Path: utzoo!attcan!uunet!wuarchive!zaphod.mps.ohio-state.edu!ncar!gatech!prism!sun13!gw.scri.fsu.edu!pepke
From: pepke@gw.scri.fsu.edu (Eric Pepke)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Invalid port in event loop
Message-ID: <1280@sun13.scri.fsu.edu>
Date: 26 Oct 90 14:55:11 GMT
References: <10804.272420f5@amherst.bitnet>
Sender: news@sun13.scri.fsu.edu
Organization: Florida State University, but I don't speak for them
Lines: 34

In article <10804.272420f5@amherst.bitnet> djvelleman@amherst.bitnet 
writes:
> What's the official policy on setting
> thePort before calling SystemTask or GetNextEvent?  What's the official
> policy on disposing of window records?  Has anyone else had a problem 
with
> this?

I don't know what the "official" policy on setting the current GrafPort 
is, but one should set it to a known good port once every time through the 
event loop, EVEN IF one's program is otherwise perfectly consistent with 
GrafPorts.

The reason for this is that you don't know what desk accessories are doing 
behing your back.  (Yes, I know that they are by default not loaded in the 
same partition under MultiFinder, but somebody will do it.)  Now, some 
desk accessories have bugs which cause them to dispose of windows without 
setting the current GrafPort correctly.  Some have bugs which cause them 
to call one of the QuickDraw routines that require a valid current 
GrafPort without setting it first.  Either will work fine with most 
programs, but when somebody runs both of these desk accessories under your 
program, KABOOM!

You can be sure that the resulting shrapnel will be blamed on your 
program, so play it safe.


Eric Pepke                                    INTERNET: pepke@gw.scri.fsu.edu
Supercomputer Computations Research Institute MFENET:   pepke@fsu
Florida State University                      SPAN:     scri::pepke
Tallahassee, FL 32306-4052                    BITNET:   pepke@fsu

Disclaimer: My employers seldom even LISTEN to my opinions.
Meta-disclaimer: Any society that needs disclaimers has too many lawyers.