/// <summary>
/// Creates a new element position.
/// </summary>
/// <param name="element">The current element.</param>
/// <param name="elementTag">The element tag of the specified element.</param>
/// <param name="elementPosition">The previous element position.</param>
/// <returns>A new element position.</returns>
private static NvgElementPosition CreateElementPosition(INvgElement element, NvgElementTag elementTag, NvgElementPosition elementPosition)
{
return(new NvgElementPosition
{
Element = element,
ElementTag = elementTag,
PreviousElementPosition = elementPosition
});
}
/// <summary>
/// Reads the next NVG element from the stream.
/// </summary>
/// <returns>The next NVG element or <code>null</code> when there are no more NVG elements.</returns>
public INvgElement ReadNextElement()
{
NvgElementPosition elementPosition = null;
INvgElement element = null;
while (_xmlTextReader.Read())
{
switch (_xmlTextReader.NodeType)
{
case XmlNodeType.Element:
var startTag = new NvgElementTag(_xmlTextReader.LocalName);
if (startTag.IsNvgTag)
{
// Read the NVG element
element = new NvgElement();
element.ConstructFromReader(_xmlTextReader);
elementPosition = CreateElementPosition(element, startTag, elementPosition);
}
else if (startTag.IsGroupTag)
{
// Read the NVG group element
element = new NvgGroupElement();
element.ConstructFromReader(_xmlTextReader);
elementPosition = CreateElementPosition(element, startTag, elementPosition);
}
else if (startTag.IsPointTag)
{
// Read the NVG point element
element = new NvgPointElement();
element.ConstructFromReader(_xmlTextReader);
elementPosition = CreateElementPosition(element, startTag, elementPosition);
}
break;
case XmlNodeType.EndElement:
var endTag = new NvgElementTag(_xmlTextReader.LocalName);
// Add children and reset the position to the matching start tag
elementPosition = AddChildren(elementPosition, endTag);
if (null != elementPosition)
{
// Reset the current element to the start tag
element = elementPosition.Element;
}
if (endTag.IsNvgTag)
{
return(element);
}
break;
}
}
return(null);
}
/// <summary>
/// Adds all children by iterating backwards using the specified element position.
/// The first element matching the specified element tag is treated as the parent element.
/// </summary>
/// <param name="elementPosition">The current element position refering to the last created child element.</param>
/// <param name="elementTag">The element tag of the parent element.</param>
/// <returns>The element position of the parent element.</returns>
private static NvgElementPosition AddChildren(NvgElementPosition elementPosition, NvgElementTag elementTag)
{
var childElements = new List <INvgElement>();
for (; null != elementPosition && !elementPosition.ElementTag.IsEqualTo(elementTag); elementPosition = elementPosition.PreviousElementPosition)
{
childElements.Add(elementPosition.Element);
}
if (null == elementPosition)
{
// No start tag found!
return(null);
}
// Add all child elements
foreach (var childElement in childElements)
{
elementPosition.Element.Children.Add(childElement);
}
return(elementPosition);
}