[9fans] vncs and warped pointers

[andrey mirtchovski <mirtchov@cpsc.ucalgary.ca>]

If you've tried vnc-ing to a Plan 9 machine from UNIX you'll know that
it doesn't really work 100% because the mouse pointer isn't warping
properly, which brings down the mood of acme editing sessions.  there
are provisions made (EncMouseWarp) for supporting this but i'm not
sure where exactly are they supposed to work.  not in tightvnc.

If you prefer vnc to drawterm however and if you'd like to have mouse
warping in acme, here are instructions on how to modify both vncs and
TightVNC to get proper warping behaviour using the protocol extensions
used by TightVNC (Plan 9 must conform to lUNIX, as usual):

On the Plan 9 side:

	plan9% diff vncs.c /sys/src/cmd/vnc/vncs.c
	684d683
	< 	v->canwarp = 1;
	1019c1018
	< 		vncwrlong(v, 0xFFFFFF18); /* extension to the protocol used by tightvnc, at least */
	---
	> 		vncwrlong(v, EncMouseWarp);
	plan9% 


On the TightVNC side, download tightvnc from www.tightvnc.com,
uncompress do the 'xmkmf; make World' dance and edit
vncviewer/cursor.c's HandleCursorPos() thusly:

	mirtchov@localrob$ diff cursor.c cursor.c.old 
	322c322,324
	<   XWarpPointer(dpy, None, desktopWin, 0, 0, 0, 0, x, y);
	---
	>   if (appData.useX11Cursor) {
	>     if (appData.fullScreen)
	>       XWarpPointer(dpy, None, desktopWin, 0, 0, 0, 0, x, y);
	324c326,335
	<   return True; 
	---
	>     return True; 
	>   }
	> 
	>   if (x >= si.framebufferWidth)
	>     x = si.framebufferWidth - 1;
	>   if (y >= si.framebufferHeight)
	>     y = si.framebufferHeight - 1;
	> 
	>   SoftCursorMove(x, y);
	>   return True;

Essentially hardcoding TightVNC to warp always. 

Hope you find it useful.  There are a few things that are still
annoying -- if acme wants to warp the cursor while you're moving it
the warp will be lost.  That's just how vncviewer was written.

andrey, who woke up way too early this morning...

ps: crashes under plan9port's rio when attempting to hide the
window...  works with twm though! :)

pps: this mail written using vncs/vncviewer + warping