[Wayland] Windows with geometry hints shrink when toggling maximize or fullscreen
See gnome-terminal #751064 and recent comments in gnome-terminal #44. When a window with geometry hints for fixed-width text is maximized or made full-screen, then toggled back to its original size, it's prone to its geometry reducing by one character, eg if it was 80x32 it may become 79x31. It isn't always 100% reproducible, but Wayland seems to be the common factor, and most VTE-based terminal apps are affected. I don't think VTE is to blame though.
I've worked around this problem in roxterm by adding a configure-event signal handler. If a window's new state is maximized or fullscreen the handler removes geometry hints, otherwise it calculates and applies them. This seems to fix it. To calculate the base-width/height fields for geometry hints roxterm reads the difference in size between the vte widget's text and the window, and I think that's how other apps typically do it too. I don't quite understand why it still "sees" the fullscreen padding while doing this, and why the padding then seems to disappear, so that repeatedly toggling maximize/fullscreen causes further shrinkage.