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

ui/gfx/win/dpi.cc

Index: ui/gfx/win/dpi.cc
diff --git a/ui/gfx/win/dpi.cc b/ui/gfx/win/dpi.cc
index c0c44d612b80a91e736f6d9eedcd2ba2a7a33fb3..8a4e4d606b1921d9c488338958de83adc6ced671 100644
--- a/ui/gfx/win/dpi.cc
+++ b/ui/gfx/win/dpi.cc
@@ -10,6 +10,7 @@
 #include "ui/gfx/geometry/point_conversions.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
+#include "ui/gfx/screen.h"
 
 namespace {
 
@@ -17,15 +18,6 @@ int kDefaultDPI = 96;
 
 float g_device_scale_factor = 0.0f;
 
-float GetUnforcedDeviceScaleFactor() {
-  // If the global device scale factor is initialized use it. This is to ensure
-  // we use the same scale factor across all callsites.
-  if (g_device_scale_factor)
-    return g_device_scale_factor;
-  return static_cast<float>(gfx::GetDPI().width()) /
-      static_cast<float>(kDefaultDPI);
-}
-
 }  // namespace
 
 namespace gfx {
@@ -35,70 +27,35 @@ void InitDeviceScaleFactor(float scale) {
   g_device_scale_factor = scale;
 }
 
-Size GetDPI() {
-  static int dpi_x = 0;
-  static int dpi_y = 0;
-  static bool should_initialize = true;
-
-  if (should_initialize) {
-    should_initialize = false;
-    base::win::ScopedGetDC screen_dc(NULL);
-    // This value is safe to cache for the life time of the app since the
-    // user must logout to change the DPI setting. This value also applies
-    // to all screens.
-    dpi_x = GetDeviceCaps(screen_dc, LOGPIXELSX);
-    dpi_y = GetDeviceCaps(screen_dc, LOGPIXELSY);
-  }
-  return Size(dpi_x, dpi_y);
+int GetDPIFromScalingFactor(float device_scaling_factor) {
+  return static_cast<float>(kDefaultDPI) * device_scaling_factor;
 }
 
 float GetDPIScale() {
   if (gfx::Display::HasForceDeviceScaleFactor())
     return gfx::Display::GetForcedDeviceScaleFactor();
-  float dpi_scale = GetUnforcedDeviceScaleFactor();
-  if (dpi_scale <= 1.25) {
-    // Force 125% and below to 100% scale. We do this to maintain previous
-    // (non-DPI-aware) behavior where only the font size was boosted.
-    dpi_scale = 1.0;
-  }
-  return dpi_scale;
-}
 
-namespace win {
-
-Point ScreenToDIPPoint(const Point& pixel_point) {
-  return ScaleToFlooredPoint(pixel_point, 1.0f / GetDPIScale());
-}
-
-Point DIPToScreenPoint(const Point& dip_point) {
-  return ScaleToFlooredPoint(dip_point, GetDPIScale());
-}
-
-Rect ScreenToDIPRect(const Rect& pixel_bounds) {
-  // It's important we scale the origin and size separately. If we instead
-  // calculated the size from the floored origin and ceiled right the size could
-  // vary depending upon where the two points land. That would cause problems
-  // for the places this code is used (in particular mapping from native window
-  // bounds to DIPs).
-  return Rect(ScreenToDIPPoint(pixel_bounds.origin()),
-              ScreenToDIPSize(pixel_bounds.size()));
-}
+  if (g_device_scale_factor)
+    return g_device_scale_factor;
 
-Rect DIPToScreenRect(const Rect& dip_bounds) {
-  // See comment in ScreenToDIPRect for why we calculate size like this.
-  return Rect(DIPToScreenPoint(dip_bounds.origin()),
-              DIPToScreenSize(dip_bounds.size()));
-}
+  static float device_scale_factor = 0.0f;
+  if (!device_scale_factor) {
+    base::win::ScopedGetDC screen_dc(NULL);
+    int dpi_x = GetDeviceCaps(screen_dc, LOGPIXELSX);
+    DCHECK(dpi_x == GetDeviceCaps(screen_dc, LOGPIXELSX));
+    device_scale_factor =
+        static_cast<float>(dpi_x) / static_cast<float>(kDefaultDPI);
+    if (device_scale_factor <= 1.25) {
+      // Force 125% and below to 100% scale. We do this to maintain previous
+      // (non-DPI-aware) behavior where only the font size was boosted.
+      device_scale_factor = 1.0;
+    }
+  }
 
-Size ScreenToDIPSize(const Size& size_in_pixels) {
-  // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
-  return ScaleToCeiledSize(size_in_pixels, 1.0f / GetDPIScale());
+  return device_scale_factor;
 }
 
-Size DIPToScreenSize(const Size& dip_size) {
-  // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
-  return ScaleToCeiledSize(dip_size, GetDPIScale());
-}
+namespace win {
 
 int GetSystemMetricsInDIP(int metric) {
   return static_cast<int>(GetSystemMetrics(metric) / GetDPIScale() + 0.5);