private string BuildLine(IReadOnlyList <ColumnX> columns)
{
verticalBorderCount = columns.Count + 1;
row1VerticalBorders = Row1?.CalculateVerticalBorderVisibility(columns.Count) ?? Enumerable.Repeat(false, verticalBorderCount).ToList();
row2VerticalBorders = Row2?.CalculateVerticalBorderVisibility(columns.Count) ?? Enumerable.Repeat(false, verticalBorderCount).ToList();
StringBuilder sb = new();
for (int i = 0; i < columns.Count; i++)
{
char cornerChar = CalculateCornerChar(i);
sb.Append(cornerChar);
char bodyChar = CalculateBodyChar();
string bodyLine = new(bodyChar, columns[i].Width);