A few years ago I had a bug like this under X + Noveau + GNOME, where Windows were reporting the wrong coordinates. It was fairly easy to find an example on st

A few years ago I had a bug like this under X + Noveau + GNOME, where Windows were reporting the wrong coordinates. It was fairly easy to find an example on stackoverflow that created a Window using Gtk, and reported it's position. Once something like that is on the bug report things tend to get fixed pretty quickly. Report the bug on the outer-most thing first, e.g. GNOME shell in this case.