Problem with fallback scrolling within GtkScrolledWindow
I have no kinetic scrolling in most applications when two-finger scrolling on my laptop touchpad. I'm not sure, but I think it used to work on this machine with xorg and the synaptics driver, and that it's not working now due to libinput. They say applications should be responsible for kinetic scrolling now, but did they intend that literally? Even if it needs to be handled client-side, I think there should be consistent support in gtk, and some global gsettings instead of apps having to provide their own options. It should be available as an option for mouse scrollwheels as well as touch devices, because some mice have wheels with no clicker, or the clicker can be turned off, and I think kinetic scrolling would be suitable for those.
At the moment the only mention of "kinetic" in GTK's API reference is for GtkScrolledWindow, and AFAICT it only works for gestures on touchscreens, not touchpad or mousewheel scrolling. Gedit and evince are the only apps I know of with touchpad kinetic scrolling. Evince seems to have implemented it in its own code for many years, but I can't work out how gedit manages it.