Make preferences less janky, preload panes on hover, allow panes to delay visibility until promise resolves (#3363)

Prevents flashes of unlocalized labels and controls without values set.
Makes switching panes feel speedier overall because of preloading.

I thought there was an issue for the flashes of uninitialized content but can't
find it now.

chrome/content/zotero/preferences/preferences.js

@@ -37,7 +37,8 @@ var Zotero_Preferences = {
 		this.content = document.getElementById('prefs-content');
 		this.helpContainer = document.getElementById('prefs-help-container');
 
-		this.navigation.addEventListener('select', () => this._onNavigationSelect());
+		this.navigation.addEventListener('mouseover', event => this._handleNavigationMouseOver(event));
+		this.navigation.addEventListener('select', () => this._handleNavigationSelect());
 		document.getElementById('prefs-search').addEventListener('command',
 			event => this._search(event.target.value));
 		
@@ -124,18 +125,28 @@ var Zotero_Preferences = {
 		}
 	},
 
-	_onNavigationSelect() {
-		for (let child of this.content.children) {
-			if (child !== this.helpContainer) {
-				child.setAttribute('hidden', true);
-			}
+	async _handleNavigationMouseOver(event) {
+		if (event.target.tagName === 'richlistitem') {
+			await this._loadPane(event.target.value);
 		}
+	},
+
+	async _handleNavigationSelect() {
 		let paneID = this.navigation.value;
 		if (paneID) {
-			this.content.scrollTop = 0;
+			let pane = this.panes.get(paneID);
 			document.getElementById('prefs-search').value = '';
-			this._search('');
-			this._loadAndDisplayPane(paneID);
+			await this._search('');
+			await this._showPane(paneID);
+			this.content.scrollTop = 0;
+			for (let child of this.content.children) {
+				if (child !== this.helpContainer && child !== pane.container) {
+					child.hidden = true;
+				}
+			}
+
+			this.helpContainer.hidden = !pane.helpURL;
+			document.getElementById('prefs-subpane-back-button').hidden = !pane.parent;
 		}
 		Zotero.Prefs.set('lastSelectedPrefPane', paneID);
 	},
@@ -201,20 +212,31 @@ var Zotero_Preferences = {
 
 		this.panes.set(id, {
 			...options,
-			imported: false,
+			loaded: false,
 			container,
 		});
 	},
 
 	/**
-	 * Display a pane's content, alongside any other panes already showing.
-	 * If the pane is not yet loaded, it will be loaded first.
+	 * Load a pane if not already loaded.
 	 *
 	 * @param {String} id
+	 * @return {Promise<void>}
 	 */
-	_loadAndDisplayPane(id) {
+	async _loadPane(id) {
 		let pane = this.panes.get(id);
-		if (!pane.imported) {
+		if (pane.loaded) {
+			return;
+		}
+		if (pane.loadPromise) {
+			await pane.loadPromise;
+			return;
+		}
+		
+		let rest = async () => {
+			// Hack - make sure the following code does not run synchronously so we can set loadPromise immediately
+			await Zotero.Promise.delay();
+			
 			if (pane.scripts) {
 				for (let script of pane.scripts) {
 					Services.scriptloader.loadSubScript(script, window);
@@ -237,17 +259,34 @@ var Zotero_Preferences = {
 				? MozXULElement.parseXULToFragment(markup, dtdFiles)
 				: this._parseXHTMLToFragment(markup, dtdFiles);
 			contentFragment = document.importNode(contentFragment, true);
+
 			this._initImportedNodesPreInsert(contentFragment);
 			pane.container.append(contentFragment);
-			pane.imported = true;
-			this._initImportedNodesPostInsert(pane.container);
-		}
+
+			await document.l10n.ready;
+			await document.l10n.translateFragment(pane.container);
+			await this._initImportedNodesPostInsert(pane.container);
+
+			pane.loaded = true;
+		};
+		pane.loadPromise = rest();
+		await pane.loadPromise;
+	},
+
+	/**
+	 * Display a pane's content, alongside any other panes already showing.
+	 * If the pane is not yet loaded, it will be loaded first.
+	 *
+	 * @param {String} id
+	 * @return {Promise<void>}
+	 */
+	async _showPane(id) {
+		await this._loadPane(id);
+
+		let pane = this.panes.get(id);
 
 		pane.container.hidden = false;
 		pane.container.children[0].dispatchEvent(new Event('showing'));
-
-		let backButton = document.getElementById('prefs-subpane-back-button');
-		backButton.hidden = !pane.parent;
 	},
 	
 	_parseXHTMLToFragment(str, entities = []) {
@@ -334,10 +373,10 @@ ${str}
 	 * @param {Element} container
 	 * @private
 	 */
-	_initImportedNodesPostInsert(container) {
+	async _initImportedNodesPostInsert(container) {
 		let attachToPreference = (elem) => {
 			if (this._observerSymbols.has(elem)) {
-				return;
+				return Promise.resolve();
 			}
 			
 			let preference = elem.getAttribute('preference');
@@ -382,9 +421,10 @@ ${str}
 			elem.addEventListener('change', this._syncToPrefOnModify.bind(this));
 
 			// Set timeout before populating the value so the pane can add listeners first
-			setTimeout(() => {
+			return new Promise(resolve => setTimeout(() => {
 				this._syncFromPref(elem, elem.getAttribute('preference'));
-			});
+				resolve();
+			}));
 		};
 		
 		let detachFromPreference = (elem) => {
@@ -395,9 +435,13 @@ ${str}
 			}
 		};
 
+		let awaitBeforeShowing = [];
+
 		// Activate `preference` attributes
+		// Do not await anything between here and the 'load' event dispatch below! That would cause 'syncfrompreference'
+		// events to be fired before 'load'!
 		for (let elem of container.querySelectorAll('[preference]')) {
-			attachToPreference(elem);
+			awaitBeforeShowing.push(attachToPreference(elem));
 		}
 		
 		new MutationObserver((mutations) => {
@@ -406,6 +450,7 @@ ${str}
 					let target = mutation.target;
 					detachFromPreference(target);
 					if (target.hasAttribute('preference')) {
+						// Don't bother awaiting these
 						attachToPreference(target);
 					}
 				}
@@ -443,9 +488,15 @@ ${str}
 		}
 
 		for (let child of container.children) {
-			child.dispatchEvent(new Event('load'));
+			let event = new Event('load');
+			event.waitUntil = (promise) => {
+				awaitBeforeShowing.push(promise);
+			};
+			child.dispatchEvent(event);
 		}
 
+		await Promise.allSettled(awaitBeforeShowing);
+
 		// If this is the first pane to be loaded, notify anyone waiting
 		// (for tests)
 		this._firstPaneLoadDeferred.resolve();
@@ -461,7 +512,7 @@ ${str}
 	 *
 	 * @param {String} [term]
 	 */
-	_search(term) {
+	_search: Zotero.Utilities.Internal.serial(async function (term) {
 		// Initial housekeeping:
 
 		// Clear existing highlights
@@ -480,11 +531,13 @@ ${str}
 			hidden.ariaHidden = false;
 		}
 
+		// Hide help button by default - _handleNavigationSelect() will show it when appropriate
+		this.helpContainer.hidden = true;
+
 		if (!term) {
 			if (this.navigation.selectedIndex == -1) {
 				this.navigation.selectedIndex = 0;
 			}
-			this.helpContainer.hidden = !this.panes.get(this.navigation.value)?.helpURL;
 			return;
 		}
 
@@ -500,7 +553,7 @@ ${str}
 				pane.container.hidden = true;
 			}
 			else {
-				this._loadAndDisplayPane(id);
+				await this._showPane(id);
 			}
 		}
 
@@ -580,7 +633,7 @@ ${str}
 				}
 			}
 		}
-	},
+	}),
 
 	/**
 	 * Search for the given term (case-insensitive) in the tree.

chrome/content/zotero/preferences/preferences_cite.xhtml

@@ -23,7 +23,7 @@
     ***** END LICENSE BLOCK *****
 -->
 
-<vbox id="zotero-prefpane-cite" onload="Zotero_Preferences.Cite.init()">
+<vbox id="zotero-prefpane-cite" onload="event.waitUntil(Zotero_Preferences.Cite.init())">
 	<vbox class="main-section" id="styles">
 		<html:h1>&zotero.preferences.cite.styles;</html:h1>
 

chrome/content/zotero/preferences/preferences_export.jsx

@@ -31,11 +31,11 @@ var VirtualizedTable = require('components/virtualized-table');
 var { makeRowRenderer } = VirtualizedTable;
 
 Zotero_Preferences.Export = {
-	init: Zotero.Promise.coroutine(function* () {
+	init: async function () {
 		this.updateQuickCopyInstructions();
-		yield this.populateQuickCopyList();
-		yield this.populateNoteQuickCopyList();
-	}),
+		await this.populateQuickCopyList();
+		await this.populateNoteQuickCopyList();
+	},
 	
 	
 	getQuickCopyTranslators: async function () {

chrome/content/zotero/preferences/preferences_export.xhtml

@@ -23,7 +23,7 @@
     ***** END LICENSE BLOCK *****
 -->
 
-<vbox id="zotero-prefpane-export" onload="Zotero_Preferences.Export.init()">	
+<vbox id="zotero-prefpane-export" onload="event.waitUntil(Zotero_Preferences.Export.init())">	
 	<groupbox id="zotero-prefpane-export-groupbox">
 		<vbox>
 			<label><html:h2>&zotero.preferences.quickCopy.caption;</html:h2></label>

test/content/support.js

@@ -113,14 +113,7 @@ var loadPrefPane = async function (paneName) {
 	var win = await loadWindow("chrome://zotero/content/preferences/preferences.xhtml", {
 		pane: id
 	});
-	var doc = win.document;
-	while (true) {
-		var pane = doc.getElementById(id);
-		if (pane) {
-			break;
-		}
-		await delay(1);
-	}
+	await win.Zotero_Preferences.waitForFirstPaneLoad();
 	return win;
 };