Add ScreenWin::GetSystemMetricsForHwnd

ui/display/win/screen_win.cc

 // 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.
 
 #include "ui/display/win/screen_win.h"
 
 #include <windows.h>
 #include <shellscalingapi.h>
 
 #include <algorithm>
@@ skipping 277 matching lines @@
   return ScaleToCeiledSize(size_in_pixels, 1.0f / GetScaleFactorForHWND(hwnd));
 }
 
 // static
 gfx::Size ScreenWin::DIPToScreenSize(HWND hwnd, const gfx::Size& dip_size) {
   float scale_factor = GetScaleFactorForHWND(hwnd);
   // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
   return ScaleToCeiledSize(dip_size, scale_factor);
 }
 
+// static
+int ScreenWin::GetSystemMetricsForHwnd(HWND hwnd, int metric) {
+  // GetSystemMetrics returns screen values based off of the primary monitor's
+  // DPI. This will further scale based off of the DPI for |hwnd|.
+  if (!g_screen_win_instance)

[oshima, 2016/06/30 19:06:12]

is this for unit test case?

[robliao, 2016/06/30 19:20:24]

Yup. This is for the unit tests.

+    return ::GetSystemMetrics(metric);
+
+  Display primary_display(g_screen_win_instance->GetPrimaryDisplay());
+  int system_metrics_result = g_screen_win_instance->GetSystemMetrics(metric);
+
+  float scale_factor = hwnd
+      ? GetScaleFactorForHWND(hwnd) / primary_display.device_scale_factor()

[oshima, 2016/06/30 19:06:12]

calling this "scale factor" is confusing. Can you call it like
the "scale_to_primary_metrics" or something like that?

[robliao, 2016/06/30 19:20:24]

I went with metrics_relative_scale_factor. How's that?

+      : 1.0f;
+  return static_cast<int>(std::round(system_metrics_result * scale_factor));
+}
+
 HWND ScreenWin::GetHWNDFromNativeView(gfx::NativeView window) const {
   NOTREACHED();
   return nullptr;
 }
 
 gfx::NativeWindow ScreenWin::GetNativeWindowFromHWND(HWND hwnd) const {
   NOTREACHED();
   return nullptr;
 }
 
@@ skipping 104 matching lines @@
 
 MONITORINFOEX ScreenWin::MonitorInfoFromWindow(HWND hwnd,
                                                DWORD default_options) const {
   return MonitorInfoFromHMONITOR(::MonitorFromWindow(hwnd, default_options));
 }
 
 HWND ScreenWin::GetRootWindow(HWND hwnd) const {
   return ::GetAncestor(hwnd, GA_ROOT);
 }
 
+int ScreenWin::GetSystemMetrics(int metric) const {
+  return ::GetSystemMetrics(metric);
+}
+
 void ScreenWin::OnWndProc(HWND hwnd,
                           UINT message,
                           WPARAM wparam,
                           LPARAM lparam) {
   if (message != WM_DISPLAYCHANGE)
     return;
 
   std::vector<display::Display> old_displays = GetAllDisplays();
   UpdateFromDisplayInfos(GetDisplayInfosFromSystem());
   change_notifier_.NotifyDisplaysChanged(old_displays, GetAllDisplays());
@@ skipping 90 matching lines @@
 ScreenWinDisplay ScreenWin::GetScreenWinDisplayVia(Getter getter,
                                                    GetterType value) {
   if (!g_screen_win_instance)
     return ScreenWinDisplay();
 
   return (g_screen_win_instance->*getter)(value);
 }
 
 }  // namespace win
 }  // namespace display