Add new Javascript-based Magnifier focus following

Focus following should work in more cases than handled previously, since we're now listening for all high-level chrome.automation focus updates, instead of low-level views::View AXEvent and related focus updates.

AX-Relnotes: New Javascript-based magnifier focus following behind flag - focus following should work in more cases than handled previously.
Bug: 1131153
Change-Id: I1e34255000a320df942462690c6a7ea1b6d0612e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2466622
Commit-Queue: Josiah Krutz <josiahk@google.com>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818175}

chrome/browser/chromeos/accessibility/magnification_manager.cc

@@ -23,6 +23,7 @@
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
+#include "ui/accessibility/accessibility_switches.h"
 #include "ui/accessibility/ax_role_properties.h"
 #include "ui/views/accessibility/ax_event_manager.h"
 #include "ui/views/accessibility/view_accessibility.h"
@@ -342,6 +343,10 @@ void MagnificationManager::HandleFocusChangedInPage(
 
 void MagnificationManager::HandleFocusChanged(const gfx::Rect& bounds_in_screen,
                                               bool is_editable) {
+  if (::switches::
+          IsExperimentalAccessibilityMagnifierNewFocusFollowingEnabled())
+    return;
+
   if (bounds_in_screen.IsEmpty())
     return;
 

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

@@ -8,6 +8,9 @@
 class Magnifier {
   constructor() {
     /** @private {!EventHandler} */
+    this.focusHandler_ = new EventHandler(
+        [], chrome.automation.EventType.FOCUS, this.onFocus_.bind(this));
+
     this.activeDescendantHandler_ = new EventHandler(
         [], chrome.automation.EventType.ACTIVE_DESCENDANT_CHANGED,
         this.onActiveDescendantChanged_.bind(this));
@@ -17,6 +20,7 @@ class Magnifier {
 
   /** Destructor to remove listener. */
   onMagnifierDisabled() {
+    this.focusHandler_.stop();
     this.activeDescendantHandler_.stop();
   }
 
@@ -26,11 +30,36 @@ class Magnifier {
    */
   init_() {
     chrome.automation.getDesktop(desktop => {
+      this.focusHandler_.setNodes(desktop);
+      this.focusHandler_.start();
       this.activeDescendantHandler_.setNodes(desktop);
       this.activeDescendantHandler_.start();
     });
   }
 
+  /**
+   * Listener for when focus is updated. Moves magnifier to include focused
+   * element in viewport.
+   *
+   * TODO(accessibility): There is a bit of magnifier shakiness on arrow down in
+   * omnibox - probably focus following fighting with caret following - maybe
+   * add timer for last focus event so that fast-following caret updates don't
+   * shake screen.
+   * TODO(accessibility): On page load, sometimes viewport moves to center of
+   * webpage instead of spotlighting first focusable page element.
+   *
+   * @param {!chrome.automation.AutomationEvent} event
+   * @private
+   */
+  onFocus_(event) {
+    const {location} = event.target;
+    if (!location) {
+      return;
+    }
+
+    chrome.accessibilityPrivate.moveMagnifierToRect(location);
+  }
+
   /**
    * Listener for when active descendant is changed. Moves magnifier to include
    * active descendant in viewport.

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

@@ -16,11 +16,18 @@ MagnifierE2ETest = class extends E2ETestBase {
     chrome.accessibilityPrivate = this.mockAccessibilityPrivate;
 
     window.RoleType = chrome.automation.RoleType;
+    window.getNextMagnifierLocation = this.getNextMagnifierLocation;
 
     // Re-initialize AccessibilityCommon with mock AccessibilityPrivate API.
     window.accessibilityCommon = new AccessibilityCommon();
   }
 
+  async getNextMagnifierLocation() {
+    return new Promise(resolve => {
+      chrome.accessibilityPrivate.registerMoveMagnifierToRectCallback(resolve);
+    });
+  }
+
   /** @override */
   testGenCppIncludes() {
     super.testGenCppIncludes();
@@ -44,6 +51,27 @@ MagnifierE2ETest = class extends E2ETestBase {
   }
 };
 
+TEST_F('MagnifierE2ETest', 'MovesScreenMagnifierToFocusedElement', function() {
+  const site = `
+        <button id="apple">Apple</button>
+        <button id="banana">Banana</button>
+      `;
+  this.runWithLoadedTree(site, async function(root) {
+    // Validate magnifier wants to move to root.
+    const rootLocation = await getNextMagnifierLocation();
+    assertTrue(RectUtil.equal(rootLocation, root.location));
+
+    // Focus banana node.
+    const banana =
+        root.find({role: RoleType.BUTTON, attributes: {name: 'Banana'}});
+    banana.focus();
+
+    // Validate magnifier wants to move to banana.
+    const bananaLocation = await getNextMagnifierLocation();
+    assertTrue(RectUtil.equal(bananaLocation, banana.location));
+  });
+});
+
 TEST_F(
     'MagnifierE2ETest', 'MovesScreenMagnifierToActiveDescendant', function() {
       const site = `
@@ -64,14 +92,11 @@ TEST_F(
         parent.doDefault();
 
         // Register and wait for rect from magnifier.
-        const rect = await new Promise(resolve => {
-          this.mockAccessibilityPrivate.registerMoveMagnifierToRectCallback(
-              resolve);
-        });
+        const rect = await getNextMagnifierLocation();
 
         // 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

@@ -57,7 +57,9 @@ var MockAccessibilityPrivate = {
    * @param {!chrome.accessibilityPrivate.ScreenRect} rect
    */
   moveMagnifierToRect: (rect) => {
-    MockAccessibilityPrivate.moveMagnifierToRectCallback_(rect);
+    if (MockAccessibilityPrivate.moveMagnifierToRectCallback_) {
+      MockAccessibilityPrivate.moveMagnifierToRectCallback_(rect);
+    }
   },
 
   /**