With xf86-input-synaptics I used to have both edge and two-finger scrolling
methods enabled at same time, but with xf86-input-libinput I can't.
Steps to Reproduce:
xinput set-prop 'SynPS/2 Synaptics TouchPad' 'libinput Scroll Method Enabled' 1 1 0
X Error of failed request: BadValue (integer parameter out of range for operation)
Major opcode of failed request: 131 (XInputExtension)
Minor opcode of failed request: 57 ()
Value in failed request: 0x121
Serial number of failed request: 20
Current serial number in output stream: 21
Ability to use two-finger and edge scrolling at same time.
According to bug 90070, this behaviour used to be enabled accidentally.
I'm using Debian Stretch amd64, libinput10 1.2.4-1, xserver-xorg-input-libinput 0.18.0-1.
Yeah, that's a design decision, we won't allow that, sorry.
So, changing second parameter type of libinput_device_config_scroll_set_method to bitmask is out of question? It even won't break ABI: looks like values of enum libinput_config_scroll_method was selected for this purpose.
Sorry if I missed something.
The API is the easy bit, the more difficult bit is making sure the implementation works as expected. And simply said it's too niche a use-case to spend a large amount of time on it.