Hi,
While trying to understand the zoom function to apply it to other GUI objects, I studied the bng and tgl objects, and in the process came up with a solution that fixed both.
For the iem_gui objects only the basic generic GUI parameters are available in a struct; x & y position coordinates, height and width. All other GUI dimensions are not accessible outside the drawing functions. The only option to get a correct zoom is to apply the zoom-factor to all appropriate dimension values in all GUI functions.
At least for bng I have this working. With some more refactoring this could be applied without adding too much to the declared mess in the objects code.
Greetings,
Fred Jan