ChromeVox: Disable following a11y events after screen off alert is received

chrome/browser/ui/ash/chrome_shell_delegate.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/ui/ash/chrome_shell_delegate.h"
 
 #include <stddef.h>
 
 #include <limits>
 
@@ skipping 269 matching lines @@
     if (profile) {
       int msg = 0;
       switch (alert) {
         case ash::A11Y_ALERT_CAPS_ON:
           msg = IDS_A11Y_ALERT_CAPS_ON;
           break;
         case ash::A11Y_ALERT_CAPS_OFF:
           msg = IDS_A11Y_ALERT_CAPS_OFF;
           break;
         case ash::A11Y_ALERT_SCREEN_ON:
+          // Enable automation manager when alert is screen-on, as it is
+          // previously disabled by alert screen-off.
+          SetAutomationManagerEnabled(profile, true);
           msg = IDS_A11Y_ALERT_SCREEN_ON;
           break;
         case ash::A11Y_ALERT_SCREEN_OFF:
           msg = IDS_A11Y_ALERT_SCREEN_OFF;
           break;
         case ash::A11Y_ALERT_WINDOW_NEEDED:
           msg = IDS_A11Y_ALERT_WINDOW_NEEDED;
           break;
         case ash::A11Y_ALERT_WINDOW_OVERVIEW_MODE_ENTERED:
           msg = IDS_A11Y_ALERT_WINDOW_OVERVIEW_MODE_ENTERED;
           break;
         case ash::A11Y_ALERT_NONE:
           msg = 0;
           break;
       }
 
       if (msg) {
         AutomationManagerAura::GetInstance()->HandleAlert(
             profile, l10n_util::GetStringUTF8(msg));
+        // After handling the alert, if the alert is screen-off, we should
+        // disable automation manager to handle any following a11y events.
+        if (alert == ash::A11Y_ALERT_SCREEN_OFF)
+          SetAutomationManagerEnabled(profile, false);
       }
     }
   }
 
   ash::AccessibilityAlert GetLastAccessibilityAlert() override {
     return ash::A11Y_ALERT_NONE;
   }
 
   bool ShouldToggleSpokenFeedbackViaTouch() override {
     DCHECK(AccessibilityManager::Get());
@@ skipping 13 matching lines @@
 
   base::TimeDelta PlayShutdownSound() const override {
     return AccessibilityManager::Get()->PlayShutdownSound();
   }
 
   void HandleAccessibilityGesture(ui::AXGesture gesture) override {
     AccessibilityManager::Get()->HandleAccessibilityGesture(gesture);
   }
 
  private:
+  void SetAutomationManagerEnabled(content::BrowserContext* context,
+                                   bool enabled) {
+    AutomationManagerAura* manager = AutomationManagerAura::GetInstance();
+    DCHECK(context);

[James Cook, 2017/02/06 16:38:45]

super nit: Do this as the first line of the function so that it's obvious it's a
precondition check.

+    if (enabled)
+      manager->Enable(context);
+    else
+      manager->Disable();
+  }
+
   DISALLOW_COPY_AND_ASSIGN(AccessibilityDelegateImpl);
 };
 
 }  // namespace
 
 ChromeShellDelegate::ChromeShellDelegate()
     : shelf_delegate_(NULL) {
   PlatformInit();
 }
 
@@ skipping 225 matching lines @@
       NOTREACHED() << "Unexpected notification " << type;
   }
 }
 
 void ChromeShellDelegate::PlatformInit() {
   registrar_.Add(this, chrome::NOTIFICATION_LOGIN_USER_PROFILE_PREPARED,
                  content::NotificationService::AllSources());
   registrar_.Add(this, chrome::NOTIFICATION_SESSION_STARTED,
                  content::NotificationService::AllSources());
 }