Path: utzoo!attcan!uunet!husc6!bloom-beacon!WSL.DEC.COM!haynes
From: haynes@WSL.DEC.COM
Newsgroups: comp.windows.x
Subject: Re: X Toolkit and continuous graphic output
Message-ID: <8807251844.AA25976@gilroy.pa.dec.com>
Date: 25 Jul 88 18:44:52 GMT
Sender: daemon@bloom-beacon.MIT.EDU
Organization: The Internet
Lines: 23

[Rusty sent me a message explaining that the program he was trying to
adapt was basically a "black box" and it's behaviour couldn't be
guaranteed, and certainly couldn't be modified. Here is my reply.]

Well, as usual with the toolkit there is a fifth, very obscure and
slightly dangerous way of doing what you want. I don't normally
recommend it since it can get you into serious trouble, but Xlib lets
you register a procedure to be called as X events come in, and before
they are queued on Xlib's event queue. You can dispatch from this
procedure, but because it is truly asynchronous, you are letting
yourself in for all sorts of potential trouble. As long as you do ALL
event dispatching from this routine, and make sure that you finish
processing an event before you dispatch the next one, you should be safe.

Realize that you will be operating in the far outer limits of expected
Xlib and toolkit behaviour, and be conservative about what you want to
accomplish, and you should be able to get away with it. I don't
remember precisely, but one of the potential pitfalls is that you may
be dispatching events into the toolkit while Xlib has the display
structure locked. If true, this will make it difficult (impossible!) to
do Xlib calls in your toolkit routines.

	-- Charles