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       1             : /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
       2             :  * This Source Code Form is subject to the terms of the Mozilla Public
       3             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       4             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       5             : 
       6             : #ifndef DISPLAYITEMCLIPCHAIN_H_
       7             : #define DISPLAYITEMCLIPCHAIN_H_
       8             : 
       9             : #include "mozilla/Assertions.h"
      10             : #include "DisplayItemClip.h"
      11             : #include "nsString.h"
      12             : 
      13             : class nsIScrollableFrame;
      14             : 
      15             : namespace mozilla {
      16             : 
      17             : struct ActiveScrolledRoot;
      18             : 
      19             : /**
      20             :  * A DisplayItemClipChain is a linked list of DisplayItemClips where each clip
      21             :  * is associated with an active scrolled root that describes what the clip
      22             :  * moves with.
      23             :  * We use a chain instead of just one intersected clip due to async scrolling:
      24             :  * A clip that moves along with a display item can be fused to the item's
      25             :  * contents when drawing the layer contents, but all other clips in the chain
      26             :  * need to be kept separate so that they can be applied at composition time,
      27             :  * after any async scroll offsets have been applied.
      28             :  * The clip chain is created during display list construction by the builder's
      29             :  * DisplayListClipState.
      30             :  * The clip chain order is determined by the active scrolled root order.
      31             :  * For every DisplayItemClipChain object |clipChain|, the following holds:
      32             :  * !clipChain->mParent || ActiveScrolledRoot::IsAncestor(clipChain->mParent->mASR, clipChain->mASR).
      33             :  * The clip chain can skip over active scrolled roots. That just means that
      34             :  * there is no clip that moves with the skipped ASR in this chain.
      35             :  */
      36       12094 : struct DisplayItemClipChain {
      37             : 
      38             :   /**
      39             :    * Get the display item clip in this chain that moves with aASR, or nullptr
      40             :    * if no such clip exists. aClipChain can be null.
      41             :    */
      42             :   static const DisplayItemClip* ClipForASR(const DisplayItemClipChain* aClipChain,
      43             :                                            const ActiveScrolledRoot* aASR);
      44             : 
      45             :   static bool Equal(const DisplayItemClipChain* aClip1, const DisplayItemClipChain* aClip2);
      46             : 
      47             :   static nsCString ToString(const DisplayItemClipChain* aClipChain);
      48             : 
      49             :   bool HasRoundedCorners() const;
      50             : 
      51             :   DisplayItemClip mClip;
      52             :   const ActiveScrolledRoot* mASR;
      53             :   const DisplayItemClipChain* mParent;
      54             : };
      55             : 
      56             : } // namespace mozilla
      57             : 
      58             : #endif /* DISPLAYITEMCLIPCHAIN_H_ */