the lowly cocoa box
I'm working with the interface builder and I've this need to have a standard box auto-expand with the app window. Furthermore, I want to control the background color and have control over the pixel size of the border. Is this possible - is there some other way. What could replace the standard box?
Interface builder gives you a lot of control over the appearance of controls and windows. It's a good idea to stick to the options provided as your application will look 'native' now and in the future when the look and feel of the UI may changed. Moreover, it's never a good idea to modify the window 'furniture' as these are inherited from the UI theme selected by the user.
However if you want something that's not provided 'out of the box' you can use a 'Custom View' for which you'll have to provide code to draw the control using graphics primitives.