[Switch Access] Handle combo boxes

Because the options in a combo box are not in the automation tree, we
will handle combo boxes by simulating arrow keys. This behavior will be
changed when the underlying data is available.

AX-Relnotes: n/a.
Bug: 996401
Change-Id: Ice9003de483a4d9cdb7edd32f97f8024ec8b477b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2231660
Commit-Queue: Anastasia Helfinstein <anastasi@google.com>
Reviewed-by: Abigail Klein <abigailbklein@google.com>
Cr-Commit-Position: refs/heads/master@{#776161}

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

@@ -65,6 +65,7 @@ run_jsbundler("switch_access_copied_files") {
     "metrics.js",
     "navigation_manager.js",
     "nodes/back_button_node.js",
+    "nodes/combo_box_node.js",
     "nodes/desktop_node.js",
     "nodes/editable_text_node.js",
     "nodes/group_node.js",
@@ -134,6 +135,7 @@ js_type_check("closure_compile") {
     ":auto_scan_manager",
     ":back_button_node",
     ":background",
+    ":combo_box_node",
     ":commands",
     ":desktop_node",
     ":editable_text_node",
@@ -157,6 +159,7 @@ js_type_check("closure_compile") {
     ":system_menu_node",
     ":tab_node",
     ":text_navigation_manager",
+    "../common:automation_predicate",
     "../common:closure_shim",
     "../common:constants",
     "../common:tree_walker",
@@ -185,6 +188,16 @@ js_library("back_button_node") {
   ]
 }
 
+js_library("combo_box_node") {
+  sources = [ "nodes/combo_box_node.js" ]
+  deps = [
+    ":event_helper",
+    ":node_wrapper",
+    ":switch_access_constants",
+  ]
+  externs_list = []
+}
+
 js_library("commands") {
   deps = [
     ":auto_scan_manager",
@@ -327,6 +340,7 @@ js_library("node_wrapper") {
     ":switch_access_constants",
     ":switch_access_node",
     ":switch_access_predicate",
+    "../common:automation_predicate",
     "../common:constants",
     "../common:tree_walker",
   ]
@@ -381,6 +395,7 @@ js_library("switch_access_predicate") {
   deps = [
     ":switch_access_constants",
     ":switch_access_node",
+    "../common:automation_predicate",
   ]
   externs_list = [ "$externs_path/automation.js" ]
 }

chrome/browser/resources/chromeos/accessibility/switch_access/nodes/combo_box_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 combo boxes.
+ * TODO(anastasi): Add a test for this class.
+ */
+class ComboBoxNode extends NodeWrapper {
+  /** @override */
+  get actions() {
+    return [SwitchAccessMenuAction.INCREMENT, SwitchAccessMenuAction.DECREMENT];
+  }
+
+  /** @override */
+  doDefaultAction() {
+    this.performAction(SwitchAccessMenuAction.INCREMENT);
+  }
+
+  /** @override */
+  onFocus() {
+    super.onFocus();
+    this.automationNode.focus();
+  }
+
+  /** @override */
+  performAction(action) {
+    // The box of options that typically pops up with combo boxes is not
+    // currently represented in the automation tree, so we work around that by
+    // selecting a value without opening the pop-up, using the up and down
+    // arrows.
+    switch (action) {
+      case SwitchAccessMenuAction.DECREMENT:
+        EventHelper.simulateKeyPress(EventHelper.KeyCode.UP_ARROW);
+        return SAConstants.ActionResponse.REMAIN_OPEN;
+      case SwitchAccessMenuAction.INCREMENT:
+        EventHelper.simulateKeyPress(EventHelper.KeyCode.DOWN_ARROW);
+        return SAConstants.ActionResponse.REMAIN_OPEN;
+    }
+    return SAConstants.ActionResponse.NO_ACTION_TAKEN;
+  }
+}

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

@@ -199,6 +199,9 @@ class NodeWrapper extends SAChildNode {
    * @return {!NodeWrapper}
    */
   static create(baseNode, parent) {
+    if (AutomationPredicate.comboBox(baseNode)) {
+      return new ComboBoxNode(baseNode, parent);
+    }
     if (SwitchAccessPredicate.isTextInput(baseNode)) {
       return new EditableTextNode(baseNode, parent);
     }

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

@@ -68,7 +68,8 @@ const SwitchAccessPredicate = {
       return true;
     }
 
-    if (SwitchAccessPredicate.isTextInput(node)) {
+    if (AutomationPredicate.comboBox(node) ||
+        SwitchAccessPredicate.isTextInput(node)) {
       return true;
     }
 
@@ -120,6 +121,9 @@ const SwitchAccessPredicate = {
     if (node.state[StateType.INVISIBLE]) {
       return false;
     }
+    if (AutomationPredicate.comboBox(node)) {
+      return false;
+    }
 
     let interestingBranchesCount =
         SwitchAccessPredicate.isActionable(node) ? 1 : 0;

chrome/browser/resources/chromeos/accessibility/switch_access_manifest.json.jinja2

@@ -12,10 +12,10 @@
   "background": {
     "scripts": [
       "common/array_util.js",
-      "switch_access/auto_scan_manager.js",
       "common/closure_shim.js",
-      "switch_access/commands.js",
       "common/constants.js",
+      "switch_access/auto_scan_manager.js",
+      "switch_access/commands.js",
       "switch_access/event_helper.js",
       "switch_access/focus_ring_manager.js",
       "switch_access/history.js",
@@ -25,6 +25,7 @@
       "switch_access/nodes/switch_access_node.js",
       "switch_access/nodes/node_wrapper.js",
       "switch_access/nodes/back_button_node.js",
+      "switch_access/nodes/combo_box_node.js",
       "switch_access/nodes/desktop_node.js",
       "switch_access/nodes/editable_text_node.js",
       "switch_access/nodes/group_node.js",
@@ -37,6 +38,7 @@
       "switch_access/switch_access_constants.js",
       "switch_access/switch_access_predicate.js",
       "switch_access/text_navigation_manager.js",
+      "common/automation_predicate.js",
       "common/tree_walker.js",
       "switch_access/background.js"
     ]