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From: rcook@eagle.wesleyan.edu
Newsgroups: comp.sys.mac.programmer
Subject: A BUG (sort of) in the FINDER
Message-ID: <1567@eagle.wesleyan.edu>
Date: 24 Sep 89 19:18:53 GMT
Lines: 31

Bug in the Finder!!

Some time ago I had written a program which ran perfectly, only when it
finished and returned to the Finder I discovered that I couldn't double- click
on anything anymore; pressing the mouse button twice merely selected the file,
but did not open it.  This only occurred in the Finder.  I could double click
to my hearts content in ResEdit or Word or LSP.  I suspected that I had
clobbered the global variable doubleTime, but I actually hadn't. 

After some investigation, I discovered that my program sets the system event
mask to disable the posting of MouseUp events, and the Finder needs MouseUps to
process a double click.  I tested this further with this 3 line wonder:

program test;
begin
  SetEventMask(EveryEvent - MUpMask);
end.

And sure enough, no double clicks.  All Finders up to the version that goes
with System 6.0.3 (and perhaps newer ones) can be brought to their knees by a
bad event mask, so watch out.  I'm surprised Larry, Steve, John, and Bruce (or
whoever they are) didn't set the mask just the way they want it when the Finder
starts up.  I suppose the rule shoule be that if you mess with the event mask,
set it to EveryEvent-KeyUpMask when the program finishes to avoid future
problems.

Tell me if you know anything more about this stuff.

                       --- Randall Cook
                           rcook%eagle@wesleyan.bitnet
                           rcook@eagle.wesleyan.bitnet