diff --git a/hw/xwin/ChangeLog b/hw/xwin/ChangeLog
index 9ddb0eb8e..2e3dd19a8 100644
--- a/hw/xwin/ChangeLog
+++ b/hw/xwin/ChangeLog
@@ -1,3 +1,11 @@
+2004-10-02  Alexander Gottwald  <ago at freedesktop dot org>
+
+	* winmouse.c (winMouseProc):
+	Make sure buttons 1-3 are mouse buttons and wheel events are 4-5
+	Document code
+	Replace ErrorF with appropriate winMsg
+	use a symbolic name for the wheel event offset
+	
 2004-10-01  Alexander Gottwald  <ago at freedesktop dot org>
 
 	* wincreatewnd.c (winCreateBoundingWindowWindowed):
diff --git a/hw/xwin/winmouse.c b/hw/xwin/winmouse.c
index 6411d7989..93b38acd4 100644
--- a/hw/xwin/winmouse.c
+++ b/hw/xwin/winmouse.c
@@ -65,21 +65,39 @@ int
 winMouseProc (DeviceIntPtr pDeviceInt, int iState)
 {
   int 			lngMouseButtons, i;
+  int			lngWheelEvents = 2;
   CARD8			*map;
   DevicePtr		pDevice = (DevicePtr) pDeviceInt;
 
   switch (iState)
     {
     case DEVICE_INIT:
+      /* Get number of mouse buttons */
       lngMouseButtons = GetSystemMetrics(SM_CMOUSEBUTTONS);
-      ErrorF ("%d mouse buttons found\n", lngMouseButtons);
-      map = malloc(sizeof(CARD8) * (lngMouseButtons + 1 + 2));
-      
-      for (i=1; i <= lngMouseButtons + 2; i++)
+
+      /* Mapping of windows events to X events:
+       * LEFT:1 MIDDLE:2 RIGHT:3
+       * SCROLL_UP:4 SCROLL_DOWN:5
+       * XBUTTON 1:6 XBUTTON 2:7 ...
+       *
+       * To map scroll wheel correctly we need at least the 3 normal buttons
+       */
+      if (lngMouseButtons < 3)
+        lngMouseButtons = 3;
+      winMsg(X_PROBED, "%d mouse buttons found\n", lngMouseButtons);
+
+      /* allocate memory: 
+       * number of buttons + 2x mouse wheel event + 1 extra (offset for map) 
+       */
+      map = malloc(sizeof(CARD8) * (lngMouseButtons + lngWheelEvents + 1));
+    
+      /* initalize button map */ 
+      map[0] = 0;
+      for (i=1; i <= lngMouseButtons + lngWheelEvents; i++)
       	map[i] = i;
       InitPointerDeviceStruct (pDevice,
 			       map,
-			       lngMouseButtons + 2, /* Buttons 4 and 5 are mouse wheel events */
+			       lngMouseButtons + lngWheelEvents,
 			       miPointerGetMotionEvents,
 			       winMouseCtrl,
 			       miPointerGetMotionBufferSize ());