[comp.windows.ms.programmer] Managing Colors

gwe@cbnews.att.com (George W. Erhart) (11/26/90)

(First let me state that I do not have the SDK, but that is another story)

I recently upgraded my machine to a 256 color capable video card. (Paradise 
1024) I noticed as I was displaying 256 GIF files using wingif, that each
GIF I loaded changed the overall color map. This has a rather anti-social
effect on other applications that might have their own idea of what the
color map should look like. 

The X window system handles this problem by managing the color map through
the server. If all requests for colors are less than the number of free color
cells in the color map, then there will be no conflicts between applications. 
If an application wants more colors than are currently available, the server
will install a separate color map for that applications window. When the input
focus (current window) moves into and out of that window, the server will flip
between the  overall color map and that window's color map. 

This is one area where windows appears to be quite backward ... any comments?
-- 
George Erhart
AT&T Bell Laboratories
att!archie!gwe

chrisg@microsoft.UUCP (Chris GUZAK) (12/05/90)

In article <1990Nov26.130804.3496@cbnews.att.com> gwe@cbnews.att.com (George W. Erhart) writes:
>(First let me state that I do not have the SDK, but that is another story)
>
>I recently upgraded my machine to a 256 color capable video card. (Paradise 
>1024) I noticed as I was displaying 256 GIF files using wingif, that each
>GIF I loaded changed the overall color map. This has a rather anti-social
>effect on other applications that might have their own idea of what the
>color map should look like. 

I don't now what wingif does (if it is a well behaved palette app) but
windows has a "palette manager" that controls who has priority in
the system palette.  The active window gets first shot at filling
the palette.  If there are more free entries other apps get those.  If
there are no more free entries colors are closest-matched to what is
in the palette.

This scheme favors the top app (the one you are working on), but gives
the best approximation to all others. 

>This is one area where windows appears to be quite backward ... any comments?
This is the way I want it to work...  I'm sure there are other designs.

>-- 
>George Erhart
>AT&T Bell Laboratories
>att!archie!gwe