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 // Copyright (c) 2008 The Chromium Authors. All rights reserved.

 // Use of this source code is governed by a BSD-style license that can be

 // found in the LICENSE file.

 #ifndef BASE_MESSAGE_PUMP_GLIB_H_

 #define BASE_MESSAGE_PUMP_GLIB_H_

 #include "base/message_pump.h"

 #include "base/observer_list.h"

 #include "base/scoped_ptr.h"

 #include "base/time.h"

 typedef union _GdkEvent GdkEvent;

 typedef struct _GMainContext GMainContext;

 typedef struct _GPollFD GPollFD;

 typedef struct _GSource GSource;

 namespace base {

 // This class implements a MessagePump needed for TYPE_UI MessageLoops on

 // OS_LINUX platforms using GLib.

 class MessagePumpForUI : public MessagePump {

  public:

   // Observer is notified prior to a GdkEvent event being dispatched. As

   // Observers are notified of every change, they have to be FAST!

   class Observer {

    public:

     virtual ~Observer() {}

     // This method is called before processing a message.

     virtual void WillProcessEvent(GdkEvent* event) = 0;

     // This method is called after processing a message.

     virtual void DidProcessEvent(GdkEvent* event) = 0;

   };

   // Dispatcher is used during a nested invocation of Run to dispatch events.

   // If Run is invoked with a non-NULL Dispatcher, MessageLoop does not

   // dispatch events (or invoke gtk_main_do_event), rather every event is

   // passed to Dispatcher's Dispatch method for dispatch. It is up to the

   // Dispatcher to dispatch, or not, the event.

   //

   // The nested loop is exited by either posting a quit, or returning false

   // from Dispatch.

   class Dispatcher {

    public:

     virtual ~Dispatcher() {}

     // Dispatches the event. If true is returned processing continues as

     // normal. If false is returned, the nested loop exits immediately.

     virtual bool Dispatch(GdkEvent* event) = 0;

   };

   MessagePumpForUI();

   virtual ~MessagePumpForUI();

   // Like MessagePump::Run, but GdkEvent objects are routed through dispatcher.

   virtual void RunWithDispatcher(Delegate* delegate, Dispatcher* dispatcher);

   virtual void Run(Delegate* delegate) { RunWithDispatcher(delegate, NULL); }

   virtual void Quit();

   virtual void ScheduleWork();

   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time);

   // Internal methods used for processing the pump callbacks.  They are

   // public for simplicity but should not be used directly.  HandlePrepare

   // is called during the prepare step of glib, and returns a timeout that

   // will be passed to the poll. HandleCheck is called after the poll

   // has completed, and returns whether or not HandleDispatch should be called.

   // HandleDispatch is called if HandleCheck returned true.

   int HandlePrepare();

   bool HandleCheck();

   void HandleDispatch();

   // Adds an Observer, which will start receiving notifications immediately.

   void AddObserver(Observer* observer);

   // Removes an Observer.  It is safe to call this method while an Observer is

   // receiving a notification callback.

   void RemoveObserver(Observer* observer);

  private:

   // We may make recursive calls to Run, so we save state that needs to be

   // separate between them in this structure type.

   struct RunState {

     Delegate* delegate;

     Dispatcher* dispatcher;

     // Used to flag that the current Run() invocation should return ASAP.

     bool should_quit;

     // Used to count how many Run() invocations are on the stack.

     int run_depth;

     // This keeps the state of whether the pump got signaled that there was new

     // work to be done. Since we eat the message on the wake up pipe as soon as

     // we get it, we keep that state here to stay consistent.

     bool has_work;

   };

   // Invoked from EventDispatcher. Notifies all observers we're about to

   // process an event.

   void WillProcessEvent(GdkEvent* event);

   // Invoked from EventDispatcher. Notifies all observers we processed an

   // event.

   void DidProcessEvent(GdkEvent* event);

   // Callback prior to gdk dispatching an event.

   static void EventDispatcher(GdkEvent* event, void* data);

   RunState* state_;

   // This is a GLib structure that we can add event sources to.  We use the

   // default GLib context, which is the one to which all GTK events are

   // dispatched.

   GMainContext* context_;

   // This is the time when we need to do delayed work.

   TimeTicks delayed_work_time_;

   // The work source.  It is shared by all calls to Run and destroyed when

   // the message pump is destroyed.

   GSource* work_source_;

   // We use a wakeup pipe to make sure we'll get out of the glib polling phase

   // when another thread has scheduled us to do some work.  There is a glib

   // mechanism g_main_context_wakeup, but this won't guarantee that our event's

   // Dispatch() will be called.

   int wakeup_pipe_read_;

   int wakeup_pipe_write_;

   // Use a scoped_ptr to avoid needing the definition of GPollFD in the header.

   scoped_ptr<GPollFD> wakeup_gpollfd_;

   // List of observers.

   ObserverList<Observer> observers_;

   DISALLOW_COPY_AND_ASSIGN(MessagePumpForUI);

 };

 }  // namespace base

 #endif  // BASE_MESSAGE_PUMP_GLIB_H_