SVG/Source/Extensions.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace Svg
{
    public static class Extensions
    {
        public static IEnumerable<SvgElement> Descendants<T>(this IEnumerable<T> source) where T : SvgElement
        {
            if (source == null) throw new ArgumentNullException("source");

            return GetDescendants<T>(source, false);
        }

        private static IEnumerable<SvgElement> GetAncestors<T>(IEnumerable<T> source, bool self) where T : SvgElement
        {
            foreach (var start in source)
            {
                if (start != null)
                {
                    for (var elem = (self ? start : start.Parent) as SvgElement; elem != null; elem = (elem.Parent as SvgElement))
                    {
                        yield return elem;
                    }
                }
            }
            yield break;
        }

        private static IEnumerable<SvgElement> GetDescendants<T>(IEnumerable<T> source, bool self) where T : SvgElement
        {
            foreach (var top in source)
            {
                if (top == null)
                    continue;

                if (self)
                    yield return top;

                var elements = new Stack<SvgElement>(top.Children.Reverse());
                while (elements.Count > 0)
                {
                    var element = elements.Pop();
                    yield return element;
                    foreach (var e in element.Children.Reverse())
                        elements.Push(e);
                }
            }
            yield break;
        }
    }
}