boxDrawingMask function

int? boxDrawingMask(String grapheme)

The line segments grapheme draws, as an OR of boxSegmentNorth etc., or null if it is not a box-drawing line/corner/junction. Double-line glyphs are mapped to their single-weight segment set (good enough for crisp borders).

Implementation

int? boxDrawingMask(String grapheme) {
  switch (grapheme) {
    case '│':
    case '║':
      return boxSegmentNorth | boxSegmentSouth;
    case '─':
    case '═':
      return boxSegmentEast | boxSegmentWest;
    case '╭':
    case '┌':
    case '╔':
      return boxSegmentSouth | boxSegmentEast;
    case '╮':
    case '┐':
    case '╗':
      return boxSegmentSouth | boxSegmentWest;
    case '╰':
    case '└':
    case '╚':
      return boxSegmentNorth | boxSegmentEast;
    case '╯':
    case '┘':
    case '╝':
      return boxSegmentNorth | boxSegmentWest;
    case '├':
    case '╠':
      return boxSegmentNorth | boxSegmentSouth | boxSegmentEast;
    case '┤':
    case '╣':
      return boxSegmentNorth | boxSegmentSouth | boxSegmentWest;
    case '┬':
    case '╦':
      return boxSegmentSouth | boxSegmentEast | boxSegmentWest;
    case '┴':
    case '╩':
      return boxSegmentNorth | boxSegmentEast | boxSegmentWest;
    case '┼':
    case '╬':
      return boxSegmentNorth |
          boxSegmentSouth |
          boxSegmentEast |
          boxSegmentWest;
    default:
      return null;
  }
}