drawString function

Implementation

Image drawString(Image image, String string,
    {required BitmapFont font,
    int? x,
    int? y,
    Color? color,
    bool rightJustify = false,
    bool wrap = false,
    Image? mask,
    Channel maskChannel = Channel.luminance}) {
  if (color?.a == 0) {
    return image;
  }

  var stringWidth = 0;
  var stringHeight = 0;

  if (x == null || y == null) {
    final chars = string.codeUnits;
    for (var c in chars) {
      if (!font.characters.containsKey(c)) {
        continue;
      }
      final ch = font.characters[c]!;
      stringWidth += ch.xAdvance;
      if (ch.height + ch.yOffset > stringHeight) {
        stringHeight = ch.height + ch.yOffset;
      }
    }
  }

  var sx = x ?? (image.width / 2).round() - (stringWidth / 2).round();
  var sy = y ?? (image.height / 2).round() - (stringHeight / 2).round();

  if (wrap) {
    final words = string.split(RegExp(r"\s+"));
    var subString = "";
    var x2 = sx;

    for (var w in words) {
      final ws = StringBuffer()
        ..write(w)
        ..write(' ');
      w = ws.toString();
      final chars = w.codeUnits;
      var wordWidth = 0;
      for (var c in chars) {
        if (!font.characters.containsKey(c)) {
          wordWidth += font.base ~/ 2;
          continue;
        }
        final ch = font.characters[c]!;
        wordWidth += ch.xAdvance;
      }
      if ((x2 + wordWidth) > image.width) {
        // If there is a word that won't fit the starting x, stop drawing
        if ((sx == x2) || (sx + wordWidth > image.width)) {
          return image;
        }

        drawString(image, subString,
            font: font,
            x: sx,
            y: sy,
            color: color,
            mask: mask,
            maskChannel: maskChannel,
            rightJustify: rightJustify);

        subString = "";
        x2 = sx;
        sy += stringHeight;
        subString += w;
        x2 += wordWidth;
      } else {
        subString += w;
        x2 += wordWidth;
      }

      if (subString.isNotEmpty) {
        drawString(image, subString,
            font: font,
            x: sx,
            y: sy,
            color: color,
            mask: mask,
            maskChannel: maskChannel,
            rightJustify: rightJustify);
      }
    }

    return image;
  }

  final origX = sx;
  final substrings = string.split(RegExp(r"[(\n|\r)]"));

  for (var ss in substrings) {
    final chars = ss.codeUnits;
    if (rightJustify == true) {
      for (var c in chars) {
        if (!font.characters.containsKey(c)) {
          sx -= font.base ~/ 2;
          continue;
        }

        final ch = font.characters[c]!;
        sx -= ch.xAdvance;
      }
    }
    for (var c in chars) {
      if (!font.characters.containsKey(c)) {
        sx += font.base ~/ 2;
        continue;
      }

      final ch = font.characters[c]!;

      final x2 = sx + ch.width;
      final y2 = sy + ch.height;
      final cIter = ch.image.iterator..moveNext();
      for (var yi = sy; yi < y2; ++yi) {
        for (var xi = sx; xi < x2; ++xi, cIter.moveNext()) {
          final p = cIter.current;
          drawPixel(image, xi + ch.xOffset, yi + ch.yOffset, p,
              filter: color, mask: mask, maskChannel: maskChannel);
        }
      }

      sx += ch.xAdvance;
    }

    sy = sy + stringHeight;
    sx = origX;
  }

  return image;
}