Plumb through screen_magnifier_focus_following preference in magnifier

Wires in screen_magnifier_focus_following preference added in crrev.com/c/2506771.

AX-Relnotes: Allow Screen Magnifier Focus Following Pref to take effect in magnifier.
Fixed: 1146583
Change-Id: Ieeb8b81d0852ce330f671f931cfa2bfb02fd4067
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2522905
Commit-Queue: Josiah Krutz <josiahk@google.com>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831245}

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

@@ -113,4 +113,5 @@ js_library("autoclick") {
 
 js_library("magnifier") {
   sources = [ "magnifier/magnifier.js" ]
+  externs_list = [ "$externs_path/settings_private.js" ]
 }

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

@@ -41,14 +41,14 @@ class AccessibilityCommon {
         this.onAutoclickUpdated_.bind(this));
 
     chrome.accessibilityFeatures.screenMagnifier.get(
-        {}, this.onMagnifierUpdated_.bind(this));
+        {}, this.onMagnifierUpdated_.bind(this, Magnifier.Type.FULL_SCREEN));
     chrome.accessibilityFeatures.screenMagnifier.onChange.addListener(
-        this.onMagnifierUpdated_.bind(this));
+        this.onMagnifierUpdated_.bind(this, Magnifier.Type.FULL_SCREEN));
 
     chrome.accessibilityFeatures.dockedMagnifier.get(
-        {}, this.onMagnifierUpdated_.bind(this));
+        {}, this.onMagnifierUpdated_.bind(this, Magnifier.Type.DOCKED));
     chrome.accessibilityFeatures.dockedMagnifier.onChange.addListener(
-        this.onMagnifierUpdated_.bind(this));
+        this.onMagnifierUpdated_.bind(this, Magnifier.Type.DOCKED));
   }
 
   /**
@@ -69,13 +69,15 @@ class AccessibilityCommon {
   }
 
   /**
+   * @param {!Magnifier.Type} type
    * @param {*} details
    * @private
    */
-  onMagnifierUpdated_(details) {
+  onMagnifierUpdated_(type, details) {
     if (details.value && !this.magnifier_) {
-      this.magnifier_ = new Magnifier();
-    } else if (!details.value && this.magnifier_) {
+      this.magnifier_ = new Magnifier(type);
+    } else if (
+        !details.value && this.magnifier_ && this.magnifier_.type === type) {
       this.magnifier_.onMagnifierDisabled();
       this.magnifier_ = null;
     }

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

@@ -6,7 +6,20 @@
  * Main class for the Chrome OS magnifier.
  */
 class Magnifier {
-  constructor() {
+  /**
+   * @param {!Magnifier.Type} type The type of magnifier in use.
+   */
+  constructor(type) {
+    /** @const {!Magnifier.Type} */
+    this.type = type;
+
+    /**
+     * Whether focus following is enabled or not, based on
+     * settings.a11y.screen_magnifier_focus_following preference.
+     * @private {boolean}
+     */
+    this.screenMagnifierFocusFollowing_;
+
     /** @private {!EventHandler} */
     this.focusHandler_ = new EventHandler(
         [], chrome.automation.EventType.FOCUS, this.onFocus_.bind(this));
@@ -29,6 +42,10 @@ class Magnifier {
    * @private
    */
   init_() {
+    chrome.settingsPrivate.getAllPrefs(this.updateFromPrefs_.bind(this));
+    chrome.settingsPrivate.onPrefsChanged.addListener(
+        this.updateFromPrefs_.bind(this));
+
     chrome.automation.getDesktop(desktop => {
       this.focusHandler_.setNodes(desktop);
       this.focusHandler_.start();
@@ -37,6 +54,35 @@ class Magnifier {
     });
   }
 
+  /**
+   * @param {!Array<!chrome.settingsPrivate.PrefObject>} prefs
+   * @private
+   */
+  updateFromPrefs_(prefs) {
+    prefs.forEach((pref) => {
+      switch (pref.key) {
+        case Magnifier.Prefs.SCREEN_MAGNIFIER_FOCUS_FOLLOWING:
+          this.screenMagnifierFocusFollowing_ = !!pref.value;
+          break;
+        default:
+          return;
+      }
+    });
+  }
+
+  /**
+   * Returns whether magnifier viewport should follow focus. Exposed for
+   * testing.
+   *
+   * TODO(crbug.com/1146595): Add Chrome OS preference to allow disabling focus
+   * following for docked magnifier.
+   */
+  shouldFollowFocus() {
+    return this.type === Magnifier.Type.DOCKED ||
+        this.type === Magnifier.Type.FULL_SCREEN &&
+        this.screenMagnifierFocusFollowing_;
+  }
+
   /**
    * Listener for when focus is updated. Moves magnifier to include focused
    * element in viewport.
@@ -53,7 +99,7 @@ class Magnifier {
    */
   onFocus_(event) {
     const {location} = event.target;
-    if (!location) {
+    if (!location || !this.shouldFollowFocus()) {
       return;
     }
 
@@ -68,7 +114,7 @@ class Magnifier {
    */
   onActiveDescendantChanged_(event) {
     const {activeDescendant} = event.target;
-    if (!activeDescendant) {
+    if (!activeDescendant || !this.shouldFollowFocus()) {
       return;
     }
 
@@ -80,3 +126,23 @@ class Magnifier {
     chrome.accessibilityPrivate.moveMagnifierToRect(location);
   }
 }
+
+/**
+ * Magnifier types.
+ * @enum {string}
+ * @const
+ */
+Magnifier.Type = {
+  FULL_SCREEN: 'fullScreen',
+  DOCKED: 'docked',
+};
+
+/**
+ * Preferences that are configurable for Magnifier.
+ * @enum {string}
+ * @const
+ */
+Magnifier.Prefs = {
+  SCREEN_MAGNIFIER_FOCUS_FOLLOWING:
+      'settings.a11y.screen_magnifier_focus_following',
+};
\ No newline at end of file

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

@@ -28,6 +28,22 @@ MagnifierE2ETest = class extends E2ETestBase {
     });
   }
 
+  async getPref(name) {
+    return new Promise(resolve => {
+      chrome.settingsPrivate.getPref(name, (ret) => {
+        resolve(ret);
+      });
+    });
+  }
+
+  async setPref(name, value) {
+    return new Promise(resolve => {
+      chrome.settingsPrivate.setPref(name, value, undefined, () => {
+        resolve();
+      });
+    });
+  }
+
   /** @override */
   testGenCppIncludes() {
     super.testGenCppIncludes();
@@ -100,3 +116,28 @@ TEST_F(
         assertTrue(RectUtil.contains(bounds, banana.location));
       });
     });
+
+
+TEST_F('MagnifierE2ETest', 'ScreenMagnifierFocusFollowingPref', function() {
+  this.newCallback(async () => {
+    // Disable focus following for full screen magnifier, and verify prefs and
+    // state.
+    await this.setPref(Magnifier.Prefs.SCREEN_MAGNIFIER_FOCUS_FOLLOWING, false);
+    pref = await this.getPref(Magnifier.Prefs.SCREEN_MAGNIFIER_FOCUS_FOLLOWING);
+    assertEquals(Magnifier.Prefs.SCREEN_MAGNIFIER_FOCUS_FOLLOWING, pref.key);
+    assertFalse(pref.value);
+    magnifier = accessibilityCommon.getMagnifierForTest();
+    assertEquals(magnifier.type, Magnifier.Type.FULL_SCREEN);
+    assertFalse(magnifier.shouldFollowFocus());
+
+    // Enable focus following for full screen magnifier, and verify prefs and
+    // state.
+    await this.setPref(Magnifier.Prefs.SCREEN_MAGNIFIER_FOCUS_FOLLOWING, true);
+    pref = await this.getPref(Magnifier.Prefs.SCREEN_MAGNIFIER_FOCUS_FOLLOWING);
+    assertEquals(Magnifier.Prefs.SCREEN_MAGNIFIER_FOCUS_FOLLOWING, pref.key);
+    assertTrue(pref.value);
+    magnifier = accessibilityCommon.getMagnifierForTest();
+    assertEquals(magnifier.type, Magnifier.Type.FULL_SCREEN);
+    assertTrue(magnifier.shouldFollowFocus());
+  })();
+});
\ No newline at end of file