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From: spolsky-joel@cs.yale.edu (Joel Spolsky)
Newsgroups: comp.windows.ms,comp.os.msdos.apps
Subject: Re: Micrografx Designer 3.01 and Windows 3.0
Message-ID: <26026@cs.yale.edu>
Date: 6 Sep 90 13:48:13 GMT
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In article <454@philpav.tds.philips.se> rzi@philpav.tds.philips.se
(Roman Zielinski) writes:
| We had discovered some problems with Micrografx Designer 3.01 running
| under windows 3.0.  If You create for example an organisational chart
| (you know boxes with text inside) and then copy it to the clipboard
| (default clipboard attributes) and try to exit Designer, you will get
| an "Unexpected application error" (do you know about expected appl
| errors :-> ).  It is 100% reproducable.

This is definitely a bug. I would give any odds that this is caused be
delayed rendering. Delayed rendering means that when you put something
in the clipboard, you don't actually put anything there, you just put
a *promise* in there. Then when somebody tries to read the clipboard,
Windows signals you to make good on your promise. This is useful when
applications (e.g. Excel) have the ability to provide the same data in
about 10 different formats. Instead of wasting memory by providing all
10 formats in the clipboard, you just issue 10 promises, and then you
only have to render those formats that are needed. The catch is that
when your application exits, windows will call in ALL the IOU's,
because it knows that you won't be around to render them any more.
So what is likely happening is that your application isn't correctly
handling render requests. Call them up and yell at them; they will
probably be glad for the bug report.

Technically, by the way, an "Unexpected Application Error" is almost
always a reference to a pointer that is outside of the program's
segments (what VAX fans call a Segmentation Error). Somebody is using
a bad pointer somewhere.

Joel Spolsky
spolsky@cs.yale.edu                                        Talk Hard.