cmapCodePoints function

Set<int> cmapCodePoints(ByteData bytes)

Code points that the Unicode cmap subtables map to a glyph other than 0 (.notdef).

Reads formats 4 and 12, on platform 0, and platform 3 encodings 1 and 10. A font with only other formats gives an empty set.

Implementation

Set<int> cmapCodePoints(ByteData bytes) {
  final cmap = fontTableRecords(bytes)?['cmap'];
  if (cmap == null) return {};
  final d = bytes;
  final base = cmap.offset;
  final out = <int>{};
  final n = d.getUint16(base + 2);
  for (var i = 0; i < n; i++) {
    final platform = d.getUint16(base + 4 + 8 * i);
    final encoding = d.getUint16(base + 6 + 8 * i);
    final unicode =
        platform == 0 || (platform == 3 && (encoding == 1 || encoding == 10));
    if (!unicode) continue;
    final t = base + d.getUint32(base + 8 + 8 * i);
    final format = d.getUint16(t);
    if (format == 4) {
      final segX2 = d.getUint16(t + 6);
      final ends = t + 14, starts = ends + segX2 + 2;
      final deltas = starts + segX2, offsets = deltas + segX2;
      for (var s = 0; s < segX2 ~/ 2; s++) {
        final end = d.getUint16(ends + 2 * s);
        final start = d.getUint16(starts + 2 * s);
        final delta = d.getInt16(deltas + 2 * s);
        final ro = d.getUint16(offsets + 2 * s);
        for (var c = start; c <= end && c != 0xffff; c++) {
          int g;
          if (ro == 0) {
            g = (c + delta) & 0xffff;
          } else {
            g = d.getUint16(offsets + 2 * s + ro + 2 * (c - start));
            if (g != 0) g = (g + delta) & 0xffff;
          }
          if (g != 0) out.add(c);
        }
      }
    } else if (format == 12) {
      final groups = d.getUint32(t + 12);
      for (var k = 0; k < groups; k++) {
        final g = t + 16 + 12 * k;
        final start = d.getUint32(g), end = d.getUint32(g + 4);
        final first = d.getUint32(g + 8);
        for (var c = start; c <= end; c++) {
          if (first + (c - start) != 0) out.add(c);
        }
      }
    }
  }
  return out;
}