transformSVGPath static method

dynamic transformSVGPath(dynamic svgPathStr)

Implementation

static transformSVGPath(svgPathStr) {
  var path = ShapePath();

  int idx = 1;
  String activeCmd;

  double x = 0;
  double y = 0;
  double nx = 0;
  double ny = 0;
  double firstX = 0, firstY = 0;
  double x1 = 0,
      x2 = 0,
      y1 = 0,
      y2 = 0,
      rx = 0,
      ry = 0,
      xar = 0,
      laf = 0,
      sf = 0,
      cx,
      cy;

  var len = svgPathStr.length;

  double eatNum() {
    int sidx;
    double c = 0.0;
    bool isFloat = false;
    String s;

    // eat delims

    while (idx < len) {
      c = svgPathStr.codeUnitAt(idx);

      if (c != COMMA && c != SPACE) break;

      idx++;
    }

    if (c == MINUS) {
      sidx = idx++;
    } else {
      sidx = idx;
    }

    // eat number

    while (idx < len) {
      c = svgPathStr.codeUnitAt(idx);

      if (DIGIT_0 <= c && c <= DIGIT_9) {
        idx++;
        continue;
      } else if (c == PERIOD) {
        idx++;
        isFloat = true;
        continue;
      }

      s = svgPathStr.substring(sidx, idx);
      // return isFloat ? num.parse(s) : int.parse( s );

      // print("s: ${s}  sidx: ${sidx} idx: ${idx} c: ${c}");

      return double.parse(s);
    }

    s = svgPathStr.substring(sidx);
    // return isFloat ? num.parse( s ) : int.parse( s );
    return double.parse(s);
  }

  bool nextIsNum() {
    var c;

    // do permanently eat any delims...

    while (idx < len) {
      c = svgPathStr.codeUnitAt(idx);

      if (c != COMMA && c != SPACE) break;

      idx++;
    }

    c = svgPathStr.codeUnitAt(idx);
    return (c == MINUS || (DIGIT_0 <= c && c <= DIGIT_9));
  }

  bool canRepeat;
  activeCmd = svgPathStr[0];

  while (idx <= len) {
    canRepeat = true;

    switch (activeCmd) {
      // moveto commands, become lineto's if repeated
      case 'M':
        x = eatNum();
        y = eatNum();

        path.moveTo(x, y);
        activeCmd = 'L';
        firstX = x;
        firstY = y;
        break;
      case 'm':
        x += eatNum();
        y += eatNum();
        path.moveTo(x, y);
        activeCmd = 'l';
        firstX = x;
        firstY = y;
        break;
      case 'Z':
      case 'z':
        canRepeat = false;
        if (x != firstX || y != firstY) path.lineTo(firstX, firstY);
        break;

      // - lines!
      case 'L':
      case 'H':
      case 'V':
        nx = (activeCmd == 'V') ? x : eatNum();
        ny = (activeCmd == 'H') ? y : eatNum();
        path.lineTo(nx, ny);
        x = nx;
        y = ny;
        break;

      case 'l':
      case 'h':
      case 'v':
        nx = (activeCmd == 'v') ? x : (x + eatNum());
        ny = (activeCmd == 'h') ? y : (y + eatNum());
        path.lineTo(nx, ny);
        x = nx;
        y = ny;
        break;

      // - cubic bezier
      case 'C':
        x1 = eatNum();
        y1 = eatNum();
        break;
      case 'S':
        if (activeCmd == 'S') {
          x1 = 2 * x - x2;
          y1 = 2 * y - y2;
        }

        x2 = eatNum();
        y2 = eatNum();
        nx = eatNum();
        ny = eatNum();
        path.bezierCurveTo(x1, y1, x2, y2, nx, ny);
        x = nx;
        y = ny;
        break;

      case 'c':
        x1 = x + eatNum();
        y1 = y + eatNum();
        break;
      case 's':
        if (activeCmd == 's') {
          x1 = 2 * x - x2;
          y1 = 2 * y - y2;
        }

        x2 = x + eatNum();
        y2 = y + eatNum();
        nx = x + eatNum();
        ny = y + eatNum();
        path.bezierCurveTo(x1, y1, x2, y2, nx, ny);
        x = nx;
        y = ny;
        break;

      // - quadratic bezier
      case 'Q':
        x1 = eatNum();
        y1 = eatNum();
        break;
      case 'T':
        if (activeCmd == 'T') {
          x1 = 2 * x - x1;
          y1 = 2 * y - y1;
        }
        nx = eatNum();
        ny = eatNum();
        path.quadraticCurveTo(x1, y1, nx, ny);
        x = nx;
        y = ny;
        break;

      case 'q':
        x1 = x + eatNum();
        y1 = y + eatNum();
        break;
      case 't':
        if (activeCmd == 't') {
          x1 = 2 * x - x1;
          y1 = 2 * y - y1;
        }

        nx = x + eatNum();
        ny = y + eatNum();
        path.quadraticCurveTo(x1, y1, nx, ny);
        x = nx;
        y = ny;
        break;

      // - elliptical arc
      case 'A':
        rx = eatNum();
        ry = eatNum();
        xar = eatNum() * DEGS_TO_RADS;
        laf = eatNum();
        sf = eatNum();
        nx = eatNum();
        ny = eatNum();
        if (rx != ry) {
          print('Forcing elliptical arc to be a circular one: $rx $ry');
        }

        // SVG implementation notes does all the math for us! woo!
        // http://www.w3.org/TR/SVG/implnote.html#ArcImplementationNotes

        // step1, using x1 as x1'

        x1 = Math.cos(xar) * (x - nx) / 2 + Math.sin(xar) * (y - ny) / 2;
        y1 = -Math.sin(xar) * (x - nx) / 2 + Math.cos(xar) * (y - ny) / 2;

        // step 2, using x2 as cx'

        var norm = Math.sqrt(
            (rx * rx * ry * ry - rx * rx * y1 * y1 - ry * ry * x1 * x1) /
                (rx * rx * y1 * y1 + ry * ry * x1 * x1));

        if (laf == sf) norm = -norm;

        x2 = norm * rx * y1 / ry;
        y2 = norm * -ry * x1 / rx;

        // step 3

        cx = Math.cos(xar) * x2 - Math.sin(xar) * y2 + (x + nx) / 2;
        cy = Math.sin(xar) * x2 + Math.cos(xar) * y2 + (y + ny) / 2;

        var u = Vector2(1, 0);
        var v = Vector2((x1 - x2) / rx, (y1 - y2) / ry);

        var startAng = Math.acos(u.dot(v) / u.length() / v.length());

        if (((u.x * v.y) - (u.y * v.x)) < 0) startAng = -startAng;

        // we can reuse 'v' from start angle as our 'u' for delta angle
        u.x = (-x1 - x2) / rx;
        u.y = (-y1 - y2) / ry;

        var deltaAng = Math.acos(v.dot(u) / v.length() / u.length());

        // This normalization ends up making our curves fail to triangulate...

        if (((v.x * u.y) - (v.y * u.x)) < 0) deltaAng = -deltaAng;

        // if ( ! sf && deltaAng > 0 ) deltaAng -= Math.PI * 2;
        // if ( sf && deltaAng < 0 ) deltaAng += Math.PI * 2;
        if (sf == 0 && deltaAng > 0) deltaAng -= Math.PI * 2;
        if (sf != 0 && deltaAng < 0) deltaAng += Math.PI * 2;

        // path.absarc( cx, cy, rx, startAng, startAng + deltaAng, sf );
        throw ("SvgPath path.absarc");

        x = nx;
        y = ny;
        break;

      default:
        throw ("Wrong path command: $activeCmd");
    }

    // just reissue the command

    if (canRepeat && nextIsNum()) continue;

    var _index = idx++;

    if (_index < len) {
      activeCmd = svgPathStr[_index];
    } else {
      activeCmd = "";
    }
  }

  return path;
}