wtf/MainThread.cpp

   1 /*
   2  * Copyright (C) 2007, 2008 Apple 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
   6  * are met:
   7  *
   8  * 1.  Redistributions of source code must retain the above copyright
   9  *     notice, this list of conditions and the following disclaimer.
  10  * 2.  Redistributions in binary form must reproduce the above copyright
  11  *     notice, this list of conditions and the following disclaimer in the
  12  *     documentation and/or other materials provided with the distribution.
  13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
  14  *     its contributors may be used to endorse or promote products derived
  15  *     from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include "config.h"
  30 #include "MainThread.h"
  31
  32 #include "StdLibExtras.h"
  33 #include "CurrentTime.h"
  34 #include "Deque.h"
  35 #include "Threading.h"
  36
  37 namespace WTF {
  38
  39 struct FunctionWithContext {
  40     MainThreadFunction* function;
  41     void* context;
  42
  43     FunctionWithContext(MainThreadFunction* function = 0, void* context = 0)
  44         : function(function)
  45         , context(context)
  46     {
  47     }
  48 };
  49
  50 typedef Deque<FunctionWithContext> FunctionQueue;
  51
  52 static bool callbacksPaused; // This global variable is only accessed from main thread.
  53
  54 Mutex& mainThreadFunctionQueueMutex()
  55 {
  56     DEFINE_STATIC_LOCAL(Mutex, staticMutex, ());
  57     return staticMutex;
  58 }
  59
  60 static FunctionQueue& functionQueue()
  61 {
  62     DEFINE_STATIC_LOCAL(FunctionQueue, staticFunctionQueue, ());
  63     return staticFunctionQueue;
  64 }
  65
  66 void initializeMainThread()
  67 {
  68     mainThreadFunctionQueueMutex();
  69     initializeMainThreadPlatform();
  70 }
  71
  72 // 0.1 sec delays in UI is approximate threshold when they become noticeable. Have a limit that's half of that.
  73 static const double maxRunLoopSuspensionTime = 0.05;
  74
  75 void dispatchFunctionsFromMainThread()
  76 {
  77     ASSERT(isMainThread());
  78
  79     if (callbacksPaused)
  80         return;
  81
  82     double startTime = currentTime();
  83
  84     FunctionWithContext invocation;
  85     while (true) {
  86         {
  87             MutexLocker locker(mainThreadFunctionQueueMutex());
  88             if (!functionQueue().size())
  89                 break;
  90             invocation = functionQueue().first();
  91             functionQueue().removeFirst();
  92         }
  93
  94         invocation.function(invocation.context);
  95
  96         // If we are running accumulated functions for too long so UI may become unresponsive, we need to
  97         // yield so the user input can be processed. Otherwise user may not be able to even close the window.
  98         // This code has effect only in case the scheduleDispatchFunctionsOnMainThread() is implemented in a way that
  99         // allows input events to be processed before we are back here.
 100         if (currentTime() - startTime > maxRunLoopSuspensionTime) {
 101             scheduleDispatchFunctionsOnMainThread();
 102             break;
 103         }
 104     }
 105 }
 106
 107 void callOnMainThread(MainThreadFunction* function, void* context)
 108 {
 109     ASSERT(function);
 110     bool needToSchedule = false;
 111     {
 112         MutexLocker locker(mainThreadFunctionQueueMutex());
 113         needToSchedule = functionQueue().size() == 0;
 114         functionQueue().append(FunctionWithContext(function, context));
 115     }
 116     if (needToSchedule)
 117         scheduleDispatchFunctionsOnMainThread();
 118 }
 119
 120 void setMainThreadCallbacksPaused(bool paused)
 121 {
 122     ASSERT(isMainThread());
 123
 124     if (callbacksPaused == paused)
 125         return;
 126
 127     callbacksPaused = paused;
 128
 129     if (!callbacksPaused)
 130         scheduleDispatchFunctionsOnMainThread();
 131 }
 132
 133 } // namespace WTF