#StackBounty: #drivers #windows-registry #touchpad #thinkpad #synaptics-touchpad Synaptics Trackpad Hysteresis/Backlash/Noise Rejection

Bounty: 50

I am using a Lenovo ThinkPad T480 with a Synaptics trackpad, running Windows 10. The issue that I am facing is with a feature that appears to come with the Synaptics drivers (since it goes away when I remove the driver) which prevents small movements from being registered on the cursor, when starting from rest or reversing the cursor direction.

This is similar to mechanical "backlash" that is usually observed when interfacing multiple gears, where there is a small "dead zone" when direction is reversed. Basically, when starting off from a stationary position on the trackpad, I have to first move my finger about 1mm before the cursor starts moving. If I reverse direction, my finger needs to move 2mm before the cursor starts moving in the opposite direction.

Although this is likely a feature that prevents movement of the cursor when tap-clicking, it greatly reduces the precision that I require to work productively.

Under Linux, I have observed people referring to this as a "noise cancellation" feature,

The synaptics has a built-in noise cancellation based on hysteresis. This means that incoming coordinates actually shift a box of predefined dimensions such that it covers the incoming coordinate, and only the boxes own center is used as input. Obviously, the smaller the box the better, but the likelyhood of noise motion coming through also increases.

where the parameters, HorizHysteresis and VertHysteresis can be used to adjust this box size.

I have been digging through the Windows 10 registry directories, HKEY_CURRENT_USERSOFTWARESynapticsSynTP and ComputerHKEY_LOCAL_MACHINESOFTWARESynapticsSynTP, looking for similar values, but to no avail.

  • Where is the registry value for this that I can use to reduce the level of noise rejection on the trackpad, in Windows 10?
  • Would it be possible to add one? If not, what could be an alternative solution?
  • Is there a different driver that I could possibly use?

Here is a similar post that unfortunately never got a solution.


Get this bounty!!!

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