ScreenWin Testability and Restructuring

ui/gfx/win/display_manager.h

+// Copyright 2016 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.
+
+#ifndef UI_GFX_WIN_DISPLAY_MANAGER_H_
+#define UI_GFX_WIN_DISPLAY_MANAGER_H_
+
+#include <windows.h>
+#include <memory>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/singleton.h"
+#include "base/observer_list.h"
+#include "ui/gfx/display.h"
+#include "ui/gfx/gfx_export.h"
+
+namespace gfx {
+
+class Point;
+class Rect;
+class SingletonHwndObserver;
+
+namespace win {
+
+class DisplayManagerObserver;
+class DisplayInfo;
+class ScreenWinDisplay;
+
+// Holds all of the ScreenWinDisplays available in the system.
+// Normally, this means there is a 1:1 correspondence between ScreenWinDisplays
+// and HMONITORS. However, in tests, we can't depend on this so we allow
+// overrides of system API functions via virtual calls.
+class GFX_EXPORT DisplayManager {

[sky, 2016/02/02 16:18:20]

Why do we need both DisplayManager and ScreenWin? AFAICT DisplayManager is only
used by ScreenWin. Why not make ScreenWin have this functionality? For the
mocking it would be clearer to have a pure virtual class.

[robliao, 2016/02/02 18:08:07]

Coming up in a next CL are some static scaling calls that can't depend on the
existence of a ScreenWin.
The scaling calls need access to physical display information that can't be
provided by unit tests that substitute their own screen harness
(gfx::TestScreen). 

The display manager separation allows these static calls to obtain physical
information and fallback to 1.0x scaling for tests that use gfx::TestScreen

+ public:
+  static DisplayManager* GetInstance();
+
+  virtual void Initialize();
+
+  void AddObserver(DisplayManagerObserver* observer);
+  void RemoveObserver(DisplayManagerObserver* observer);
+
+  const std::vector<ScreenWinDisplay>& GetScreenWinDisplays();
+
+  // Returns the ScreenWinDisplay closest to or enclosing |hwnd|.
+  ScreenWinDisplay GetScreenWinDisplayNearestHWND(HWND hwnd) const;
+
+  // Returns the ScreenWinDisplay closest to or enclosing |screen_rect|.
+  ScreenWinDisplay GetScreenWinDisplayNearestScreenRect(
+      const Rect& screen_rect) const;
+
+  // Returns the ScreenWinDisplay closest to or enclosing |screen_point|.
+  ScreenWinDisplay GetScreenWinDisplayNearestScreenPoint(
+      const Point& screen_point) const;
+
+  // Returns the ScreenWinDisplay corresponding to the primary monitor.
+  ScreenWinDisplay GetPrimaryScreenWinDisplay() const;
+
+  // Virtual to support mocking by unit tests.
+  virtual MONITORINFOEX MonitorInfoFromScreenPoint(
+      const gfx::Point& screen_point) const;
+  virtual MONITORINFOEX MonitorInfoFromScreenRect(const gfx::Rect& screen_rect)
+      const;
+  virtual MONITORINFOEX MonitorInfoFromWindow(HWND hwnd, DWORD default_options)
+      const;
+  virtual HWND GetRootWindow(HWND hwnd) const;
+
+ protected:
+  friend std::default_delete<DisplayManager>;
+
+  static void SetInstanceForTesting(scoped_ptr<DisplayManager> display_manager);
+
+  DisplayManager();
+  virtual ~DisplayManager();
+
+  void UpdateFromDisplayInfos(const std::vector<DisplayInfo>& display_infos);
+
+ private:
+  ScreenWinDisplay GetScreenWinDisplay(const MONITORINFOEX& monitor_info) const;
+  void WndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
+
+  scoped_ptr<gfx::SingletonHwndObserver> singleton_hwnd_observer_;
+  base::ObserverList<DisplayManagerObserver, true> observer_list_;
+  std::vector<ScreenWinDisplay> screen_win_displays_;
+
+  DISALLOW_COPY_AND_ASSIGN(DisplayManager);
+};
+
+}  // namespace win
+}  // namespace gfx
+
+#endif  // UI_GFX_WIN_DISPLAY_MANAGER_H_