[Switch Access] Create DesktopNode type

The desktop needs to be fundamentally different from other root nodes
in Switch Access because it is the only root that does not have a back
button.

Bug: 1054482
Change-Id: I47d1f8f5383d271debf1ef5749c106015102679a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2065732
Commit-Queue: Anastasia Helfinstein <anastasi@google.com>
Reviewed-by: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744043}

chrome/browser/resources/chromeos/accessibility/switch_access/BUILD.gn

@@ -73,6 +73,7 @@ run_jsbundler("switch_access_copied_files") {
     "metrics.js",
     "navigation_manager.js",
     "nodes/back_button_node.js",
+    "nodes/desktop_node.js",
     "nodes/editable_text_node.js",
     "nodes/group_node.js",
     "nodes/keyboard_node.js",
@@ -114,6 +115,7 @@ js2gtest("switch_access_extjs_tests") {
   sources = [
     "auto_scan_manager_test.js",
     "navigation_manager_test.js",
+    "nodes/desktop_node_test.js",
     "nodes/node_wrapper_test.js",
     "nodes/tab_node_test.js",
     "switch_access_predicate_test.js",
@@ -179,6 +181,7 @@ js_type_check("closure_compile") {
     ":back_button_node",
     ":background",
     ":commands",
+    ":desktop_node",
     ":editable_text_node",
     ":event_helper",
     ":focus_ring_manager",
@@ -231,6 +234,12 @@ js_library("commands") {
   externs_list = [ "$externs_path/accessibility_private.js" ]
 }
 
+js_library("desktop_node") {
+  sources = [ "nodes/desktop_node.js" ]
+  deps = [ ":node_wrapper" ]
+  externs_list = [ "$externs_path/automation.js" ]
+}
+
 js_library("editable_text_node") {
   sources = [ "nodes/editable_text_node.js" ]
   deps = [
@@ -330,6 +339,7 @@ js_library("metrics") {
 
 js_library("navigation_manager") {
   deps = [
+    ":desktop_node",
     ":focus_ring_manager",
     ":keyboard_node",
     ":menu_manager",

chrome/browser/resources/chromeos/accessibility/switch_access/manifest.json.jinja2

@@ -23,6 +23,7 @@
       "nodes/switch_access_node.js",
       "nodes/node_wrapper.js",
       "nodes/back_button_node.js",
+      "nodes/desktop_node.js",
       "nodes/editable_text_node.js",
       "nodes/group_node.js",
       "nodes/keyboard_node.js",

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

@@ -16,7 +16,7 @@ class NavigationManager {
     this.desktop_ = desktop;
 
     /** @private {!SARootNode} */
-    this.group_ = RootNodeWrapper.buildDesktopTree(this.desktop_);
+    this.group_ = DesktopNode.build(this.desktop_);
 
     /** @private {!SAChildNode} */
     this.node_ = this.group_.firstChild;
@@ -113,8 +113,7 @@ class NavigationManager {
       return NavigationManager.instance.group_;
     }
 
-    const desktopRoot =
-        RootNodeWrapper.buildDesktopTree(NavigationManager.instance.desktop_);
+    const desktopRoot = DesktopNode.build(NavigationManager.instance.desktop_);
     console.log(desktopRoot.debugString(
         wholeTree, '', NavigationManager.instance.node_));
     return desktopRoot;
@@ -198,7 +197,7 @@ class NavigationManager {
     }
 
     // If there is no valid node in the group stack, go to the desktop.
-    navigator.setGroup_(RootNodeWrapper.buildDesktopTree(navigator.desktop_));
+    navigator.setGroup_(DesktopNode.build(navigator.desktop_));
     navigator.groupStack_ = [];
   }
 
@@ -333,7 +332,7 @@ class NavigationManager {
     }
 
     this.groupStack_ = [];
-    let group = RootNodeWrapper.buildDesktopTree(this.desktop_);
+    let group = DesktopNode.build(this.desktop_);
     while (ancestorList.length > 0) {
       const ancestor = ancestorList.pop();
       if (ancestor.role === chrome.automation.RoleType.DESKTOP) {

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

@@ -43,7 +43,7 @@ SwitchAccessNavigationManagerTest.prototype = {
 function moveToPageContents() {
   const navigator = NavigationManager.instance;
   // Start from the desktop node.
-  navigator.group_ = RootNodeWrapper.buildDesktopTree(navigator.desktop_);
+  navigator.group_ = DesktopNode.build(navigator.desktop_);
   navigator.node_ = navigator.group_.firstChild;
 
   // The first item should be the browser window.

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

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * This class handles interactions with the desktop automation node.
+ */
+class DesktopNode extends RootNodeWrapper {
+  /**
+   * @param {!AutomationNode} autoNode The automation node representing the
+   *     desktop.
+   */
+  constructor(autoNode) {
+    super(autoNode);
+  }
+
+  // ================= General methods =================
+
+  /** @override */
+  equals(other) {
+    // The underlying automation tree only has one desktop node, so all
+    // DesktopNode instances are equal.
+    return other instanceof DesktopNode;
+  }
+
+  /** @override */
+  isValidGroup() {
+    return true;
+  }
+
+  // ================= Private methods =================
+
+  /** @override */
+  refresh_() {
+    // Find the currently focused child.
+    let focusedChild = null;
+    for (const child of this.children) {
+      if (child.isFocused()) {
+        focusedChild = child;
+        break;
+      }
+    }
+
+    // Update this DesktopNode's children.
+    const childConstructor = (node) => NodeWrapper.create(node, this);
+    DesktopNode.findAndSetChildren(this, childConstructor);
+
+    // Set the new instance of that child to be the focused node.
+    for (const child of this.children) {
+      if (child.isEquivalentTo(focusedChild)) {
+        NavigationManager.forceFocusedNode(child);
+        return;
+      }
+    }
+
+    // If the previously focused node no longer exists, focus the first node in
+    // the group.
+    NavigationManager.forceFocusedNode(this.children[0]);
+  }
+
+  // ================= Static methods =================
+
+  /**
+   * @param {!AutomationNode} desktop
+   * @return {!DesktopNode}
+   */
+  static build(desktop) {
+    const root = new DesktopNode(desktop);
+    const childConstructor = (autoNode) => NodeWrapper.create(autoNode, root);
+
+    DesktopNode.findAndSetChildren(root, childConstructor);
+    return root;
+  }
+
+  /** @override */
+  static findAndSetChildren(root, childConstructor) {
+    const interestingChildren = RootNodeWrapper.getInterestingChildren(root);
+
+    if (interestingChildren.length < 1) {
+      throw SwitchAccess.error(
+          SAConstants.ErrorType.MALFORMED_DESKTOP,
+          'Desktop node must have at least 1 interesting child.');
+    }
+
+    root.children = interestingChildren.map(childConstructor);
+  }
+}

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

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+GEN_INCLUDE(['../switch_access_e2e_test_base.js']);
+
+/**
+ * @constructor
+ * @extends {SwitchAccessE2ETest}
+ */
+function SwitchAccessDesktopNodeTest() {
+  SwitchAccessE2ETest.call(this);
+}
+
+SwitchAccessDesktopNodeTest.prototype = {
+  __proto__: SwitchAccessE2ETest.prototype,
+};
+
+TEST_F('SwitchAccessDesktopNodeTest', 'Build', function() {
+  this.runWithLoadedTree('', (desktop) => {
+    const desktopNode = DesktopNode.build(desktop);
+
+    const children = desktopNode.children;
+    for (let i = 0; i < children.length; i++) {
+      const child = children[i];
+      // The desktop tree should not include a back button.
+      assertFalse(child instanceof BackButtonNode);
+
+      // Check that the children form a loop.
+      const next = children[(i + 1) % children.length];
+      assertEquals(
+          next, child.next, 'next not properly initialized on child ' + i);
+      // We add children.length to ensure the value is greater than zero.
+      const previous = children[(i - 1 + children.length) % children.length];
+      assertEquals(
+          previous, child.previous,
+          'previous not properly initialized on child ' + i);
+    }
+  });
+});

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

@@ -302,7 +302,7 @@ class RootNodeWrapper extends SARootNode {
 
   /**
    * Refreshes the children of this root node.
-   * @private
+   * @protected
    */
   refresh_() {
     // Find the currently focused child.
@@ -340,26 +340,6 @@ class RootNodeWrapper extends SARootNode {
 
   // ================= Static methods =================
 
-  /**
-   * @param {!AutomationNode} desktop
-   * @return {!RootNodeWrapper}
-   */
-  static buildDesktopTree(desktop) {
-    const root = new RootNodeWrapper(desktop);
-    const interestingChildren = RootNodeWrapper.getInterestingChildren(root);
-
-    if (interestingChildren.length < 1) {
-      throw SwitchAccess.error(
-          SAConstants.ErrorType.MALFORMED_DESKTOP,
-          'Desktop node must have at least 1 interesting child.');
-    }
-
-    const childConstructor = (autoNode) => NodeWrapper.create(autoNode, root);
-    root.children = interestingChildren.map(childConstructor);
-
-    return root;
-  }
-
   /**
    * @param {!AutomationNode} rootNode
    * @return {!RootNodeWrapper}

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

@@ -16,29 +16,6 @@ SwitchAccessNodeWrapperTest.prototype = {
   __proto__: SwitchAccessE2ETest.prototype,
 };
 
-TEST_F('SwitchAccessNodeWrapperTest', 'BuildDesktopTree', function() {
-  this.runWithLoadedTree('', (desktop) => {
-    const desktopRootNode = RootNodeWrapper.buildDesktopTree(desktop);
-
-    const children = desktopRootNode.children;
-    for (let i = 0; i < children.length; i++) {
-      const child = children[i];
-      // The desktop tree should not include a back button.
-      assertFalse(child instanceof BackButtonNode);
-
-      // Check that the children form a loop.
-      const next = children[(i + 1) % children.length];
-      assertEquals(
-          next, child.next, 'next not properly initialized on child ' + i);
-      // We add children.length to ensure the value is greater than zero.
-      const previous = children[(i - 1 + children.length) % children.length];
-      assertEquals(
-          previous, child.previous,
-          'previous not properly initialized on child ' + i);
-    }
-  });
-});
-
 TEST_F('SwitchAccessNodeWrapperTest', 'AsRootNode', function() {
   const website = `<div aria-label="outer">
                      <div aria-label="inner">
@@ -75,46 +52,45 @@ TEST_F('SwitchAccessNodeWrapperTest', 'AsRootNode', function() {
 
 TEST_F('SwitchAccessNodeWrapperTest', 'Equals', function() {
   this.runWithLoadedTree('', (desktop) => {
-    const desktopRootNode = RootNodeWrapper.buildDesktopTree(desktop);
+    const desktopNode = DesktopNode.build(desktop);
 
-    let childGroup = desktopRootNode.firstChild;
+    let childGroup = desktopNode.firstChild;
     let i = 0;
-    while (!childGroup.isGroup() && i < desktopRootNode.children.length) {
+    while (!childGroup.isGroup() && i < desktopNode.children.length) {
       childGroup = childGroup.next;
       i++;
     }
     childGroup = childGroup.asRootNode();
 
-    assertFalse(desktopRootNode.equals(), 'Root node equals nothing');
+    assertFalse(desktopNode.equals(), 'Root node equals nothing');
     assertFalse(
-        desktopRootNode.equals(new SARootNode()),
+        desktopNode.equals(new SARootNode()),
         'Different type root nodes are equal');
     assertFalse(
-        new SARootNode().equals(desktopRootNode),
+        new SARootNode().equals(desktopNode),
         'Equals is not symmetric? Different types of root are equal');
     assertFalse(
-        desktopRootNode.equals(childGroup),
+        desktopNode.equals(childGroup),
         'Groups with different children are equal');
     assertFalse(
-        childGroup.equals(desktopRootNode),
+        childGroup.equals(desktopNode),
         'Equals is not symmetric? Groups with different children are equal');
 
     assertTrue(
-        desktopRootNode.equals(desktopRootNode),
+        desktopNode.equals(desktopNode),
         'Equals is not reflexive? (root node)');
-    const desktopCopy = RootNodeWrapper.buildDesktopTree(desktop);
+    const desktopCopy = DesktopNode.build(desktop);
     assertTrue(
-        desktopRootNode.equals(desktopCopy), 'Two desktop roots are not equal');
+        desktopNode.equals(desktopCopy), 'Two desktop roots are not equal');
     assertTrue(
-        desktopCopy.equals(desktopRootNode),
+        desktopCopy.equals(desktopNode),
         'Equals is not symmetric? Two desktop roots aren\'t equal');
 
-    const wrappedNode = desktopRootNode.firstChild;
+    const wrappedNode = desktopNode.firstChild;
     assertTrue(
         wrappedNode instanceof NodeWrapper,
         'Child node is not of type NodeWrapper');
-    assertGT(
-        desktopRootNode.children.length, 1, 'Desktop root has only 1 child');
+    assertGT(desktopNode.children.length, 1, 'Desktop root has only 1 child');
 
     assertFalse(wrappedNode.equals(), 'Child NodeWrapper equals nothing');
     assertFalse(
@@ -124,14 +100,14 @@ TEST_F('SwitchAccessNodeWrapperTest', 'Equals', function() {
         new BackButtonNode().equals(wrappedNode),
         'Equals is not symmetric? NodeWrapper equals a BackButtonNode');
     assertFalse(
-        wrappedNode.equals(desktopRootNode.lastChild),
+        wrappedNode.equals(desktopNode.lastChild),
         'Children with different base nodes are equal');
     assertFalse(
-        desktopRootNode.lastChild.equals(wrappedNode),
+        desktopNode.lastChild.equals(wrappedNode),
         'Equals is not symmetric? Nodes with different base nodes are equal');
 
     const equivalentWrappedNode =
-        NodeWrapper.create(wrappedNode.baseNode_, desktopRootNode);
+        NodeWrapper.create(wrappedNode.baseNode_, desktopNode);
     assertTrue(
         wrappedNode.equals(wrappedNode),
         'Equals is not reflexive? (child node)');