tmux: add 'focusEvents'

With `tmux-sensible` being disabled by default, add an easy toggle to
enable this functionality.

Disabled by default, as in upstream `tmux`.

modules/programs/tmux.nix

@@ -95,6 +95,7 @@ let
     ''}
 
     set  -g mouse             ${boolToStr cfg.mouse}
+    set  -g focus-events      ${boolToStr cfg.focusEvents}
     setw -g aggressive-resize ${boolToStr cfg.aggressiveResize}
     setw -g clock-mode-style  ${if cfg.clock24 then "24" else "12"}
     set  -s escape-time       ${toString cfg.escapeTime}
@@ -191,6 +192,15 @@ in {
         '';
       };
 
+      focusEvents = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          On supported terminals, request focus events and pass them through to
+          applications running in tmux.
+        '';
+      };
+
       historyLimit = mkOption {
         default = 2000;
         example = 5000;

tests/modules/programs/tmux/default-shell.conf

@@ -19,6 +19,7 @@ set -g mode-keys   emacs
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/disable-confirmation-prompt.conf

@@ -19,6 +19,7 @@ bind-key -N "Kill the current pane" x kill-pane
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/emacs-with-plugins.conf

@@ -19,6 +19,7 @@ set -g mode-keys   emacs
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize on
 setw -g clock-mode-style  24
 set  -s escape-time       500

tests/modules/programs/tmux/mouse-enabled.conf

@@ -17,6 +17,7 @@ set -g mode-keys   emacs
 
 
 set  -g mouse             on
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/prefix.conf

@@ -22,6 +22,7 @@ bind -N "Send the prefix key through to the application" \
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/shortcut-without-prefix.conf

@@ -23,6 +23,7 @@ bind C-a last-window
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize off
 setw -g clock-mode-style  12
 set  -s escape-time       500

tests/modules/programs/tmux/vi-all-true.conf

@@ -19,6 +19,7 @@ set -g mode-keys   vi
 
 
 set  -g mouse             off
+set  -g focus-events      off
 setw -g aggressive-resize on
 setw -g clock-mode-style  24
 set  -s escape-time       500