The plan9 /dev/mouse protocol doesn't send *release* button message
when using wheel buttons. With that fix the vnc server can now handle
successive wheel button messages.

Reference: /n/sources/patch/applied/vncv-wheel-fix
Date: Mon Jan 23 20:23:38 CET 2006

--- /sys/src/cmd/vnc/wsys.c	Mon Jan 23 20:17:30 2006
+++ /sys/src/cmd/vnc/wsys.c	Mon Jan 23 20:17:26 2006
@@ -147,8 +147,14 @@
 				m.xy.y = atoi(start+1+12);
 				m.buttons = atoi(start+1+2*12) & 0x1F;
 				m.xy = subpt(m.xy, screen->r.min);
-				if(ptinrect(m.xy, Rpt(ZP, v->dim)))
+				if(ptinrect(m.xy, Rpt(ZP, v->dim))){
 					mouseevent(v, m);
+					/* send wheel button *release* */ 
+					if ((m.buttons & 0x7) != m.buttons) {
+						m.buttons &= 0x7;
+						mouseevent(v, m);
+					}
+				}
 			} else
 				eresized();