// For the AttackTransition example from ITransitionGUI.
// Draw the hit time as a highlighted area.
public void OnTimelineBackgroundGUI()
{
    if (Event.current.type != EventType.Repaint)
        return;

    Color previousColor = GUI.color;
    TimelineGUI timelineGUI = TimelineGUI.Current;

    float start = timelineGUI.SecondsToPixels(_HitStartTime);
    float end = timelineGUI.SecondsToPixels(_HitEndTime);
    Rect area = new Rect(
        start,
        0,
        end - start,
        timelineGUI.Area.height - timelineGUI.TickHeight);

    Color color = new Color(0.9f, 0.4f, 0.25f, 0.5f);

    EditorGUI.DrawRect(area, color);

    GUI.color = previousColor;
}