minimize redraw events after resizing/moving windows in multiwindow mode

[Oliver Schmidt <oschmidt-mailinglists@gmx.de>]

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Hi,

in multiwindow mode the modal moving/resizing of windows causes a lot of 
redraw events send to the X clients after the userse releases the mouse 
button. During the moving/resizing client windows are not redrawn as 
long as the mouse button is pressed. But all redraw/resizing events are 
queued and executed step after step after moving/resizing ends.

Some clients collect and combine multiple redraw or resizing events, 
other clients (e.g. xterm) simply execute each redraw or sizing event.

The enclosed patch minimizes the events for clients to only one event 
after the user releases the mouse button to end the moving/resizing. 
This improves the user experience and reduces strange screen flickerings 
especially on slow platforms.

The enclosed patch modifies winmultiwindowwndproc.c such that the 
windows events WM_ENTERSIZEMOVE and WM_EXITSIZEMOVE are considered that 
are send from windows if the modal window resizing/moving begins or 
ends. Only after WM_EXITSIZEMOVE the redraw/resizing is executed. The 
patch is against the sources of xserver-cygwin version 1.10.3-1.

Best regards,
Oliver

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diff --git a/cygwin/hw/xwin/winmultiwindowwndproc.c b/cygwin/hw/xwin/winmultiwindowwndproc.c
index bd84c05..5f536d0 100644
--- a/cygwin/hw/xwin/winmultiwindowwndproc.c
+++ b/cygwin/hw/xwin/winmultiwindowwndproc.c
@@ -321,6 +321,7 @@ winTopLevelWindowProc (HWND hwnd, UINT message,
   static Bool		s_fTracking = FALSE;
   Bool			needRestack = FALSE;
   LRESULT		ret;
+  static Bool           hasEnteredSizeMove = FALSE;
 
 #if CYGDEBUG
   winDebugWin32Message("winTopLevelWindowProc", hwnd, message, wParam, lParam);
@@ -871,7 +872,8 @@ winTopLevelWindowProc (HWND hwnd, UINT message,
 
     case WM_MOVE:
       /* Adjust the X Window to the moved Windows window */
-      winAdjustXWindow (pWin, hwnd);
+      if (!hasEnteredSizeMove) winAdjustXWindow (pWin, hwnd);
+      /* else: Wait for WM_EXITSIZEMOVE */
       return 0;
 
     case WM_SHOWWINDOW:
@@ -1012,6 +1014,16 @@ winTopLevelWindowProc (HWND hwnd, UINT message,
       */
       break; 
 
+    case WM_ENTERSIZEMOVE:
+      hasEnteredSizeMove = TRUE;
+      return 0;
+
+    case WM_EXITSIZEMOVE:
+      /* Adjust the X Window to the moved Windows window */
+      hasEnteredSizeMove = FALSE;
+      winAdjustXWindow (pWin, hwnd);
+      return 0;
+
     case WM_SIZE:
       /* see dix/window.c */
 #if CYGWINDOWING_DEBUG
@@ -1036,9 +1048,13 @@ winTopLevelWindowProc (HWND hwnd, UINT message,
 		(int)(GetTickCount ()));
       }
 #endif
-      /* Adjust the X Window to the moved Windows window */
-      winAdjustXWindow (pWin, hwnd);
-      if (wParam == SIZE_MINIMIZED) winReorderWindowsMultiWindow();
+      if (!hasEnteredSizeMove)
+        {
+          /* Adjust the X Window to the moved Windows window */
+          winAdjustXWindow (pWin, hwnd);
+          if (wParam == SIZE_MINIMIZED) winReorderWindowsMultiWindow();
+        }
+        /* else: wait for WM_EXITSIZEMOVE */
       return 0; /* end of WM_SIZE handler */
 
     case WM_STYLECHANGING:


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