Re: Why is "set" a class method of NSColor?
Re: Why is "set" a class method of NSColor?
- Subject: Re: Why is "set" a class method of NSColor?
- From: Jack Boyce <email@hidden>
- Date: Thu, 3 Dec 2009 18:54:19 -0800
Argh, never mind. I overlooked an important section of the Cocoa Drawing
Guide.
Jack
On Thu, Dec 3, 2009 at 6:46 PM, Jack Boyce <email@hidden> wrote:
> I'm learning Cocoa, trying to understand certain "magical" features where
> it isn't obvious how things work under the hood. (KVO and isa-swizzling is
> another prime example.)
>
> Can someone kindly explain, or point me to an explanation for, what's
> really happening with:
> [[NSColor blueColor] set];
>
> In other APIs one commonly sees methods on the target view for setting
> things like pen color and transformations. I.e., why is it not:
> [myView setPenColor:[NSColor blueColor]];
>
> In particular, how does the NSColor object know which NSView you're talking
> about when you send it the 'set' message? My current hypothesis is that
> information like pen color is recorded somehow in the [NSGraphicsContext
> currentContext] object for the current thread, but I can't confirm this in
> the docs. This would imply Cocoa is doing work behind the scenes to set up
> the NSGraphicsContext before it calls your view's drawFrame: method, and
> then cleaning up when you return. Is the idea then that one should only
> draw within the drawFrame: method of NSView, and only from the main thread
> (when Cocoa calls it)? I.e., there is no multi-threaded drawing in Cocoa?
>
> Thanks,
> Jack
>
>
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