base/run_loop.h

   1 // Copyright (c) 2012 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 BASE_RUN_LOOP_H_
   6 #define BASE_RUN_LOOP_H_
   7
   8 #include "base/base_export.h"
   9 #include "base/callback.h"
  10 #include "base/memory/weak_ptr.h"
  11 #include "base/message_loop.h"
  12
  13 namespace base {
  14 #if defined(OS_ANDROID)
  15 class MessagePumpForUI;
  16 #endif
  17
  18 #if defined(OS_IOS)
  19 class MessagePumpUIApplication;
  20 #endif
  21
  22 // Helper class to Run a nested MessageLoop. Please do not use nested
  23 // MessageLoops in production code! If you must, use this class instead of
  24 // calling MessageLoop::Run/Quit directly. RunLoop::Run can only be called once
  25 // per RunLoop lifetime. Create a RunLoop on the stack and call Run/Quit to run
  26 // a nested MessageLoop.
  27 class BASE_EXPORT RunLoop {
  28  public:
  29   RunLoop();
  30 #if !defined(OS_MACOSX) && !defined(OS_ANDROID)
  31   explicit RunLoop(MessageLoop::Dispatcher* dispatcher);
  32 #endif
  33   ~RunLoop();
  34
  35 #if !defined(OS_MACOSX) && !defined(OS_ANDROID)
  36   void set_dispatcher(MessageLoop::Dispatcher* dispatcher) {
  37     dispatcher_ = dispatcher;
  38   }
  39 #endif
  40
  41   // Run the current MessageLoop. This blocks until Quit is called. Before
  42   // calling Run, be sure to grab an AsWeakPtr or the QuitClosure in order to
  43   // stop the MessageLoop asynchronously. MessageLoop::Quit and QuitNow will
  44   // also trigger a return from Run, but those are deprecated.
  45   void Run();
  46
  47   // Run the current MessageLoop until it doesn't find any tasks or messages in
  48   // the queue (it goes idle). WARNING: This may never return! Only use this
  49   // when repeating tasks such as animated web pages have been shut down.
  50   void RunUntilIdle();
  51
  52   bool running() const { return running_; }
  53
  54   // Quit an earlier call to Run(). There can be other nested RunLoops servicing
  55   // the same task queue (MessageLoop); Quitting one RunLoop has no bearing on
  56   // the others. Quit can be called before, during or after Run. If called
  57   // before Run, Run will return immediately when called. Calling Quit after the
  58   // RunLoop has already finished running has no effect.
  59   //
  60   // WARNING: You must NEVER assume that a call to Quit will terminate the
  61   // targetted message loop. If a nested message loop continues running, the
  62   // target may NEVER terminate. It is very easy to livelock (run forever) in
  63   // such a case.
  64   void Quit();
  65
  66   // Convenience method to get a closure that safely calls Quit (has no effect
  67   // if the RunLoop instance is gone).
  68   //
  69   // Example:
  70   //   RunLoop run_loop;
  71   //   PostTask(run_loop.QuitClosure());
  72   //   run_loop.Run();
  73   base::Closure QuitClosure();
  74
  75  private:
  76   friend class ::MessageLoop;
  77 #if defined(OS_ANDROID)
  78   // Android doesn't support the blocking MessageLoop::Run, so it calls
  79   // BeforeRun and AfterRun directly.
  80   friend class base::MessagePumpForUI;
  81 #endif
  82
  83 #if defined(OS_IOS)
  84   // iOS doesn't support the blocking MessageLoop::Run, so it calls
  85   // BeforeRun directly.
  86   friend class base::MessagePumpUIApplication;
  87 #endif
  88
  89   // Return false to abort the Run.
  90   bool BeforeRun();
  91   void AfterRun();
  92
  93   MessageLoop* loop_;
  94
  95   // WeakPtrFactory for QuitClosure safety.
  96   base::WeakPtrFactory<RunLoop> weak_factory_;
  97
  98   // Parent RunLoop or NULL if this is the top-most RunLoop.
  99   RunLoop* previous_run_loop_;
 100
 101 #if !defined(OS_MACOSX) && !defined(OS_ANDROID)
 102   MessageLoop::Dispatcher* dispatcher_;
 103 #endif
 104
 105   // Used to count how many nested Run() invocations are on the stack.
 106   int run_depth_;
 107
 108   bool run_called_;
 109   bool quit_called_;
 110   bool running_;
 111
 112   // Used to record that QuitWhenIdle() was called on the MessageLoop, meaning
 113   // that we should quit Run once it becomes idle.
 114   bool quit_when_idle_received_;
 115
 116   DISALLOW_COPY_AND_ASSIGN(RunLoop);
 117 };
 118
 119 }  // namespace base
 120
 121 #endif  // BASE_RUN_LOOP_H_