ILSpy/ILSpy/Controls/TreeView/TreeIndentConverter.cs

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using System;
using System.Globalization;

using Avalonia.Data.Converters;

namespace ILSpy.Controls.TreeView
{
	/// <summary>Converts a node's <c>Level</c> to the pixel width of its indentation spacer.</summary>
	public sealed class TreeIndentConverter : IValueConverter
	{
		// 18.5 = icon-centre (25) - expander-centre (6.5): one step puts a child's +/- box directly
		// under its parent's icon, so the connector line passes through both.
		public const double IndentStep = 18.5;

		public static readonly TreeIndentConverter Instance = new();

		public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
			// Both trees show the root's children as the top level (ShowRoot=false), which are at
			// Level 1 -- so the visible top level sits at indent 0, not one step in.
			=> value is int level ? Math.Max(0, level - 1) * IndentStep : 0d;

		public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
			=> throw new NotSupportedException();
	}
}