ui/gfx/win/dpi.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ui/gfx/win/dpi.h"
   6
   7 #include <windows.h>
   8 #include "base/win/scoped_hdc.h"
   9 #include "ui/gfx/display.h"
  10 #include "ui/gfx/point_conversions.h"
  11 #include "ui/gfx/rect_conversions.h"
  12 #include "ui/gfx/size_conversions.h"
  13
  14 namespace {
  15
  16 int kDefaultDPIX = 96;
  17 int kDefaultDPIY = 96;
  18
  19 bool force_highdpi_for_testing = false;
  20
  21 float g_device_scale_factor = 0.0f;
  22
  23 float GetUnforcedDeviceScaleFactor() {
  24   // If the global device scale factor is initialized use it. This is to ensure
  25   // we use the same scale factor across all callsites.
  26   if (g_device_scale_factor)
  27     return g_device_scale_factor;
  28   return static_cast<float>(gfx::GetDPI().width()) /
  29       static_cast<float>(kDefaultDPIX);
  30 }
  31
  32 }  // namespace
  33
  34 namespace gfx {
  35
  36 void InitDeviceScaleFactor(float scale) {
  37   DCHECK_NE(0.0f, scale);
  38   g_device_scale_factor = scale;
  39 }
  40
  41 Size GetDPI() {
  42   static int dpi_x = 0;
  43   static int dpi_y = 0;
  44   static bool should_initialize = true;
  45
  46   if (should_initialize) {
  47     should_initialize = false;
  48     base::win::ScopedGetDC screen_dc(NULL);
  49     // This value is safe to cache for the life time of the app since the
  50     // user must logout to change the DPI setting. This value also applies
  51     // to all screens.
  52     dpi_x = GetDeviceCaps(screen_dc, LOGPIXELSX);
  53     dpi_y = GetDeviceCaps(screen_dc, LOGPIXELSY);
  54   }
  55   return Size(dpi_x, dpi_y);
  56 }
  57
  58 float GetDPIScale() {
  59   if (gfx::Display::HasForceDeviceScaleFactor())
  60     return gfx::Display::GetForcedDeviceScaleFactor();
  61   float dpi_scale = GetUnforcedDeviceScaleFactor();
  62   if (dpi_scale <= 1.25) {
  63     // Force 125% and below to 100% scale. We do this to maintain previous
  64     // (non-DPI-aware) behavior where only the font size was boosted.
  65     dpi_scale = 1.0;
  66   }
  67   return dpi_scale;
  68 }
  69
  70 namespace win {
  71
  72 Point ScreenToDIPPoint(const Point& pixel_point) {
  73   return ToFlooredPoint(ScalePoint(pixel_point, 1.0f / GetDPIScale()));
  74 }
  75
  76 Point DIPToScreenPoint(const Point& dip_point) {
  77   return ToFlooredPoint(ScalePoint(dip_point, GetDPIScale()));
  78 }
  79
  80 Rect ScreenToDIPRect(const Rect& pixel_bounds) {
  81   // It's important we scale the origin and size separately. If we instead
  82   // calculated the size from the floored origin and ceiled right the size could
  83   // vary depending upon where the two points land. That would cause problems
  84   // for the places this code is used (in particular mapping from native window
  85   // bounds to DIPs).
  86   return Rect(ScreenToDIPPoint(pixel_bounds.origin()),
  87               ScreenToDIPSize(pixel_bounds.size()));
  88 }
  89
  90 Rect DIPToScreenRect(const Rect& dip_bounds) {
  91   // See comment in ScreenToDIPRect for why we calculate size like this.
  92   return Rect(DIPToScreenPoint(dip_bounds.origin()),
  93               DIPToScreenSize(dip_bounds.size()));
  94 }
  95
  96 Size ScreenToDIPSize(const Size& size_in_pixels) {
  97   // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
  98   return ToCeiledSize(ScaleSize(size_in_pixels, 1.0f / GetDPIScale()));
  99 }
 100
 101 Size DIPToScreenSize(const Size& dip_size) {
 102   // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
 103   return ToCeiledSize(ScaleSize(dip_size, GetDPIScale()));
 104 }
 105
 106 int GetSystemMetricsInDIP(int metric) {
 107   return static_cast<int>(GetSystemMetrics(metric) / GetDPIScale() + 0.5);
 108 }
 109
 110 }  // namespace win
 111 }  // namespace gfx