pre.js

//alert user on thrown exceptions
window.onerror = function() {main_body.innerHTML += '<br>Error, press F12 to see JavaScript console';};

//async the css setting, otherwise it applies to first load
css('body', 'transition', 'background-color 0.5s, color 0.5s');

var rebindingkeynumber = -1;
window['changekeybind'] = function(number) {
	css('#c' + rebindingkeynumber, 'font-weight', 'normal'); //if you click on different rebinds in succession, stop rebinding the first
	if (rebindingkeynumber === number) {
		rebindingkeynumber = -1; //if you click the same rebind twice, stop rebinding entirely
		return;
	}
	rebindingkeynumber = number;
	css('#c' + rebindingkeynumber, 'font-weight', 'bold');
}

//links are tabbable only if they aren't keybound
function keybound_links_nontabbable() {
	for (var n in keycoderaw) {
		var possible_link = document.getElementById('l' + n);
		if (possible_link !== null)
			possible_link.setAttribute('tabindex', keyboard_shortcuts_enabled ? '-1' : '0');
	}
}

window['flip_keyboard_enabled'] = function() {
	keyboard_shortcuts_enabled = !keyboard_shortcuts_enabled;
	rebindingkeynumber = -1;
	write_keyboard_shortcut_text();

	for (var n in keycoderaw)
		css('#c' + n, 'font-weight', 'normal');
	keybound_links_nontabbable();
}

//keyboard shortcuts are enabled when the main module is loaded.
document.onkeypress = function(e) {
	if (e.repeat) return; //chrome seems to always give e.repeat=false. use this to diagnose: "document.onkeypress = function(e) {console.log(e.repeat);}"
	if (rebindingkeynumber !== -1) {
		//note: e.which is required, instead of e.charCode, because charCode doesn't support Enter
		switch (e.which) {
		case 0:
			alert('Only glyphs are supported, like letters, numbers, and punctuation. That excludes keys like arrows and Ctrl. This is because of javascript problems.');
			return;
		case 13:
			alert("Enter is a disallowed keybind, because you need Enter to select links when tabbing. Plus, Enter causes trouble with javascript's fromCharCode().");
			return;
		case 32:
			alert('Space is not recommended because it is invisible and will scroll your page down.');
			return;
		}
		//for (var i in keycoderaw) if (keycoderaw[i] === e.which) return; //this is annoying for intermediate state changes
		keycoderaw[rebindingkeynumber] = e.which;
		var key_text = String.fromCharCode(e.which);
		localStorage.setItem('keycode ' + rebindingkeynumber, key_text);
		css('#l' + rebindingkeynumber + '::after', 'content', '\'' + key_text + '\'');
		document.getElementById('c' + rebindingkeynumber).textContent = '[' + key_text + ']';
		css('#c' + rebindingkeynumber, 'font-weight', 'normal');
		rebindingkeynumber = -1;
		return;
	}
	for (var n in keycoderaw) {
		if ((e.which === keycoderaw[n]) && keyboard_shortcuts_enabled) {
			_i(-n - 1);
			return;
		}
	}
	if (e.which === 13) { //trigger onclick() with enter key. 13 = enter key.
		if (typeof document.activeElement.onmousedown === 'function') document.activeElement.onmousedown();
		return;
	}
};

window['change_history_retention'] = function() {
	switch (history_retention) {
		case 0:
			history_retention = 1; break;
		case 1:
			history_retention = 10; break;
		case 10:
			history_retention = 100; break;
		case 100:
			history_retention = 0; break;
	} 
	history_number_option.textContent = 'History kept: ' + history_retention;
	localStorage.setItem('history_retention', history_retention);
	//clear_old_history(); //don't clear it until something happens. otherwise just changing the settings will wipe history.
}


window['flip_page_order'] = function flip_page_order() {
	history_above = !history_above;
	set_page_order();
	localStorage.setItem('history_above', history_above);
};

window['invert_color'] = function() {localStorage.setItem('invert_color', document.body.classList.toggle('nightmode'));};

function insert_history(text) {
	if (history_retention !== 0) {
		var new_history = document.createElement('li');
		new_history.innerHTML = UTF8ToString(text);
		history_container.insertBefore(new_history, history_container.firstChild);
		//history_container.prepend(new_history); //no IE11 support? and prependChild doesn't exist
	}
	while (history_container.childElementCount > history_retention)
		history_container.removeChild(history_container.lastChild);

	css('#history_separator', 'display', history_container.hasChildNodes() ? '' : 'none'); //we toggle on the item count rather than history_retention, because setting history_retention makes the bar appear and disappear. when the option is on the bottom, it wobbles up and down when clicking the History Retention button, which is annoying. also, this makes the bar disappear on the first page, which makes sense.
}

function new_message(text) {
	main_body.innerHTML = UTF8ToString(text);
	keybound_links_nontabbable();
	if (history_above) main_body.scrollIntoView(true);
	else scrollTo(0, 0);
}