I've converted Icon Mangler to use the new file handling code, and added support for dropping an icon onto the application's icon in order to edit it. I've cleaned up some of the refreshing code, but no luck in removing the weird bugs. I'm going to go step by step with the debugger to see what I'm doing wrong...
No luck doing that. I've changed around the drawing of the image well, so that I don't have to use clipping regions anymore. It turns out that if you use the DrawThemeWell function, you can control whether or not the content should be cleared to white. I changed the image well into a user pane, and associated a drawing function to it, which uses the DrawThemeWell function. It looks good, but now I've run into even bigger problems. Now the image well refuses to handle clicks, and the refreshing doesn't work either. Oh well, hopefully I can find a way out of this mess.
I've fixed things up a bit. It turned out I had to do my own routine to handle clicks within in the control. It's a very simple one (it automatically returns true) because the control is rectangular, so a click withing the control rect automatically equals a click within the control (this wouldn't be so easy if I had rounded corners, or an irregular shape). But the refreshing is still very weird, and I'm not much better off than I was before I decided to change my method.