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// Copyright 2014 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/util/display_util.h"
#include "base/logging.h"
namespace ui {
namespace {
// A list of bogus sizes in mm that should be ignored.
// See crbug.com/136533. The first element maintains the minimum
// size required to be valid size.
const int kInvalidDisplaySizeList[][2] = {
{40, 30},
{50, 40},
{160, 90},
{160, 100},
};
// The DPI threshold to detect high density screen.
// Higher DPI than this will use device_scale_factor=2.
const unsigned int kHighDensityDPIThresholdSmall = 170;
// The HiDPI threshold for large (usually external) monitors. Lower threshold
// makes sense for large monitors, because such monitors should be located
// farther from the user's face usually. See http://crbug.com/348279
const unsigned int kHighDensityDPIThresholdLarge = 150;
// The width threshold in mm for "large" monitors.
const int kLargeDisplayWidthThresholdMM = 500;
// 1 inch in mm.
const float kInchInMm = 25.4f;
} // namespace
bool IsDisplaySizeBlackListed(const gfx::Size& physical_size) {
// Ignore if the reported display is smaller than minimum size.
if (physical_size.width() <= kInvalidDisplaySizeList[0][0] ||
physical_size.height() <= kInvalidDisplaySizeList[0][1]) {
VLOG(1) << "Smaller than minimum display size";
return true;
}
for (size_t i = 1; i < arraysize(kInvalidDisplaySizeList); ++i) {
const gfx::Size size(kInvalidDisplaySizeList[i][0],
kInvalidDisplaySizeList[i][1]);
if (physical_size == size) {
VLOG(1) << "Black listed display size detected:" << size.ToString();
return true;
}
}
return false;
}
float GetScaleFactor(const gfx::Size& physical_size_in_mm,
const gfx::Size& screen_size_in_pixels) {
if (IsDisplaySizeBlackListed(physical_size_in_mm))
return 1.0f;
const unsigned int dpi = static_cast<unsigned int>(
kInchInMm * screen_size_in_pixels.width() / physical_size_in_mm.width());
const unsigned int threshold =
(physical_size_in_mm.width() >= kLargeDisplayWidthThresholdMM) ?
kHighDensityDPIThresholdLarge : kHighDensityDPIThresholdSmall;
return (dpi > threshold) ? 2.0f : 1.0f;
}
} // namespace ui
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