
When using fractional scaling this matters, so that you don't miss a line of pixels at the edge of the clip rectangle by rounding down. This was observed as a line of corrupt pixels in Firefox (Wayland) tooltips. Related to: https://gitlab.gnome.org/GNOME/mutter/-/issues/1500 Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1554>