[C# Markup] Enhancement request: Add more functionality to brush or color property setter extension methods

[baskren]

I'm in the process of migration from my home-brewed C# markup to Uno's C# markup. 99% of my home-brew version is redundant (or inferior) to Uno's C# markup. However, there is a small feature (that I use a lot) that I'd like to see if it would make sense to add to Uno's markup: Color/Brush conversions. The below examples are for the Shape.Fill() extension methods, but the concept would apply to Brush or Color property setters.

uint to Brush or Color conversion:

Since it's easy to specify a hex value as a uint in C#, create Brush or Color property setter extension methods that take a uint value:

    public static TElement Fill<TElement>(this TElement element, uint hex) where TElement : ElementType
    { element.Fill = new SolidColorBrush(ColorExtensions.ColorFromUint(hex)); return element; }

where ColorExtensions.ColorFromUint(uint hex) is:

    public static Color ColorFromUint(uint argb)
        => global::Microsoft.UI.ColorHelper.FromArgb((byte)(argb >> 24), (byte)(argb >> 16), (byte)(argb >> 8), (byte)argb);

usage:

    var rect = new Rectangle()
                        .Fill(0xFFe8b950);

Enhance string to Brush or Color conversions to support CSS notations:

For example, Uno's C# markup, the extension method is:

public static T Fill<T>(this T element, string hexString) where T : Shape
{
    Color color = (Color)XamlBindingHelper.ConvertValue(typeof(Color), hexString);
    element.Fill = new SolidColorBrush(color);
    return element;
}

where as, in my home-brew code (and similarly in Avalonia) it is:

    public static TElement Fill<TElement>(this TElement element, string color) where TElement : ElementType
    { element.Fill = new SolidColorBrush(ColorExtensions.ColorFromString(color)); return element; }

where ColorExtensions.ColorFromString(string color) is:

    public static Color ColorFromString(this string s)
    {
        if (s.ToLower().StartsWith("rgb(", StringComparison.OrdinalIgnoreCase))
        {
            //var values = s.Substring(4, s.Length - 5).Split(',').Select(int.Parse).ToArray();
            var components = s[4..^1].Split(',');
            if (components.Length != 3)
                throw new FormatException($"Could not parse [{s}] into RGB integer components");
            var r = byte.Parse(components[0]);
            var g = byte.Parse(components[1]);
            var b = byte.Parse(components[2]);
            return Color.FromArgb(1, r, g, b);
        }
        if (s.ToLower().StartsWith("rgba(", StringComparison.OrdinalIgnoreCase))
        {
            //var values = s.Substring(5, s.Length - 6).Split(',').Select(int.Parse).ToArray();
            var components = s[5..^1].Split(',');
            if (components.Length != 4)
                throw new FormatException($"Could not parse [{s}] into RGBA integer components");
            var r = byte.Parse(components[0]);
            var g = byte.Parse(components[1]);
            var b = byte.Parse(components[2]);
            var a = byte.Parse(components[3]);
            return Color.FromArgb(a, r, g, b);
        }
        if (s.StartsWith("#", StringComparison.OrdinalIgnoreCase))
        {
            var color = ColorFromHex(s);
            return color;
        }
        var colorName = s.ToLower();
        return colorName switch
        {
            "aliceblue" => ColorFromHex("F0F8FF"),
            "antiquewhite" => ColorFromHex("FAEBD7"),
            "aqua" => ColorFromHex("00FFFF"),
            "aquamarine" => ColorFromHex("7FFFD4"),
            "azure" => ColorFromHex("F0FFFF"),
            "beige" => ColorFromHex("F5F5DC"),
            "bisque" => ColorFromHex("FFE4C4"),
            "black" => ColorFromHex("000000"),
            "blanchedalmond" => ColorFromHex("FFEBCD"),
            "blue" => ColorFromHex("0000FF"),
            "blueviolet" => ColorFromHex("8A2BE2"),
            "brown" => ColorFromHex("A52A2A"),
            "burlywood" => ColorFromHex("DEB887"),
            "cadetblue" => ColorFromHex("5F9EA0"),
            "chartreuse" => ColorFromHex("7FFF00"),
            "chocolate" => ColorFromHex("D2691E"),
            "coral" => ColorFromHex("FF7F50"),
            "cornflowerblue" => ColorFromHex("6495ED"),
            "cornsilk" => ColorFromHex("FFF8DC"),
            "crimson" => ColorFromHex("DC143C"),
            "cyan" => ColorFromHex("00FFFF"),
            "darkblue" => ColorFromHex("00008B"),
            "darkcyan" => ColorFromHex("008B8B"),
            "darkgoldenrod" => ColorFromHex("B8860B"),
            "darkgray" => ColorFromHex("A9A9A9"),
            "darkgrey" => ColorFromHex("A9A9A9"),
            "darkgreen" => ColorFromHex("006400"),
            "darkkhaki" => ColorFromHex("BDB76B"),
            "darkmagenta" => ColorFromHex("8B008B"),
            "darkolivegreen" => ColorFromHex("556B2F"),
            "darkorange" => ColorFromHex("FF8C00"),
            "darkorchid" => ColorFromHex("9932CC"),
            "darkred" => ColorFromHex("8B0000"),
            "darksalmon" => ColorFromHex("E9967A"),
            "darkseagreen" => ColorFromHex("8FBC8F"),
            "darkslateblue" => ColorFromHex("483D8B"),
            "darkslategray" => ColorFromHex("2F4F4F"),
            "darkslategrey" => ColorFromHex("2F4F4F"),
            "darkturquoise" => ColorFromHex("00CED1"),
            "darkviolet" => ColorFromHex("9400D3"),
            "deeppink" => ColorFromHex("FF1493"),
            "deepskyblue" => ColorFromHex("00BFFF"),
            "dimgray" => ColorFromHex("696969"),
            "dimgrey" => ColorFromHex("696969"),
            "dodgerblue" => ColorFromHex("1E90FF"),
            "firebrick" => ColorFromHex("B22222"),
            "floralwhite" => ColorFromHex("FFFAF0"),
            "forestgreen" => ColorFromHex("228B22"),
            "fuchsia" => ColorFromHex("FF00FF"),
            "gainsboro" => ColorFromHex("DCDCDC"),
            "ghostwhite" => ColorFromHex("F8F8FF"),
            "gold" => ColorFromHex("FFD700"),
            "goldenrod" => ColorFromHex("DAA520"),
            "gray" => ColorFromHex("808080"),
            "grey" => ColorFromHex("808080"),
            "green" => ColorFromHex("008000"),
            "greenyellow" => ColorFromHex("ADFF2F"),
            "honeydew" => ColorFromHex("F0FFF0"),
            "hotpink" => ColorFromHex("FF69B4"),
            "indianred " => ColorFromHex("CD5C5C"),
            "indigo " => ColorFromHex("4B0082"),
            "ivory" => ColorFromHex("FFFFF0"),
            "khaki" => ColorFromHex("F0E68C"),
            "lavender" => ColorFromHex("E6E6FA"),
            "lavenderblush" => ColorFromHex("FFF0F5"),
            "lawngreen" => ColorFromHex("7CFC00"),
            "lemonchiffon" => ColorFromHex("FFFACD"),
            "lightblue" => ColorFromHex("ADD8E6"),
            "lightcoral" => ColorFromHex("F08080"),
            "lightcyan" => ColorFromHex("E0FFFF"),
            "lightgoldenrodyellow" => ColorFromHex("FAFAD2"),
            "lightgray" => ColorFromHex("D3D3D3"),
            "lightgrey" => ColorFromHex("D3D3D3"),
            "lightgreen" => ColorFromHex("90EE90"),
            "lightpink" => ColorFromHex("FFB6C1"),
            "lightsalmon" => ColorFromHex("FFA07A"),
            "lightseagreen" => ColorFromHex("20B2AA"),
            "lightskyblue" => ColorFromHex("87CEFA"),
            "lightslategray" => ColorFromHex("778899"),
            "lightslategrey" => ColorFromHex("778899"),
            "lightsteelblue" => ColorFromHex("B0C4DE"),
            "lightyellow" => ColorFromHex("FFFFE0"),
            "lime" => ColorFromHex("00FF00"),
            "limegreen" => ColorFromHex("32CD32"),
            "linen" => ColorFromHex("FAF0E6"),
            "magenta" => ColorFromHex("FF00FF"),
            "maroon" => ColorFromHex("800000"),
            "mediumaquamarine" => ColorFromHex("66CDAA"),
            "mediumblue" => ColorFromHex("0000CD"),
            "mediumorchid" => ColorFromHex("BA55D3"),
            "mediumpurple" => ColorFromHex("9370DB"),
            "mediumseagreen" => ColorFromHex("3CB371"),
            "mediumslateblue" => ColorFromHex("7B68EE"),
            "mediumspringgreen" => ColorFromHex("00FA9A"),
            "mediumturquoise" => ColorFromHex("48D1CC"),
            "mediumvioletred" => ColorFromHex("C71585"),
            "midnightblue" => ColorFromHex("191970"),
            "mintcream" => ColorFromHex("F5FFFA"),
            "mistyrose" => ColorFromHex("FFE4E1"),
            "moccasin" => ColorFromHex("FFE4B5"),
            "navajowhite" => ColorFromHex("FFDEAD"),
            "navy" => ColorFromHex("000080"),
            "oldlace" => ColorFromHex("FDF5E6"),
            "olive" => ColorFromHex("808000"),
            "olivedrab" => ColorFromHex("6B8E23"),
            "orange" => ColorFromHex("FFA500"),
            "orangered" => ColorFromHex("FF4500"),
            "orchid" => ColorFromHex("DA70D6"),
            "palegoldenrod" => ColorFromHex("EEE8AA"),
            "palegreen" => ColorFromHex("98FB98"),
            "paleturquoise" => ColorFromHex("AFEEEE"),
            "palevioletred" => ColorFromHex("DB7093"),
            "papayawhip" => ColorFromHex("FFEFD5"),
            "peachpuff" => ColorFromHex("FFDAB9"),
            "peru" => ColorFromHex("CD853F"),
            "pink" => ColorFromHex("FFC0CB"),
            "plum" => ColorFromHex("DDA0DD"),
            "powderblue" => ColorFromHex("B0E0E6"),
            "purple" => ColorFromHex("800080"),
            "rebeccapurple" => ColorFromHex("663399"),
            "red" => ColorFromHex("FF0000"),
            "rosybrown" => ColorFromHex("BC8F8F"),
            "royalblue" => ColorFromHex("4169E1"),
            "saddlebrown" => ColorFromHex("8B4513"),
            "salmon" => ColorFromHex("FA8072"),
            "sandybrown" => ColorFromHex("F4A460"),
            "seagreen" => ColorFromHex("2E8B57"),
            "seashell" => ColorFromHex("FFF5EE"),
            "sienna" => ColorFromHex("A0522D"),
            "silver" => ColorFromHex("C0C0C0"),
            "skyblue" => ColorFromHex("87CEEB"),
            "slateblue" => ColorFromHex("6A5ACD"),
            "slategray" => ColorFromHex("708090"),
            "slategrey" => ColorFromHex("708090"),
            "snow" => ColorFromHex("FFFAFA"),
            "springgreen" => ColorFromHex("00FF7F"),
            "steelblue" => ColorFromHex("4682B4"),
            "tan" => ColorFromHex("D2B48C"),
            "teal" => ColorFromHex("008080"),
            "thistle" => ColorFromHex("D8BFD8"),
            "tomato" => ColorFromHex("FF6347"),
            "turquoise" => ColorFromHex("40E0D0"),
            "violet" => ColorFromHex("EE82EE"),
            "wheat" => ColorFromHex("F5DEB3"),
            "white" => ColorFromHex("FFFFFF"),
            "whitesmoke" => ColorFromHex("F5F5F5"),
            "yellow" => ColorFromHex("FFFF00"),
            "yellowgreen" => ColorFromHex("9ACD32"),
            _ => default(Color),
        };
    }

where ColorExtensions.ColorFromHex(string hex) is:

    public static Color ColorFromHex(string hex)
    {
        // Undefined
        if (hex.Length < 3)
            return default(Color);
        var idx = hex[0] == '#' ? 1 : 0;

        switch (hex.Length - idx)
        {
            case 3: //#rgb => ffrrggbb
                var t1 = ToHexD(hex[idx++]);
                var t2 = ToHexD(hex[idx++]);
                var t3 = ToHexD(hex[idx]);

                return ColorFromRgb((int)t1, (int)t2, (int)t3);

            case 4: //#argb => aarrggbb
                var f1 = ToHexD(hex[idx++]);
                var f2 = ToHexD(hex[idx++]);
                var f3 = ToHexD(hex[idx++]);
                var f4 = ToHexD(hex[idx]);
                return ColorFromRgba((int)f2, (int)f3, (int)f4, (int)f1);

            case 6: //#rrggbb => ffrrggbb
                return ColorFromRgb((int)(ToHex(hex[idx++]) << 4 | ToHex(hex[idx++])),
                    (int)(ToHex(hex[idx++]) << 4 | ToHex(hex[idx++])),
                    (int)(ToHex(hex[idx++]) << 4 | ToHex(hex[idx])));

            case 8: //#aarrggbb
                var a1 = ToHex(hex[idx++]) << 4 | ToHex(hex[idx++]);
                return ColorFromRgba((int)(ToHex(hex[idx++]) << 4 | ToHex(hex[idx++])),
                    (int)(ToHex(hex[idx++]) << 4 | ToHex(hex[idx++])),
                    (int)(ToHex(hex[idx++]) << 4 | ToHex(hex[idx])),
                    (int)a1);

            default: //everything else will result in unexpected results
                return default(Color);
        }
    }

    private static uint ToHex(char c)
    {
        var x = (ushort)c;
        if (x >= '0' && x <= '9')
            return (uint)(x - '0');

        x |= 0x20;
        if (x >= 'a' && x <= 'f')
            return (uint)(x - 'a' + 10);
        return 0;
    }

    private static uint ToHexD(char c)
    {
        var j = ToHex(c);
        return (j << 4) | j;
    }

I thought this might be a good first "pull request" for me but I failed to find the code base for Uno's C# markup in the public repos.