What is the `accessKey` parameter of GM_registerMenuCommand() and how to use it?

Question

I was looking at the GM_registerMenuCommand function in Tampermonkey and I noticed a third parameter called accessKey and thought it is to pass a hotkey to trigger this command.

What's the format of the parameter passed and am I wrong in assuming this is what it does?

I couldn't find documentation on the parameter anywhere. Does anyone here ever used it before?

Answer 1

The syntax for that function is:

GM_registerMenuCommand (menuName, callbackFunction, accessKey)

• Where accessKey, if supplied, must be a single letter of the string passed-in as menuName.
  It is a menu "access key" used to facilitate Good UI by adding keyboard-only support.

From Menu Design Guidelines^{(Number 8)}:

Dropdowns (both menus and boxes) should support not only mouse input, but keys as well. In dropdown menus, access keys should enable users to quickly select a visible option without using the mouse. In a dropdown box, users should be able to type a letter and quickly navigate to options starting with that letter.

^{(Emphasis added.)}

Important: Access keys are different from, and in addition to, any command shortcuts ("hotkeys").

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Here's a sample working Tampermonkey script that illustrates the use:

// ==UserScript==
// @name     _GM_registerMenuCommand demo
// @match    https://stackoverflow.com/questions/56024629/*
// @match    *://YOUR_SERVER.COM/YOUR_PATH/*
// @grant    GM_registerMenuCommand
// ==/UserScript==

/*-- GM_registerMenuCommand (menuName, callbackFunction, accessKey)
*/
GM_registerMenuCommand ("Say Hello", helloFunc, "H");

function helloFunc () {
    console.log ("Say hello to my little script.");
}

If you install and run this via Tampermonkey you will see (click for larger image):

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Notes:

1. Violentmonkey ignores the accessKey parameter, for now.
2. Greasemonkey 4+ has borked this feature.  Per usual.
3. You can set a keyboard command to activate the Tampermonkey icon/menu in Chrome.
4. Keyboard icon activation currently does not seem to work in Firefox, but a workaround is scheduled for Firefox version 67.