I just got a 4-button trackball mouse without a mousewheel (many of those don't have a mousewheel, for some reason), and I would like to make one of those buttons act like the middle mouse button (for the purpose of autoscrolling). The 4-buttons, by default, are for left click, right click, back and forward (i.e. back/forward a page while web browsing). I changed the back/forward buttons to act like page-up and page-down (using xte and xbindkeys as suggested in an answer to a question somewhere on StackExchange), but I wasn't completely satisfied with that; so, I'd like to turn one of those buttons (the back button) into the middle mouse button, and do something creative with the other one, but I don't know how to make one mouse button simulate another (nor do I know the name of the middle mouse button). I do, however, know how to make a mouse button represent a key or key combination on a keyboard (or how to make it launch a program or script). Edit: I found out a way to remap mouse buttons, but it doesn't seem to work with Button-2 (that's the right button, right? I'm wanting the button that makes a circle with arrows appear and when you move the mouse it scrolls in the direction you move it; also, when you click a link with it, it opens it in a new tab, and such).
Anyway, here's what I attempted putting in my .xbindkeysrc file:
"xte 'mouseclick 2'"
b:8
Note: Pressing left-click and right-click at the same time doesn't simulate the middle mouse button on my OS (Xubuntu 17.04) with my mouse.
xbindkeysandxteare additional applications that intercept X events. It's cleaner to just change the button map, e.g. withxinput --set-button-mapor via properties, depending on how your trackball works. Seeman xinput, andman evdevif you want to record the buttonmap in anxorg.confto make it work automatically on boot.