I was using this tool already in 2005(!) and recently re-discovered it when I set up again a multi-monitor multi-system desktop at home. Synergy allows to share keyboard and mouse between different systems by defining virtual expansions at the edges of the ‘server’. Layout is configurable. It is even possible to share the input between different operating systems!
Use the nightly build-download-archive, because for the stable release they charge at least 10$ (since 2014 ).
- install at both systems
- define one as server
- enter the server-IP at the client
- configure a expansion-setup for the screens, done!
edit 20190319: url for the repo not working anymore, use https://sourceforge.net/projects/synergy-stable-builds/ (v1.8.8) instead. Worked on OSX <--> Win10.