layoutCampusMapRoomLabel function

Implementation

CampusMapRoomLabelLayout layoutCampusMapRoomLabel({
  required List<List<Offset>> rings,
  required String number,
  required String name,
  required Color color,
  TextScaler textScaler = TextScaler.noScaling,
}) {
  final exterior = rings.first;
  final path = ui.Path()..fillType = .evenOdd;
  for (final ring in rings) {
    path.addPolygon(ring, true);
  }
  final bounds = path.getBounds();
  var center = bounds.center;

  var sin = 0.0;
  var cos = 0.0;
  for (var i = 1; i < exterior.length; i++) {
    final edge = exterior[i] - exterior[i - 1];
    final angle = math.atan2(edge.dy, edge.dx);
    sin += edge.distance * math.sin(4 * angle);
    cos += edge.distance * math.cos(4 * angle);
  }
  var angle = math.atan2(sin, cos) / 4;
  Rect rotatedBounds(double radians) {
    final points = exterior.map((point) {
      final local = point - center;
      return Offset(
        local.dx * math.cos(radians) + local.dy * math.sin(radians),
        -local.dx * math.sin(radians) + local.dy * math.cos(radians),
      );
    }).toList();
    return (ui.Path()..addPolygon(points, true)).getBounds();
  }

  var area = rotatedBounds(angle);
  if (area.height > area.width) {
    angle += math.pi / 2;
    area = rotatedBounds(angle);
  }
  if (angle > math.pi / 2) angle -= math.pi;
  if (rings.length > 1 ||
      _isConcave(exterior) ||
      area.width < area.height * 2 ||
      angle.abs() < math.pi / 36) {
    angle = 0;
  }

  Offset rotate(Offset point, double radians) => Offset(
    point.dx * math.cos(radians) - point.dy * math.sin(radians),
    point.dx * math.sin(radians) + point.dy * math.cos(radians),
  );
  final localRings = [
    for (final ring in rings)
      [for (final point in ring) rotate(point - center, -angle)],
  ];
  area = campusMapInteriorLabelRect(localRings) ?? _interiorSquare(localRings);
  center += rotate(area.center, angle);
  final width = area.width * 0.88;
  final height = area.height * 0.88;
  var fontSize = math.min(14.0, math.min(width, height) / 4);
  TextPainter emptyPainter() => TextPainter(
    text: const TextSpan(text: ''),
    textDirection: .ltr,
  )..layout();
  TextPainter createPainter() {
    if (width <= 0 || height <= 0) return emptyPainter();
    final characters = name.characters.toList();
    final perRow = math.max(1, (width / textScaler.scale(fontSize)).floor());
    final lines = math.max(1, (characters.length / perRow).ceil());
    final balanced = math.max(1, (characters.length / lines).ceil());
    final wrapped = [
      for (var start = 0; start < characters.length; start += balanced)
        characters
            .sublist(start, math.min(start + balanced, characters.length))
            .join(),
    ].join('\n');
    final text = [
      if (number.isNotEmpty && !name.contains(number)) number,
      if (wrapped.isNotEmpty) wrapped,
    ].join('\n');
    // An empty centered paragraph can produce a NaN paint offset in Flutter.
    // Unnamed map features still have geometry, but need no text layout.
    if (text.isEmpty) return emptyPainter();
    return TextPainter(
      text: TextSpan(
        text: text.spaced,
        style: TextStyle(
          color: color,
          fontSize: fontSize,
          height: 1.2,
          fontWeight: .w500,
        ),
      ),
      textAlign: .center,
      textDirection: .ltr,
      textScaler: textScaler,
    )..layout(maxWidth: width);
  }

  var painter = createPainter();
  // Re-measure after shrinking because wrapping can change the line count.
  while (painter.height > height && fontSize > 0.01) {
    fontSize *= 0.85;
    painter.dispose();
    painter = createPainter();
  }
  if (painter.height > height) {
    // Sub-pixel spaces cannot display readable text; don't paint a clipped name.
    painter.dispose();
    painter = emptyPainter();
  }
  return CampusMapRoomLabelLayout(
    center: center,
    angle: angle,
    clipPath: path,
    textPainter: painter,
  );
}