Re: [9fans] vnc[vs] implementation question

["Russ Cox" <rsc@plan9.bell-labs.com>]

> in XaoS' case, unfortunately, one can't use this approach, because the
> pixels are written by the program in CMAP8 format (and the image used
> in loadimage(); is alloc-ed in CMAP8 too) and if the screen is
> anything else loadimage(screen, ...); fails...

you could have two images, the cmap8 one and one
the depth of the screen.  then do

	loadimage(icmap8);
	draw(iscreenchan, icmap8);
	draw(screen, iscreenchan);

the final draw is the only one that can be seen.
by making it a draw between images of the same
format you've reduced it to memmove, so the flicker
should go away.  conversion from cmap8 goes significantly
slower than memmove.

> it'd be great to have routines that convert between format en masse
> (similar to the ones in color(2)), but that's just as expensive as
> doing a loadimage();draw() combination.

again, i don't think it's the total expense
so much as the speed of the operation that the
user actually sees.