[rescue] Weird Silicon Graphics o2 graphics issues

[Andrew Weiss]

On Thursday, October 2, 2003, at 03:05 PM, Joshua D. Boyd wrote:

> On Thu, Oct 02, 2003 at 02:52:50PM -0400, Andrew Weiss wrote:
>
>> I never understood really why X was designed in this broken way.  Why
>> "use-up" colors at all?... A little bit of extra logic and you could
>> display all visible apps with any color they want.  I think even early
>> versions of Windows did this so X is not alone.
>
> I haven't seen evidence that Windows could ever do that on a 256 color
> display, nor can I think of any possible way to pull that off on a VGA
> card.  A VGA card can only display 256 colors on the screen at a time
> reguardless of how many applications there are running.

You misunderstand.  I said Windows also had problems with flashing 
color maps when switching between apps at 8 bit color and below.
>
> To give each app their own 256 color colorspace is not an easy task to
> implement on plain frame buffers.  I can think of several ways to
> implement a frame buffer that would allow that, but each such way would
> only be able to accomodate up to a fixed number of programs on the
> screen at once.  Given a truecolor frame buffer though, giving each 256
> color program it's own 256 color colorspace is an easy enough trick, if
> done in software.

<cue partial ignorance>
What I fail to understand is why have a colorspace (a reserved one) at 
all.  The app wants a color out of 256 possible values... send it to 
the screen at that spot (pixel).  I don't get the notion of firing up 
one app that grabs all these colors and then another app cannot use 
them while it is in the background...or may even generate errors about 
not enough colors available.  It's not as if one app physically sucks 
all the color into a pot and nobody else can have any...they're on the 
same screen...or is this a memory limitation whereby you are stepping 
into the same spot in the frame buffer's memory which needs to be 
protected?
</partial ignorance>

Andrew