Gradient editor - Initial implementation

src/Avalonia/Artemis.UI.Shared/Converters/WidthNormalizedConverter.cs

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+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using Avalonia.Controls;
+using Avalonia.Data.Converters;
+
+namespace Artemis.UI.Shared.Converters;
+
+/// <summary>
+///     Converts the width in percentage to a real number based on the width of the given parent
+/// </summary>
+public class WidthNormalizedConverter : IMultiValueConverter
+{
+    #region Implementation of IMultiValueConverter
+
+    /// <inheritdoc />
+    public object? Convert(IList<object?> values, Type targetType, object? parameter, CultureInfo culture)
+    {
+        object? first = values.FirstOrDefault();
+        object? second = values.Skip(1).FirstOrDefault();
+        if (first is float value && second is double totalWidth)
+            return (totalWidth / 1.0) * value;
+
+        return 0.0;
+    }
+
+    #endregion
+}