System.Windows.Forms.ListBox.IndexAtClientPoint C# (CSharp) Method

		private int IndexAtClientPoint (int x, int y)
		{	
			if (Items.Count == 0)
				return -1;
			
			if (x < 0)
				x = 0;
			else if (x > ClientRectangle.Right)
				x = ClientRectangle.Right;

			if (y < 0)
				y = 0;
			else if (y > ClientRectangle.Bottom)
				y = ClientRectangle.Bottom;

			for (int i = top_index; i <= last_visible_index; i++)
				if (GetItemDisplayRectangle (i, top_index).Contains (x, y))
					return i;

			return -1;
		}