Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!wasatch!cs.utexas.edu!pp!milano!titan!janssen@titan.sw.mcc.com
From: janssen@titan.sw.mcc.com (Bill Janssen)
Newsgroups: comp.windows.x
Subject: Re: CLX and inverting pixels
Summary: Use copy-area
Message-ID: <1870@titan.sw.mcc.com>
Date: 8 Jan 89 02:15:07 GMT
References: <34700004@zaphod>
Sender: janssen@titan.sw.mcc.com
Organization: MCC Software Technology
Lines: 15

In article <34700004@zaphod>, doug@zaphod writes:
>This is really a question about CLX and not Xlib.  In CLX I cannot find 
>a way to operate on a section of pixmap without uploading the bits,
>operating on them and then downloading the bits:

How about `copy-area'?

(defun invert-area (SELF X Y WIDTH HEIGHT)
  (let ((Gc (xlib:create-gcontext :drawable SELF :function boole-c1))
	)
    (xlib:copy-area SELF Gc X Y WIDTH HEIGHT SELF X Y)
    (xlib:free-context Gc)
    ))

Bill