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From: cjmchale@cs.tcd.ie (Ciaran McHale)
Newsgroups: comp.windows.x
Subject: Re: XDrawLine event driven ?
Message-ID: <1991Mar4.112554.5459@cs.tcd.ie>
Date: 4 Mar 91 11:25:54 GMT
References: <1991Mar3.231115@csd.uwo.ca>
Organization: DSG, Dept. of Comp. Sci., Trinity College, Dublin.
Lines: 37

In <1991Mar3.231115@csd.uwo.ca> bradd@csd.uwo.ca (krusty the klown) writes:

>Whenever a window appears over the lines and disappears, or the
>application is iconified, the lines (or portions of) disappear.
>I suppose this is because the lines from XDrawLine are not
>event driven (ie: no auto refresh).

An application is responsible for redrawing (parts of) any
of its windows which have become obscured and then re-exposed.
What you should do is look out for Expose events and then
redraw the window's contents. The Expose event data
structure contains information to tell you which portion of
the window you need to redraw so you only have to redraw
the necessary section.

Oliver Jones' book on Xlib programming has some good
examples and advice on how to handle Expose events. It might
be of some use. From the monthly X bibliography popting...

Jones, Oliver, Introduction to the X Window System, Prentice-Hall, 1988,
     1989.  ISBN 0-13-499997-5. An excellent introduction to programming
     with Xlib.  Written with the programmer in mind, this book includes
     many practical tips that are not found anywhere else. This book is not
     as broad as the O'Reilly Xlib tutorial and doesn't offer as many exam-
     ples as the Johnson & Reichard book, but Jones is probably the most
     experienced X programmer of this group and this shows in the quality
     and depth of the material in the book. Originally written for X11R1,
     recent printings have included corrections and additions.  The sixth
     printing should have X11R4 material.


Ciaran.
-- 
Ciaran McHale		"Verbosity says it all"			      ____
Department of Computer Science, Trinity College, Dublin 2, Ireland.   \  /
Telephone: +353-1-772941 ext 1538	FAX: +353-1-772204	       \/
Telex: 93782 TCD EI			email: cjmchale@cs.tcd.ie