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      1 /*
      2  * Copyright (C) 2013 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef PartialLayoutState_h
     32 #define PartialLayoutState_h
     33 
     34 #include "core/rendering/RenderObject.h"
     35 
     36 namespace WebCore {
     37 
     38 class PartialLayoutState {
     39     friend class PartialLayoutDisabler;
     40 public:
     41     PartialLayoutState()
     42         : m_shouldStop(false)
     43         , m_stopAtRenderer(0)
     44         , m_disableCount(0)
     45     {
     46     }
     47 
     48     // True if we plan to do a partial layout, or are in the process of stopping a partial layout.
     49     bool isPartialLayout() const { return m_stopAtRenderer || m_shouldStop; }
     50 
     51     bool isStopping() const { return m_shouldStop; }
     52     bool checkPartialLayoutComplete(const RenderObject*);
     53     void setStopAtRenderer(const RenderObject* renderer) { m_stopAtRenderer = renderer; }
     54     void reset() { m_shouldStop = false; m_stopAtRenderer = 0; }
     55 
     56 private:
     57     void disable() { ASSERT(!m_shouldStop); m_disableCount++; }
     58     void enable() { ASSERT(m_disableCount > 0); m_disableCount--; }
     59     const RenderObject* stopAtRenderer() const { return m_disableCount > 0 ? 0 : m_stopAtRenderer; }
     60 
     61     bool m_shouldStop;
     62     const RenderObject* m_stopAtRenderer;
     63     int m_disableCount;
     64 };
     65 
     66 inline bool PartialLayoutState::checkPartialLayoutComplete(const RenderObject* renderer)
     67 {
     68     if (m_shouldStop)
     69         return true;
     70 
     71     if (renderer == stopAtRenderer()) {
     72         m_shouldStop = true;
     73         m_stopAtRenderer = 0;
     74         return true;
     75     }
     76 
     77     return false;
     78 }
     79 
     80 class PartialLayoutDisabler {
     81     WTF_MAKE_NONCOPYABLE(PartialLayoutDisabler);
     82 public:
     83     PartialLayoutDisabler(PartialLayoutState& partialLayout, bool disable = true)
     84         : m_partialLayout(partialLayout)
     85         , m_disable(disable)
     86     {
     87         if (m_disable)
     88             m_partialLayout.disable();
     89     }
     90 
     91     ~PartialLayoutDisabler()
     92     {
     93         if (m_disable)
     94             m_partialLayout.enable();
     95     }
     96 private:
     97     PartialLayoutState& m_partialLayout;
     98     bool m_disable;
     99 };
    100 
    101 } // namespace WebCore
    102 
    103 #endif // PartialLayoutState_h
    104