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// Copyright 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/dpi.h"
#include <windows.h>
#include "base/win/scoped_hdc.h"
#include "ui/display/display.h"
namespace display {
namespace win {
namespace {
const float kDefaultDPI = 96.f;
float g_device_scale_factor = 0.f;
gfx::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 gfx::Size(dpi_x, dpi_y);
}
} // namespace
void SetDefaultDeviceScaleFactor(float scale) {
DCHECK_NE(0.f, scale);
g_device_scale_factor = scale;
}
float GetDPIScale() {
if (Display::HasForceDeviceScaleFactor())
return Display::GetForcedDeviceScaleFactor();
return GetUnforcedDeviceScaleFactor();
}
float GetUnforcedDeviceScaleFactor() {
return g_device_scale_factor ? g_device_scale_factor
: GetScalingFactorFromDPI(GetDPI().width());
}
int GetDPIFromScalingFactor(float device_scaling_factor) {
return kDefaultDPI * device_scaling_factor;
}
float GetScalingFactorFromDPI(int dpi) {
return static_cast<float>(dpi) / kDefaultDPI;
}
} // namespace win
} // namespace display
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