Set focus events parameter on

tmux.conf

@@ -48,6 +48,7 @@ set -g visual-activity off
 set -g visual-bell off
 set -g visual-silence off
 set -g word-separators " -_@"
+set-option -g focus-events on
 run-shell 'powerline-config tmux setup'
 bind c new-window      -c "#{pane_current_path}"
 bind | split-window -h -c "#{pane_current_path}"