Add shortcut keys to ui scaling

ash/accelerators/accelerator_controller.cc

Index: ash/accelerators/accelerator_controller.cc
diff --git a/ash/accelerators/accelerator_controller.cc b/ash/accelerators/accelerator_controller.cc
index 8194d90d71fb5136a4eb9bf1f3871b2139e249cb..9bcf23318c5ec3949a5bd6c252948b3b756ca02c 100644
--- a/ash/accelerators/accelerator_controller.cc
+++ b/ash/accelerators/accelerator_controller.cc
@@ -154,7 +154,7 @@ bool HandleRotateActiveWindow() {
   return true;
 }
 
-const gfx::Display::Rotation GetNextRotation(gfx::Display::Rotation current) {
+gfx::Display::Rotation GetNextRotation(gfx::Display::Rotation current) {
   switch (current) {
     case gfx::Display::ROTATE_0:
       return gfx::Display::ROTATE_90;
@@ -169,13 +169,45 @@ const gfx::Display::Rotation GetNextRotation(gfx::Display::Rotation current) {
   return gfx::Display::ROTATE_0;
 }
 
+float GetNextScale(float scale, bool up) {
+  // These scales are equivalent to 1024, 1280, 1600 and 1920 pixel width
+  // respectively on 2560 pixel width 2x density display.
+  static const float kScales[] = {0.8f, 1.0f, 1.25f, 1.5f};
+  static const size_t kScaleTableSize = arraysize(kScales);
+  for (size_t i = 0; i < kScaleTableSize; ++i) {
+    if (kScales[i] == scale) {
+      if (up && i != kScaleTableSize -1)

[James Cook, 2013/03/15 17:09:38]

nit: "kScaleTableSize - 1"

+        return kScales[i + 1];
+      if (!up && i != 0)
+        return kScales[i - 1];
+      return kScales[i];
+    }
+  }
+  // Fallback to 1.0f if the |scale| wasn't in the list.
+  return 1.0f;
+}
+
+bool HandleScaleUI(bool up) {
+  // UI Scaling is effective only on internal display.
+  int64 display_id = gfx::Display::InternalDisplayId();
+#if defined(OS_CHROMEOS)
+  // On linux desktop, allow ui scalacing on the first dislpay.
+  if (!base::chromeos::IsRunningOnChromeOS())
+    display_id = Shell::GetInstance()->display_manager()->first_display_id();
+#endif
+  const gfx::Display& display = Shell::GetInstance()->display_manager()->
+      GetDisplayForId(display_id);
+  const DisplayInfo& display_info = Shell::GetInstance()->display_manager()->
+      GetDisplayInfo(display);
+  Shell::GetInstance()->display_manager()->SetDisplayUIScale(
+      display.id(), GetNextScale(display_info.ui_scale(), up));
+  return true;
+}
+
 // Rotates the screen.
 bool HandleRotateScreen() {
-  aura::Window* active_window = wm::GetActiveWindow();
-  if (!active_window)
-    return false;
-  const gfx::Display& display =
-      Shell::GetScreen()->GetDisplayNearestWindow(active_window);
+  gfx::Point point = Shell::GetScreen()->GetCursorScreenPoint();
+  gfx::Display display = Shell::GetScreen()->GetDisplayNearestPoint(point);
   const DisplayInfo& display_info =
       Shell::GetInstance()->display_manager()->GetDisplayInfo(display);
   Shell::GetInstance()->display_manager()->SetDisplayRotation(
@@ -758,6 +790,10 @@ bool AcceleratorController::PerformAction(int action,
       }
       break;
     }
+    case SCALE_UI_UP:
+      return HandleScaleUI(true /* up */);
+    case SCALE_UI_DOWN:
+      return HandleScaleUI(false /* down */);
     case ROTATE_WINDOW:
       return HandleRotateActiveWindow();
     case ROTATE_SCREEN:
@@ -767,7 +803,7 @@ bool AcceleratorController::PerformAction(int action,
     case TOGGLE_ROOT_WINDOW_FULL_SCREEN:
       return HandleToggleRootWindowFullScreen();
     case DISPLAY_TOGGLE_SCALE:
-      internal::DisplayManager::ToggleDisplayScale();
+      internal::DisplayManager::ToggleDisplayScaleFactor();
       return true;
     case MAGNIFY_SCREEN_ZOOM_IN:
       return HandleMagnifyScreen(1);