/// <summary>
/// Adds a composition to this mixin.
/// </summary>
/// <param name="name">The name.</param>
/// <param name="shaderSourceElement">The shader source element.</param>
/// <returns>Returns the index of the composition in the array.</returns>
public int AddCompositionToArray(string name, ShaderSource shaderSourceElement)
{
ShaderSource shaderSource;
if (!Compositions.TryGetValue(name, out shaderSource))
Compositions.Add(name, shaderSource = new ShaderArraySource());
var shaderArraySource = (ShaderArraySource)shaderSource;
shaderArraySource.Add(shaderSourceElement);
return shaderArraySource.Values.Count - 1;
}