Long press menu (shift+f6) to toggle spoken feedback.

ash/accelerators/magnifier_key_scroller.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 "ash/accelerators/magnifier_key_scroller.h"
+
+#include "ash/accelerators/key_hold_detector.h"
+#include "ash/ash_switches.h"
+#include "ash/magnifier/magnification_controller.h"
+#include "ash/shell.h"
+#include "base/command_line.h"
+
+namespace ash {
+namespace {
+bool magnifier_key_scroller_enabled = false;
+}
+
+// static
+bool MagnifierKeyScroller::IsEnabled() {
+  return (magnifier_key_scroller_enabled ||
+          CommandLine::ForCurrentProcess()->HasSwitch(
+              switches::kAshEnableMagnifierKeyScroller)) &&
+      ash::Shell::GetInstance()->magnification_controller()->IsEnabled();
+}
+
+// static
+void MagnifierKeyScroller::SetEnabled(bool enabled) {
+  magnifier_key_scroller_enabled = enabled;
+}
+
+// static
+scoped_ptr<ui::EventHandler> MagnifierKeyScroller::CreateHandler() {
+  scoped_ptr<KeyHoldDetector::Delegate> delegate(new MagnifierKeyScroller());
+  return scoped_ptr<ui::EventHandler>(new KeyHoldDetector(delegate.Pass()));
+}
+
+bool MagnifierKeyScroller::ShouldProcessEvent(const ui::KeyEvent* event) const {
+  return IsEnabled() &&
+      (event->key_code() == ui::VKEY_UP ||
+       event->key_code() == ui::VKEY_DOWN ||
+       event->key_code() == ui::VKEY_LEFT ||
+       event->key_code() == ui::VKEY_RIGHT);
+}
+
+bool MagnifierKeyScroller::IsStartEvent(const ui::KeyEvent* event) const {
+  return event->type() == ui::ET_KEY_PRESSED &&
+      event->flags() & ui::EF_SHIFT_DOWN;
+}
+
+void MagnifierKeyScroller::OnKeyHold(const ui::KeyEvent* event) {
+  MagnificationController* controller =
+      Shell::GetInstance()->magnification_controller();
+  switch (event->key_code()) {
+    case ui::VKEY_UP:
+      controller->SetScrollDirection(MagnificationController::SCROLL_UP);
+      break;
+    case ui::VKEY_DOWN:
+      controller->SetScrollDirection(MagnificationController::SCROLL_DOWN);
+      break;
+    case ui::VKEY_LEFT:
+      controller->SetScrollDirection(MagnificationController::SCROLL_LEFT);
+      break;
+    case ui::VKEY_RIGHT:
+      controller->SetScrollDirection(MagnificationController::SCROLL_RIGHT);
+      break;
+    default:
+      NOTREACHED() << "Unknown keyboard_code:" << event->key_code();
+  }
+}
+
+void MagnifierKeyScroller::OnKeyUnhold(const ui::KeyEvent* event) {
+  MagnificationController* controller =
+      Shell::GetInstance()->magnification_controller();
+  controller->SetScrollDirection(MagnificationController::SCROLL_NONE);
+}
+
+MagnifierKeyScroller::MagnifierKeyScroller() {}
+
+MagnifierKeyScroller::~MagnifierKeyScroller() {}
+
+}  // namespace ash