Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!husc6!sunfs3!kent
From: kent@sunfs3.camex.uucp (Kent Borg)
Newsgroups: comp.sys.mac.programmer
Subject: Being switched while recording a picture
Summary: What precautions to take?
Keywords: picture switch GetNextEvent picSave grafPort GWorld 32-Bit QuickDraw MultiFinder
Message-ID: <580@sunfs3.camex.uucp>
Date: 19 Dec 89 00:10:36 GMT
Reply-To: kent@lloyd.UUCP (Kent Borg)
Organization: Camex, Inc., Boston, Mass USA
Lines: 31

What are the implications of being switched out while recording a
picture?

I have been working on TIFF -> PICT code for what seems like forever.
Trying to be nice while converting the data, I decided that I should
allow myself to be switched out once each time through my main
data conversion loop.

I didn't occur to me an innocent looking GetNextEvent could have been
causing me all this grief I have been suffering, but it looks like it
has.  Being switched out while in the midst of recording a picture
seems less than a good idea--now that I have noticed it.  How can I do
this safely?

My current idea is to save my grafPort's picSave handle, substitute
nil, call GetNextEvent (I know, use WaitNextEvent--but in this case I
think it reduces down to the same call), then replace the picSave I
cleverly preserved.  (see IM I-189)

No go.  Still dies.  There seems to be more to it than I am currently
handling.

One important detail: the grafPort I am using to record this picture
is actually one of those new-fangled offscreen GWorlds that 32-Bit
QuickDraw gives us.  Anybody played with them yet?


-- 
Kent Borg                lloyd!kent@husc6.harvard.edu  or  ...!husc6!lloyd!kent
MacNet: kentborg                              H:(617) 776-6899  W:(617)426-3577
"The wall has been opened.  One of the most insurmountable borders in Europe
 has become a German dance floor."  -Christoph Hein, NYT Magazine, 17 Dec 1989