Change colour of standard progress bar using Quartz filters

I need 2 different colours: Yellow, Green. Is it smart to use Quartz filters on standard progress bar, because sometimes I can see rendering problems after doing s开发者_开发百科o.

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As a general rule, it's better to fully replace system artwork than it is to try to tweak it. Tweaks mean you have a very strong dependency on stuff that isn't API - what the artwork looks like and how it gets to the screen. For example, what would happen to you if (assuming Mac OS X here) the progress bar changed to be implemented using CALayers? Probably nothing good.

This 'tweak vs replace' business applies to things higher level than artwork as well. This along the line of why people often say they favor composition over subclassing.

I work on the Cocoa frameworks, so I'm often looking at apps that are broken on new or intermediate versions of the operating system. Apps doing things like you're talking about tend to be very fragile.