Introduce MessagePump to represent the native message pump used to drive a

MessageLoop.  A MessageLoop now has a MessagePump.

This will make it possible to port the MessagePump interface to other platforms
as well as to use an IO completion port for our worker threads on Windows.

Currently, there is only MessagePumpWin, which attempts to preserve the
pre-existing behavior of the MessageLoop.

API changes to MessageLoop:

1.  MessageLoop::Quit means return from Run when the MessageLoop would
otherwise wait for more work.

2.  MessageLoop::Quit can no longer be called outside the context of an active Run
call.  So, things like this:
  MessageLoop::current()->Quit();
  MessageLoop::current()->Run();
are now:
  MessageLoop::current()->RunAllPending();

3.  MessageLoop::Quit can no longer be called from other threads.  This means that
PostTask(..., new MessageLoop::QuitTask()) must be used explicitly to Quit across
thread boundaries.

4.  No protection is made to deal with nested MessageLoops involving watched
objects or APCs.  In fact, an assertion is added to flag such cases.  This is a
temporary measure until object watching and APC facilities are removed in favor
of a MessagePump designed around an IO completion port.

As part of this CL, I also changed the automation system to use an
IPC::ChannelProxy instead of an IPC::Channel.  This moves the automation IPC
onto Chrome's IO thread where it belongs.  I also fixed some abuses of
RefCounted in the AutomationProvider class.  It was deleting itself in some
cases!  This led to having to fix the ownership model for AutomationProvider,
which explains the changes to AutomationProviderList and so on.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@928 0039d316-1c4b-4281-b951-d872f2087c98

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_