There's two unfortunately-elements here:
- I haven't managed yet to make a native-WPF backend to work yet with Xwt (the ones I tried seems to only work with XAML). It's anyway in the TODO list. For now this uses System.Windows.Forms, which was a reference which the WPF backend used anyway.
- This temporary SWF solution only works with System.Drawing.Icon (as well as one of the other WPF alternatives), so I added a hack to check for the extension when the file is loaded from the resource. Feedback welcome about how to improve this!
At least I tested this with Mac, and the icon file (.ico) still works, so let's use icons instead of PNGs for all platforms for now when using the StatusIcon.