On 27/01/2005 08:04 Pm, George Warner wrote:
> on 1/27/05 3:35 AM, Mike Kluev at <email@hidden> wrote:
>
>> On Wed, 26 Jan 2005 09:26:42, George Warner <email@hidden> wrote:
>>
>>> Actually, you can do this. As long as the area's being drawn to by the
>>> different thread don't overlap then Quartz can handle the same context being
>>> used my multiple threads. Internally it serializes accesses to the context.
>>
>> George, I am curious if such internal serialization is really needed
>> if areas being drawn don't overlap.
>
> Absolutely. One thread could call:
>
> CGContextScaleCTM(context, 1.0f, -1.0f);
>
> And the other:
>
> CGContextScaleCTM(context, 3.0f, 1.0f);
>
> If they're both using the same context then which ever one executes last
> will effect drawing in the other thread. Something isn't going to look
> right.
>
> Note however that the internal serialization doesn't prevent messed up
> drawing in that other thread. But it does prevent crashes caused by
> non-reentrant code.
>
> Assuming that both threads are using the same Scale, transform, etc. then
> one thread drawing a square and another a circle should still work as
> expected. At the API level all operations can be assumed to be atomic.
Oops, I misread what you wrote before and was thinking about drawing
to one canvas via different contexts.
Mike
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