Popups with relative position x < 0 && y < 0 are not shown (after move-to-rect)
When tooltip is created with x < 0 and y < 0 (which is correct, for instance when we show tooltip of something outside of latest/topmost popup window) Gtk silently fails to map that window. The code says:
/* Don't map crazy temp that GTK+ uses for internal X11 shenanigans. */ if (window->window_type == GDK_WINDOW_TEMP && window->x < 0 && window->y < 0) return FALSE;
which is not valid on Wayland I guess.
This causes Firefox bug https://bugzilla.mozilla.org/show_bug.cgi?id=1717451