Refactor Windows DPI Point, Rect, and Size for Multiple Monitor DPI Awareness

ui/gfx/screen_win.h

 // Copyright (c) 2012 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_SCREEN_WIN_H_
 #define UI_GFX_SCREEN_WIN_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/display_change_notifier.h"
+#include "ui/gfx/geometry/point.h"

[sky, 2015/10/29 15:51:51]

you should be able to forward declare the types.

[robliao, 2015/11/07 00:56:40]

Indeed! Done.

+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/geometry/size.h"
 #include "ui/gfx/gfx_export.h"
 #include "ui/gfx/screen.h"
 #include "ui/gfx/win/singleton_hwnd_observer.h"
 
 namespace gfx {
 
 class GFX_EXPORT ScreenWin : public Screen {
  public:
   ScreenWin();
   ~ScreenWin() override;
 
+  // Converts a screen pixel point to a DIP point.
+  // The DPI scale is performed relative to the display containing the screen
+  // pixel point maintaining a constant origin on both Screen and DIP (same as
+  // Windows).
+  static Point ScreenToDIPPoint(const Point& pixel_point);
+
+  // Converts a DIP point to a screen pixel point.
+  // The DPI scale is performed relative to the display containing the DIP point
+  // maintaining a constant origin on both Screen and DIP (same as Windows).
+  static Point DIPToScreenPoint(const Point& dip_point);
+
+  // Converts a client pixel point relative to |hwnd| to a DIP point.
+  // The DPI scale is performed relative to |hwnd| using an origin of (0, 0).
+  static Point ClientToDIPPoint(HWND hwnd, const Point& client_point);

[sky, 2015/10/29 15:51:51]

What is a client point?

[robliao, 2015/11/07 00:56:40]

It's generally a point in an HWND's coordinate system. I used terminology from
Windows
(https://msdn.microsoft.com/en-us/library/windows/desktop/ms633503(v=vs.85).aspx),
but if there is a more Chromium idiomatic term, I'm happy to update this.

+
+  // Converts a client DIP point relative to |hwnd| to a client pixel point.
+  // The DPI scale is performed relative to |hwnd| using an origin of (0, 0).
+  static Point DIPToClientPoint(HWND hwnd, const Point& dip_point);
+
+  // WARNING: there is no right way to scale sizes and rects. The implementation
+  // of these strives to maintain a constant size by scaling the size
+  // independent of the origin. An alternative is to get the enclosing rect,
+  // which is the right way for some situations. Understand which you need
+  // before blindly assuming this is the right way.
+
+  // Converts a screen rect to a DIP rect.
+  // The DPI scale is performed relative to the display nearest to |hwnd|
+  // maintaining a constant origin on both Screen and DIP (same as Windows).
+  // If |hwnd| is null, scaling will be performed to the display nearest to
+  // |pixel_bounds|.
+  static Rect ScreenToDIPRect(HWND hwnd, const Rect& pixel_bounds);
+
+  // Converts a DIP rect to a screen rect.
+  // The DPI scale is performed relative to the display nearest to |hwnd|
+  // maintaining a constant origin on both Screen and DIP (same as Windows).
+  // If |hwnd| is null, scaling will be performed to the display nearest to
+  // |dip_bounds|.
+  static Rect DIPToScreenRect(HWND hwnd, const Rect& dip_bounds);
+
+  // Converts a client rect to a DIP rect.
+  // The DPI scale is performed relative to |hwnd| using an origin of (0, 0).
+  static Rect ClientToDIPRect(HWND hwnd, const Rect& pixel_bounds);
+
+  // Converts a DIP rect to a client rect.
+  // The DPI scale is performed relative to |hwnd| using an origin of (0, 0).
+  static Rect DIPToClientRect(HWND hwnd, const Rect& dip_bounds);
+
+  // Converts a screen size to a DIP size.
+  // The DPI scale is performed relative to the display nearest to |hwnd|.
+  static Size ScreenToDIPSize(HWND hwnd, const Size& size_in_pixels);
+
+  // Converts a DIP size to a screen size.
+  // The DPI scale is performed relative to the display nearest to |hwnd|.
+  static Size DIPToScreenSize(HWND hwnd, const Size& dip_size);
+
  protected:
   // Overridden from gfx::Screen:
   gfx::Point GetCursorScreenPoint() override;
   gfx::NativeWindow GetWindowUnderCursor() override;
   gfx::NativeWindow GetWindowAtScreenPoint(const gfx::Point& point) override;
   int GetNumDisplays() const override;
   std::vector<gfx::Display> GetAllDisplays() const override;
   gfx::Display GetDisplayNearestWindow(gfx::NativeView window) const override;
   gfx::Display GetDisplayNearestPoint(const gfx::Point& point) const override;
   gfx::Display GetDisplayMatching(const gfx::Rect& match_rect) const override;
   gfx::Display GetPrimaryDisplay() const override;
   void AddObserver(DisplayObserver* observer) override;
   void RemoveObserver(DisplayObserver* observer) override;
 
   // Returns the HWND associated with the NativeView.
   virtual HWND GetHWNDFromNativeView(NativeView window) const;
 
   // Returns the NativeView associated with the HWND.
   virtual NativeWindow GetNativeWindowFromHWND(HWND hwnd) const;
 
  private:
+  static gfx::Display GetDisplayNearestHWND(HWND hwnd);
+  static gfx::Display GetDisplayNearestRect(const Rect& rect);
+  static gfx::Display GetDisplayNearestScreenPoint(const Point& screen_point);
+  static float GetScaleFactorForHWND(HWND hwnd);
+  static float GetScaleFactorForScreenPoint(const Point& screen_point);
+
   void OnWndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
 
   // Helper implementing the DisplayObserver handling.
   gfx::DisplayChangeNotifier change_notifier_;
 
   scoped_ptr<SingletonHwndObserver> singleton_hwnd_observer_;
 
   // Current list of displays.
   std::vector<gfx::Display> displays_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenWin);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_SCREEN_WIN_H_