ShrlAlgoToolkit/WPFluent/Hardware/DpiHelper.cs

using WPFluent.Interop;
using WPFluent.Win32;


namespace WPFluent.Hardware;

/// <summary>
/// Provides access to various DPI-related methods.
/// </summary>
internal static class DpiHelper
{
    /// <summary>
    /// Default DPI value.
    /// </summary>
    internal const int DefaultDpi = 96;

    [ThreadStatic]
    private static Matrix _transformToDevice;

    [ThreadStatic]
    private static Matrix _transformToDip;

    public static float ScaleX => GetScale().X;
    public static float ScaleY => GetScale().Y;

    private static (float X, float Y) GetScale()
    {
        nint hdc = User32.GetDC(0);
        float scaleX = Gdi32.GetDeviceCaps(hdc, Gdi32.DeviceCap.LOGPIXELSX);
        float scaleY = Gdi32.GetDeviceCaps(hdc, Gdi32.DeviceCap.LOGPIXELSY);
        _ = User32.ReleaseDC(IntPtr.Zero, hdc);
        return new(scaleX / 96f, scaleY / 96f);
    }

    /// <summary>
    /// Convert a point in system coordinates to a point in device independent pixels (1/96").
    /// </summary>
    /// <returns>Returns the parameter converted to the device independent coordinate system.</returns>
    public static Point DevicePixelsToLogical(Point devicePoint, double dpiScaleX, double dpiScaleY)
    {
        _transformToDip = Matrix.Identity;
        _transformToDip.Scale(1d / dpiScaleX, 1d / dpiScaleY);

        return _transformToDip.Transform(devicePoint);
    }

    public static Rect DeviceRectToLogical(Rect deviceRectangle, double dpiScaleX, double dpiScaleY)
    {
        Point topLeft = DevicePixelsToLogical(
            new Point(deviceRectangle.Left, deviceRectangle.Top),
            dpiScaleX,
            dpiScaleY);
        Point bottomRight = DevicePixelsToLogical(
            new Point(deviceRectangle.Right, deviceRectangle.Bottom),
            dpiScaleX,
            dpiScaleY);

        return new Rect(topLeft, bottomRight);
    }

    public static Size DeviceSizeToLogical(Size deviceSize, double dpiScaleX, double dpiScaleY)
    {
        Point pt = DevicePixelsToLogical(new Point(deviceSize.Width, deviceSize.Height), dpiScaleX, dpiScaleY);

        return new Size(pt.X, pt.Y);
    }

    // TODO: Look into utilizing preprocessor symbols for more functionality
    // ----
    // There is an opportunity to check against NET46 if we can use
    // VisualTreeHelper in this class. We are currently not utilizing
    // it because it is not available in .NET Framework 4.6 (available
    // starting 4.6.2). For now, there is no need to overcomplicate this
    // solution for some infrequent DPI calculations. However, if this
    // becomes more central to various implementations, we may want to
    // look into fleshing it out a bit further.
    // ----
    // Reference: https://docs.microsoft.com/en-us/dotnet/standard/frameworks

    /// <summary>
    /// Gets the DPI values from <see cref="SystemParameters"/>.
    /// </summary>
    /// <returns>
    /// The DPI values from <see cref="SystemParameters"/>. If the property cannot be accessed, the default value <see
    /// langword="96"/> is returned.
    /// </returns>
    public static DisplayDpi GetSystemDpi()
    {
        System.Reflection.PropertyInfo? dpiXProperty = typeof(SystemParameters).GetProperty(
            "DpiX",
            System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);

        if (dpiXProperty == null)
        {
            return new DisplayDpi(DefaultDpi, DefaultDpi);
        }

        System.Reflection.PropertyInfo? dpiYProperty = typeof(SystemParameters).GetProperty(
            "Dpi",
            System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);

        if (dpiYProperty == null)
        {
            return new DisplayDpi(DefaultDpi, DefaultDpi);
        }

        return new DisplayDpi((int)dpiXProperty.GetValue(null, null)!, (int)dpiYProperty.GetValue(null, null)!);
    }

    /*
    /// <summary>
    /// Occurs when application DPI is changed.
    /// </summary>
    public static event EventHandler<DpiChangedEventArgs> DpiChanged;
    */

    /// <summary>
    /// Gets DPI of the selected <see cref="Window"/>.
    /// </summary>
    /// <param name="window">The window that you want to get information about.</param>
    public static DisplayDpi GetWindowDpi(Window? window)
    {
        if (window is null)
        {
            return new DisplayDpi(DefaultDpi, DefaultDpi);
        }

        return GetWindowDpi(new WindowInteropHelper(window).Handle);
    }

    /// <summary>
    /// Gets DPI of the selected <see cref="Window"/> based on it's handle.
    /// </summary>
    /// <param name="windowHandle">Handle of the window that you want to get information about.</param>
    public static DisplayDpi GetWindowDpi(IntPtr windowHandle)
    {
        if (windowHandle == IntPtr.Zero || !UnsafeNativeMethods.IsValidWindow(windowHandle))
        {
            return new DisplayDpi(DefaultDpi, DefaultDpi);
        }

        var windowDpi = (int)User32.GetDpiForWindow(windowHandle);

        return new DisplayDpi(windowDpi, windowDpi);
    }

    /// <summary>
    /// Convert a point in device independent pixels (1/96") to a point in the system coordinates.
    /// </summary>
    /// <param name="logicalPoint">A point in the logical coordinate system.</param>
    /// <param name="dpiScaleX">Horizontal DPI scale.</param>
    /// <param name="dpiScaleY">Vertical DPI scale.</param>
    /// <returns>Returns the parameter converted to the system's coordinates.</returns>
    public static Point LogicalPixelsToDevice(Point logicalPoint, double dpiScaleX, double dpiScaleY)
    {
        _transformToDevice = Matrix.Identity;
        _transformToDevice.Scale(dpiScaleX, dpiScaleY);

        return _transformToDevice.Transform(logicalPoint);
    }

    public static Rect LogicalRectToDevice(Rect logicalRectangle, double dpiScaleX, double dpiScaleY)
    {
        Point topLeft = LogicalPixelsToDevice(
            new Point(logicalRectangle.Left, logicalRectangle.Top),
            dpiScaleX,
            dpiScaleY);
        Point bottomRight = LogicalPixelsToDevice(
            new Point(logicalRectangle.Right, logicalRectangle.Bottom),
            dpiScaleX,
            dpiScaleY);

        return new Rect(topLeft, bottomRight);
    }

    public static Size LogicalSizeToDevice(Size logicalSize, double dpiScaleX, double dpiScaleY)
    {
        Point pt = LogicalPixelsToDevice(new Point(logicalSize.Width, logicalSize.Height), dpiScaleX, dpiScaleY);

        return new Size { Width = pt.X, Height = pt.Y };
    }

    public static Thickness LogicalThicknessToDevice(Thickness logicalThickness, double dpiScaleX, double dpiScaleY)
    {
        Point topLeft = LogicalPixelsToDevice(
            new Point(logicalThickness.Left, logicalThickness.Top),
            dpiScaleX,
            dpiScaleY);
        Point bottomRight = LogicalPixelsToDevice(
            new Point(logicalThickness.Right, logicalThickness.Bottom),
            dpiScaleX,
            dpiScaleY);

        return new Thickness(topLeft.X, topLeft.Y, bottomRight.X, bottomRight.Y);
    }
}