Sorry, I didn't try originally. I've played around with it, and no, I can't get it to accept a child control. As you say, 3Impact takes over input, like how pressing escape closes the Window by default. I guess that would be problem if it was attached to a child control instead of the window.
I haven't tried a canvas yet ( still can't figure out what mods the canvas wants imported, apparently MaxGUI and Max2d is not enough ) but I suspect the result would be the same.
I haven't tried a canvas yet ( still can't figure out what mods the canvas wants imported, apparently MaxGUI and Max2d is not enough ) but I suspect the result would be the same.