Thanks for speedy reply !
Putting the window size as the "resolution" was maybe not ideal, but if I had put the desktop resolution, you'd see the same message with a bigger number like 1600x1200. I'm rather surprised that DP 3/4/5 mistakes the image(canvas) size with the editor size, especially since it is able to edit images larger than screen, and edit in a few overscan resolutions.
I'll build up a few tests images where I put the image size in the "screen size" fields, and see if they work better (I think I have DP4 on UAE)
User feedback is the only way to improve the program, so don't hesitate to report problems
