Implement MessageLoopForUI using GLib. This gets some exercise from...

base/message_pump_glib.h

+// 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 <glib.h>
+
+#include "base/message_pump.h"
+#include "base/time.h"
+
+namespace base {
+
+// This class implements a MessagePump needed for TYPE_UI MessageLoops on
+// OS_LINUX platforms using GLib.
+class MessagePumpForUI : public MessagePump {
+ public:
+  MessagePumpForUI();
+  ~MessagePumpForUI();
+
+  virtual void Run(Delegate* delegate);
+  virtual void Quit();
+  virtual void ScheduleWork();
+  virtual void ScheduleDelayedWork(const Time& delayed_work_time);
+
+ 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 {
+    // This is the delegate argument passed to Run.
+    Delegate* delegate;
+    // This tells us when to exit the event pump.
+    bool keep_running;
+    // This tells our work source when to dispatch DoWork and DoDelayedWork.
+    bool should_do_work;
+    // This tells our idle source when to dispatch DoIdleWork.
+    bool should_do_idle_work;
+    // Unlike the work source, which is shared by all calls to Run, each Run
+    // call gets its own idle source because we need to destroy it when we have
+    // no idle work, and we don't want to destroy someone else's source.
+    GSource* idle_source;
+  };
+
+  struct WorkSource : GSource {
+    MessagePumpForUI* self;
+  };
+
+  // The source with these callbacks remain in the main loop forever.  They
+  // will dispatch DoWork and DoDelayedWork, and calculate when and how long
+  // to block when GLib calls poll internally.
+  static GSourceFuncs WorkSourceFuncs;
+  static gboolean WorkSourcePrepare(GSource* source, gint* timeout_ms);
+  static gboolean WorkSourceCheck(GSource* source);
+  static gboolean WorkSourceDispatch(GSource* source, GSourceFunc unused_func,
+                                     gpointer unused_data);
+
+  // The source that uses these callbacks is added as an idle source, which
+  // means GLib will call it when there is no other work to do.  We continue
+  // doing work as long as DoIdleWork or the other work functions return true.
+  // Once no work remains, we remove the idle source so GLib will block instead
+  // of firing it.  Then we re-add it when we wake up.
+  static GSourceFuncs IdleSourceFuncs;
+  static gboolean IdleSourcePrepare(GSource* source, gint* timeout_ms);
+  static gboolean IdleSourceCheck(GSource* source);
+  static gboolean IdleSourceDispatch(GSource* source, GSourceFunc unused_func,
+                                     gpointer unused_data);
+
+  // This adds a GLib source to the main loop.
+  GSource* AddSource(GSourceFuncs* funcs, gint priority,
+                     GPollFD* optional_poll_fd);
+
+  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.
+  Time delayed_work_time_;
+
+  // We use a pipe to schedule work in a thread-safe way that doesn't interfere
+  // with our state.  When ScheduleWork is called, we write into the pipe which
+  // ensures poll will not sleep, since we use the read end as an event source.
+  // When we find data pending on the pipe, we clear it out and know we have
+  // been given new work.
+  int write_fd_work_scheduled_;
+  int read_fd_work_scheduled_;
+
+  // The work source.  It is shared by all calls to Run and destroyed when
+  // the message pump is destroyed.
+  GSource* work_source_;
+
+  DISALLOW_COPY_AND_ASSIGN(MessagePumpForUI);
+};
+
+}  // namespace base
+
+#endif  // BASE_MESSAGE_PUMP_GLIB_H_