The default bindings for menus allow for keyboard selection of menu entries. The selection process is started by pressing <Alt-x>, where x is the distinguishing letter for a menubutton. The underline attribute of a menubutton is used to highlight the appropriate letter. The underline value is a number that specifies a character position, and the count starts at zero. For example, a File menu with a highlighted F is created like this:
menubutton .menubar.file -text File -underline 0 \
When the user types <Alt-f> over the main window, the menu is posted. The case of the highlighted letter is not important.
After a menu is posted, the arrow keys change the selected entry. The <Up> and <Down> keys move within a menu, and the <Left> and <Right> keys move between adjacent menus. The bindings assume that you create your menus from left to right.
If any of the menu entries have a letter highlighted with the -underline option, typing that letter invokes that menu entry. For example, an Export entry that is invoked by typing x can be created like this:
.menubar.file.m add command -label Export -underline 1 \
The <space> and <Return> keys invoke the menu entry that is currently selected. The <Escape> key aborts the menu selection and removes the menu.