move debouncing logic to separate Debouncer class, and use it for list view

While the normal GUI is re-rendered at most every 100 msec, the list is
re-rendered at most every second (since it is very expensive to render).

webroot/js/gui.js

@@ -1,4 +1,5 @@
 import * as domlib from './domlib';
+import * as lib from './lib';
 import {MenuView} from './element/menu';
 import Navigo from '../node_modules/navigo/lib/navigo';
 import View from './view';
@@ -11,8 +12,14 @@ const router = new Navigo(null, true, '#'),
 
 export {router};
 
+
 let init = false,
-	currentView = new View();
+	currentView = new View(),
+	debouncer = new lib.Debouncer(GUI_RENDER_DEBOUNCER_TIME, "gui render");
+
+export function render () {
+	debouncer.run(renderView);
+}
 
 function renderView () {
 	if (!document.body) {
@@ -36,26 +43,6 @@ function renderView () {
 }
 
 
-let renderDebounceTimer = null,
-	numRenderCallsSkipped = 0;
-
-export function render () {
-	if (renderDebounceTimer == null) {
-		renderView();
-		renderDebounceTimer = window.setTimeout(() => {
-			renderDebounceTimer = null;
-			if (numRenderCallsSkipped > 0) {
-				console.log("skipped " + numRenderCallsSkipped + " render calls; calling render() now");
-				numRenderCallsSkipped = 0;
-				render();
-			}
-		}, GUI_RENDER_DEBOUNCER_TIME);
-	} else {
-		console.log("skip rendering");
-		numRenderCallsSkipped++;
-	}
-}
-
 export function setView (toView) {
 	currentView.unbind();
 	currentView = toView;

webroot/js/lib.js

@@ -23,3 +23,31 @@ export function FromNowAgo(timeString) {
 	time /= 24;
 	return Math.round(time) + ' d';
 }
+
+
+/// Suppresses multiple rapid calls to a function, and instead calls the target function when a timeout has elapsed.
+export class Debouncer {
+	constructor (timeoutMsec, description) {
+		this.timeoutMsec = timeoutMsec;
+		this.desc = description;
+
+		this.timer = null;
+		this.numCallsSkipped = 0;
+	}
+
+	run (actualFunction) {
+		if (this.timer == null) {
+			actualFunction();
+			this.timer = window.setTimeout(() => {
+				this.timer = null;
+				if (this.numCallsSkipped > 0) {
+					console.log("skipped " + this.numCallsSkipped + " " + this.desc + " calls; running " + this.desc + " now");
+					this.numCallsSkipped = 0;
+					this.run(actualFunction);
+				}
+			}, this.timeoutMsec);
+		} else {
+			this.numCallsSkipped++;
+		}
+	}
+};

webroot/js/view/list.js

@@ -1,5 +1,6 @@
 import * as domlib from '../domlib';
 import * as gui from '../gui';
+import * as lib from '../lib';
 import * as socket from '../socket';
 import * as store from '../store';
 import config from '../config';
@@ -10,6 +11,7 @@ export class ListView extends View {
 
 	constructor () {
 		super();
+		this.debouncer = new lib.Debouncer(1000, "list render");
 		const table = domlib.newAt(this.el, 'table'),
 			thead = domlib.newAt(table, 'thead');
 
@@ -387,6 +389,10 @@ export class ListView extends View {
 	}
 
 	render () {
+		this.debouncer.run(this.renderView);
+	}
+
+	renderView () {
 		if (this.editing && this.tbody) {
 			return;
 		}