using System;
using System.Runtime.InteropServices;
using System.Windows;

public static class PrimaryScreen
{
    #region Win32 API
    [DllImport("user32.dll")]
    static extern IntPtr GetDC(IntPtr ptr);
    [DllImport("gdi32.dll")]
    static extern int GetDeviceCaps(
        IntPtr hdc, // handle to DC
        int nIndex // index of capability
    );
    [DllImport("user32.dll", EntryPoint = "ReleaseDC")]
    static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDc);
    #endregion

    #region DeviceCaps常量
    const int HORZRES = 8;
    const int VERTRES = 10;
    const int LOGPIXELSX = 88;
    const int LOGPIXELSY = 90;
    const int DESKTOPVERTRES = 117;
    const int DESKTOPHORZRES = 118;
    #endregion

    #region 属性

    /// <summary>
    /// 当前系统DPI_X 大小 一般为96
    /// </summary>
    public static int DpiX
    {
        get
        {
            var hdc = GetDC(IntPtr.Zero);
            var dpiX = GetDeviceCaps(hdc, LOGPIXELSX);
            ReleaseDC(IntPtr.Zero, hdc);
            return dpiX;
        }
    }

    /// <summary>
    /// 当前系统DPI_Y 大小 一般为96
    /// </summary>
    public static int DpiY
    {
        get
        {
            var hdc = GetDC(IntPtr.Zero);
            var dpiX = GetDeviceCaps(hdc, LOGPIXELSY);
            ReleaseDC(IntPtr.Zero, hdc);
            return dpiX;
        }
    }

    /// <summary>
    /// 获取真实设置的桌面分辨率大小
    /// </summary>
    public static Size Desktop
    {
        get
        {
            var hdc = GetDC(IntPtr.Zero);
            var size = new Size
            {
                Width = GetDeviceCaps(hdc, DESKTOPHORZRES),
                Height = GetDeviceCaps(hdc, DESKTOPVERTRES)
            };
            ReleaseDC(IntPtr.Zero, hdc);
            return size;
        }
    }

    /// <summary>
    /// 获取屏幕分辨率当前物理大小
    /// </summary>
    public static Size WorkingArea
    {
        get
        {
            var hdc = GetDC(IntPtr.Zero);
            var size = new Size
            {
                Width = GetDeviceCaps(hdc, HORZRES),
                Height = GetDeviceCaps(hdc, VERTRES)
            };
            ReleaseDC(IntPtr.Zero, hdc);
            return size;
        }
    }

    /// <summary>
    /// 获得横轴缩放比
    /// 此参数为[控制面板-设置-显示-更改文本、应用等项目的大小]所显示的百分比
    /// </summary>
    public static float ScaleX => DpiX / 96f;

    /// <summary>
    /// 获得纵轴缩放比
    /// 此参数为[控制面板-设置-显示-更改文本、应用等项目的大小]所显示的百分比
    /// </summary>
    public static float ScaleY => DpiY / 96f;

    #endregion

    public static float GetPositionScale()
    {
        var hdc = GetDC(IntPtr.Zero);
        var dpiX = GetDeviceCaps(hdc, LOGPIXELSX);
        ReleaseDC(IntPtr.Zero, hdc);
        var scale = Convert.ToInt32(dpiX / 96f * 100);
        switch (scale)
        {
            case 125:
                return .8f;
            case 150:
                return .65f;
            case 175:
                return .575f;
            default:
                return 1f;
        }
    }
}