Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!munnari.oz.au!labtam!graeme
From: graeme@labtam.labtam.oz (Graeme Gill)
Newsgroups: comp.windows.x
Subject: Re: Window Managers
Summary: Slightly more efficient
Message-ID: <5691@labtam.labtam.oz>
Date: 5 Dec 90 04:02:49 GMT
References: <7422@castle.ed.ac.uk> <3055@gazette.bcm.tmc.edu>
Organization: Labtam Information Systems Pty. Ltd., Melbourne, Australia
Lines: 29

In article <3055@gazette.bcm.tmc.edu>, etaylor@wilkins.iaims.bcm.tmc.edu (Eric Taylor) writes:
> 
> The general concept is that you draw a line using
> GXXor.  You draw a line the first time and it inverts
> the colors beneath it.  The draw the same line in
> exactly the same place again and the colors invert
> again giving you the original pixels.
 
 	The GC for drawing this line is as follows :
 
         Pixel white = WhitePixel(dpy,screen) ;
         Pixel black = BlackPixel(dpy,screen) ;
         values.foreground = black ^ white ;
         values.background = white ;
         values.line_width = 0 ;
         values.function = GXxor ;
         values.plane_mask = values.foreground ;
                             ^^^^^^^^^^^^^^^^^
etc.

	Setting the plane mask is both un-necessary, and potentially
slow on some systems. Systems with screen pixmap depth > 1 may or
may not have hardware support for the plane mask, hence it is best
to leave all planes enabled. Setting the foreground to the xor of the
two colours concerned is sufficient to restrict the operation to
the appropriate planes.

	Graeme Gill
	Labtam I. S. Pty. Ltd.