Menu Keymaps

A keymap can operate as a menu as well as defining bindings for keyboard keys and mouse buttons. Menus are usually actuated with the mouse, but they can function with the keyboard also. If a menu keymap is active for the next input event, that activates the keyboard menu feature.

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Licensed under the GNU GPL license.
https://www.gnu.org/software/emacs/manual/html_node/elisp/Menu-Keymaps.html