Created attachment 131959 [details] evemu I have a Lenovo Thinkpad X1 Carbon Generation 4, on Fedora 26 KDE with libinput-1.7.3-1.fc26.x86_64. The touchpad settings are horrible and there's no way to change them besides modifying source files and recompiling lib-input. Acceleration is not necessary nor wanted on a touchpad of this size and turning it off (TOUCHPAD_ACCELERATION = 1.0) provides a better experience which more closely resembles Windows with Synaptic drivers. Secondly, small movements, such as moving the cursor in a small circle (an example of which is provided in the attachment), is very janky and unresponsive independent of speed.
There's also a problem with slow movements which for some reason turns decelerates the pointer speed enormously which makes it hard to target buttons and which do not resemble Synaptic or Windows defaults nor is necessary for accuracy on such a touchpad. These settings may be sane for most touchpads but they are not in this case so please provide means for changing them without recompiling.
# Size in mm: 100x57 is this correct for your touchpad? I just tried this by returning 1.0 * TP_MAGIC_SLOWDOWN from touchpad_accel_profile_linear() which I believe is what your patch you posted on IRC does. The result is... odd. It's way too slow for fast movement, it takes multiple swipes to get across the screen, it's too fast for slow movements - pixel precision is painful. So I'm not sure what's going on, but I have a hard time believing this works that much better on the X1 than on the devices I have here - it's (almost) the same hardware. My touchpad is the same size as yours. The jankyness at slow speed is an effect of bug 100436, afaict but I haven't had time to debug that bit yet.
The touchpad dimensions are correct. No acceleration, corresponding to TOUCHPAD_ACCELERATION = 1.0, is the default setting in Windows with Synaptic drivers. Not only is it the default, which seems to me alone should warrant the possibility of such a setting in Libinput, it is also a sane default because no acceleration makes for predictable cursor movement. Predictability is the key here, because although a single swipe alone cannot cross the whole screen, learning to double-swipe with high accuracy is easy, in contrast to achieving the same accuracy with threshold activated, speed dependent cursor acceleration. In Windows, it's not to fast for slow movements and pixel precision is certainly not awful, though with no acceleration that's certainly true in Libinput because of the two previously mentioned issues -- a) small movements are incorrectly registered or not registered at all, as shown in the previous attachment and b) slow movements have a too steep deceleration curve.
(In reply to t.soernes from comment #3) > The touchpad dimensions are correct. No acceleration, corresponding to > TOUCHPAD_ACCELERATION = 1.0, is the default setting in Windows with Synaptic > drivers. fwiw, I have a new Dell XPS here with a synaptics i2c touchpad and this is *not* the default. Did you toggle the EPP checkbox to get the flat acceleration profile? I'm willing to merge a patch to add a flat acceleration profile for touchpads, but I don't think I have the time in the foreseeable future to write that patch, I have a bunch of other things on my todo list right now.
Duplicate of bug 98839. The fix for bug 98839 resolves the issue with not responding to small movements, and janky cursor movement when moving in a small circle. I have also re-tested the fix for bug 98839 on an X1 Carbon gen 4 today! It works well. Due for release in libinput 1.10.
Duplicate of bug 98839. You will find libinput 1.10 is better for the X1 Carbon gen4. *** This bug has been marked as a duplicate of bug 98839 ***
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