[gtk/gtk-2-24] GDK W32: Always process all available messages

[LRN <ruslanizhb src gnome org>]

commit bfdac2f70e005b2504cc3f4ebbdab328974d005a
Author: Jeremy Tan <jtanx outlook com>
Date:   Sat Sep 17 17:19:59 2016 +0800

    GDK W32: Always process all available messages
    
    The GLib main loop blocks on MsgWaitForMultipleObjectsEx to
    determine if there are any incoming messages while also allowing
    for background tasks to run. If all available messages are not
    processed after MsgWaitForMultipleObjectsEx has signaled that
    there are available, CPU usage will skyrocket.
    
    From my limited understanding (by inspection of profiling
    under Visual Studio):
    Key is pressed - MsgWaitForMultipleObjectsEx unblocks, and
    sends message to GDK's event handler. Some event is now queued.
    
    g_poll unblocks, calls the g_event_dispatch which finally
    resolves to gdk_event_dispatch. This then calls
    _gdk_win32_display_queue_events, but since a message is already
    queued, it fails to call PeekMessage and returns immediately.
    
    At the next iteration, g_poll again calls MsgWaitForMultipleObjectsEx
    which queues yet another event and returns almost immediately, since
    there are events available which haven't been processed by PeekMessage.
    
    The dispatch function is then called and the process repeats.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=771568

 gdk/win32/gdkevents-win32.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
---
diff --git a/gdk/win32/gdkevents-win32.c b/gdk/win32/gdkevents-win32.c
index 9b09edd052..e52f21c52e 100644
--- a/gdk/win32/gdkevents-win32.c
+++ b/gdk/win32/gdkevents-win32.c
@@ -3622,8 +3622,7 @@ _gdk_events_queue (GdkDisplay *display)
   if (modal_win32_dialog != NULL)
     return;
   
-  while (!_gdk_event_queue_find_first (display) &&
-        PeekMessageW (&msg, NULL, 0, 0, PM_REMOVE))
+  while (PeekMessageW (&msg, NULL, 0, 0, PM_REMOVE))
     {
       TranslateMessage (&msg);
       DispatchMessageW (&msg);