enable middle-click scroll

This transforms x/y movement into scroll events when the middle-click
button is held on an input device. It compensates for the
less-than-perfect scroll wheel position on my otherwise-great new
trackball.

Remove the variable, or set it to something other than True, to prevent
the task from being run.

group_vars/all

@@ -205,3 +205,5 @@ himawaripy:
     run_boot_delay: 2min
     run_on: trusted
     flags: --auto-offset --level 4
+
+middle_click_scroll: True

roles/x/files/30-scroll.conf

@@ -0,0 +1,6 @@
+Section "InputClass"
+        Identifier "libinput middle click scroll"
+        Driver "libinput"
+        Option "ScrollMethod" "button"
+        Option "ScrollButton" "2"
+EndSection

roles/x/tasks/main.yml

@@ -24,6 +24,10 @@
 - name: Add user to video group
   user: name={{ user.name }} groups=video append=yes
 
+- name: Enable middle-click scrolling
+  copy: src=30-scroll.conf dest=/etc/X11/xorg.conf.d/30-scroll.conf
+  when: middle_click_scroll is defined and middle_click_scroll == True
+
 - include: sxhkd.yml
 - include: unclutter.yml
 - include: autorandr.yml