/// <summary>
/// Clears the history graph.</summary>
public void Clear()
{
this._history = null;
this._criterion = null;
InvalidateVisual();
}
/// <summary>
/// Draws a new history graph based on the specified ranking criterion.</summary>
/// <param name="criterion">
/// A <see cref="FactionHistory"/> object whose recorded possessions to show, or a <see
/// cref="String"/> identifying the ranking criterion for all factions.</param>
/// <remarks><para>
/// <b>DrawGraph</b> draws two or more graphs representing the recorded possessions in a
/// specified <see cref="FactionHistory"/>, or another criterion throughout the entire
/// <see cref="History"/> of the associated <see cref="WorldState"/>.
/// </para><para>
/// Except for the initial <see cref="FactionHistory.FactionEventType.Create"/> event,
/// all event turn indices are displayed as one greater than recorded, so that the turn
/// count axis is one-based rather than zero-based.</para></remarks>
public void DrawGraph(object criterion)
{
this._history = criterion as FactionHistory;
this._criterion = (this._history == null ?
criterion as string : this._history.Id);
InvalidateVisual();
}
