When running with eglfs_kms with at least two screens connected, one would expect the mouse cursor (done via the drm cursor plane) to behave in a sane way with the default virtual desktop behavior, meaning it should only be shown on one screen at a time.
This is not the case currently because the implementation assumes that moving (as in drmModeMoveCursor) the cursor to an out of range location will result in a hidden cursor. While this used to work on some systems, it leads to artifacts on some others. We should rather disable and enble the cursor when moving out and then back in to the screen's bounds.
On some systems the result is artifacts on the screen where the cursor is not in range. See attached photo. There the cursor is shown correctly on the below screen, but is leading to artifacts on the top one.