linuxcaffe; distros and desktops

Lennart Sorensen lsorense-1wCw9BSqJbv44Nm34jS7GywD8/FfD2ys at public.gmane.org
Fri Oct 29 19:15:24 UTC 2004


On Fri, Oct 29, 2004 at 03:01:39PM -0400, Taavi Burns wrote:
> AFAIK all of the currently implemented transparency schemes involve heavy
> communication between the X server and the X client: the X client does the
> rendering, fetching current screen state from the X server, and then dumps
> the composited image back to the X server.  I wouldn't want to do that on
> the wire.
> 
> When things get to the point where the X client program just says "This is my
> alpha channel" and the X server composites everything, then the speed will
> be quite acceptable.  Using proper compositing like this has other advantages,
> too (like the elimination of 'tearing' when dragging one window across another,
> because no application ever has to redraw itself because as far as
> it's concerned,
> it's never obscured.
> 
> Things were done all ugly-like in the past because things were rendered direclty
> onto video memory, which was all being displayed on the screen.  I
> seem to recall
> hearing that some of the high end UNIX workstation video cards got around this
> with multiplane setups and stuff...but this also tended to limit
> colour depth...I think.

I know some SGI's used to have only 256 colour palletes, but they had
one pallete per running program and could handle a rather large number
of programs at once, so effectively you were getting much more than 256
colour, but each application was limited.  Perhaps they did it to do
planes for alpha channels and such.  They also ran opengl on them as far
as I know (or perhaps irisgl at the time).

> I'm probably in way over my head at this point in the discussion.
> 
> Nope, the WM can run on the terminal server.  I was only speaking of
> transparency
> being computed on the thin client (X server) vs the
> server+lotsofchatteronthewire
> (X client).

Yeah when NCD had the WM (motif in their case) on the X display, it
really wasn't very fast at it, although perhaps largely due to lack of
processing power on the device.

Lennart Sorensen
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