Do you use the designer, or do you code your gui manually?

[wysota]

What is the pixmap function and how do I use it?

You probably don't need it - it is a function you can write to generate pixmaps according to a name. You can substitute the default pixmap generation process (based on a filepath) with it.

I've been writing most of my interface code by hand since I need to assign icons containing multiple pixmap sizes to QActions , but if it was possible to do in designer I would switch.

You wouldn't see the result in (current) Designer. If icons are your only problem, you can write a simple routine that would set the icons in code and layout the gui in Designer.