow, ancestor,
aOutFramesWithProps, false)) {
return false;
}
}
// Convert 'aOverflow' into the coordinate space of the nearest stacking
// context or display port ancestor and update 'currentFrame' to point to
// that frame.
aOverflow = nsLayoutUtils::TransformFrameRectToAncestor(
currentFrame, aOverflow, aStopAtFrame, nullptr, nullptr,
/* aStopAtStackingContextAndDisplayPortAndOOFFrame = */ true,
&currentFrame);
if (IsInPreserve3DContext(currentFrame)) {
return false;
}
MOZ_ASSERT(currentFrame);
if (nsLayoutUtils::FrameHasDisplayPort(currentFrame)) {
CRR_LOG("Frame belongs to displayport frame %p\n", currentFrame);
nsIScrollableFrame* sf = do_QueryFrame(currentFrame);
MOZ_ASSERT(sf);
nsRect displayPort;
DebugOnly<bool> hasDisplayPort = nsLayoutUtils::GetDisplayPort(
currentFrame->GetContent(), &displayPort, RelativeTo::ScrollPort);
MOZ_ASSERT(hasDisplayPort);
// get it relative to the scrollport (from the scrollframe)
nsRect r = aOverflow - sf->GetScrollPortRect().TopLeft();
r.IntersectRect(r, displayPort);
if (!r.IsEmpty()) {
nsRect* rect = currentFrame->GetProperty(
nsDisplayListBuilder::DisplayListBuildingDisplayPortRect());
if (!rect) {
rect = new nsRect();
currentFrame->SetProperty(
nsDisplayListBuilder::DisplayListBuildingDisplayPortRect(), rect);
currentFrame->SetHasOverrideDirtyRegion(true);
aOutFramesWithProps.AppendElement(currentFrame);
}
rect->UnionRect(*rect, r);
CRR_LOG("Adding area to displayport draw area: %d %d %d %d\n", r.x, r.y,
r.width, r.height);
// TODO: Can we just use MarkFrameForDisplayIfVisible, plus
// MarkFramesForDifferentAGR to ensure that this displayport, plus any
// items that move relative to it get rebuilt, and then not contribute
// to the root dirty area?
aOverflow = sf->GetScrollPortRect();
} else {
// Don't contribute to the root dirty area at all.
aOverflow.SetEmpty();
}
} else {
aOverflow.IntersectRect(
aOverflow, currentFrame->GetVisualOverflowRectRelativeToSelf());
}
if (aOverflow.IsEmpty()) {
break;
}
if (currentFrame != aBuilder.RootReferenceFrame() &&
currentFrame->IsStackingContext() &&
currentFrame->IsFixedPosContainingBlock()) {
CRR_LOG("Frame belongs to stacking context frame %p\n", currentFrame);
// If we found an intermediate stacking context with an existing display
// item then we can store the dirty rect there and stop. If we couldn't
// find one then we need to keep bubbling up to the next stacking context.
nsDisplayItem* wrapperItem =
GetFirstDisplayItemWithChildren(currentFrame);
if (!wrapperItem) {
continue;
}
// Store the stacking context relative dirty area such
// that display list building will pick it up when it
// gets to it.
nsDisplayListBuilder::DisplayListBuildingData* data =
currentFrame->GetProperty(
nsDisplayListBuilder::DisplayListBuildingRect());
if (!data) {
data = new nsDisplayListBuilder::DisplayListBuildingData();
currentFrame->SetProperty(
nsDisplayListBuilder::DisplayListBuildingRect(), data);
currentFrame->SetHasOverrideDirtyRegion(true);
aOutFramesWithProps.AppendElement(currentFrame);
}
CRR_LOG("Adding area to stacking context draw area: %d %d %d %d\n",
aOverflow.x, aOverflow.y, aOverflow.width, aOverflow.height);
data->mDirtyRect.UnionRect(data->mDirtyRect, aOverflow);
if (!aStopAtStackingContext) {
// Continue ascending the frame tree until we reach aStopAtFrame.
continue;
}
// Grab the visible (display list building) rect for children of this
// wrapper item and convert into into coordinate relative to the current
// frame.
nsRect previousVisible = wrapperItem->GetBuildingRectForChildren();
if (wrapperItem->ReferenceFrameForChildren() ==
wrapperItem->ReferenceFrame()) {
previousVisible -= wrapperItem->ToReferenceFrame();
} else {
MOZ_ASSERT(wrapperItem->ReferenceFrameForChildren() ==
wrapperItem->Frame());
}
if (!previousVisible.Contains(aOverflow)) {
// If the overflow area of the changed frame isn't contained within the
// old item, then we might change the size of the item and need to
// update its sorting accordingly. Keep propagating the overflow area up
// so that we build intersecting items for sorting.
continue;
}
if (!data->mModifiedAGR) {
data->mModifiedAGR = *aAGR;
} else if (data->mModifiedAGR != *aAGR) {
data->mDirtyRect = currentFrame->GetVisualOverflowRectRelativeToSelf();
CRR_LOG(
"Found multiple modified AGRs within this stacking context, "
"giving up\n");
}
// Don't contribute to the root dirty area at all.
aOverflow.SetEmpty();
*aAGR = nullptr;
break;
}
}
return true;
}
bool RetainedDisplayListBuilder::ProcessFrame(
nsIFrame* aFrame, nsDisplayListBuilder& aBuilder, nsIFrame* aStopAtFrame,
nsTArray<nsIFrame*>& aOutFramesWithProps, const bool aStopAtStackingContext,
nsRect* aOutDirty, AnimatedGeometryRoot** aOutModifiedAGR) {
if (aFrame->HasOverrideDirtyRegion()) {
aOutFramesWithProps.AppendElement(aFrame);
}
if (aFrame->HasAnyStateBits(NS_FRAME_IN_POPUP)) {
return true;
}
// TODO: There is almost certainly a faster way of doing this, probably can be
// combined with the ancestor walk for TransformFrameRectToAncestor.
AnimatedGeometryRoot* agr =
aBuilder.FindAnimatedGeometryRootFor(aFrame)->GetAsyncAGR();
CRR_LOG("Processing frame %p with agr %p\n", aFrame, agr->mFrame);
// Convert the frame's overflow rect into the coordinate space
// of the nearest stacking context that has an existing display item.
// We store that as a dirty rect on that stacking context so that we build
// all items that intersect the changed frame within the stacking context,
// and then we use MarkFrameForDisplayIfVisible to make sure the stacking
// context itself gets built. We don't need to build items that intersect
// outside of the stacking context, since we know the stacking context item
// exists in the old list, so we can trivially merge without needing other
// items.
nsRect overflow = aFrame->GetVisualOverflowRectRelativeToSelf();
// If the modified frame is also a caret frame, include the caret area.
// This is needed because some frames (for example text frames without text)
// might have an empty overflow rect.
if (aFrame == aBuilder.GetCaretFrame()) {
overflow.UnionRect(overflow, aBuilder.GetCaretRect());
}
if (!ProcessFrameInternal(aFrame, aBuilder, &agr, overflow, aStopAtFrame,
aOutFramesWithProps, aStopAtStackingContext)) {
return false;
}
if (!overflow.IsEmpty()) {
aOutDirty->UnionRect(*aOutDirty, overflow);
CRR_LOG("Adding area to root draw area: %d %d %d %d\n", overflow.x,
overflow.y, overflow.width, overflow.height);
// If we get changed frames from multiple AGRS, then just give up as it gets
// really complex to track which items would need to be marked in
// MarkFramesForDifferentAGR.
if (!*aOutModifiedAGR) {
CRR_LOG("Setting %p as root stacking context AGR\n", agr);
*aOutModifiedAGR = agr;
} else if (agr && *aOutModifiedAGR != agr) {
CRR_LOG("Found multiple AGRs in root stacking context, giving up\n");
return false;
}
}
return true;
}
static void AddFramesForContainingBlock(nsIFrame* aBlock,
const nsFrameList& aFrames,
nsTArray<nsIFrame*>& aExtraFrames) {
for (nsIFrame* f : aFrames) {
if (!f->IsFrameModified() && AnyContentAncestorModified(f, aBlock)) {
CRR_LOG("Adding invalid OOF %p\n", f);
aExtraFrames.AppendElement(f);
}
}
}
// Placeholder descendants of aFrame don't contribute to aFrame's overflow area.
// Find all the containing blocks that might own placeholders under us, walk
// their OOF frames list, and manually invalidate any frames that are
// descendants of a modified frame (us, or another frame we'll get to soon).
// This is combined with the work required for MarkFrameForDisplayIfVisible,
// so that we can avoid an extra ancestor walk, and we can reuse the flag
// to detect when we've already visited an ancestor (and thus all further
// ancestors must also be visited).
void FindContainingBlocks(nsIFrame* aFrame, nsTArray<nsIFrame*>& aExtraFrames) {
for (nsIFrame* f = aFrame; f;
f = nsLayoutUtils::GetParentOrPlaceholderForCrossDoc(f)) {
if (f->ForceDescendIntoIfVisible()) return;
f->SetForceDescendIntoIfVisible(true);
CRR_LOG("Considering OOFs for %p\n", f);
AddFramesForContainingBlock(f, f->GetChildList(nsIFrame::kFloatList),
aExtraFrames);
AddFramesForContainingBlock(f, f->GetChildList(f->GetAbsoluteListID()),
aExtraFrames);
}
}
/**
* Given a list of frames that has been modified, computes the region that we
* need to do display list building for in order to build all modified display
* items.
*
* When a modified frame is within a stacking context (with an existing display
* item), then we only contribute to the build area within the stacking context,
* as well as forcing display list building to descend to the stacking context.
* We don't need to add build area outside of the stacking context (and force
* items above/below the stacking context container item to be built), since
* just matching the position of the stacking context container item is
* sufficient to ensure correct ordering during merging.
*
* We need to rebuild all items that might intersect with the modified frame,
* both now and during async changes on the compositor. We do this by rebuilding
* the area covered by the changed frame, as well as rebuilding all items that
* have a different (async) AGR to the changed frame. If we have changes to
* multiple AGRs (within a stacking context), then we rebuild that stacking
* context entirely.
*
* @param aModifiedFrames The list of modified frames.
* @param aOutDirty The result region to use for display list building.
* @param aOutModifiedAGR The modified AGR for the root stacking context.
* @param aOutFramesWithProps The list of frames to which we attached partial
* build data so that it can be cleaned up.
*
* @return true if we succesfully computed a partial rebuild region, false if a
* full build is required.
*/
bool RetainedDisplayListBuilder::ComputeRebuildRegion(
nsTArray<nsIFrame*>& aModifiedFrames, nsRect* aOutDirty,
AnimatedGeometryRoot** aOutModifiedAGR,
nsTArray<nsIFrame*>& aOutFramesWithProps) {
CRR_LOG("Computing rebuild regions for %zu frames:\n",
aModifiedFrames.Length());
nsTArray<nsIFrame*> extraFrames;
for (nsIFrame* f : aModifiedFrames) {
MOZ_ASSERT(f);
mBuilder.AddFrameMarkedForDisplayIfVisible(f);
FindContainingBlocks(f, extraFrames);
if (!ProcessFrame(f, mBuilder, mBuilder.RootReferenceFrame(),
aOutFramesWithProps, true, aOutDirty, aOutModifiedAGR)) {
return false;
}
}
for (nsIFrame* f : extraFrames) {
mBuilder.MarkFrameModifiedDuringBuilding(f);
if (!ProcessFrame(f, mBuilder, mBuilder.RootReferenceFrame(),
aOutFramesWithProps, true, aOutDirty, aOutModifiedAGR)) {
return false;
}
}
return true;
}
/*
* A simple early exit heuristic to avoid slow partial display list rebuilds.
*/
static bool ShouldBuildPartial(nsTArray<nsIFrame*>& aModifiedFrames) {
if (aModifiedFrames.Length() > gfxPrefs::LayoutRebuildFrameLimit()) {
return false;
}
for (nsIFrame* f : aModifiedFrames) {
MOZ_ASSERT(f);
const LayoutFrameType type = f->Type();
// If we have any modified frames of the following types, it is likely that
// doing a partial rebuild of the display list will be slower than doing a
// full rebuild.
// This is because these frames either intersect or may intersect with most
// of the page content. This is either due to display port size or different
// async AGR.
if (type == LayoutFrameType::Viewport ||
type == LayoutFrameType::PageContent ||
type == LayoutFrameType::Canvas || type == LayoutFrameType::Scrollbar) {
return false;
}
}
return true;
}
static void ClearFrameProps(nsTArray<nsIFrame*>& aFrames) {
for (nsIFrame* f : aFrames) {
if (f->HasOverrideDirtyRegion()) {
f->SetHasOverrideDirtyRegion(false);
f->DeleteProperty(nsDisplayListBuilder::DisplayListBuildingRect());
f->DeleteProperty(
nsDisplayListBuilder::DisplayListBuildingDisplayPortRect());
}
f->SetFrameIsModified(false);
}
}
class AutoClearFramePropsArray {
public:
explicit AutoClearFramePropsArray(size_t aCapacity) : mFrames(aCapacity) {}
AutoClearFramePropsArray() = default;
~AutoClearFramePropsArray() { ClearFrameProps(mFrames); }
nsTArray<nsIFrame*>& Frames() { return mFrames; }
bool IsEmpty() const { return mFrames.IsEmpty(); }
private:
nsTArray<nsIFrame*> mFrames;
};
void RetainedDisplayListBuilder::ClearFramesWithProps() {
AutoClearFramePropsArray modifiedFrames;
AutoClearFramePropsArray framesWithProps;
GetModifiedAndFramesWithProps(&mBuilder, &modifiedFrames.Frames(),
&framesWithProps.Frames());
}
auto RetainedDisplayListBuilder::AttemptPartialUpdate(
nscolor aBackstop, mozilla::DisplayListChecker* aChecker)
-> PartialUpdateResult {
mBuilder.RemoveModifiedWindowRegions();
mBuilder.ClearWindowOpaqueRegion();
if (mBuilder.ShouldSyncDecodeImages()) {
MarkFramesWithItemsAndImagesModified(&mList);
}
mBuilder.EnterPresShell(mBuilder.RootReferenceFrame());
// We set the override dirty regions during ComputeRebuildRegion or in
// nsLayoutUtils::InvalidateForDisplayPortChange. The display port change also
// marks the frame modified, so those regions are cleared here as well.
AutoClearFramePropsArray modifiedFrames(64);
AutoClearFramePropsArray framesWithProps;
GetModifiedAndFramesWithProps(&mBuilder, &modifiedFrames.Frames(),
&framesWithProps.Frames());
// Do not allow partial builds if the retained display list is empty, or if
// ShouldBuildPartial heuristic fails.
bool shouldBuildPartial =
!mList.IsEmpty() && ShouldBuildPartial(modifiedFrames.Frames());
// We don't support retaining with overlay scrollbars, since they require
// us to look at the display list and pick the highest z-index, which
// we can't do during partial building.
if (mBuilder.DisablePartialUpdates()) {
shouldBuildPartial = false;
mBuilder.SetDisablePartialUpdates(false);
}
if (mPreviousCaret != mBuilder.GetCaretFrame()) {
if (mPreviousCaret) {
if (mBuilder.MarkFrameModifiedDuringBuilding(mPreviousCaret)) {
modifiedFrames.Frames().AppendElement(mPreviousCaret);
}
}
if (mBuilder.GetCaretFrame()) {
if (mBuilder.MarkFrameModifiedDuringBuilding(mBuilder.GetCaretFrame())) {
modifiedFrames.Frames().AppendElement(mBuilder.GetCaretFrame());
}
}
mPreviousCaret = mBuilder.GetCaretFrame();
}
nsRect modifiedDirty;
AnimatedGeometryRoot* modifiedAGR = nullptr;
if (!shouldBuildPartial ||
!ComputeRebuildRegion(modifiedFrames.Frames(), &modifiedDirty,
&modifiedAGR, framesWithProps.Frames()) ||
!PreProcessDisplayList(&mList, modifiedAGR)) {
mBuilder.LeavePresShell(mBuilder.RootReferenceFrame(), nullptr);
mList.DeleteAll(&mBuilder);
return PartialUpdateResult::Failed;
}
// This is normally handled by EnterPresShell, but we skipped it so that we
// didn't call MarkFrameForDisplayIfVisible before ComputeRebuildRegion.
nsIScrollableFrame* sf = mBuilder.RootReferenceFrame()
->PresShell()
->GetRootScrollFrameAsScrollable();
if (sf) {
nsCanvasFrame* canvasFrame = do_QueryFrame(sf->GetScrolledFrame());
if (canvasFrame) {
mBuilder.MarkFrameForDisplayIfVisible(canvasFrame,
mBuilder.RootReferenceFrame());
}
}
modifiedDirty.IntersectRect(
modifiedDirty,
mBuilder.RootReferenceFrame()->GetVisualOverflowRectRelativeToSelf());
mBuilder.SetDirtyRect(modifiedDirty);
mBuilder.SetPartialUpdate(true);
nsDisplayList modifiedDL;
mBuilder.RootReferenceFrame()->BuildDisplayListForStackingContext(
&mBuilder, &modifiedDL);
if (!modifiedDL.IsEmpty()) {
nsLayoutUtils::AddExtraBackgroundItems(
mBuilder, modifiedDL, mBuilder.RootReferenceFrame(),
nsRect(nsPoint(0, 0), mBuilder.RootReferenceFrame()->GetSize()),
mBuilder.RootReferenceFrame()->GetVisualOverflowRectRelativeToSelf(),
aBackstop);
}
mBuilder.SetPartialUpdate(false);
if (mBuilder.PartialBuildFailed()) {
mBuilder.SetPartialBuildFailed(false);
mBuilder.LeavePresShell(mBuilder.RootReferenceFrame(), nullptr);
mList.DeleteAll(&mBuilder);
modifiedDL.DeleteAll(&mBuilder);
return PartialUpdateResult::Failed;
}
if (aChecker) {
aChecker->Set(&modifiedDL, "TM");
}
// printf_stderr("Painting --- Modified list (dirty %d,%d,%d,%d):\n",
// modifiedDirty.x, modifiedDirty.y, modifiedDirty.width,
// modifiedDirty.height);
// nsFrame::PrintDisplayList(&mBuilder, modifiedDL);
// |modifiedDL| can sometimes be empty here. We still perform the
// display list merging to prune unused items (for example, items that
// are not visible anymore) from the old list.
// TODO: Optimization opportunity. In this case, MergeDisplayLists()
// unnecessarily creates a hashtable of the old items.
// TODO: Ideally we could skip this if result is NoChange, but currently when
// we call RestoreState on nsDisplayWrapList it resets the clip to the base
// clip, and we need the UpdateBounds call (within MergeDisplayLists) to
// move it to the correct inner clip.
PartialUpdateResult result = PartialUpdateResult::NoChange;
Maybe<const ActiveScrolledRoot*> dummy;
if (MergeDisplayLists(&modifiedDL, &mList, &mList, dummy)) {
result = PartialUpdateResult::Updated;
}
// printf_stderr("Painting --- Merged list:\n");
// nsFrame::PrintDisplayList(&mBuilder, mList);
mBuilder.LeavePresShell(mBuilder.RootReferenceFrame(), List());
return result;
}
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