vpat 44: scaffold keyboard tab selection focus (#4069)

Do not move focus from the tab onto the editor/input
during keyboard navigation to not change context per
https://www.w3.org/WAI/WCAG21/Understanding/on-input.

Focus will still shift if tab selection changed on mouse click.

Also:

- added focus ring to tabs. Additional mouseup handling
to prevent the focus ring from briefly appearing on click.
- on Escape from within the editor, focus the current
tab.
- on shift-tab from the beginning of the editor,
tab out of the editor to previous element.

chrome/content/scaffold/scaffold.js

@@ -103,6 +103,15 @@ var Scaffold = new function () {
 		});
 
 		document.getElementById('tabpanels').addEventListener('select', event => Scaffold.handleTabSelect(event));
+		document.getElementById('tabs').addEventListener('mousedown', (event) => {
+			// Record if tab selection will happen due to a mouse click vs keyboard nav.
+			if (event.clientX === 0 && event.clientY === 0) return;
+			document.getElementById('tabs').setAttribute("clicked", true);
+		}, true);
+		// Record that click has happened for better focus-ring handling in the stylesheet
+		document.addEventListener("mouseup", (_) => {
+			document.getElementById('tabs').removeAttribute("clicked");
+		});
 		
 		let lastTranslatorID = Zotero.Prefs.get('scaffold.lastTranslatorID');
 		if (lastTranslatorID) {
@@ -157,6 +166,10 @@ var Scaffold = new function () {
 		this.initCodeEditor();
 		this.initTestsEditor();
 
+		this.addEditorKeydownHandlers(_editors.import);
+		this.addEditorKeydownHandlers(_editors.code);
+		this.addEditorKeydownHandlers(_editors.tests);
+
 		// Set font size from general pref
 		Zotero.UIProperties.registerRoot(document.getElementById('scaffold-pane'));
 
@@ -864,24 +877,31 @@ var Scaffold = new function () {
 			return;
 		}
 
-		// Focus editor when switching to tab
 		var tab = document.getElementById('tabs').selectedItem.id.match(/^tab-(.+)$/)[1];
-		switch (tab) {
-			case 'import':
-			case 'code':
-			case 'tests':
-				// the select event's default behavior is to focus the selected tab.
-				// we don't want to prevent *all* of the event's default behavior,
-				// but we do want to focus the editor instead of the tab.
-				// so this stupid hack waits 10 ms for event processing to finish
-				// before focusing the editor.
-				setTimeout(() => {
-					document.getElementById(`editor-${tab}`).focus();
-					_editors[tab].focus();
-				}, 10);
-				break;
+		let tabPanel = document.getElementById("left-tabbox").selectedPanel;
+		// The select event's default behavior is to focus the selected tab.
+		// we don't want to prevent *all* of the event's default behavior,
+		// but we do want to focus an element inside of tabpanel instead of the tab
+		// (unless tabs are being navigated via keyboard)
+		// so this stupid hack focuses the desired element after skipping a tick
+		if (document.getElementById('tabs').getAttribute("clicked")) {
+			setTimeout(() => {
+				let toFocus = tabPanel.querySelector("[focus-on-tab-select]");
+				if (toFocus) {
+					toFocus.focus();
+					// activate editor that is being focused, if any
+					if (toFocus.src.includes("monaco.html")) {
+						_editors[tab].focus();
+					}
+				}
+				else {
+					// if no specific element set, just tab into the panel
+					setTimeout(() => {
+						Services.focus.moveFocus(window, document.getElementById('tabs').selectedItem, Services.focus.MOVEFOCUS_FORWARD, 0);
+					});
+				}
+			});
 		}
-
 		let codeTabBroadcaster = document.getElementById('code-tab-only');
 		if (tab == 'code') {
 			codeTabBroadcaster.removeAttribute('disabled');
@@ -907,6 +927,31 @@ var Scaffold = new function () {
 		}
 	};
 
+	// Add special keydown handling for the editors
+	this.addEditorKeydownHandlers = function (editor) {
+		let doc = editor.getDomNode().ownerDocument;
+		let tabbox = document.getElementById("left-tabbox");
+		// On shift-tab from the start of the first line, tab out of the editor.
+		// Use capturing listener, since Shift-Tab keydown events do not propagate to the document.
+		doc.addEventListener("keydown", (event) => {
+			if (event.key == "Tab" && event.shiftKey) {
+				let position = editor.getPosition();
+				if (position.column == 1 && position.lineNumber == 1) {
+					Services.focus.moveFocus(window, event.target, Services.focus.MOVEFOCUS_BACKWARD, 0);
+					event.preventDefault();
+				}
+			}
+		}, true);
+		// On Escape, focus the selected tab. Use non-capturing listener to not
+		// do anything on Escape events handled by the editor (e.g. to dismiss autocomplete popup)
+		doc.addEventListener("keydown", (event) => {
+			if (event.key == "Escape") {
+				tabbox.selectedTab.focus();
+			}
+		});
+	};
+
+
 	this.listFieldsForItemType = function (itemType) {
 		var outputObject = {};
 		outputObject.itemType = Zotero.ItemTypes.getName(itemType);

chrome/content/scaffold/scaffold.xhtml

@@ -468,7 +468,7 @@
 					</tabpanel>
 					<tabpanel flex="1" id="tabpanel-code">
 						<vbox flex="1">
-							<iframe src="monaco/monaco.html" id="editor-code" flex="1" onmousedown="this.focus()"/>
+							<iframe src="monaco/monaco.html" id="editor-code" focus-on-tab-select="true" flex="1" onmousedown="this.focus()"/>
 						</vbox>
 					</tabpanel>
 					<tabpanel flex="1" id="tabpanel-tests">
@@ -490,6 +490,7 @@
 									seltype="multiple"
 									onselect="Scaffold.handleTestSelect(event)"
 									context="testing-context-menu"
+									focus-on-tab-select="true"
 								/>
 							</vbox>
 							<hbox id="testing-buttons">
@@ -533,7 +534,7 @@
 								<button observes="validate-tests" label="&scaffold.testing.create.import;" tooltiptext="Create a new test from the current import data" oncommand="Scaffold.saveTestFromCurrent('import')" />
 								<button observes="validate-tests" label="&scaffold.testing.create.search;" tooltiptext="Create a new test from the current search data" oncommand="Scaffold.saveTestFromCurrent('search')" />
 							</hbox>
-							<iframe src="monaco/monaco.html" id="editor-import" flex="1" onmousedown="this.focus()"/>
+							<iframe src="monaco/monaco.html" id="editor-import" flex="1" focus-on-tab-select="true" onmousedown="this.focus()"/>
 						</vbox>
 					</tabpanel>
 				</tabpanels>

scss/scaffold.scss

@@ -82,7 +82,8 @@ browser,
 #left-tabbox {
 	flex: 1;
 	min-width: 500px;
-	margin: 5px;
+	margin: 0 5px 5px 5px;
+	padding-top: 5px; // padding at the top for focus-ring of tabs to not cutoff tabs focusring
 	overflow: clip;
 	
 	tabpanel {
@@ -212,3 +213,9 @@ browser,
 		}
 	}
 }
+
+// show focusring only during keyboard navigation
+#tabs:not([clicked]) tab:focus-visible {
+	outline: none;
+	box-shadow: 0 0 0 var(--width-focus-border) var(--color-focus-border);
+}