How do you make the touchpad ignore touch input from the thumb when it's resting at the bottom of the touchpad?
I'll answer my own question: it's all in the driver and software. Both can implement thumb-rejection, but one must do it.
In the Windows world, Microsoft Precision Touchpads seem to do a much better job of this than typical Synaptics or Elan touchpads using manufacturer-supplied drivers. Still not as good as Apple trackpads sadly.
In the Linux world, the best results I've found require using libinput with the "areas" click method. This defines a line at the bottom of the pad that completely ignored all touches and is used only for clicking. If you don't like the virtual middle-mouse button and your distro doesn't provide an interface for disabling it, put the following in your RC file to turn it into another left-click button: xinput --set-button-map <touchpad id> 1 1 3
If using the Synaptics driver, there are more customization options, but it can be trickier to set up. The information in some or all of these links will help:
- https://wiki.archlinux.org/index.php/Touchpad_Synaptics#Bottom_edge_correction
- https://askubuntu.com/questions/221664/how-to-tune-touchpad-for-smaller-area
- https://forums.linuxmint.com/viewtopic.php?f=208&t=198752
- https://ubuntuforums.org/showthread.php?t=1440747
- https://ubuntuforums.org/showthread.php?t=2204700#post13214229
- https://bugzilla.kernel.org/attachment.cgi?id=164671
- http://pastebin.com/raw/4v9JP2pe
- https://wiki.debian.org/SynapticsTouchpad