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 // Copyright (c) 2009 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.

 #include "base/message_pump_win.h"

 #include <math.h>

 #include "base/message_loop.h"

 #include "base/histogram.h"

 #include "base/win_util.h"

 using base::Time;

 namespace base {

 static const wchar_t kWndClass[] = L"Chrome_MessagePumpWindow";

 // Message sent to get an additional time slice for pumping (processing) another

 // task (a series of such messages creates a continuous task pump).

 static const int kMsgHaveWork = WM_USER + 1;

 //-----------------------------------------------------------------------------

 // MessagePumpWin public:

 void MessagePumpWin::AddObserver(Observer* observer) {

   observers_.AddObserver(observer);

 }

 void MessagePumpWin::RemoveObserver(Observer* observer) {

   observers_.RemoveObserver(observer);

 }

 void MessagePumpWin::WillProcessMessage(const MSG& msg) {

   FOR_EACH_OBSERVER(Observer, observers_, WillProcessMessage(msg));

 }

 void MessagePumpWin::DidProcessMessage(const MSG& msg) {

   FOR_EACH_OBSERVER(Observer, observers_, DidProcessMessage(msg));

 }

 void MessagePumpWin::RunWithDispatcher(

     Delegate* delegate, Dispatcher* dispatcher) {

   RunState s;

   s.delegate = delegate;

   s.dispatcher = dispatcher;

   s.should_quit = false;

   s.run_depth = state_ ? state_->run_depth + 1 : 1;

   RunState* previous_state = state_;

   state_ = &s;

   DoRunLoop();

   state_ = previous_state;

 }

 void MessagePumpWin::Quit() {

   DCHECK(state_);

   state_->should_quit = true;

 }

 //-----------------------------------------------------------------------------

 // MessagePumpWin protected:

 int MessagePumpWin::GetCurrentDelay() const {

   if (delayed_work_time_.is_null())

     return -1;

   // Be careful here.  TimeDelta has a precision of microseconds, but we want a

   // value in milliseconds.  If there are 5.5ms left, should the delay be 5 or

   // 6?  It should be 6 to avoid executing delayed work too early.

   double timeout =

       ceil((delayed_work_time_ - TimeTicks::Now()).InMillisecondsF());

   // If this value is negative, then we need to run delayed work soon.

   int delay = static_cast<int>(timeout);

   if (delay < 0)

     delay = 0;

   return delay;

 }

 //-----------------------------------------------------------------------------

 // MessagePumpForUI public:

 MessagePumpForUI::MessagePumpForUI() {

   InitMessageWnd();

 }

 MessagePumpForUI::~MessagePumpForUI() {

   DestroyWindow(message_hwnd_);

   UnregisterClass(kWndClass, GetModuleHandle(NULL));

 }

 void MessagePumpForUI::ScheduleWork() {

   if (InterlockedExchange(&have_work_, 1))

     return;  // Someone else continued the pumping.

   // Make sure the MessagePump does some work for us.

   PostMessage(message_hwnd_, kMsgHaveWork, reinterpret_cast<WPARAM>(this), 0);

   // In order to wake up any cross-process COM calls which may currently be

   // pending on the main thread, we also have to post a UI message.

   PostMessage(message_hwnd_, WM_NULL, 0, 0);

 }

 void MessagePumpForUI::ScheduleDelayedWork(const TimeTicks& delayed_work_time) {

   //

   // We would *like* to provide high resolution timers.  Windows timers using

   // SetTimer() have a 10ms granularity.  We have to use WM_TIMER as a wakeup

   // mechanism because the application can enter modal windows loops where it

   // is not running our MessageLoop; the only way to have our timers fire in

   // these cases is to post messages there.

   //

   // To provide sub-10ms timers, we process timers directly from our run loop.

   // For the common case, timers will be processed there as the run loop does

   // its normal work.  However, we *also* set the system timer so that WM_TIMER

   // events fire.  This mops up the case of timers not being able to work in

   // modal message loops.  It is possible for the SetTimer to pop and have no

   // pending timers, because they could have already been processed by the

   // run loop itself.

   //

   // We use a single SetTimer corresponding to the timer that will expire

   // soonest.  As new timers are created and destroyed, we update SetTimer.

   // Getting a spurrious SetTimer event firing is benign, as we'll just be

   // processing an empty timer queue.

   //

   delayed_work_time_ = delayed_work_time;

   int delay_msec = GetCurrentDelay();

   DCHECK(delay_msec >= 0);

   if (delay_msec < USER_TIMER_MINIMUM)

     delay_msec = USER_TIMER_MINIMUM;

   // Create a WM_TIMER event that will wake us up to check for any pending

   // timers (in case we are running within a nested, external sub-pump).

   SetTimer(message_hwnd_, reinterpret_cast<UINT_PTR>(this), delay_msec, NULL);

 }

 void MessagePumpForUI::PumpOutPendingPaintMessages() {

   // If we are being called outside of the context of Run, then don't try to do

   // any work.

   if (!state_)

     return;

   // Create a mini-message-pump to force immediate processing of only Windows

   // WM_PAINT messages.  Don't provide an infinite loop, but do enough peeking

   // to get the job done.  Actual common max is 4 peeks, but we'll be a little

   // safe here.

   const int kMaxPeekCount = 20;

   bool win2k = win_util::GetWinVersion() <= win_util::WINVERSION_2000;

   int peek_count;

   for (peek_count = 0; peek_count < kMaxPeekCount; ++peek_count) {

     MSG msg;

     if (win2k) {

       if (!PeekMessage(&msg, NULL, WM_PAINT, WM_PAINT, PM_REMOVE))

         break;

     } else {

       if (!PeekMessage(&msg, NULL, 0, 0, PM_REMOVE | PM_QS_PAINT))

         break;

     }

     ProcessMessageHelper(msg);

     if (state_->should_quit)  // Handle WM_QUIT.

       break;

   }

   // Histogram what was really being used, to help to adjust kMaxPeekCount.

   DHISTOGRAM_COUNTS("Loop.PumpOutPendingPaintMessages Peeks", peek_count);

 }

 //-----------------------------------------------------------------------------

 // MessagePumpForUI private:

 // static

 LRESULT CALLBACK MessagePumpForUI::WndProcThunk(

     HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam) {

   switch (message) {

     case kMsgHaveWork:

       reinterpret_cast<MessagePumpForUI*>(wparam)->HandleWorkMessage();

       break;

     case WM_TIMER:

       reinterpret_cast<MessagePumpForUI*>(wparam)->HandleTimerMessage();

       break;

   }

   return DefWindowProc(hwnd, message, wparam, lparam);

 }

 void MessagePumpForUI::DoRunLoop() {

   // IF this was just a simple PeekMessage() loop (servicing all possible work

   // queues), then Windows would try to achieve the following order according

   // to MSDN documentation about PeekMessage with no filter):

   //    * Sent messages

   //    * Posted messages

   //    * Sent messages (again)

   //    * WM_PAINT messages

   //    * WM_TIMER messages

   //

   // Summary: none of the above classes is starved, and sent messages has twice

   // the chance of being processed (i.e., reduced service time).

   for (;;) {

     // If we do any work, we may create more messages etc., and more work may

     // possibly be waiting in another task group.  When we (for example)

     // ProcessNextWindowsMessage(), there is a good chance there are still more

     // messages waiting.  On the other hand, when any of these methods return

     // having done no work, then it is pretty unlikely that calling them again

     // quickly will find any work to do.  Finally, if they all say they had no

     // work, then it is a good time to consider sleeping (waiting) for more

     // work.

     bool more_work_is_plausible = ProcessNextWindowsMessage();

     if (state_->should_quit)

       break;

     more_work_is_plausible |= state_->delegate->DoWork();

     if (state_->should_quit)

       break;

     more_work_is_plausible |=

         state_->delegate->DoDelayedWork(&delayed_work_time_);

     // If we did not process any delayed work, then we can assume that our

     // existing WM_TIMER if any will fire when delayed work should run.  We

     // don't want to disturb that timer if it is already in flight.  However,

     // if we did do all remaining delayed work, then lets kill the WM_TIMER.

     if (more_work_is_plausible && delayed_work_time_.is_null())

       KillTimer(message_hwnd_, reinterpret_cast<UINT_PTR>(this));

     if (state_->should_quit)

       break;

     if (more_work_is_plausible)

       continue;

     more_work_is_plausible = state_->delegate->DoIdleWork();

     if (state_->should_quit)

       break;

     if (more_work_is_plausible)

       continue;

     WaitForWork();  // Wait (sleep) until we have work to do again.

   }

 }

 void MessagePumpForUI::InitMessageWnd() {

   HINSTANCE hinst = GetModuleHandle(NULL);

   WNDCLASSEX wc = {0};

   wc.cbSize = sizeof(wc);

   wc.lpfnWndProc = WndProcThunk;

   wc.hInstance = hinst;

   wc.lpszClassName = kWndClass;

   RegisterClassEx(&wc);

   message_hwnd_ =

       CreateWindow(kWndClass, 0, 0, 0, 0, 0, 0, HWND_MESSAGE, 0, hinst, 0);

   DCHECK(message_hwnd_);

 }

 void MessagePumpForUI::WaitForWork() {

   // Wait until a message is available, up to the time needed by the timer

   // manager to fire the next set of timers.

   int delay = GetCurrentDelay();

   if (delay < 0)  // Negative value means no timers waiting.

     delay = INFINITE;

   DWORD result;

   result = MsgWaitForMultipleObjectsEx(0, NULL, delay, QS_ALLINPUT,

                                        MWMO_INPUTAVAILABLE);

   if (WAIT_OBJECT_0 == result) {

     // A WM_* message is available.

     // If a parent child relationship exists between windows across threads

     // then their thread inputs are implicitly attached.

     // This causes the MsgWaitForMultipleObjectsEx API to return indicating

     // that messages are ready for processing (specifically mouse messages

     // intended for the child window. Occurs if the child window has capture)

     // The subsequent PeekMessages call fails to return any messages thus

     // causing us to enter a tight loop at times.

     // The WaitMessage call below is a workaround to give the child window

     // sometime to process its input messages.

     MSG msg = {0};

     DWORD queue_status = GetQueueStatus(QS_MOUSE);

     if (HIWORD(queue_status) & QS_MOUSE &&

        !PeekMessage(&msg, NULL, WM_MOUSEFIRST, WM_MOUSELAST, PM_NOREMOVE)) {

       WaitMessage();

     }

     return;

   }

   DCHECK_NE(WAIT_FAILED, result) << GetLastError();

 }

 void MessagePumpForUI::HandleWorkMessage() {

   // If we are being called outside of the context of Run, then don't try to do

   // any work.  This could correspond to a MessageBox call or something of that

   // sort.

   if (!state_) {

     // Since we handled a kMsgHaveWork message, we must still update this flag.

     InterlockedExchange(&have_work_, 0);

     return;

   }

   // Let whatever would have run had we not been putting messages in the queue

   // run now.  This is an attempt to make our dummy message not starve other

   // messages that may be in the Windows message queue.

   ProcessPumpReplacementMessage();

   // Now give the delegate a chance to do some work.  He'll let us know if he

   // needs to do more work.

   if (state_->delegate->DoWork())

     ScheduleWork();

 }

 void MessagePumpForUI::HandleTimerMessage() {

   KillTimer(message_hwnd_, reinterpret_cast<UINT_PTR>(this));

   // If we are being called outside of the context of Run, then don't do

   // anything.  This could correspond to a MessageBox call or something of

   // that sort.

   if (!state_)

     return;

   state_->delegate->DoDelayedWork(&delayed_work_time_);

   if (!delayed_work_time_.is_null()) {

     // A bit gratuitous to set delayed_work_time_ again, but oh well.

     ScheduleDelayedWork(delayed_work_time_);

   }

 }

 bool MessagePumpForUI::ProcessNextWindowsMessage() {

   // If there are sent messages in the queue then PeekMessage internally

   // dispatches the message and returns false. We return true in this

   // case to ensure that the message loop peeks again instead of calling

   // MsgWaitForMultipleObjectsEx again.

   bool sent_messages_in_queue = false;

   DWORD queue_status = GetQueueStatus(QS_SENDMESSAGE);

   if (HIWORD(queue_status) & QS_SENDMESSAGE)

     sent_messages_in_queue = true;

   MSG msg;

   if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))

     return ProcessMessageHelper(msg);

   return sent_messages_in_queue;

 }

 bool MessagePumpForUI::ProcessMessageHelper(const MSG& msg) {

   if (WM_QUIT == msg.message) {

     // Repost the QUIT message so that it will be retrieved by the primary

     // GetMessage() loop.

     state_->should_quit = true;

     PostQuitMessage(static_cast<int>(msg.wParam));

     return false;

   }

   // While running our main message pump, we discard kMsgHaveWork messages.

   if (msg.message == kMsgHaveWork && msg.hwnd == message_hwnd_)

     return ProcessPumpReplacementMessage();

   WillProcessMessage(msg);

   if (state_->dispatcher) {

     if (!state_->dispatcher->Dispatch(msg))

       state_->should_quit = true;

   } else {

     TranslateMessage(&msg);

     DispatchMessage(&msg);

   }

   DidProcessMessage(msg);

   return true;

 }

 bool MessagePumpForUI::ProcessPumpReplacementMessage() {

   // When we encounter a kMsgHaveWork message, this method is called to peek

   // and process a replacement message, such as a WM_PAINT or WM_TIMER.  The

   // goal is to make the kMsgHaveWork as non-intrusive as possible, even though

   // a continuous stream of such messages are posted.  This method carefully

   // peeks a message while there is no chance for a kMsgHaveWork to be pending,

   // then resets the have_work_ flag (allowing a replacement kMsgHaveWork to

   // possibly be posted), and finally dispatches that peeked replacement.  Note

   // that the re-post of kMsgHaveWork may be asynchronous to this thread!!

   MSG msg;

   bool have_message = false;

   if (MessageLoop::current()->os_modal_loop()) {

     // We only peek out WM_PAINT and WM_TIMER here for reasons mentioned above.

     have_message = PeekMessage(&msg, NULL, WM_PAINT, WM_PAINT, PM_REMOVE) ||

                    PeekMessage(&msg, NULL, WM_TIMER, WM_TIMER, PM_REMOVE);

   } else {

     have_message = (0 != PeekMessage(&msg, NULL, 0, 0, PM_REMOVE));

     if (have_message && msg.message == WM_NULL)

       have_message = (0 != PeekMessage(&msg, NULL, 0, 0, PM_REMOVE));

   }

   DCHECK(!have_message || kMsgHaveWork != msg.message ||

          msg.hwnd != message_hwnd_);

   // Since we discarded a kMsgHaveWork message, we must update the flag.

   int old_have_work = InterlockedExchange(&have_work_, 0);

   DCHECK(old_have_work);

   // We don't need a special time slice if we didn't have_message to process.

   if (!have_message)

     return false;

   // Guarantee we'll get another time slice in the case where we go into native

   // windows code.   This ScheduleWork() may hurt performance a tiny bit when

   // tasks appear very infrequently, but when the event queue is busy, the

   // kMsgHaveWork events get (percentage wise) rarer and rarer.

   ScheduleWork();

   return ProcessMessageHelper(msg);

 }

 //-----------------------------------------------------------------------------

 // MessagePumpForIO public:

 MessagePumpForIO::MessagePumpForIO() {

   port_.Set(CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 1));

   DCHECK(port_.IsValid());

 }

 void MessagePumpForIO::ScheduleWork() {

   if (InterlockedExchange(&have_work_, 1))

     return;  // Someone else continued the pumping.

   // Make sure the MessagePump does some work for us.

   BOOL ret = PostQueuedCompletionStatus(port_, 0,

                                         reinterpret_cast<ULONG_PTR>(this),

                                         reinterpret_cast<OVERLAPPED*>(this));

   DCHECK(ret);

 }

 void MessagePumpForIO::ScheduleDelayedWork(const TimeTicks& delayed_work_time) {

   // We know that we can't be blocked right now since this method can only be

   // called on the same thread as Run, so we only need to update our record of

   // how long to sleep when we do sleep.

   delayed_work_time_ = delayed_work_time;

 }

 void MessagePumpForIO::RegisterIOHandler(HANDLE file_handle,

                                          IOHandler* handler) {

   ULONG_PTR key = reinterpret_cast<ULONG_PTR>(handler);

   HANDLE port = CreateIoCompletionPort(file_handle, port_, key, 1);

   DCHECK(port == port_.Get());

 }

 //-----------------------------------------------------------------------------

 // MessagePumpForIO private:

 void MessagePumpForIO::DoRunLoop() {

   for (;;) {

     // If we do any work, we may create more messages etc., and more work may

     // possibly be waiting in another task group.  When we (for example)

     // WaitForIOCompletion(), there is a good chance there are still more

     // messages waiting.  On the other hand, when any of these methods return

     // having done no work, then it is pretty unlikely that calling them

     // again quickly will find any work to do.  Finally, if they all say they

     // had no work, then it is a good time to consider sleeping (waiting) for

     // more work.

     bool more_work_is_plausible = state_->delegate->DoWork();

     if (state_->should_quit)

       break;

     more_work_is_plausible |= WaitForIOCompletion(0, NULL);

     if (state_->should_quit)

       break;

     more_work_is_plausible |=

         state_->delegate->DoDelayedWork(&delayed_work_time_);

     if (state_->should_quit)

       break;

     if (more_work_is_plausible)

       continue;

     more_work_is_plausible = state_->delegate->DoIdleWork();

     if (state_->should_quit)

       break;

     if (more_work_is_plausible)

       continue;

     WaitForWork();  // Wait (sleep) until we have work to do again.

   }

 }

 // Wait until IO completes, up to the time needed by the timer manager to fire

 // the next set of timers.

 void MessagePumpForIO::WaitForWork() {

   // We do not support nested IO message loops. This is to avoid messy

   // recursion problems.

   DCHECK(state_->run_depth == 1) << "Cannot nest an IO message loop!";

   int timeout = GetCurrentDelay();

   if (timeout < 0)  // Negative value means no timers waiting.

     timeout = INFINITE;

   WaitForIOCompletion(timeout, NULL);

 }

 bool MessagePumpForIO::WaitForIOCompletion(DWORD timeout, IOHandler* filter) {

   IOItem item;

   if (completed_io_.empty() || !MatchCompletedIOItem(filter, &item)) {

     // We have to ask the system for another IO completion.

     if (!GetIOItem(timeout, &item))

       return false;

     if (ProcessInternalIOItem(item))

       return true;

   }

   if (item.context->handler) {

     if (filter && item.handler != filter) {

       // Save this item for later

       completed_io_.push_back(item);

     } else {

       DCHECK(item.context->handler == item.handler);

       item.handler->OnIOCompleted(item.context, item.bytes_transfered,

                                   item.error);

     }

   } else {

     // The handler must be gone by now, just cleanup the mess.

     delete item.context;

   }

   return true;

 }

 // Asks the OS for another IO completion result.

 bool MessagePumpForIO::GetIOItem(DWORD timeout, IOItem* item) {

   memset(item, 0, sizeof(*item));

   ULONG_PTR key = 0;

   OVERLAPPED* overlapped = NULL;

   if (!GetQueuedCompletionStatus(port_.Get(), &item->bytes_transfered, &key,

                                  &overlapped, timeout)) {

     if (!overlapped)

       return false;  // Nothing in the queue.

     item->error = GetLastError();

     item->bytes_transfered = 0;

   }

   item->handler = reinterpret_cast<IOHandler*>(key);

   item->context = reinterpret_cast<IOContext*>(overlapped);

   return true;

 }

 bool MessagePumpForIO::ProcessInternalIOItem(const IOItem& item) {

   if (this == reinterpret_cast<MessagePumpForIO*>(item.context) &&

       this == reinterpret_cast<MessagePumpForIO*>(item.handler)) {

     // This is our internal completion.

     DCHECK(!item.bytes_transfered);

     InterlockedExchange(&have_work_, 0);

     return true;

   }

   return false;

 }

 // Returns a completion item that was previously received.

 bool MessagePumpForIO::MatchCompletedIOItem(IOHandler* filter, IOItem* item) {

   DCHECK(!completed_io_.empty());

   for (std::list<IOItem>::iterator it = completed_io_.begin();

        it != completed_io_.end(); ++it) {

     if (!filter || it->handler == filter) {

       *item = *it;

       completed_io_.erase(it);

       return true;

     }

   }

   return false;

 }

 }  // namespace base