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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/. */
#ifndef mozilla_OverflowChangedTracker_h
#define mozilla_OverflowChangedTracker_h
#include "mozilla/HashTable.h"
#include "nsContainerFrame.h"
#include "nsIFrame.h"
#include "nsTArray.h"
namespace mozilla {
/**
* Helper class that collects a list of frames that need
* UpdateOverflow() called on them, and coalesces them
* to avoid walking up the same ancestor tree multiple times.
*/
class OverflowChangedTracker {
public:
enum ChangeKind {
/**
* The frame was explicitly added as a result of
* nsChangeHint_UpdatePostTransformOverflow and hence may have had a style
* change that changes its geometry relative to parent, without reflowing.
*/
TRANSFORM_CHANGED,
/**
* The overflow areas of children have changed
* and we need to call UpdateOverflow on the frame.
*/
CHILDREN_CHANGED,
};
OverflowChangedTracker() : mSubtreeRoot(nullptr) {}
~OverflowChangedTracker() {
NS_ASSERTION(mEntries.empty(), "Need to flush before destroying!");
}
/**
* Add a frame that has had a style change, and needs its
* overflow updated.
*
* If there are pre-transform overflow areas stored for this
* frame, then we will call FinishAndStoreOverflow with those
* areas instead of UpdateOverflow().
*
* If the overflow area changes, then UpdateOverflow will also
* be called on the parent.
*/
void AddFrame(nsIFrame* aFrame, ChangeKind aChangeKind) {
MOZ_ASSERT(
aFrame->FrameMaintainsOverflow(),
"Why add a frame that doesn't maintain overflow to the tracker?");
if (auto p = mEntries.lookupForAdd(aFrame)) {
p->value() = std::max(p->value(), aChangeKind);
} else {
// Ignore failure to add an entry; this could result in cosmetic
// errors but is non-fatal.
(void)mEntries.add(p, aFrame, aChangeKind);
}
}
/**
* Remove a frame.
*/
void RemoveFrame(nsIFrame* aFrame) {
if (!mEntries.empty()) {
mEntries.remove(aFrame);
}
}
/**
* Set the subtree root to limit overflow updates. This must be set if and
* only if currently reflowing aSubtreeRoot, to ensure overflow changes will
* still propagate correctly.
*/
void SetSubtreeRoot(const nsIFrame* aSubtreeRoot) {
mSubtreeRoot = aSubtreeRoot;
}
/**
* Update the overflow of all added frames, and clear the entry list.
*
* Start from those deepest in the frame tree and works upwards. This stops
* us from processing the same frame twice.
*/
void Flush() {
// Collect all the entries into an array, sort by depth, and process them
// from the deepest upwards.
AutoTArray<Entry, 8> sortedEntries;
// We use fallible allocations to avoid crashing on OOM; in the event that
// of allocation failure, we'll effectively ignore the entries that weren't
// added to the array, which could result in painting glitches but should
// be otherwise harmless.
(void)sortedEntries.SetCapacity(mEntries.count(), fallible);
for (auto iter = mEntries.iter(); !iter.done(); iter.next()) {
nsIFrame* frame = iter.get().key();
uint32_t depth = frame->GetDepthInFrameTree();
ChangeKind kind = iter.get().value();
if (!sortedEntries.AppendElement(Entry(frame, depth, kind), fallible)) {
break;
}
}
mEntries.clearAndCompact();
sortedEntries.Sort();
while (!sortedEntries.IsEmpty()) {
Entry entry = sortedEntries.PopLastElement();
nsIFrame* frame = entry.mFrame;
bool overflowChanged = false;
if (entry.mChangeKind == CHILDREN_CHANGED) {
// Need to union the overflow areas of the children.
// Only update the parent if the overflow changes.
overflowChanged = frame->UpdateOverflow();
} else {
// Take a faster path that doesn't require unioning the overflow areas
// of our children.
NS_ASSERTION(
frame->GetProperty(nsIFrame::DebugInitialOverflowPropertyApplied()),
"InitialOverflowProperty must be set first.");
OverflowAreas* overflow =
frame->GetProperty(nsIFrame::InitialOverflowProperty());
if (overflow) {
// FinishAndStoreOverflow will change the overflow areas passed in,
// so make a copy.
OverflowAreas overflowCopy = *overflow;
frame->FinishAndStoreOverflow(overflowCopy, frame->GetSize());
} else {
nsRect bounds(nsPoint(0, 0), frame->GetSize());
OverflowAreas boundsOverflow;
boundsOverflow.SetAllTo(bounds);
frame->FinishAndStoreOverflow(boundsOverflow, bounds.Size());
}
// We can't tell if the overflow changed, so be conservative
overflowChanged = true;
}
// If the frame style changed (e.g. positioning offsets)
// then we need to update the parent with the overflow areas of its
// children.
if (overflowChanged) {
nsIFrame* parent = frame->GetParent();
// It's possible that the parent is already in a nondisplay context,
// should not add it to the list if that's true.
if (parent && parent != mSubtreeRoot &&
parent->FrameMaintainsOverflow()) {
Entry parentEntry(parent, entry.mDepth - 1, CHILDREN_CHANGED);
auto index = sortedEntries.IndexOfFirstElementGt(parentEntry);
if (index > 0 && sortedEntries[index - 1] == parentEntry) {
// Update the existing entry if the new value is stronger.
Entry& existing = sortedEntries[index - 1];
existing.mChangeKind =
std::max(existing.mChangeKind, CHILDREN_CHANGED);
} else {
// Add new entry. We ignore failure here; we'll just potentially
// miss some updates that ought to happen.
// (Allocation failure seems unlikely here anyhow, as we just
// popped an element off the array at the top of the loop.)
(void)sortedEntries.InsertElementAt(index, parentEntry, fallible);
}
}
}
}
}
private:
/* Entry type used for the sorted array in Flush(). */
struct Entry {
Entry(nsIFrame* aFrame, uint32_t aDepth,
ChangeKind aChangeKind = CHILDREN_CHANGED)
: mFrame(aFrame), mDepth(aDepth), mChangeKind(aChangeKind) {}
/**
* Note that "equality" tests only the frame pointer.
*/
bool operator==(const Entry& aOther) const {
return mFrame == aOther.mFrame;
}
/**
* Sort by depth in the tree, and break ties with the frame pointer.
*/
bool operator<(const Entry& aOther) const {
if (mDepth == aOther.mDepth) {
return mFrame < aOther.mFrame;
}
return mDepth < aOther.mDepth;
}
nsIFrame* mFrame;
/* Depth in the frame tree */
uint32_t mDepth;
ChangeKind mChangeKind;
};
/* A collection of frames to be processed. */
HashMap<nsIFrame*, ChangeKind> mEntries;
/* Don't update overflow of this frame or its ancestors. */
const nsIFrame* mSubtreeRoot;
};
} // namespace mozilla
#endif
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