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

ui/gfx/screen_win.h

Index: ui/gfx/screen_win.h
diff --git a/ui/gfx/screen_win.h b/ui/gfx/screen_win.h
index 9ece286e919750ac1e1ec8bf167d4548aeec364f..17b37f54a668043f2600285ccb72e88b8570a863 100644
--- a/ui/gfx/screen_win.h
+++ b/ui/gfx/screen_win.h
@@ -8,6 +8,9 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/display_change_notifier.h"
+#include "ui/gfx/geometry/point.h"
+#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"
@@ -19,6 +22,61 @@ class GFX_EXPORT ScreenWin : public Screen {
   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 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);
+
+  // Converts a client DIP point relative to |hwnd| to a client point.

[scottmg, 2015/10/28 18:48:21]

Is this point or pixel?

[robliao, 2015/10/29 00:30:24]

pixel point for consistency with the above. As part of a future refactor, we
should probably agree on a terminology for physical screen pixels vs DIP pixels.
We're currently conflating Screen to represent the dimension format as well as
the coordinate system.

+  // The DPI scale is performed relative to |hwnd| using an origin of (0, 0).
+  static Point DIPToClientPoint(HWND hwnd, const Point& dip_pount);

[scottmg, 2015/10/28 18:48:21]

"pount"

[robliao, 2015/10/29 00:30:24]

Done.

+
+  // 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;
@@ -40,6 +98,12 @@ class GFX_EXPORT ScreenWin : public Screen {
   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.