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I've been planning to switch to using libinput instead of the Synaptics driver, most notably to be able to use libinput-gestures.

However, after trying it out (everything seems to work, btw) I noticed that the 2-finger scrolling behaviour seems to be different on libinput. Basically, it only scrolls when I'm physically touching the touchpad. What I usually do with Synaptics when scrolling through long documents/webpages/... is briefly flicking my fingers on the touchpad and letting it keep scrolling until it slows down and stops. On libinput, it will start scrolling as expected, but it will stop instantly when I remove my fingers from the touchpad.

I really like that idea of giving momentum to the content as it scrolls, it feels natural to me at this point, so if possible I'd like to know if that's something that can be done on libinput.

Thanks a lot for your answers !

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You're talking about "kinetic scrolling". If you're using GNOME and really want kinetic scrolling now, you could try applying this patch and building GNOME. Or wait until it's implemented in your desktop environment of choice.

libinput documentation says:

The X.Org synaptics driver implemented kinetic scrolling in the driver. It measures the scroll speed and once the finger leaves the touchpad the driver keeps sending scroll events for a predetermined time. This effectively provides for kinetic scrolling without client support but triggers an unfixable bug: the client cannot know that the events are from a kinetic scroll source. Scroll events in X are always sent to the current cursor position, a movement of the cursor after lifting the finger will send the kinetic scroll events to the new client, something the user does not usually expect. A key event during the kinetic scroll procedure causes side-effects such as triggering zoom.

libinput does not implement kinetic scrolling for touchpads. Instead it provides the libinput_event_pointer_get_axis_source() function that enables callers to implement kinetic scrolling on a per-widget basis, see Scroll sources.

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    Thank you for your answer. It's true that kinetic scrolling seems to cause issues when it's enabled, like in the Synaptics driver, I've had that zooming problem happen quite a few times personnally. Would have been nice if libinput let user choose their preferred behaviour and set it as disabled by default, though. – Philippe Lepaffe Nov 18 '16 at 16:06

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