Add Fullscreen Magnifier support for active-descendant focus-following

Plumb through active-descendant focus-following for full-screen magnifier in Chrome OS.

Bug: 1131153
Change-Id: I8bc79096768449a231221cd8f354f80c966033a9
AX-Relnotes: Adds Magnifier support for active-descendant focus-following
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2440763
Commit-Queue: Josiah Krutz <josiahk@google.com>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816468}

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

@@ -60,6 +60,7 @@ js2gtest("accessibility_common_extjs_tests") {
   sources = [
     "accessibility_common_test.js",
     "autoclick/autoclick_test.js",
+    "magnifier/magnifier_test.js",
   ]
   gen_include_files = [
     "../common/rect_util.js",
@@ -88,6 +89,7 @@ js_library("accessibility_common") {
   deps = [
     ":autoclick",
     ":magnifier",
+    "../common:event_handler",
     "../common:instance_checker",
   ]
   externs_list = [

chrome/browser/resources/chromeos/accessibility/accessibility_common/accessibility_common_loader.js

@@ -71,6 +71,7 @@ class AccessibilityCommon {
     if (details.value && !this.magnifier_) {
       this.magnifier_ = new Magnifier();
     } else if (!details.value && this.magnifier_) {
+      this.magnifier_.onMagnifierDisabled();
       this.magnifier_ = null;
     }
   }

chrome/browser/resources/chromeos/accessibility/accessibility_common/magnifier/magnifier.js

@@ -6,5 +6,48 @@
  * Main class for the Chrome OS magnifier.
  */
 class Magnifier {
-  constructor() {}
+  constructor() {
+    /** @private {!EventHandler} */
+    this.activeDescendantHandler_ = new EventHandler(
+        [], chrome.automation.EventType.ACTIVE_DESCENDANT_CHANGED,
+        this.onActiveDescendantChanged_.bind(this));
+
+    this.init_();
+  }
+
+  /** Destructor to remove listener. */
+  onMagnifierDisabled() {
+    this.activeDescendantHandler_.stop();
+  }
+
+  /**
+   * Initializes Magnifier.
+   * @private
+   */
+  init_() {
+    chrome.automation.getDesktop(desktop => {
+      this.activeDescendantHandler_.setNodes(desktop);
+      this.activeDescendantHandler_.start();
+    });
+  }
+
+  /**
+   * Listener for when active descendant is changed. Moves magnifier to include
+   * active descendant in viewport.
+   * @param {!chrome.automation.AutomationEvent} event
+   * @private
+   */
+  onActiveDescendantChanged_(event) {
+    const {activeDescendant} = event.target;
+    if (!activeDescendant) {
+      return;
+    }
+
+    const {location} = activeDescendant;
+    if (!location) {
+      return;
+    }
+
+    chrome.accessibilityPrivate.moveMagnifierToRect(location);
+  }
 }

chrome/browser/resources/chromeos/accessibility/accessibility_common/magnifier/magnifier_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(['../../common/testing/e2e_test_base.js']);
+GEN_INCLUDE(['../../common/testing/mock_accessibility_private.js']);
+GEN_INCLUDE(['../../common/rect_util.js']);
+
+/**
+ * Magnifier feature using accessibility common extension browser tests.
+ */
+MagnifierE2ETest = class extends E2ETestBase {
+  constructor() {
+    super();
+    this.mockAccessibilityPrivate = MockAccessibilityPrivate;
+    chrome.accessibilityPrivate = this.mockAccessibilityPrivate;
+
+    window.RoleType = chrome.automation.RoleType;
+
+    // Re-initialize AccessibilityCommon with mock AccessibilityPrivate API.
+    window.accessibilityCommon = new AccessibilityCommon();
+  }
+
+  /** @override */
+  testGenCppIncludes() {
+    super.testGenCppIncludes();
+    GEN(`
+#include "chrome/browser/chromeos/accessibility/magnification_manager.h"
+#include "chrome/common/extensions/extension_constants.h"
+#include "content/public/test/browser_test.h"
+    `);
+  }
+
+  /** @override */
+  testGenPreamble() {
+    super.testGenPreamble();
+    GEN(`
+    base::Closure load_cb =
+        base::Bind(&chromeos::MagnificationManager::SetMagnifierEnabled,
+            base::Unretained(chromeos::MagnificationManager::Get()),
+            true);
+    WaitForExtension(extension_misc::kAccessibilityCommonExtensionId, load_cb);
+      `);
+  }
+};
+
+TEST_F(
+    'MagnifierE2ETest', 'MovesScreenMagnifierToActiveDescendant', function() {
+      const site = `
+    <div role="group" id="parent" aria-activedescendant="apple">
+      <div id="apple" role="treeitem">Apple</div>
+      <div id="banana" role="treeitem">Banana</div>
+    </div>
+    <script>
+      const parent = document.getElementById('parent');
+      parent.addEventListener('click', function() {
+        parent.setAttribute('aria-activedescendant', 'banana');
+      });
+      </script>
+  `;
+      this.runWithLoadedTree(site, async function(root) {
+        // Click parent to change active descendant from apple to banana.
+        const parent = root.find({role: RoleType.GROUP});
+        parent.doDefault();
+
+        // Register and wait for rect from magnifier.
+        const rect = await new Promise(resolve => {
+          this.mockAccessibilityPrivate.registerMoveMagnifierToRectCallback(
+              resolve);
+        });
+
+        // Validate rect from magnifier is rect of banana.
+        const bananaNode =
+            root.find({role: RoleType.TREE_ITEM, attributes: {name: 'Banana'}});
+        assertTrue(RectUtil.equal(rect, bananaNode.location));
+      }, {returnPage: true});
+    });

chrome/browser/resources/chromeos/accessibility/common/testing/mock_accessibility_private.js

@@ -19,6 +19,7 @@ var MockAccessibilityPrivate = {
   /** @private {!Array<!chrome.accessibilityPrivate.ScreenRect>} */
   focusRingRects_: [],
   handleScrollableBoundsForPointFoundCallback_: null,
+  moveMagnifierToRectCallback_: null,
 
   // Methods from AccessibilityPrivate API. //
 
@@ -28,15 +29,15 @@ var MockAccessibilityPrivate = {
      * @param {function<number, number>} listener
      */
     addListener: (listener) => {
-      boundsListener_ = listener;
+      MockAccessibilityPrivate.boundsListener_ = listener;
     },
 
     /**
      * Removes the listener.
      */
     removeListener: (listener) => {
-      if (boundsListener_ == listener) {
-        boundsListener_ = null;
+      if (MockAccessibilityPrivate.boundsListener_ == listener) {
+        MockAccessibilityPrivate.boundsListener_ = null;
       }
     }
   },
@@ -46,8 +47,17 @@ var MockAccessibilityPrivate = {
    * @param {!chrome.accessibilityPrivate.ScreenRect} bounds
    */
   handleScrollableBoundsForPointFound: (bounds) => {
-    scrollableBounds_ = bounds;
-    handleScrollableBoundsForPointFoundCallback_();
+    MockAccessibilityPrivate.scrollableBounds_ = bounds;
+    MockAccessibilityPrivate.handleScrollableBoundsForPointFoundCallback_();
+  },
+
+  /**
+   * Called when AccessibilityCommon wants to move the magnifier viewport to
+   * include a specific rect.
+   * @param {!chrome.accessibilityPrivate.ScreenRect} rect
+   */
+  moveMagnifierToRect: (rect) => {
+    MockAccessibilityPrivate.moveMagnifierToRectCallback_(rect);
   },
 
   /**
@@ -57,7 +67,7 @@ var MockAccessibilityPrivate = {
    * @param {!Array<!FocusRingInfo>} focusRingInfos
    */
   setFocusRings: (focusRingInfos) => {
-    focusRingRects_ = focusRingInfos[0].rects;
+    MockAccessibilityPrivate.focusRingRects_ = focusRingInfos[0].rects;
   },
 
   // Methods for testing. //
@@ -75,18 +85,29 @@ var MockAccessibilityPrivate = {
    */
   callOnScrollableBoundsForPointRequested:
       (x, y, handleScrollableBoundsForPointFoundCallback) => {
-        handleScrollableBoundsForPointFoundCallback_ =
+        MockAccessibilityPrivate.handleScrollableBoundsForPointFoundCallback_ =
             handleScrollableBoundsForPointFoundCallback;
-        boundsListener_(x, y);
+        MockAccessibilityPrivate.boundsListener_(x, y);
       },
 
+  /**
+   * Called to register a stubbed callback for moveMagnifierToRect.
+   * When magnifier identifies a desired rect to move the viewport to,
+   * moveMagnifierToRectCallback will be called with that desired rect.
+   * @param {!function<>} moveMagnifierToRectCallback
+   */
+  registerMoveMagnifierToRectCallback: (moveMagnifierToRectCallback) => {
+    MockAccessibilityPrivate.moveMagnifierToRectCallback_ =
+        moveMagnifierToRectCallback;
+  },
+
   /**
    * Gets the scrollable bounds which were found by the AccessibilityCommon
    * extension.
    * @return {Array<!chrome.AccessibilityPrivate.ScreenRect>}
    */
   getScrollableBounds: () => {
-    return scrollableBounds_;
+    return MockAccessibilityPrivate.scrollableBounds_;
   },
 
   /**
@@ -95,6 +116,6 @@ var MockAccessibilityPrivate = {
    * @return {Array<!chrome.AccessibilityPrivate.ScreenRect>}
    */
   getFocusRings: () => {
-    return focusRingRects_;
+    return MockAccessibilityPrivate.focusRingRects_;
   },
 };
\ No newline at end of file