[NTLUG:Discuss] Colors in X

[Steve Baker]

xiao li wrote:
> 
> In this program, the white color is toggled to black, black color to 
> white, and all other colors to black. I just change the colormap, then 
> call XStoreColors() and XFlush(). Let X server to redraw the color. This 
> program runs correctly on Solaris or Windows NT if there is a X server 
> installed.
> 
> This method has a limitation. You can't use more than 256 colors( if you 
> know a way can get rid of this limitation, please tell me!! ). I am 
> running this program on Redhat 7.1 and 7.3 Linux locally. But if I run 
> this program on Linux machine but use xhost to display it on other 
> platform, then it can work fine. So I guess it is because of the X 
> server. Do I need to change or update the redhat x server?? Or how can I 
> configure it to make it works with my blink function??

I don't think you can assume the existance of a colour map in X.  Certainly
there isn't one when the display is in 24 or 32 bit modes - just think how
big the table would have to be!

So - I *suspect* you are somehow getting a display mode that doesn't have
a colour table.

However, I'm not an X guru - so this could easily be complete nonsense.

At any rate - in this modern age where graphics adaptors can generally
manage 24 bits per pixel quite easily - it would be a bad idea to assume
that there is some hardware colour table there to be tweaked.  It's
quite likely that the underlying driver is EMULATING a colour table
by re-rendering the image from scratch or something.

I think you should just redraw the parts of the image you want to
blink.  That's likely to be more efficient on modern graphics
hardware - and it's sure as heck more portable.
---------------------------- Steve Baker -------------------------
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