[Chromecast] Handle device scale factor correctly

chromecast/graphics/cast_screen.cc

 // Copyright 2015 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 "chromecast/graphics/cast_screen.h"
 
 #include <stdint.h>
 
 #include "ui/aura/env.h"
 #include "ui/display/screen.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace chromecast {
 
 namespace {
 
 const int64_t kDisplayId = 1;
 
-const int k720pWidth = 1280;
-const int k720pHeight = 720;
-
-// When CastScreen is first initialized, we may not have any display info
-// available. These constants hold the initial size that we default to, and
-// the size can be updated when we have actual display info at hand with
-// UpdateDisplaySize().
-const int kInitDisplayWidth = k720pWidth;
-const int kInitDisplayHeight = k720pHeight;
-
 }  // namespace
 
 CastScreen::~CastScreen() {
 }
 
-void CastScreen::SetDisplayResizeCallback(const DisplayResizeCallback& cb) {
-  DCHECK(!cb.is_null());
-  display_resize_cb_ = cb;
-}
-
-void CastScreen::UpdateDisplaySize(const gfx::Size& size) {
-  display_.SetScaleAndBounds(1.0f, gfx::Rect(size));
-  if (!display_resize_cb_.is_null())
-    display_resize_cb_.Run(Size(size.width(), size.height()));
-}
-
 gfx::Point CastScreen::GetCursorScreenPoint() {
   return aura::Env::GetInstance()->last_mouse_location();
 }
 
 bool CastScreen::IsWindowUnderCursor(gfx::NativeWindow window) {
   NOTIMPLEMENTED();
   return false;
 }
 
 gfx::NativeWindow CastScreen::GetWindowAtScreenPoint(const gfx::Point& point) {
@@ skipping 24 matching lines @@
 }
 
 display::Display CastScreen::GetPrimaryDisplay() const {
   return display_;
 }
 
 void CastScreen::AddObserver(display::DisplayObserver* observer) {}
 
 void CastScreen::RemoveObserver(display::DisplayObserver* observer) {}
 
-CastScreen::CastScreen() : display_(kDisplayId) {
-  display_.SetScaleAndBounds(1.0f,
-                             gfx::Rect(kInitDisplayWidth, kInitDisplayHeight));
+CastScreen::CastScreen(const gfx::Size& size) : display_(kDisplayId) {
+  // Device scale factor computed relative to 720p display
+  const float device_scale_factor = size.height() / 720.0f;
+  display_.SetScaleAndBounds(device_scale_factor, gfx::Rect(size));
 }
 
 }  // namespace chromecast