[Switch Access] Wait to set listener on keyboard

Previously, Switch Access would try to set a listener on the keyboard
node, regardless of whether the node was found in the tree.

This change checks if the keyboard is found, and if not sets a callback
for when the node is found.

It also re-orders the calls in enterKeyboard() to reduce the times when
focus is drawn back to the text field after it has shifted to the
keyboard.

AX-Relnotes: n/a.
Bug: None.
Change-Id: I79663f1bc3297ce8e468e38f0364bd7e3a90f01a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2302748
Commit-Queue: Anastasia Helfinstein <anastasi@google.com>
Reviewed-by: Akihiro Ota <akihiroota@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790071}

chrome/browser/resources/chromeos/accessibility/switch_access/navigation_manager.js

@@ -49,8 +49,8 @@ class NavigationManager {
    */
   static enterKeyboard() {
     const navigator = NavigationManager.instance;
-    const keyboard = KeyboardRootNode.buildTree();
     navigator.node_.automationNode.focus();
+    const keyboard = KeyboardRootNode.buildTree();
     navigator.jumpTo_(keyboard);
   }
 

chrome/browser/resources/chromeos/accessibility/switch_access/nodes/keyboard_node.js

@@ -134,18 +134,18 @@ class KeyboardRootNode extends RootNodeWrapper {
     KeyboardRootNode.loadKeyboard_();
     AutoScanManager.setInKeyboard(true);
 
-    if (!KeyboardRootNode.keyboardObject_) {
+    const keyboardObject = KeyboardRootNode.getKeyboardObject();
+    if (!keyboardObject) {
       throw SwitchAccess.error(
           SAConstants.ErrorType.MISSING_KEYBOARD,
           'Could not find keyboard in the automation tree',
           true /* shouldRecover */);
     }
     const keyboard =
-        new AutomationTreeWalker(
-            KeyboardRootNode.keyboardObject_, constants.Dir.FORWARD, {
-              visit: (node) => SwitchAccessPredicate.isGroup(node, null),
-              root: (node) => node === KeyboardRootNode.keyboardObject_
-            })
+        new AutomationTreeWalker(keyboardObject, constants.Dir.FORWARD, {
+          visit: (node) => SwitchAccessPredicate.isGroup(node, null),
+          root: (node) => node === keyboardObject
+        })
             .next()
             .node;
 
@@ -158,10 +158,18 @@ class KeyboardRootNode extends RootNodeWrapper {
    * Start listening for keyboard open/closed.
    */
   static startWatchingVisibility() {
+    const keyboardObject = KeyboardRootNode.getKeyboardObject();
+    if (!keyboardObject) {
+      const isKeyboard = (n) => n.role === chrome.automation.RoleType.KEYBOARD;
+      SwitchAccess.findNodeMatchingPredicate(
+          isKeyboard, KeyboardRootNode.startWatchingVisibility);
+      return;
+    }
+
     KeyboardRootNode.isVisible_ =
-        SwitchAccessPredicate.isVisible(KeyboardRootNode.keyboardObject_);
+        SwitchAccessPredicate.isVisible(keyboardObject);
 
-    KeyboardRootNode.keyboardObject_.addEventListener(
+    keyboardObject.addEventListener(
         chrome.automation.EventType.ARIA_ATTRIBUTE_CHANGED,
         KeyboardRootNode.checkVisibilityChanged_, false /* capture */);
   }
@@ -174,7 +182,7 @@ class KeyboardRootNode extends RootNodeWrapper {
    */
   static checkVisibilityChanged_(event) {
     const currentlyVisible =
-        SwitchAccessPredicate.isVisible(KeyboardRootNode.keyboardObject_);
+        SwitchAccessPredicate.isVisible(KeyboardRootNode.getKeyboardObject());
     if (currentlyVisible === KeyboardRootNode.isVisible_) {
       return;
     }
@@ -199,7 +207,7 @@ class KeyboardRootNode extends RootNodeWrapper {
    * @return {AutomationNode}
    * @private
    */
-  static get keyboardObject_() {
+  static getKeyboardObject() {
     if (!this.object_ || !this.object_.role) {
       this.object_ = NavigationManager.desktopNode.find(
           {role: chrome.automation.RoleType.KEYBOARD});

chrome/browser/resources/chromeos/accessibility/switch_access/switch_access.js

@@ -18,10 +18,8 @@ class SwitchAccess {
       NavigationManager.initialize(desktop);
 
       Commands.initialize();
-      SwitchAccessPreferences.initialize();
-
-      // This can throw an error, so it is done last.
       KeyboardRootNode.startWatchingVisibility();
+      SwitchAccessPreferences.initialize();
     });
   }