ui/gfx/win/dpi.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/gfx/win/dpi.h"

#include <windows.h>
#include "base/win/scoped_hdc.h"
#include "ui/gfx/display.h"
#include "ui/gfx/point_conversions.h"
#include "ui/gfx/rect_conversions.h"
#include "ui/gfx/size_conversions.h"

namespace {

int kDefaultDPIX = 96;
int kDefaultDPIY = 96;

bool force_highdpi_for_testing = false;

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>(kDefaultDPIX);
}

}  // namespace

namespace gfx {

void InitDeviceScaleFactor(float scale) {
  DCHECK_NE(0.0f, 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);
}

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 ToFlooredPoint(ScalePoint(pixel_point, 1.0f / GetDPIScale()));
}

Point DIPToScreenPoint(const Point& dip_point) {
  return ToFlooredPoint(ScalePoint(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()));
}

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()));
}

Size ScreenToDIPSize(const Size& size_in_pixels) {
  // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
  return ToCeiledSize(ScaleSize(size_in_pixels, 1.0f / GetDPIScale()));
}

Size DIPToScreenSize(const Size& dip_size) {
  // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
  return ToCeiledSize(ScaleSize(dip_size, GetDPIScale()));
}

int GetSystemMetricsInDIP(int metric) {
  return static_cast<int>(GetSystemMetrics(metric) / GetDPIScale() + 0.5);
}

}  // namespace win
}  // namespace gfx