Fixes bad scroll wheel behavior for external mice. Map extra mouse buttons (3 and 4 out of zero-indexed button list) to forward and back shortcuts in OSX.
This is a very hacky program to get some functionality out of the extra buttons on a mouse that has more buttons than Apple thinks you'd ever use. What it does is map the thumb buttons to forward and back shortcuts that work in web browsers on OSX (as well as in Finder). The shortcuts are Command-[ and Command-].
This also now handles another OSX / macOS annoyance with scroll wheels; a small motion of the wheel (one click) will do nothing. This now intercepts scroll wheel events and translates a single click of the wheel to one line of scrolling. It will otherwise work as before, except that no matter how slow you move your scroll wheel, one click == one line, always
I am not an OSX developer so this is not guaranteed to be good code, or recommended for anyone ever. You should test it from the terminal before trying to make it start up with your computer.
You will need to install Xcode, and then use Xcode to install the command-line tools. After that, you can compile:
gcc -Wall -o mtExtraButtons mtExtraButtons.c -framework ApplicationServices
This program has been tested on only one computer running OSX 10.11 (El Capitan) and macOS 10.12 (Sierra).