For years I’ve been using App Wrapper to include ICNS files in my apps, so much so that I forgot how to use it in Xojo.
[quote=303211:@Norman Palardy]If you drag in an ICNS only some sizes actually have masks
Some sizes are PNG’s with transparency - not a mask[/quote]
I think the thing is in the Preview section of the Icon interface, it shows the image as if it doesn’t have a mask (solid black background).