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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
#ifndef mozilla_OverflowChangedTracker_h
#define mozilla_OverflowChangedTracker_h
#include "nsIFrame.h"
#include "nsContainerFrame.h"
#include "mozilla/SplayTree.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(mEntryList.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?");
uint32_t depth = aFrame->GetDepthInFrameTree();
Entry* entry = nullptr;
if (!mEntryList.empty()) {
entry = mEntryList.find(Entry(aFrame, depth));
}
if (entry == nullptr) {
// Add new entry.
mEntryList.insert(new Entry(aFrame, depth, aChangeKind));
} else {
// Update the existing entry if the new value is stronger.
entry->mChangeKind = std::max(entry->mChangeKind, aChangeKind);
}
}
/**
* Remove a frame.
*/
void RemoveFrame(nsIFrame* aFrame) {
if (mEntryList.empty()) {
return;
}
uint32_t depth = aFrame->GetDepthInFrameTree();
if (mEntryList.find(Entry(aFrame, depth))) {
delete mEntryList.remove(Entry(aFrame, depth));
}
}
/**
* 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() {
while (!mEntryList.empty()) {
Entry* entry = mEntryList.removeMin();
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 =
mEntryList.find(Entry(parent, entry->mDepth - 1));
if (parentEntry) {
parentEntry->mChangeKind =
std::max(parentEntry->mChangeKind, CHILDREN_CHANGED);
} else {
mEntryList.insert(
new Entry(parent, entry->mDepth - 1, CHILDREN_CHANGED));
}
}
}
delete entry;
}
}
private:
struct Entry : SplayTreeNode<Entry> {
Entry(nsIFrame* aFrame, uint32_t aDepth,
ChangeKind aChangeKind = CHILDREN_CHANGED)
: mFrame(aFrame), mDepth(aDepth), mChangeKind(aChangeKind) {}
bool operator==(const Entry& aOther) const {
return mFrame == aOther.mFrame;
}
/**
* Sort by *reverse* 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; /* reverse, want "min" to be deepest */
}
static int compare(const Entry& aOne, const Entry& aTwo) {
if (aOne == aTwo) {
return 0;
} else if (aOne < aTwo) {
return -1;
} else {
return 1;
}
}
nsIFrame* mFrame;
/* Depth in the frame tree */
uint32_t mDepth;
ChangeKind mChangeKind;
};
/* A list of frames to process, sorted by their depth in the frame tree */
SplayTree<Entry, Entry> mEntryList;
/* Don't update overflow of this frame or its ancestors. */
const nsIFrame* mSubtreeRoot;
};
} // namespace mozilla
#endif