On mice, scrollbars are always triggered temporarily. On proximity to an scrollbar, it will be switched to full-width.
3bcf5e2 scrolledwindow: Show scrollbars upon captured motion events
gtk/gtkscrolledwindow.c | 168 ++++++++++++++++++++++++++++++++++++-----------
1 file changed, 129 insertions(+), 39 deletions(-)
Upstream: git.gnome.org