The Tor Browser: layout/base/RestyleTracker.h@b8a032363ba2 (annotated)

layout/base/RestyleTracker.h@b8a032363ba2 (annotated)

layout/base/RestyleTracker.h

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- 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:
   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,
     /**
      * The overflow areas of children have changed
      * and we need to call UpdateOverflow on the frame.
      * Also call UpdateOverflow on the parent even if the
      * overflow areas of the frame does not change.
      */
     CHILDREN_AND_PARENT_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) {
     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_AND_PARENT_CHANGED) {
         // Need to union the overflow areas of the children.
         // Always update the parent, even if the overflow does not change.
         frame->UpdateOverflow();
         overflowChanged = true;
       } else 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.
 #ifdef DEBUG
         bool hasInitialOverflowPropertyApplied = false;
         frame->Properties().Get(nsIFrame::DebugInitialOverflowPropertyApplied(),
                                  &hasInitialOverflowPropertyApplied);
         NS_ASSERTION(hasInitialOverflowPropertyApplied,
                      "InitialOverflowProperty must be set first.");
 #endif
         nsOverflowAreas* overflow =
           static_cast<nsOverflowAreas*>(frame->Properties().Get(nsIFrame::InitialOverflowProperty()));
         if (overflow) {
           // FinishAndStoreOverflow will change the overflow areas passed in,
           // so make a copy.
           nsOverflowAreas overflowCopy = *overflow;
           frame->FinishAndStoreOverflow(overflowCopy, frame->GetSize());
         } else {
           nsRect bounds(nsPoint(0, 0), frame->GetSize());
           nsOverflowAreas 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();
         if (parent && parent != mSubtreeRoot) {
           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;
 };
 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 */

The Tor Browser / annotate

layout/base/RestyleTracker.h@b8a032363ba2 (annotated)

layout/base/RestyleTracker.h