text: /*
   * Copyright (C) 2011, 2013 Apple Inc. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
   * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include "config.h"
  #include "LayerChangesFlusher.h"
  
  #if USE(CA)
  
  #include "AbstractCACFLayerTreeHost.h"
  #include "StructuredExceptionHandlerSuppressor.h"
  #include <wtf/NeverDestroyed.h>
  #include <wtf/StdLibExtras.h>
  #include <wtf/Vector.h>
  
  namespace WebCore {
  
  LayerChangesFlusher& LayerChangesFlusher::singleton()
  {
      static NeverDestroyed<LayerChangesFlusher> flusher;
      return flusher;
  }
  
  LayerChangesFlusher::LayerChangesFlusher()
      : m_hook(0)
      , m_isCallingHosts(false)
  {
  }
  
  void LayerChangesFlusher::flushPendingLayerChangesSoon(AbstractCACFLayerTreeHost* host)
  {
      if (!m_hostsWithChangesToFlush.add(host).isNewEntry || m_hook)
          return;
  
      setHook();
  }
  
  void LayerChangesFlusher::cancelPendingFlush(AbstractCACFLayerTreeHost* host)
  {
      m_hostsWithChangesToFlush.remove(host);
  
      if (!m_hostsWithChangesToFlush.isEmpty() || !m_hook)
          return;
  
      // We handle removing the hook when we finish calling out to the hosts, so we shouldn't
      // mess with it while we're in the process of calling them.
      if (m_isCallingHosts)
          return;
  
      removeHook();
  }
  
  LRESULT LayerChangesFlusher::hookCallback(int code, WPARAM wParam, LPARAM lParam)
  {
      // Suppress the exception handler Windows puts around all hook calls so we can 
      // crash for debugging purposes if an exception is hit. 
      ExceptionRegistration registrationStruct; // Note: must be stack allocated.
      StructuredExceptionHandlerSuppressor suppressor(registrationStruct);
      return singleton().hookFired(code, wParam, lParam);
  }
  
  LRESULT LayerChangesFlusher::hookFired(int code, WPARAM wParam, LPARAM lParam)
  {
      ASSERT(m_hook);
  
      // Calling out to the hosts can cause m_hostsWithChangesToFlush to be modified, so we copy it
      // into a Vector first.
      auto hosts = copyToVector(m_hostsWithChangesToFlush);
      m_hostsWithChangesToFlush.clear();
  
      m_isCallingHosts = true;
      for (size_t i = 0; i < hosts.size(); ++i)
          hosts[i]->flushPendingLayerChangesNow();
      m_isCallingHosts = false;
  
      LRESULT result = ::CallNextHookEx(m_hook, code, wParam, lParam);
  
      if (m_hook && m_hostsWithChangesToFlush.isEmpty()) {
          // We won't have any work to do next time around, so just remove our hook.
          removeHook();
      }
  
      return result;
  }
  
  void LayerChangesFlusher::setHook()
  {
      ASSERT(!m_hook);
      ASSERT(!m_isCallingHosts);
  
      DWORD threadID = ::GetCurrentThreadId();
  
      m_hook = ::SetWindowsHookExW(WH_GETMESSAGE, hookCallback, 0, threadID);
      ASSERT_WITH_MESSAGE(m_hook, "::SetWindowsHookExW failed with error %lu", ::GetLastError());
  
      // Post a message to the message queue to prevent ::GetMessage from blocking, which will ensure
      // our hook is called soon.
      ::PostThreadMessageW(threadID, WM_NULL, 0, 0);
  }
  
  void LayerChangesFlusher::removeHook()
  {
      ASSERT(m_hook);
      ASSERT(!m_isCallingHosts);
  
      if (!::UnhookWindowsHookEx(m_hook))
          ASSERT_WITH_MESSAGE(false, "::UnhookWindowsHookEx failed with error %lu", ::GetLastError());
  
      m_hook = 0;
  }
  
  } // namespace WebCore
  
  #endif
  