Re: XForms: deleting a line

Steve Lamont (
Wed, 20 Aug 97 07:26:05 PDT

To subscribers of the xforms list from (Steve Lamont) :

> > If you're doing something like rubber banding, you can use Xor
> > drawing.
> >
> Has anyone written the code to do this? I would like to select
> regions from an xyplot, and I am relatively lazy, uh, I mean I don't
> want to "reinvent the wheel", so...

Basically, the idea is

fl_drawmode( GXxor );
if ( !first_time_through )
fl_drawmode( GXcopy );

That's it.

You may need to experiment with the color to get it right. I
generally would set the GC's foreground color to 0xff.

There is an Xlib oriented discussion of this in Volume I of the
O'Reilly series -- I think under the topic of "rubber banding."

I actually don't bother with the Xor drawing much any more. I just
double buffer and redraw the entire object with a new box. Most
systems are fast enough these days that there's very little noticable


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