How to change default black screen to white in motif app?

"Valeri" <ambal007@netzero.net> wrote in message
news:1166475757.906227.20570@f1g2000cwa.googlegroups.com...[color=blue]
> How to change default black screen to white in motif app?
> Hi.
> I have motif application. When I press left mouse button and
> drag it I have rectangular with black lines, but background
> changes periodically from white to black. How to keep
> steady white background? Is it default black screen here?
> I use:
> XSetForeground(thedisp , thegc ,
> BlackPixel(thedisp , DefaultScreen(thedisp))) ;
> XSetFunction(thedisp , thegc , GXinvert) ;//GXxor gave me yellow rect
> lines
> Valeri.
> [email]ambal007@netzero.net[/email]
>[/color]

I am not clear what it is you are actually trying to do.
If you are trying to drag a black rectangle across a white field,
(called "rubberbanding") you really do need to use GXxor.

However, the color you want to use is not BlackPixel.
You should use
Pixel p = BlackPixel ^ w;

where 'w' is primary color of the background over which you
are drawing (in your case, it is WhitePixel);

Also, you need to "remember" each draw. The next time you
draw your rectangle in its new position, you need to first
re-draw the former position, using GXXor. This will restore
whatever was there before you drew the reectangle last time.

Note that the rectangle will be black only over those portions
of the screen that are currently white. If you cross any text,
for example, the line that goes throught the text will be neither
black nor white nor the text color, but some other color
defined by pixel "Black ^ White ^ textColor".

Ensuring that the rectangle is ALWAYS black, regardless
of the color of things it crosses over, is much more
difficult to do; you will have to use overlay planes.
--
Fred L. Kleinschmidt
Boeing Associate Technical Fellow
Technical Architect, Software Reuse Project