On Oct 1, 2009, at 6:41 AM, Andrew wrote:
Hi All,
So clearly the UIGraphicsBeginImageContext() set of calls are not
thread safe, I was attempting to use them in an NSOperation and they
are causing a crash, further research has shown me that I need to
drop down into the CG calls to do what I want to do.
.....and presumably I could have been forewarned if I had looked at
the 'UI' at the front of the function, and had read that as a Sign.
I am, however, very interested...for my own curiosity...in why they
are not? my mental image of that call had it simply wrapping the
CGBitmapContextCreate() set of calls, and they are thread safe.
what is it doing that renders it not thread safe, does anyone know?
At the very least, it needs to call UIGraphicsPushContext to set the
current "ui graphics context", which is documented as needing to be
done on the main thread (which implies that there is a single, global
"ui graphics context" variable use by all of UIKit to indicate where
all UIKit based drawing should go).
Glenn Andreas gandr...@gandreas.com
<http://www.gandreas.com/> wicked fun!
Mad, Bad, and Dangerous to Know
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