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From: ch@maths.tcd.ie (Charles Bryant)
Newsgroups: comp.sys.mac.programmer
Subject: When does OpenPicture return NIL
Keywords: OpenPicture
Message-ID: <129@maths.tcd.ie>
Date: 10 Nov 88 18:48:14 GMT
Organization: Maths Dept., Trinity College, Dublin
Lines: 21

Under what circumstances does OpenPicture() return 0 (i.e. NIL)?

I have a redraw function which creates temporary Pictures and Kills them before
returning. This function works except when printing (after PrOpenDoc). I
did a lot of tracing with MacsBug and added a lot of checks and finally
found that OpenPicture was returning 0. I have not run out of memory, and the
rect passed to OpenPicture is valid. I can't think of any other reason why
OpenPicture might return 0. Is this an error indication (not mentioned in IM).
If I try to use the 'es' command (Exit to shell) from MacsBug after OpenPicture
has returned, I get an invalid address trap when Lightspeed starts redrawing its
windows. Is this just because the program has stopped between a PrOpenDoc and
its PrCloseDoc, or does it indicate that memory has been corrupted?

Thanks in advance.
[Please mail me any suggestions (instead of posting) - particularly if
I've missed something obvious :-]
	Charles Bryant
-- 

		Charles Bryant.
Working at Datacode Electronics Ltd.