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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef EventDispatchForbiddenScope_h
      6 #define EventDispatchForbiddenScope_h
      7 
      8 #include "wtf/MainThread.h"
      9 #include "wtf/TemporaryChange.h"
     10 
     11 namespace blink {
     12 
     13 #if ENABLE(ASSERT)
     14 
     15 class EventDispatchForbiddenScope {
     16 public:
     17     EventDispatchForbiddenScope()
     18     {
     19         if (!isMainThread())
     20             return;
     21         ++s_count;
     22     }
     23 
     24     ~EventDispatchForbiddenScope()
     25     {
     26         if (!isMainThread())
     27             return;
     28         ASSERT(s_count);
     29         --s_count;
     30     }
     31 
     32     static bool isEventDispatchForbidden()
     33     {
     34         if (!isMainThread())
     35             return false;
     36         return s_count;
     37     }
     38 
     39     class AllowUserAgentEvents {
     40     public:
     41         AllowUserAgentEvents()
     42             : m_change(s_count, 0)
     43         {
     44         }
     45 
     46         ~AllowUserAgentEvents()
     47         {
     48             ASSERT(!s_count);
     49         }
     50 
     51         TemporaryChange<unsigned> m_change;
     52     };
     53 
     54 private:
     55     static unsigned s_count;
     56 };
     57 
     58 #else
     59 
     60 class EventDispatchForbiddenScope {
     61 public:
     62     EventDispatchForbiddenScope() { }
     63 
     64     class AllowUserAgentEvents {
     65     public:
     66         AllowUserAgentEvents() { }
     67     };
     68 };
     69 
     70 #endif // ENABLE(ASSERT)
     71 
     72 } // namespace blink
     73 
     74 #endif // EventDispatchForbiddenScope_h
     75