Re: What paradigm behind NSColor's drawing methods?

FROM : Jerry Krinock
DATE : Fri Feb 01 22:18:27 2008

On 2008 Feb, 01, at 12:47, glenn andreas wrote:

> What circumstances are you running into that not having an explicit 
> drawing context parameter is a problem?


Drawing a focus ring, in -drawRect of a custom control...

[NSGraphicsContext saveGraphicsState];
NSSetFocusRingStyle(NSFocusRingOnly);
[[NSColor keyboardFocusIndicatorColor] set];
NSFrameRect([self visibleRect]);
[NSGraphicsContext restoreGraphicsState];

In the Cocoa Drawing Guide I read that:

"Important: Saving and restoring the current graphics state is an 
expensive operation and should done as little as possible. With the 
exception of clipping paths, most state attributes can be undone 
manually in your code without saving and restoring the entire state."

They seem to be suggesting that instead of -saveGraphicsState and -
restoreGraphicsState, I should manually "get" the color and the 
FocusRingStyle before "setting", so I can set them back to their 
original values after I am done.  But I can't do that because there 
are no getters for these.

As far as the rest of your reply, OK I understand that there are many 
other methods that use the drawing context as an implied "object", 
that this is done for convenience, and I should orient my thinking 
into this paradigm.  Thanks for the explanation.