From: buzz@bear.com (Buzz Moschetti)
Subject: Re: XCopyPlane Question
Reply-To: buzz@bear.com (Buzz Moschetti)
Organization: Bear, Stearns & Co. - FAST
Lines: 16
In-reply-to: whaley@sigma.kpc.com's message of 15 Apr 93 18:39:31 GMT

In article <WHALEY.93Apr15103931@sigma.kpc.com> whaley@sigma.kpc.com (Ken Whaley) writes:
>   Actually, I must also ask the FAQ's #1 most popular reason why graphics
>   don't show up: do you wait for an expose event before drawing your
>   rectangle?

Suppose you have an idle app with a realized and mapped Window that contains
Xlib graphics.  A button widget, when pressed, will cause a new item
to be drawn in the Window.  This action clearly should not call XCopyArea() 
(or equiv) directly; instead, it should register the existence of the new
item in a memory structure and let the expose event handler take care
of rendering the image because at that time it is guaranteed that the
Window is mapped.

The problem, of course, is that no expose event is generated if the window
is visible and mapped.  Do you know the best way to "tickle" a window so
that the expose event handler will be invoked to draw this new item?
