On Mon, 5 Jan 1998, Matthias Rarey wrote:
> To subscribers of the xforms list from Matthias Rarey <Matthias.Rarey@gmd.de> :
> I recently upgraded to V0.88 which reminds me to an old problem
> concerning colortables for glcanvases on linux systems. I am
It's not linux, but rather the combination of several things. One is graphics
hardware that is limited to one colormap, like many PC machines running linux
are. SGI or newer sun hardware that can do multiple colormaps and 16 or 24
bit truecolor hardware won't have this problem. Another thing is using a
window manager that is a twm deritivate, that handles a specific case of
colormaps wrong. Most linux installations use fvwm as the window manager,
which has this bug.
> The glcanvas seems to have the wrong colortable on linux systems.
> While simple graphics using only red/green/blue like the gl demos
> in the forms distribution work, scenes with more colors (especially
> when lighting is used) look like they are based on a wrong colortable.
> I looked around in the gl.c file coming with the library and found
> out that removing the fl_set_canvas_colormap statement (l.182 in
> V0.88) solves the problem (whatever this means?).
So, the gl_canvas has the default colormap, doesn't it? You can tell if all
the colors on the rest of the screen are still correct. If you give the
canvas a colormap with fl_set_canvas_colormap is never gets installed, so the
colors are wrong.
> On SGI computer with OpenGL the application works fine as well
> as on SUN computers running Solaris (without a change in gl.c).
I bet the sun computers either hard 24-bit hardware, and/or were using olwm
which doesn't have the bug.
> Has anybody seen something similar or has an idea what may cause
> this behaviour? I can send a more detailed description if this
> is of further interest.
I think I know exactly what's wrong here, and it's quite a large can of worms.
Try checking the mailing list archives, there was a discussion of it not too
long ago.
|Gazing up to the breeze of the heavens \ on a quest, meaning, reason |
|came to be, how it begun \ all alone in the family of the sun |
|curiosity teasing everyone \ on our home, third stone from the sun. |
|Trent Piepho (xyzzy@u.washington.edu) -- Metallica |
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