http://d.hatena.ne.jp/Griever/20090322/1237726174

OperaStyle_menuAccessKey.uc.js

// ==UserScript==
// @name           OperaStyle_menuAccessKey.uc.js
// @namespace      http://d.hatena.ne.jp/Griever/
// @author         Griever
// @include        main
// @version        0.0.2くらい
// @compatibility  Firefox 4
// ==/UserScript==

(function(){

window.menuAccessKey = {
	hintkeys: new String('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'),
	addTarget: [
		$('contentAreaContextMenu'),
		, $('placesContext')
		, $('backForwardMenu')
		, $('navigator-toolbox')
		, $('browser-bottombox')
		, document.getElementById('tabContextMenu') || 
		  document.getAnonymousElementByAttribute(gBrowser, 'anonid', 'tabContextMenu')
	],

	init: function(){
		this.addTarget.forEach(function(elem){
			if (elem)
				elem.addEventListener('popupshowing', this, false);
		}, this);
		window.addEventListener('unload', this, false);
	},

	uninit: function(){
		this.addTarget.forEach(function(elem){
			if (elem)
				elem.removeEventListener('popupshowing', this, false);
		}, this);
		window.removeEventListener('unload', this, false);
	},

	handleEvent: function(e){
		switch (e.type) {
			case 'unload':
				this.uninit();
				return;
			case 'popupshowing':
				this.popupshowing(e);
				break;
		}
	},

	popupshowing: function(e) {
		var popup = e.originalTarget;
		if (popup.localName.indexOf('popup') == -1)
			return;
		
		var hintkeys = this.hintkeys.toUpperCase();
		
		// popupshown よりは早く動いて欲しい
		var self = this;
		setTimeout(function(){
			// accesskey を付ける要素を取得し、hintkeys から存在する accesskey を削除
			var list = Array.filter(popup.children, function(elem){
				if (!elem.hasAttribute('label') || elem.clientHeight === 0)
					return false;
				
				var accesskey = elem.getAttribute('accesskey');
				if (accesskey) {
					hintkeys = hintkeys.replace(accesskey.toUpperCase(), '');
				}else{
					return true;
				}
			});
			
			self.addAccessKey(list, hintkeys);
		}, 0);

/* アクセスキーを消す
		popup.addEventListener('popuphidden', function(e){
			if (e.target != popup)
				return;
			popup.removeEventListener(e.type, arguments.callee, false);
			self.removeAccessKey(list);
		}, false);
*/
	},

	addAccessKey: function(list, hintkeys){
		list.some(function(elem) {
			if (hintkeys === '')
				return true;

			var key;
			if (new RegExp('[' + hintkeys + ']', "i").test(elem.getAttribute('label'))) {
				key = RegExp.lastMatch.toUpperCase();
				hintkeys = hintkeys.replace(key, '');
			} else {
				key = hintkeys[0];
				hintkeys = hintkeys.substr(1);
			}
			elem.setAttribute("accesskey", key);
		});
	},

	removeAccessKey: function(list){
		list.forEach(function(elem) {
			if (elem)
				elem.removeAttribute("accesskey");
		});
	},

}

window.menuAccessKey.init();

function $(id) document.getElementById(id);

})();