Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!crackers!m2c!umvlsi!umaecs!amh!djvelleman
From: djvelleman@amherst.bitnet
Newsgroups: comp.sys.mac.programmer
Subject: Invalid port in event loop
Message-ID: <10804.272420f5@amherst.bitnet>
Date: 23 Oct 90 10:52:37 GMT
Lines: 20


  Last week I posted a question about calling SystemTask or GetNextEvent with
thePort not set to a legal GrafPort.  The more I think about this, the more
concerned I am about potential problems.
  Suppose I close a window and then call DisposeWindow to dispose of the window
record.  If that window was the current grafport, won't thePort now be invalid?
If I return to the main event loop without doing something about this, will my
program crash?
  I know many people don't dispose of window records when they close windows,
but surely lots of people call DisposDialog when they're done with a dialog.
Won't this cause the same problem?
  Perhaps my diagnosis of my bug was wrong, but I don't think so.  At any
rate, setting the port to a valid grafport before going to the main event loop
stopped the program from crashing.  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?
  Dan Velleman
  Math Dept.
  Amherst College