Add key based scrolling on magnified screen for kiosk mode.

ash/magnifier/magnifier_key_scroller.cc

Index: ash/magnifier/magnifier_key_scroller.cc
diff --git a/ash/magnifier/magnifier_key_scroller.cc b/ash/magnifier/magnifier_key_scroller.cc
new file mode 100644
index 0000000000000000000000000000000000000000..745fe8a59c841a367e540a0d914d707d96d31d53
--- /dev/null
+++ b/ash/magnifier/magnifier_key_scroller.cc
@@ -0,0 +1,146 @@
+// 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/magnifier/magnifier_key_scroller.h"
+
+#include <X11/Xlib.h>
+
+#undef RootWindow
+#undef Status
+
+#include "ash/ash_switches.h"
+#include "ash/magnifier/magnification_controller.h"
+#include "ash/shell.h"
+#include "base/command_line.h"
+#include "base/message_loop/message_loop.h"
+#include "ui/aura/root_window.h"
+#include "ui/aura/window_tracker.h"
+
+namespace ash {
+namespace {
+
+bool magnifier_key_scroller_enabled = false;
+
+void ScrollScreen(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 DispatchPressedEvent(XEvent native_event,
+                          scoped_ptr<aura::WindowTracker> tracker) {
+  // The target window may be gone.
+  if (tracker->windows().empty())
+    return;
+  aura::Window* target = *(tracker->windows().begin());
+  ui::KeyEvent event(&native_event, false);
+  event.set_flags(event.flags() | ui::EF_IS_SYNTHESIZED);
+  ui::EventDispatchDetails result ALLOW_UNUSED =
+      target->GetDispatcher()->OnEventFromSource(&event);
+}
+
+void PostPressedEvent(ui::KeyEvent* event) {
+  // Modify RELEASED event to PRESSED event.
+  XEvent xkey = *(event->native_event());
+  xkey.xkey.type = KeyPress;
+  xkey.xkey.state |= ShiftMask;
+  scoped_ptr<aura::WindowTracker> tracker(new aura::WindowTracker);
+  tracker->Add(static_cast<aura::Window*>(event->target()));
+
+  base::MessageLoopForUI::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&DispatchPressedEvent, xkey, base::Passed(&tracker)));
+}
+
+}  // namespace
+
+// 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;
+}
+
+MagnifierKeyScroller::MagnifierKeyScroller()
+    : state_(INITIAL) {}
+
+MagnifierKeyScroller::~MagnifierKeyScroller() {}
+
+void MagnifierKeyScroller::OnKeyEvent(
+    ui::KeyEvent* event) {
+  if (!IsEnabled())
+    return;
+
+  if (event->key_code() != ui::VKEY_UP &&
+      event->key_code() != ui::VKEY_DOWN &&
+      event->key_code() != ui::VKEY_LEFT &&
+      event->key_code() != ui::VKEY_RIGHT) {
+    return;
+  }
+
+  if (event->type() == ui::ET_KEY_PRESSED &&
+      event->flags() & ui::EF_SHIFT_DOWN) {
+    switch (state_) {
+      case INITIAL:
+        // Pass through posted event.
+        if (event->flags() & ui::EF_IS_SYNTHESIZED) {
+          event->set_flags(event->flags() & ~ui::EF_IS_SYNTHESIZED);
+          return;
+        }
+        state_ = PRESSED;
+        // Don't process ET_KEY_PRESSED event yet. The ET_KEY_PRESSED
+        // event will be generated upon ET_KEY_RELEASEED event below.
+        event->StopPropagation();
+        break;
+      case PRESSED:
+        state_ = HOLD;
+        // pass through
+      case HOLD:
+        ScrollScreen(event);
+        event->StopPropagation();
+        break;
+      }
+  } else if (event->type() == ui::ET_KEY_RELEASED) {
+    switch (state_) {
+      case INITIAL:
+        break;
+      case PRESSED: {
+        PostPressedEvent(event);
+        event->StopPropagation();
+        break;
+      }
+      case HOLD: {
+        MagnificationController* controller =
+            Shell::GetInstance()->magnification_controller();
+        controller->SetScrollDirection(MagnificationController::SCROLL_NONE);
+        event->StopPropagation();
+        break;
+      }
+    }
+    state_ = INITIAL;
+  }
+}
+
+}  // namespace ash