When using vncv on a terminal with software cursor (vesa, rpi) the
mouse cursor leaves a trail.  This seem to be caused by the fact that
vncv loads picture updates with loadimage(2) directly to screen.
Loading to an offscreen image followed by a draw(2) to screen removes
the artifact.

Reference: /n/sources/patch/applied/vncv-curtrail
Date: Tue May  7 11:01:08 CES 2013
Signed-off-by: yarikos@gmail.com

--- /sys/src/cmd/vnc/draw.c	Tue May  7 10:45:47 2013
+++ /sys/src/cmd/vnc/draw.c	Tue May  7 10:45:42 2013
@@ -106,6 +106,7 @@
 static void
 updatescreen(Rectangle r)
 {
+	Image* img;
 	int b, bb;
 
 	lockdisplay(display);
@@ -120,10 +121,15 @@
 	/*
 	 * assume load image fails only because of resize
 	 */
+	img = allocimage(display, r, screen->chan, 0, DNofill);
+	if(img == nil)
+		sysfatal("updatescreen: %r");
 	b = Dx(r) * pixb * Dy(r);
-	bb = loadimage(screen, rectaddpt(r, screen->r.min), pixbuf, b);
+	bb = loadimage(img, r, pixbuf, b);
 	if(bb != b && verbose)
 		fprint(2, "loadimage %d on %R for %R returned %d: %r\n", b, rectaddpt(r, screen->r.min), screen->r, bb);
+	draw(screen, rectaddpt(r, screen->r.min), img, nil, r.min);
+	freeimage(img);
 	unlockdisplay(display);
 }