Override keyboard shortcuts in Gmail

keyboard.user.js

// ==UserScript==
// @name         Gmail Keyboard Shortcuts
// @namespace    com.gmail.keyboard
// @version      1.0.4
// @description  Override keyboard shortcuts in Gmail
// @author       Dan Hlavenka
// @updateURL    https://gist.githubusercontent.com/DanH42/ab83bf856abc7731bec0b0c35bef155d/raw
// @match        https://mail.google.com/mail/*
// @grant        none
// ==/UserScript==

// Custom shortcuts
var KEYBOARD_OVERRIDES = {
	"sa": "*a", // Select all
	"sn": "*n", // Select none
	"sr": "*r", // Select read
	"su": "*u", // Select unread
	"s*": "*s", // Select starred
	"st": "*t", // Select unstarred

	"mr": "I",  // Mark read
	"mu": "U",  // Mark unread

	"g*": "gs", // Goto starred
	"gs": "gt", // Goto Sent

	"*": "s",   // Star

	"`c": "c",  // Compose
	"`/": "/",  // Search

	// Macros

	"zs": "*u  I  *n  gi  u", // Select unread, mark read, select none, goto inbox, reload

	// Unchanged shortcuts

	"gi": "gi", // Goto inbox
	"gd": "gd", // Goto Drafts
	"ga": "ga", // Goto all mail
	"u": "u",   // Back to threadlist (refresh)
	"j": "j",   // Down
	"k": "k",   // Up
	"x": "x",   // Selext conversation
	"e": "e",   // Archive
	"+": "+",   // Mark important
	"=": "+",   // Mark important, but you didn't hold shift
	"-": "-",   // Mark unimportant
	"?": "?",   // Help (won't be accurate, but useful for editing shortcuts here)
};

// Time in ms to wait between simulated keypresses
var MACRO_DELAY = 15;

var KEY_EVENTS = ["keydown", "keypress", "keyup"];

(function(){
	'use strict';

	// Don't run in frames
	if(window !== parent)
		return;

	var capsWarningTimeout = null;

	// Check if the currently focused element is a textbox
	var isActiveElementEditable = function(){
		if(document.activeElement.isContentEditable)
			return true;
		if(["INPUT", "TEXTAREA", "IFRAME"].indexOf(document.activeElement.tagName) !== -1)
			return true;
		return false;
	};

	// Simulate a keypress
	var pressKey = function(key){
		// Space = pause
		if(key === " ")
			return;

		var el = document.activeElement;
		var keyCode = key.charCodeAt(0);

		for(var i = 0; i < KEY_EVENTS.length; i++)
			setTimeout(keyEvent.bind(this, el, KEY_EVENTS[i], key, keyCode), i * 5);
	};

	var keyEvent = function(el, type, key, keyCode){
		var event = document.createEvent("Events");

		if(event.initEvent)
			event.initEvent(type, true, true);

		event.keyCode = keyCode;
		event.charCode = keyCode;
		event.which = keyCode;
		event.key = key;
		if(key.toLowerCase() !== key)
			event.shiftKey = true;

		el.dispatchEvent(event);
	};

	// Keep track of multi-character shortcuts
	var stack = "";
	var stackTimeout = null;
	var startStackTimeout = function(){
		if(stackTimeout)
			clearTimeout(stackTimeout);
		stackTimeout = setTimeout(clearStack, 500);
	};
	var clearStack = function(){
		if(stackTimeout){
			clearTimeout(stackTimeout);
			stackTimeout = null;
		}
		stack = "";
	};

	// Check if a keypress matches at least one viable override
	var isPossibleMatch = function(key){
		var search = stack + key;
		for(var command in KEYBOARD_OVERRIDES){
			if(command.startsWith(search))
				return true;
		}
		return false;
	};

	var handleKeyEvent = function(e){
		if(
			// Don't respond to our own events
			!e.isTrusted ||
			// Don't capture keypresses that use modifier keys
			e.ctrlKey || e.altKey || e.metaKey ||
			// Don't capture keypresses in text boxes
			isActiveElementEditable() ||
			// Only handle single-character keys
			e.key.length !== 1
		)
			return;

		// Detect caps lock
		if(e.key !== e.key.toLowerCase() && e.shiftKey === false)
			showCapsWarning();

		// Suppress keyup/keydown events without any additional logic
		if(e.type !== "keypress"){
			e.stopPropagation();
			return;
		}

		// Only add a keypress to the stack if it's a potential match for a command
		if(isPossibleMatch(e.key)){
			stack += e.key;
			if(KEYBOARD_OVERRIDES[stack]){
				var action = KEYBOARD_OVERRIDES[stack];
				console.log("MATCH", stack);
				setTimeout(console.log.bind(this, "DONE"), action.length * MACRO_DELAY);
				clearStack();

				// Perform an action if we have a match
				for(var i = 0; i < action.length; i++)
					setTimeout(pressKey.bind(this, action[i]), i * MACRO_DELAY);
			}else{
				// If the keypress isn't an exact match (multi-key shortcuts), reset the timer
				startStackTimeout();
			}
		}else{
			// If the keypress won't result in a valid command, clear the stack
			clearStack();
		}

		// Cancel the keypress
		e.stopPropagation();
		e.preventDefault();
		return false;
	};

	var showCapsWarning = function(){
		capsWarningTimeout && clearTimeout(capsWarningTimeout);

		var oldCapsWarning = document.getElementById('capsWarning');
		oldCapsWarning && oldCapsWarning.remove();

		var capsWarning = document.createElement('div');
		capsWarning.id = "capsWarning";
		capsWarning.style.background = "rgba(0, 0, 0, .9)";
		capsWarning.style.color = "white";
		capsWarning.style.position = "fixed";
		capsWarning.style.top = "50%";
		capsWarning.style.left = "50%";
		capsWarning.style.width = "200px";
		capsWarning.style.height = "40px";
		capsWarning.style.marginTop = "-30px";
		capsWarning.style.marginLeft = "-110px";
		capsWarning.style.fontSize = "32px";
		capsWarning.style.textAlign = "center";
		capsWarning.style.padding = "20px";
		capsWarning.style.borderRadius = "10px";
		capsWarning.style.opacity = "1";
		capsWarning.style.transition = "opacity 2s";
		capsWarning.innerText = "Caps Lock";

		document.body.appendChild(capsWarning);

		capsWarningTimeout = setTimeout(function(){
			capsWarning.style.opacity = "0";

			capsWarningTimeout = setTimeout(function(){
				capsWarning && capsWarning.remove();
				capsWarningTimeout = null;
			}, 2100);
		}, 100);
	};

	for(var i = 0; i < KEY_EVENTS.length; i++)
		window.addEventListener(KEY_EVENTS[i], handleKeyEvent, true);
})();