RestyleTracker.h
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */
/**
* A class which manages pending restyles. This handles keeping track
* of what nodes restyles need to happen on and so forth.
*/
#ifndef mozilla_RestyleTracker_h
#define mozilla_RestyleTracker_h
#include "mozilla/dom/Element.h"
#include "nsDataHashtable.h"
#include "nsIFrame.h"
#include "mozilla/SplayTree.h"
namespace mozilla {
class RestyleManager;
/**
* 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:
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) {
uint32_t depth = aFrame->GetDepthInFrameTree();
if (mEntryList.empty() ||
!mEntryList.find(Entry(aFrame, depth))) {
// All frames in mEntryList at this stage have STYLE_CHANGED so we don't
// need to worry about setting the STYLE_CHANGED flag if 'find'
// returns true.
mEntryList.insert(new Entry(aFrame, depth, STYLE_CHANGED));
}
}
/**
* 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;
if (entry->mFlags & CHILDREN_CHANGED) {
// Need to union the overflow areas of the children.
overflowChanged = frame->UpdateOverflow();
} else {
nsOverflowAreas* pre = static_cast<nsOverflowAreas*>
(frame->Properties().Get(frame->PreTransformOverflowAreasProperty()));
if (pre) {
// Since we have the pre-transform-overflow-areas, we can take a
// faster path that doesn't require unioning the overflow areas
// of our children.
// FinishAndStoreOverflow will change the overflow areas passed in,
// so make a copy.
nsOverflowAreas overflowAreas = *pre;
frame->FinishAndStoreOverflow(overflowAreas, frame->GetSize());
// We can't tell if the overflow changed, so be conservative
overflowChanged = true;
} else {
// We can't take the faster path here. Do it the hard way.
overflowChanged = frame->UpdateOverflow();
}
}
// 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 || (entry->mFlags & STYLE_CHANGED)) {
nsIFrame *parent = frame->GetParent();
if (parent && parent != mSubtreeRoot) {
Entry* parentEntry = mEntryList.find(Entry(parent, entry->mDepth - 1));
if (parentEntry) {
parentEntry->mFlags |= CHILDREN_CHANGED;
} else {
mEntryList.insert(new Entry(parent, entry->mDepth - 1, CHILDREN_CHANGED));
}
}
}
delete entry;
}
}
private:
enum {
/**
* Set if the overflow areas of children have changed so we need to call
* UpdateOverflow on the frame.
*/
CHILDREN_CHANGED = 0x01,
/**
* True if the frame was explicitly added and hence may have had a style
* change that changes its geometry relative to parent, without reflowing.
* In this case we must update overflow on the frame's parent even if
* this frame's overflow did not change.
*/
STYLE_CHANGED = 0x02
};
struct Entry : SplayTreeNode<Entry>
{
Entry(nsIFrame* aFrame, uint32_t aDepth, uint8_t aFlags = 0)
: mFrame(aFrame)
, mDepth(aDepth)
, mFlags(aFlags)
{}
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;
uint8_t mFlags;
};
/* 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;
};
class RestyleTracker {
public:
typedef mozilla::dom::Element Element;
RestyleTracker(uint32_t aRestyleBits) :
mRestyleBits(aRestyleBits),
mHaveLaterSiblingRestyles(false)
{
NS_PRECONDITION((mRestyleBits & ~ELEMENT_ALL_RESTYLE_FLAGS) == 0,
"Why do we have these bits set?");
NS_PRECONDITION((mRestyleBits & ELEMENT_PENDING_RESTYLE_FLAGS) != 0,
"Must have a restyle flag");
NS_PRECONDITION((mRestyleBits & ELEMENT_PENDING_RESTYLE_FLAGS) !=
ELEMENT_PENDING_RESTYLE_FLAGS,
"Shouldn't have both restyle flags set");
NS_PRECONDITION((mRestyleBits & ~ELEMENT_PENDING_RESTYLE_FLAGS) != 0,
"Must have root flag");
NS_PRECONDITION((mRestyleBits & ~ELEMENT_PENDING_RESTYLE_FLAGS) !=
(ELEMENT_ALL_RESTYLE_FLAGS & ~ELEMENT_PENDING_RESTYLE_FLAGS),
"Shouldn't have both root flags");
}
void Init(RestyleManager* aRestyleManager) {
mRestyleManager = aRestyleManager;
}
uint32_t Count() const {
return mPendingRestyles.Count();
}
/**
* Add a restyle for the given element to the tracker. Returns true
* if the element already had eRestyle_LaterSiblings set on it.
*/
bool AddPendingRestyle(Element* aElement, nsRestyleHint aRestyleHint,
nsChangeHint aMinChangeHint);
/**
* Process the restyles we've been tracking.
*/
void ProcessRestyles() {
// Fast-path the common case (esp. for the animation restyle
// tracker) of not having anything to do.
if (mPendingRestyles.Count()) {
DoProcessRestyles();
}
}
// Return our ELEMENT_HAS_PENDING_(ANIMATION_)RESTYLE bit
uint32_t RestyleBit() const {
return mRestyleBits & ELEMENT_PENDING_RESTYLE_FLAGS;
}
// Return our ELEMENT_IS_POTENTIAL_(ANIMATION_)RESTYLE_ROOT bit
uint32_t RootBit() const {
return mRestyleBits & ~ELEMENT_PENDING_RESTYLE_FLAGS;
}
struct RestyleData {
nsRestyleHint mRestyleHint; // What we want to restyle
nsChangeHint mChangeHint; // The minimal change hint for "self"
};
/**
* If the given Element has a restyle pending for it, return the
* relevant restyle data. This function will clear everything other
* than a possible eRestyle_LaterSiblings hint for aElement out of
* our hashtable. The returned aData will never have an
* eRestyle_LaterSiblings hint in it.
*
* The return value indicates whether any restyle data was found for
* the element. If false is returned, then the state of *aData is
* undefined.
*/
bool GetRestyleData(Element* aElement, RestyleData* aData);
/**
* The document we're associated with.
*/
inline nsIDocument* Document() const;
struct RestyleEnumerateData : public RestyleData {
nsRefPtr<Element> mElement;
};
private:
/**
* Handle a single mPendingRestyles entry. aRestyleHint must not
* include eRestyle_LaterSiblings; that needs to be dealt with
* before calling this function.
*/
inline void ProcessOneRestyle(Element* aElement,
nsRestyleHint aRestyleHint,
nsChangeHint aChangeHint);
/**
* The guts of our restyle processing.
*/
void DoProcessRestyles();
typedef nsDataHashtable<nsISupportsHashKey, RestyleData> PendingRestyleTable;
typedef nsAutoTArray< nsRefPtr<Element>, 32> RestyleRootArray;
// Our restyle bits. These will be a subset of ELEMENT_ALL_RESTYLE_FLAGS, and
// will include one flag from ELEMENT_PENDING_RESTYLE_FLAGS and one flag
// that's not in ELEMENT_PENDING_RESTYLE_FLAGS.
uint32_t mRestyleBits;
RestyleManager* mRestyleManager; // Owns us
// A hashtable that maps elements to RestyleData structs. The
// values only make sense if the element's current document is our
// document and it has our RestyleBit() flag set. In particular,
// said bit might not be set if the element had a restyle posted and
// then was moved around in the DOM.
PendingRestyleTable mPendingRestyles;
// An array that keeps track of our possible restyle roots. This
// maintains the invariant that if A and B are both restyle roots
// and A is an ancestor of B then A will come after B in the array.
// We maintain this invariant by checking whether an element has an
// ancestor with the restyle root bit set before appending it to the
// array.
RestyleRootArray mRestyleRoots;
// True if we have some entries with the eRestyle_LaterSiblings
// flag. We need this to avoid enumerating the hashtable looking
// for such entries when we can't possibly have any.
bool mHaveLaterSiblingRestyles;
};
inline bool RestyleTracker::AddPendingRestyle(Element* aElement,
nsRestyleHint aRestyleHint,
nsChangeHint aMinChangeHint)
{
RestyleData existingData;
existingData.mRestyleHint = nsRestyleHint(0);
existingData.mChangeHint = NS_STYLE_HINT_NONE;
// Check the RestyleBit() flag before doing the hashtable Get, since
// it's possible that the data in the hashtable isn't actually
// relevant anymore (if the flag is not set).
if (aElement->HasFlag(RestyleBit())) {
mPendingRestyles.Get(aElement, &existingData);
} else {
aElement->SetFlags(RestyleBit());
}
bool hadRestyleLaterSiblings =
(existingData.mRestyleHint & eRestyle_LaterSiblings) != 0;
existingData.mRestyleHint =
nsRestyleHint(existingData.mRestyleHint | aRestyleHint);
NS_UpdateHint(existingData.mChangeHint, aMinChangeHint);
mPendingRestyles.Put(aElement, existingData);
// We can only treat this element as a restyle root if we would
// actually restyle its descendants (so either call
// ReResolveStyleContext on it or just reframe it).
if ((aRestyleHint & (eRestyle_Self | eRestyle_Subtree)) ||
(aMinChangeHint & nsChangeHint_ReconstructFrame)) {
for (const Element* cur = aElement; !cur->HasFlag(RootBit()); ) {
nsIContent* parent = cur->GetFlattenedTreeParent();
// Stop if we have no parent or the parent is not an element or
// we're part of the viewport scrollbars (because those are not
// frametree descendants of the primary frame of the root
// element).
// XXXbz maybe the primary frame of the root should be the root scrollframe?
if (!parent || !parent->IsElement() ||
// If we've hit the root via a native anonymous kid and that
// this native anonymous kid is not obviously a descendant
// of the root's primary frame, assume we're under the root
// scrollbars. Since those don't get reresolved when
// reresolving the root, we need to make sure to add the
// element to mRestyleRoots.
(cur->IsInNativeAnonymousSubtree() && !parent->GetParent() &&
cur->GetPrimaryFrame() &&
cur->GetPrimaryFrame()->GetParent() != parent->GetPrimaryFrame())) {
mRestyleRoots.AppendElement(aElement);
break;
}
cur = parent->AsElement();
}
// At this point some ancestor of aElement (possibly aElement
// itself) is in mRestyleRoots. Set the root bit on aElement, to
// speed up searching for an existing root on its descendants.
aElement->SetFlags(RootBit());
}
mHaveLaterSiblingRestyles =
mHaveLaterSiblingRestyles || (aRestyleHint & eRestyle_LaterSiblings) != 0;
return hadRestyleLaterSiblings;
}
} // namespace mozilla
#endif /* mozilla_RestyleTracker_h */
