// ==UserScript==
// @name        gmail_unread_toggle
// @namespace	http://ma.la/
// @include     http://mail.google.com/mail/*
// @include     https://mail.google.com/mail/*
// @version     1.0
// ==/UserScript==

(function(){
	var f = document.getElementById("s");
	if(f){
		var q = f.elements[0];
		var btn = document.createElement("button");
		btn.addEventListener("click", function(){
			if(q.value.indexOf("is:unread") == -1){
				q.value += " is:unread"
			} else {
				q.value = q.value.replace(/\s*is:unread\s*/," ")
			}
		}, true);
		btn.innerHTML = "is:unread";
		f.appendChild(btn);
	}
})();