SvgPaintServerFactory.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Globalization;
using System.Linq;

namespace Svg
{
    internal class SvgPaintServerFactory : TypeConverter
    {
        private static readonly SvgColourConverter _colourConverter;

        static SvgPaintServerFactory()
        {
            _colourConverter = new SvgColourConverter();
        }

        public static SvgPaintServer Create(string value, SvgDocument document)
        {
            // If it's pointing to a paint server
            if (string.IsNullOrEmpty(value))
            {
                return SvgColourServer.NotSet;
            }
            else if (value == "inherit")
            {
                return SvgColourServer.Inherit;
            }
            else if (value == "currentColor")
            {
                return new SvgDeferredPaintServer(document, value);
            }
            else
            {
                var servers = new List<SvgPaintServer>();
                
                while (!string.IsNullOrEmpty(value))
                {
                    if (value.StartsWith("url(#"))
                    {
                        var leftParen = value.IndexOf(')', 5);
                        Uri id = new Uri(value.Substring(5, leftParen - 5), UriKind.Relative);
                        value = value.Substring(leftParen + 1).Trim();
                        servers.Add((SvgPaintServer)document.IdManager.GetElementById(id));
                    }
                    // If referenced to to a different (linear or radial) gradient
                    else if (document.IdManager.GetElementById(value) != null && document.IdManager.GetElementById(value).GetType().BaseType == typeof(SvgGradientServer))
                    {
                        return (SvgPaintServer)document.IdManager.GetElementById(value);
                    }
                    else if (value.StartsWith("#")) // Otherwise try and parse as colour
                    {
                        switch(CountHexDigits(value, 1))
                        {
                            case 3:
                                servers.Add(new SvgColourServer((Color)_colourConverter.ConvertFrom(value.Substring(0, 4))));
                                value = value.Substring(4).Trim();
                                break;
                            case 6:
                                servers.Add(new SvgColourServer((Color)_colourConverter.ConvertFrom(value.Substring(0, 7))));
                                value = value.Substring(7).Trim();
                                break;
                            default:
                                return new SvgDeferredPaintServer(document, value);
                        }
                    }
                    else
                    {
                        return new SvgColourServer((Color)_colourConverter.ConvertFrom(value.Trim()));
                    }
                }

                if (servers.Count > 1)
                {
                    return new SvgFallbackPaintServer(servers[0], servers.Skip(1));
                }
                return servers[0];
            } 
                
                
        }

        private static int CountHexDigits(string value, int start)
        {
            int i = Math.Max(start, 0);
            int count = 0;
            while (i < value.Length && 
                   ((value[i] >= '0' && value[i] <= '9') ||
                    (value[i] >= 'a' && value[i] <= 'f') ||
                    (value[i] >= 'A' && value[i] <= 'F')))
            {
                count++;
                i++;
            }
            return count;
        }
        
        public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)
        {
            if (value is string)
            {
            	var s = (string) value;
                if (String.Equals(s.Trim(), "none", StringComparison.OrdinalIgnoreCase) || string.IsNullOrEmpty(s) || s.Trim().Length < 1)
            		return SvgPaintServer.None;
            	else
                	return SvgPaintServerFactory.Create(s, (SvgDocument)context);
            }

            return base.ConvertFrom(context, culture, value);
        }

        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            if (sourceType == typeof(string))
            {
                return true;
            }

            return base.CanConvertFrom(context, sourceType);
        }

        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        {
            if (destinationType == typeof(string))
            {
                return true;
            }

            return base.CanConvertTo(context, destinationType);
        }

        public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType)
        {
            if (destinationType == typeof(string))
            {
                //check for none
                if (value == SvgPaintServer.None) return "none";

                var colourServer = value as SvgColourServer;

                if (colourServer != null)
                {
                    return new SvgColourConverter().ConvertTo(colourServer.Colour, typeof(string));
                }

                if (value != null)
                {
                    return string.Format(CultureInfo.InvariantCulture, "url(#{0})", ((SvgPaintServer)value).ID);
                }
                else
                {
                	return "none";
                }
            }

            return base.ConvertTo(context, culture, value, destinationType);
        }
    }
}