Fix keyboard accessibility in conflict-resolution dialog

It's now possible to tab through the panes and the buttons, and
left/right-arrow also change the selection, so you can use Left/Right +
Return to move through multiple conflicts.

Fixes #3395

chrome/content/zotero/elements/itemBox.js

@@ -37,6 +37,7 @@
 			this.hideEmptyFields = false;
 			this.clickByRow = false;
 			this.clickByItem = false;
+			this.preventFocus = false;
 			
 			this.clickHandler = null;
 			this.blurHandler = null;
@@ -1005,10 +1006,12 @@
 			}
 			td.appendChild(addButton);
 
-			for (const domEl of [th, toggleButton, removeButton, addButton]) {
-				domEl.setAttribute('tabindex', '0');
-				domEl.addEventListener('keypress', this.handleKeyPress.bind(this));
-				domEl.addEventListener('focusin', this.updateLastFocused.bind(this));
+			if (!this.preventFocus) {
+				for (const domEl of [th, toggleButton, removeButton, addButton]) {
+					domEl.setAttribute('tabindex', '0');
+					domEl.addEventListener('keypress', this.handleKeyPress.bind(this));
+					domEl.addEventListener('focusin', this.updateLastFocused.bind(this));
+				}
 			}
 			
 			this._creatorCount++;

chrome/content/zotero/elements/mergeGroup.js

@@ -51,6 +51,18 @@
 			this._leftPane = this._id('left-pane');
 			this._rightPane = this._id('right-pane');
 			this._mergePane = this._id('merge-pane');
+			
+			// Select pane with left/right arrow key
+			this.addEventListener('keypress', (event) => {
+				if (event.key == "ArrowRight" && !this._rightPane.hasAttribute("selected")) {
+					this.choosePane(this._rightPane);
+					this.rightPane.groupbox.focus();
+				}
+				else if (event.key == "ArrowLeft" && !this._leftPane.hasAttribute("selected")) {
+					this.choosePane(this._leftPane);
+					this._leftPane.groupbox.focus();
+				}
+			});
 		}
 		
 		get data() {
@@ -267,12 +279,12 @@
 			this.append(document.importNode(this.content, true));
 			
 			this.parent = document.querySelector('merge-group');
+			this.isLeftPane = this.id == 'left-pane';
+			this.isRightPane = this.id == 'right-pane';
 			this.isMergePane = this.id == 'merge-pane';
 			
 			if (!this.isMergePane) {
-				this.box.onclick = function () {
-					this.parent.choosePane(this);
-				}.bind(this);
+				this.groupbox.onclick = this.handleClick.bind(this);
 			}
 		}
 		
@@ -280,7 +292,7 @@
 			return this.parent.type;
 		}
 		
-		get box() {
+		get groupbox() {
 			return this.querySelector('groupbox');
 		}
 		
@@ -326,7 +338,7 @@
 			var button = this._class('choose-button');
 			button.label = Zotero.getString('sync.conflict.chooseThisVersion');
 			if (this.showButton) {
-				button.onclick = () => this.parent.choosePane(this);
+				button.onclick = this.handleClick.bind(this);
 				button.style.visibility = 'visible';
 			}
 			else {
@@ -403,6 +415,17 @@
 			objbox.setAttribute("flex", "1");
 			objbox.mode = this.type == 'file' ? 'filemerge' : 'merge';
 			
+			// Keyboard accessibility
+			objbox.preventFocus = true;
+			if (!this.isMergePane) {
+				this.groupbox.setAttribute('tabindex', 0);
+				this.groupbox.addEventListener('keypress', (event) => {
+					if (event.key == " ") {
+						this.handleClick();
+					}
+				});
+			}
+			
 			// Store JSON
 			this._data = val;
 			
@@ -427,8 +450,8 @@
 			}
 		}
 		
-		click() {
-			this.box.click();
+		handleClick() {
+			this.parent.choosePane(this);
 		}
 		
 		_class(className) {

chrome/skin/default/zotero/merge.css

@@ -93,7 +93,9 @@ merge-group:not([mergetype="note"]) #right-pane:active attachment-box #title {
 }
 
 #left-pane:hover:not([selected=true]) h2,
-#right-pane:hover:not([selected=true]) h2 {
+#left-pane groupbox:focus:not([selected=true]) h2,
+#right-pane:hover:not([selected=true]) h2,
+#right-pane groupbox:focus:not([selected=true]) h2 {
 	text-decoration: underline;
 }