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

chrome/browser/ui/aura/accessibility/automation_manager_aura.cc

 // Copyright 2014 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/aura/accessibility/automation_manager_aura.h"
 
 #include <stddef.h>
 
 #include <vector>
 
 #include "base/memory/singleton.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/api/automation_internal/automation_event_router.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/common/extensions/chrome_extension_messages.h"
+#include "chrome/grit/generated_resources.h"
 #include "content/public/browser/ax_event_notification_details.h"
 #include "content/public/browser/browser_context.h"
 #include "ui/accessibility/ax_action_data.h"
 #include "ui/accessibility/ax_enums.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window.h"
+#include "ui/base/l10n/l10n_util.h"
 #include "ui/views/accessibility/ax_aura_obj_wrapper.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
 
 #if defined(OS_CHROMEOS)
 #include "ash/wm/window_util.h"  // nogncheck
 #endif
 
 using content::BrowserContext;
 using extensions::AutomationEventRouter;
 
+namespace {
+
+bool IsScreenOffAlert(const std::string& text) {
+  return text == l10n_util::GetStringUTF8(IDS_A11Y_ALERT_SCREEN_OFF);
+}
+
+bool IsScreenOnAlert(const std::string& text) {
+  return text == l10n_util::GetStringUTF8(IDS_A11Y_ALERT_SCREEN_ON);
+}
+
+}  // namespace
+
 // static
 AutomationManagerAura* AutomationManagerAura::GetInstance() {
   return base::Singleton<AutomationManagerAura>::get();
 }
 
 void AutomationManagerAura::Enable(BrowserContext* context) {
   enabled_ = true;
   if (!current_tree_.get())
     current_tree_.reset(new AXTreeSourceAura());
   ResetSerializer();
@@ skipping 25 matching lines @@
     return;
 
   views::AXAuraObjWrapper* aura_obj = view ?
       views::AXAuraObjCache::GetInstance()->GetOrCreate(view) :
       current_tree_->GetRoot();
   SendEvent(nullptr, aura_obj, event_type);
 }
 
 void AutomationManagerAura::HandleAlert(content::BrowserContext* context,
                                         const std::string& text) {
-  if (!enabled_)
+  if (!enabled_ && !IsScreenOnAlert(text))
     return;
 
   views::AXAuraObjWrapper* obj =
       static_cast<AXRootObjWrapper*>(current_tree_->GetRoot())
           ->GetAlertForText(text);
   SendEvent(context, obj, ui::AX_EVENT_ALERT);
+
+  if (IsScreenOffAlert(text))

[David Tseng, 2017/02/03 00:27:15]

I wouldn't want to check against this string every single time an alert gets
fired.

How about adding AutomationManagerAura to subscribe to screen on/off
notifications? 

[Qiang(Joe) Xu, 2017/02/03 02:46:54]

Screen on/off info may come from chromeos::power_manager_client. Power button
event is processed in ash/. I feel it has code dependency issue and timing
issue.

Another way is ChromeShellDelegate::TriggerAccessibilityAlert to pass in the
screen on/off information of the alert. WDYT?

+    Disable();
+  else if (IsScreenOnAlert(text))
+    Enable(context);
 }
 
 void AutomationManagerAura::PerformAction(
     const ui::AXActionData& data) {
   CHECK(enabled_);
 
   switch (data.action) {
     case ui::AX_ACTION_DO_DEFAULT:
       current_tree_->DoDefault(data.target_node_id);
       break;
@@ skipping 99 matching lines @@
 
   processing_events_ = false;
   auto pending_events_copy = pending_events_;
   pending_events_.clear();
   for (size_t i = 0; i < pending_events_copy.size(); ++i) {
     SendEvent(context,
               pending_events_copy[i].first,
               pending_events_copy[i].second);
   }
 }