Using an image for background in a DocumentWindow

I’m trying to get an image as my background. So far I have managed to load the image to an internalCachedImage, but I am unable to figure out how to display it correctly.

All the examples I see draw it in the paint or repaint functions. I am using a DocumentWindow for my application and do not see an existing paint or repaint function in the files.

Am I missing something?

Oh, I am using a contentComponent to place my buttons.

Override the paint method of your content component and paint your background image there.