{
if (tp.row < this.Src.Row)
return Rectangle.Empty;
+ //画面外にある時は計算する必要がそもそもない
+ if (tp.row - this.Src.Row > this.LineCountOnScreen)
+ return Rectangle.Empty;
double radius = width / 2;
Point point = this.GetPostionFromTextPoint(tp);
double lineHeight = this.render.emSize.Height;