public Drawing(DrawingSettings settings, ReadOnlyTree <string, Layer> layers, string currentLayerName, string author)
{
if (settings == null)
{
throw new ArgumentNullException("settings");
}
if (layers == null)
{
throw new ArgumentNullException("layers");
}
if (layers.Count == 0)
{
throw new ArgumentException("At least one layer must be specified.");
}
if (currentLayerName == null)
{
throw new ArgumentNullException("currentLayerName");
}
if (!layers.KeyExists(currentLayerName))
{
throw new InvalidOperationException("The current layer is not part of the layers collection.");
}
this.settings = settings;
this.layers = layers;
this.currentLayerName = currentLayerName;
this.author = author;
}
private static Layer GetOrCreateLayer(ref ReadOnlyTree <string, Layer> layers, string layerName)
{
Layer layer = null;
// entities without a layer go to '0'
layerName = layerName ?? "0";
if (layers.KeyExists(layerName))
{
layer = layers.GetValue(layerName);
}
else
{
// add the layer if previously undefined
layer = new Layer(layerName);
layers = layers.Insert(layer.Name, layer);
}
return(layer);
}