At work, I have a desktop with a monitor and a few running tmux sessions. At home, I frequently ssh into that desktop and enter my running tmux sessions. When I ssh from home, I do not want to use X11, so I do not use the -X flag. When I go back to work (after ssh'ing from home) and use those tmux sessions on desktop, I can no longer do anything that would spawn a GUI. I can't open files in evince. When I try use matplotlib, I get a : cannot connect to X server message.After ssh'ing and opening an existing tmux session from home, how do I later reattach the ability to open up GUI stuff on the desktop?The ssh'ing from home seems to make the tmux session forget that it can spawn GUI stuff.EDIT: 
In tmux session, cannot connect to X server after ssh'ing
ssh;x11;tmux
All I need to do is set the DISPLAY environment variable to :0.0. I think the issue was that I am using the fish shell, and I need to use the -x flag to set when doing this:set -x DISPLAY :0.0