diff -ur xfwm4-4.1.99.2/src/client.c xfwm4-4.1.99.2.h/src/client.c
--- xfwm4-4.1.99.2/src/client.c	2004-12-12 10:42:38.000000000 +0100
+++ xfwm4-4.1.99.2.h/src/client.c	2005-01-09 21:39:39.730531145 +0100
@@ -2309,6 +2309,39 @@
 }
 
 void
+clientDecOpacity (Client * c)
+{
+	ScreenInfo *screen_info = NULL;
+DisplayInfo *display_info = NULL;
+screen_info = c->screen_info;
+display_info = screen_info->display_info;
+   if ( c->opacity > 0x10000000 )
+   {
+	c->opacity -= 0x08000000;
+	compositorWindowSetOpacity (display_info, c->frame, c->opacity);
+   }
+}
+
+void
+clientIncOpacity (Client * c)
+{
+ScreenInfo *screen_info = NULL;
+DisplayInfo *display_info = NULL;
+screen_info = c->screen_info;
+display_info = screen_info->display_info;
+   if ( c->opacity < NET_WM_OPAQUE )
+   {
+	c->opacity += 0x08000000;
+	compositorWindowSetOpacity (display_info, c->frame, c->opacity);
+   }
+   else
+   {
+	c->opacity = NET_WM_OPAQUE;
+	compositorWindowSetOpacity (display_info, c->frame, c->opacity);
+   }
+}
+
+void
 clientShade (Client * c)
 {
     XWindowChanges wc;
Nur in xfwm4-4.1.99.2/src: client.c~.
diff -ur xfwm4-4.1.99.2/src/compositor.c xfwm4-4.1.99.2.h/src/compositor.c
--- xfwm4-4.1.99.2/src/compositor.c	2004-12-12 12:53:55.000000000 +0100
+++ xfwm4-4.1.99.2.h/src/compositor.c	2005-01-09 22:07:31.990176825 +0100
@@ -754,7 +754,7 @@
                 double opacity = SHADOW_OPACITY;
                 if (cw->mode == WINDOW_TRANS)
                 {
-                    opacity = opacity * ((double) cw->opacity) / ((double) NET_WM_OPAQUE);
+                    opacity = opacity * ((double) cw->opacity) / ((double) NET_WM_OPAQUE) * ((double) cw->opacity) / ((double) NET_WM_OPAQUE);
                 }
                 cw->shadow = shadow_picture (screen_info, opacity,
                                              cw->attr.width + 2 * cw->attr.border_width,
Nur in xfwm4-4.1.99.2/src: compositor.c~.
diff -ur xfwm4-4.1.99.2/src/events.c xfwm4-4.1.99.2.h/src/events.c
--- xfwm4-4.1.99.2/src/events.c	2004-12-11 17:41:06.000000000 +0100
+++ xfwm4-4.1.99.2.h/src/events.c	2005-01-09 20:57:43.900252399 +0100
@@ -770,19 +770,23 @@
     }
     else if (ev->button == Button4)
     {
-        /* Mouse wheel scroll up */
+	clientIncOpacity(c);
+
+        /* Mouse wheel scroll up 
         if (!FLAG_TEST (c->flags, CLIENT_FLAG_SHADED))
         {
             clientShade (c);
-        }
+        }*/
     }
     else if (ev->button == Button5)
     {
-        /* Mouse wheel scroll down */
+	clientDecOpacity(c);
+
+        /* Mouse wheel scroll down 
         if (FLAG_TEST (c->flags, CLIENT_FLAG_SHADED))
         {
             clientUnshade (c);
-        }
+        }*/
     }
 }