/// <summary>
/// Get the character property engine that should be used for interpreting the character at ich.
/// </summary>
public static ILgCharacterPropertyEngine GetCharPropEngineAtOffset(ITsString tss, ILgWritingSystemFactory wsf, int ich)
{
int ws = GetWsAtOffset(tss, ich);
return (ws > 0) ? wsf.get_CharPropEngine(ws) : null;
}