On Fri, 22 Jun 2001, Johnny Billquist wrote:

> [-- sixel vnc client --]
>
> A full screen? Hmmm, quite a while. Each bytes carry six bits of data
> (hence sixel), maximum speed might be 38400, but it might be 19200 as
> well. I don't remember the resolution on the screen, but it's not *that*
> bad. Finally, you have sixteen colors on the VT340. I'm not sure how they
> are encoded in the sixel patterns, but I would assume each pixel can hold
> any color, which means four bits per pixel. Quite a lot of data...
>
> No, you can not address individual pixels, but if you have a copy of the
> image on memory, you can make the modifications, and then update a smaller
> part of the screen.

	That should work quite well with vnc's approach to screen updates
	- generally it will update a set of rectangular areas.

	Of course you probably have four 'displays':
		1) remote master display
		2) vnc client display updated from master over rfb (vnc)
		3) copy of data sent to sixel display
		4) sixel display

	You really want to batch updates between 2) and 3) to stop the
	serial link from 3) to 4) being too much of a bottleneck. Actually
	a second copy of the vnc rfb (remote frame buffer) might not be
	too bad an idea there.

	You probably want to include periodic answerback requests to
	allow the vnc client to gauge how much data is still 'in the
	pipe' to minimise sending data which is just going to be
	overwritten immediately afterwards (hence the second rfb)

	Sounds like real fun :)

-- 
		David/absolute		-- www.netbsd.org: No hype required --