When this option is not empty, it will be used for the icon text of the window. This happens only when the 'icon' option is on. Only works if the terminal supports setting window icon text (currently only X11 GUI and terminals with a non-empty 't_IS' option). Does not work for MS-Windows. When Vim was compiled with HAVE_X11 defined, the original icon will be restored if possible X11. When this option contains printf-style '%' items, they will be expanded according to the rules used for 'statusline'. See 'titlestring' for example settings. This option cannot be set in a modeline when 'modelineexpr' is off. not available when compiled without the +statusline feature

(default "")