display.h

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef FLUTTER_SHELL_COMMON_DISPLAY_H_
#define FLUTTER_SHELL_COMMON_DISPLAY_H_
 
#include <optional>
 
#include "flutter/fml/macros.h"
#include "flutter/shell/common/variable_refresh_rate_reporter.h"
 
namespace flutter {
 
/// Unique ID per display that is stable until the Flutter application restarts.
/// See also: `flutter::Display`
typedef size_t DisplayId;
 
/// To be used when the display refresh rate is unknown.
static constexpr double kUnknownDisplayRefreshRate = 0;
 
/// The POD of a |Display|. This data is for a point in time and suitable
/// for copying.
struct DisplayData {
  DisplayId id;
  double width;
  double height;
  double pixel_ratio;
  double refresh_rate;
};
 
/// Display refers to a graphics hardware system consisting of a framebuffer,
/// typically a monitor or a screen. This class holds the various display
/// settings.
class Display {
 public:
  //------------------------------------------------------------------------------
  /// @brief Construct a new Display object in case where the display id of the
  /// display is known.
  Display(DisplayId display_id,
          double refresh_rate,
          double width,
          double height,
          double device_pixel_ratio)
      : display_id_(display_id),
        refresh_rate_(refresh_rate),
        width_(width),
        height_(height),
        device_pixel_ratio_(device_pixel_ratio) {}
 
  virtual ~Display() = default;
 
  // Get the display's maximum refresh rate in the unit of frame per second.
  // Return `kUnknownDisplayRefreshRate` if the refresh rate is unknown.
  virtual double GetRefreshRate() const;
 
  /// Returns the `DisplayId` of the display.
  DisplayId GetDisplayId() const { return display_id_; }
 
  /// The width of the display in physical pixels.
  virtual double GetWidth() const { return width_; }
 
  /// The height of the display in physical pixels.
  virtual double GetHeight() const { return height_; }
 
  /// The device pixel ratio of the display.
  virtual double GetDevicePixelRatio() const { return device_pixel_ratio_; }
 
  DisplayData GetDisplayData() {
    return DisplayData{
        .id = GetDisplayId(),
        .width = GetWidth(),
        .height = GetHeight(),
        .pixel_ratio = GetDevicePixelRatio(),
        .refresh_rate = GetRefreshRate(),
    };
  }
 
 private:
  DisplayId display_id_;
  double refresh_rate_;
  double width_;
  double height_;
  double device_pixel_ratio_;
 
  FML_DISALLOW_COPY_AND_ASSIGN(Display);
};
 
}  // namespace flutter
 
#endif  // FLUTTER_SHELL_COMMON_DISPLAY_H_