This came form the follow discussion on IRC: 6:19 PM <tonikitoo> smfr: since ScrollAnimator has hooks for when mouse enters/leaves/clicks an overlay scrollbar area. 6:20 PM <tonikitoo> These hooks are what behavior similarly with and without the patch. 6:22 PM <tonikitoo> I have not tried ref test yet, but have not seen recent overlay scrollbar changes come with tests. 6:22 PM <tonikitoo> smfr: Do you have any pointers? 6:22 PM <smfr> we probably need to make a way to say “draw scrollbars now for testing" 6:23 PM <smfr> s/draw/make visible/ 6:23 PM <tonikitoo> (For me to look at) 6:24 PM <tonikitoo> Hum, thought of this too. The hardest part of testing this on mac is that overlay scrollbars only show up when actually scrolling. 6:25 PM <tonikitoo> A always on mode for it could help. 6:31 PM <tonikitoo> smfr: So, to wrap up: a always-on mode for overlay scrollbars + a mismatch ref test would make you happy with it? 6:32 PM <tonikitoo> IIRC webkit/gtk+ has its overlay scrollbars always on. 6:34 PM <smfr> tonikitoo: yes! 6:35 PM <smfr> tonikitoo: probably two separate patches 6:35 PM <smfr> tonikitoo: also note that overlay scrollbars have three modes: hidden, narrow, wide 6:37 PM <tonikitoo> Sounds good. If my understanding is correct, 'wide' happens when scrolls (say with mouse wheel) gets triggered with mouse is hovering the scrollbar, right? 6:37 PM <tonikitoo> Where 'narrow' is the thumb-only mode. 6:38 PM <tonikitoo> smfr: does it sounds correct? 6:38 PM <smfr> right 6:38 PM <smfr> ideally we could call internals to set the bars in either mode 6:38 PM <tonikitoo> K. Will give it a try. Thanks!