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 /* -*- 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 */