NSImage lockFocus/unlockFocus bug?

[Stefan Urbanek]

Hi again,

I was trying to play with [NSImage lockFocusOnRepresentation:myBitmapRep]. It
looks like it creates some cached image representation. 

According to:

http://developer.apple.com/documentation/Cocoa/Reference/ApplicationKit/ObjC_classic/Classes/NSImage_index.html

...it is fine, however I would expect, that [image unlockFocus] will flush the
graphics into my focused representation:

"A successful lockFocusOnRepresentation: message must be balanced by a
subsequent unlockFocus message to the same NSImage. These messages bracket the
code that draws the image."

As I get no visible result, i think the method combination is not working
properely and lockFocusOnRepresentation should raise an exception:

"If lockFocusOnRepresentation: is unable to focus on the representation, it
raises an NSImageCacheException."

I am missing something here or doing something wrong?

Stefan