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From: mouse@lightning.mcrcim.mcgill.EDU (der Mouse)
Newsgroups: comp.windows.x
Subject: Re:  XDrawLine event driven ?
Message-ID: <9103040706.AA27256@lightning.McRCIM.McGill.EDU>
Date: 4 Mar 91 07:06:35 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 28

> I've managed to get real nifty looking lines on my screen, but there
> is just one problem:

> 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).

Quite right.  This is what Expose events are all about: if your
application is one where window damage matters, you have to be prepared
to redraw arbitrary pieces of your window.

To get Expose events on a window, set ExposureMask in the window's
input-mask at creation time, or use XSelectInput.  Each Expose event
indicates a rectangle that needs repairing; it is up to your code to do
whatever is necessary to arrange this.

> BTW, I'm using the Athena widgets (but that shouldn't matter, should
> it?)

I don't know.  The above is written from an Xlib perspective; what it
amounts to in toolkit or widget terms someone else will have to
explain.

					der Mouse

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