1 files changed, 216 insertions, 0 deletions
diff --git a/base/message_pump_win.h b/base/message_pump_win.h
new file mode 100644
index 0000000..6699fde
--- /dev/null
+++ b/base/message_pump_win.h
@@ -0,0 +1,216 @@
+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef BASE_MESSAGE_PUMP_WIN_H_
+#define BASE_MESSAGE_PUMP_WIN_H_
+
+#include <vector>
+
+#include <windows.h>
+
+#include "base/lock.h"
+#include "base/message_pump.h"
+#include "base/observer_list.h"
+#include "base/time.h"
+
+namespace base {
+
+// MessagePumpWin implements a "traditional" Windows message pump.  It contains
+// a nearly infinite loop that peeks out messages, and then dispatches them.
+// Intermixed with those peeks are callouts to DoWork for pending tasks,
+// DoDelayedWork for pending timers, and OnObjectSignaled for signaled objects.
+// When there are no events to be serviced, this pump goes into a wait state.
+// In most cases, this message pump handles all processing.
+//
+// However, when a task, or windows event, invokes on the stack a native dialog
+// box or such, that window typically provides a bare bones (native?) message
+// pump.  That bare-bones message pump generally supports little more than a
+// peek of the Windows message queue, followed by a dispatch of the peeked
+// message.  MessageLoop extends that bare-bones message pump to also service
+// Tasks, at the cost of some complexity.
+//
+// The basic structure of the extension (refered to as a sub-pump) is that a
+// special message, kMsgHaveWork, is repeatedly injected into the Windows
+// Message queue.  Each time the kMsgHaveWork message is peeked, checks are
+// made for an extended set of events, including the availability of Tasks to
+// run.
+//
+// After running a task, the special message kMsgHaveWork is again posted to
+// the Windows Message queue, ensuring a future time slice for processing a
+// future event.  To prevent flooding the Windows Message queue, care is taken
+// to be sure that at most one kMsgHaveWork message is EVER pending in the
+// Window's Message queue.
+//
+// There are a few additional complexities in this system where, when there are
+// no Tasks to run, this otherwise infinite stream of messages which drives the
+// sub-pump is halted.  The pump is automatically re-started when Tasks are
+// queued.
+//
+// A second complexity is that the presence of this stream of posted tasks may
+// prevent a bare-bones message pump from ever peeking a WM_PAINT or WM_TIMER.
+// Such paint and timer events always give priority to a posted message, such as
+// kMsgHaveWork messages.  As a result, care is taken to do some peeking in
+// between the posting of each kMsgHaveWork message (i.e., after kMsgHaveWork
+// is peeked, and before a replacement kMsgHaveWork is posted).
+//
+// NOTE: Although it may seem odd that messages are used to start and stop this
+// flow (as opposed to signaling objects, etc.), it should be understood that
+// the native message pump will *only* respond to messages.  As a result, it is
+// an excellent choice.  It is also helpful that the starter messages that are
+// placed in the queue when new task arrive also awakens DoRunLoop.
+//
+class MessagePumpWin : public MessagePump {
+ public:
+  // Used with WatchObject to asynchronously monitor the signaled state of a
+  // HANDLE object.
+  class Watcher {
+   public:
+    virtual ~Watcher() {}
+    // Called from MessageLoop::Run when a signalled object is detected.
+    virtual void OnObjectSignaled(HANDLE object) = 0;
+  };
+
+  // An Observer is an object that receives global notifications from the
+  // MessageLoop.
+  //
+  // NOTE: An Observer implementation should be extremely fast!
+  //
+  class Observer {
+   public:
+    virtual ~Observer() {}
+
+    // This method is called before processing a message.
+    // The message may be undefined in which case msg.message is 0
+    virtual void WillProcessMessage(const MSG& msg) = 0;
+
+    // This method is called when control returns from processing a UI message.
+    // The message may be undefined in which case msg.message is 0
+    virtual void DidProcessMessage(const MSG& msg) = 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 TranslateMessage), rather every message 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(const MSG& msg) = 0;
+  };
+
+  MessagePumpWin();
+  ~MessagePumpWin();
+
+  // Have the current thread's message loop watch for a signaled object.
+  // Pass a null watcher to stop watching the object.
+  void WatchObject(HANDLE, Watcher*);
+
+  // Add an Observer, which will start receiving notifications immediately.
+  void AddObserver(Observer* observer);
+
+  // Remove an Observer.  It is safe to call this method while an Observer is
+  // receiving a notification callback.
+  void RemoveObserver(Observer* observer);
+
+  // Give a chance to code processing additional messages to notify the
+  // message loop observers that another message has been processed.
+  void WillProcessMessage(const MSG& msg);
+  void DidProcessMessage(const MSG& msg);
+
+  // Applications can call this to encourage us to process all pending WM_PAINT
+  // messages.  This method will process all paint messages the Windows Message
+  // queue can provide, up to some fixed number (to avoid any infinite loops).
+  void PumpOutPendingPaintMessages();
+
+  // Like MessagePump::Run, but MSG objects are routed through dispatcher.
+  void RunWithDispatcher(Delegate* delegate, Dispatcher* dispatcher);
+
+  // MessagePump methods:
+  virtual void Run(Delegate* delegate) { RunWithDispatcher(delegate, NULL); }
+  virtual void Quit();
+  virtual void ScheduleWork();
+  virtual void ScheduleDelayedWork(const TimeDelta& delay);
+
+ private:
+  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;
+  };
+
+  static LRESULT CALLBACK WndProcThunk(
+      HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
+  void InitMessageWnd();
+  void HandleWorkMessage();
+  void HandleTimerMessage();
+  void DoRunLoop();
+  void WaitForWork();
+  bool ProcessNextWindowsMessage();
+  bool ProcessMessageHelper(const MSG& msg);
+  bool ProcessPumpReplacementMessage();
+  bool ProcessNextObject();
+  bool SignalWatcher(size_t object_index);
+  int GetCurrentDelay() const;
+
+  // A hidden message-only window.
+  HWND message_hwnd_;
+
+  // A vector of objects (and corresponding watchers) that are routinely
+  // serviced by this message pump.
+  std::vector<HANDLE> objects_;
+  std::vector<Watcher*> watchers_;
+
+  ObserverList<Observer> observers_;
+
+  // The time at which delayed work should run.
+  Time delayed_work_time_;
+
+  // A boolean value used to indicate if there is a kMsgDoWork message pending
+  // in the Windows Message queue.  There is at most one such message, and it
+  // can drive execution of tasks when a native message pump is running.
+  LONG have_work_;
+
+  // State for the current invocation of Run.
+  RunState* state_;
+};
+
+}  // namespace base
+
+#endif  // BASE_MESSAGE_PUMP_WIN_H_