base/message_pump_glib.h

   1 // Copyright (c) 2011 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_MESSAGE_PUMP_GLIB_H_
   6 #define BASE_MESSAGE_PUMP_GLIB_H_
   7 #pragma once
   8
   9 #include "base/memory/scoped_ptr.h"
  10 #include "base/message_pump.h"
  11 #include "base/observer_list.h"
  12 #include "base/time.h"
  13
  14 typedef union _GdkEvent GdkEvent;
  15 typedef struct _GMainContext GMainContext;
  16 typedef struct _GPollFD GPollFD;
  17 typedef struct _GSource GSource;
  18
  19 namespace base {
  20
  21 // This class implements a MessagePump needed for TYPE_UI MessageLoops on
  22 // OS_LINUX platforms using GLib.
  23 class MessagePumpForUI : public MessagePump {
  24  public:
  25   // Observer is notified prior to a GdkEvent event being dispatched. As
  26   // Observers are notified of every change, they have to be FAST!
  27   class Observer {
  28    public:
  29     virtual ~Observer() {}
  30
  31     // This method is called before processing a message.
  32     virtual void WillProcessEvent(GdkEvent* event) = 0;
  33
  34     // This method is called after processing a message.
  35     virtual void DidProcessEvent(GdkEvent* event) = 0;
  36   };
  37
  38   // Dispatcher is used during a nested invocation of Run to dispatch events.
  39   // If Run is invoked with a non-NULL Dispatcher, MessageLoop does not
  40   // dispatch events (or invoke gtk_main_do_event), rather every event is
  41   // passed to Dispatcher's Dispatch method for dispatch. It is up to the
  42   // Dispatcher to dispatch, or not, the event.
  43   //
  44   // The nested loop is exited by either posting a quit, or returning false
  45   // from Dispatch.
  46   class Dispatcher {
  47    public:
  48     virtual ~Dispatcher() {}
  49     // Dispatches the event. If true is returned processing continues as
  50     // normal. If false is returned, the nested loop exits immediately.
  51     virtual bool Dispatch(GdkEvent* event) = 0;
  52   };
  53
  54   MessagePumpForUI();
  55   virtual ~MessagePumpForUI();
  56
  57   // Like MessagePump::Run, but GdkEvent objects are routed through dispatcher.
  58   virtual void RunWithDispatcher(Delegate* delegate, Dispatcher* dispatcher);
  59
  60   // Run a single iteration of the mainloop. A return value of true indicates
  61   // that an event was handled. |block| indicates if it should wait if no event
  62   // is ready for processing.
  63   virtual bool RunOnce(GMainContext* context, bool block);
  64
  65   // Internal methods used for processing the pump callbacks.  They are
  66   // public for simplicity but should not be used directly.  HandlePrepare
  67   // is called during the prepare step of glib, and returns a timeout that
  68   // will be passed to the poll. HandleCheck is called after the poll
  69   // has completed, and returns whether or not HandleDispatch should be called.
  70   // HandleDispatch is called if HandleCheck returned true.
  71   int HandlePrepare();
  72   bool HandleCheck();
  73   void HandleDispatch();
  74
  75   // Adds an Observer, which will start receiving notifications immediately.
  76   void AddObserver(Observer* observer);
  77
  78   // Removes an Observer.  It is safe to call this method while an Observer is
  79   // receiving a notification callback.
  80   void RemoveObserver(Observer* observer);
  81
  82   // Dispatch an available GdkEvent. Essentially this allows a subclass to do
  83   // some task before/after calling the default handler (EventDispatcher).
  84   virtual void DispatchEvents(GdkEvent* event);
  85
  86   // Overridden from MessagePump:
  87   virtual void Run(Delegate* delegate);
  88   virtual void Quit();
  89   virtual void ScheduleWork();
  90   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time);
  91
  92  protected:
  93   // Returns the dispatcher for the current run state (|state_->dispatcher|).
  94   Dispatcher* GetDispatcher();
  95
  96  private:
  97   // We may make recursive calls to Run, so we save state that needs to be
  98   // separate between them in this structure type.
  99   struct RunState;
 100
 101   // Invoked from EventDispatcher. Notifies all observers we're about to
 102   // process an event.
 103   void WillProcessEvent(GdkEvent* event);
 104
 105   // Invoked from EventDispatcher. Notifies all observers we processed an
 106   // event.
 107   void DidProcessEvent(GdkEvent* event);
 108
 109   // Callback prior to gdk dispatching an event.
 110   static void EventDispatcher(GdkEvent* event, void* data);
 111
 112   RunState* state_;
 113
 114   // This is a GLib structure that we can add event sources to.  We use the
 115   // default GLib context, which is the one to which all GTK events are
 116   // dispatched.
 117   GMainContext* context_;
 118
 119   // This is the time when we need to do delayed work.
 120   TimeTicks delayed_work_time_;
 121
 122   // The work source.  It is shared by all calls to Run and destroyed when
 123   // the message pump is destroyed.
 124   GSource* work_source_;
 125
 126   // We use a wakeup pipe to make sure we'll get out of the glib polling phase
 127   // when another thread has scheduled us to do some work.  There is a glib
 128   // mechanism g_main_context_wakeup, but this won't guarantee that our event's
 129   // Dispatch() will be called.
 130   int wakeup_pipe_read_;
 131   int wakeup_pipe_write_;
 132   // Use a scoped_ptr to avoid needing the definition of GPollFD in the header.
 133   scoped_ptr<GPollFD> wakeup_gpollfd_;
 134
 135   // List of observers.
 136   ObserverList<Observer> observers_;
 137
 138   DISALLOW_COPY_AND_ASSIGN(MessagePumpForUI);
 139 };
 140
 141 }  // namespace base
 142
 143 #endif  // BASE_MESSAGE_PUMP_GLIB_H_