Method contains

core/src/processing/core/PShape.java:3068–3108

Return true if this x, y coordinate is part of this shape. Only works with PATH shapes or GROUP shapes that contain other GROUPs or PATHs. This method is not imperfect and doesn't account for all cases (not all complex shapes: concave shapes or holes may have issues).

(float x, float y)

   * (not all complex shapes: concave shapes or holes may have issues).
   */
  public boolean contains(float x, float y) {
    if (family == PATH || family == GEOMETRY) {
      PVector p = new PVector(x, y);
      if (matrix != null) {
        // apply the inverse transformation matrix to the point coordinates
        PMatrix inverseCoords = matrix.get();
        // TODO why is this called twice? [fry 190724]
        // commit was https://github.com/processing/processing/commit/027fc7a4f8e8d0a435366eae754304eea282512a
        inverseCoords.invert();  // maybe cache this?
        inverseCoords.invert();  // maybe cache this?
        inverseCoords.mult(new PVector(x, y), p);
      }

      // http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html
      boolean c = false;
      for (int i = 0, j = vertexCount-1; i < vertexCount; j = i++) {
        if (((vertices[i][Y] > p.y) != (vertices[j][Y] > p.y)) &&
            (p.x <
                (vertices[j][X]-vertices[i][X]) *
                (y-vertices[i][Y]) /
                (vertices[j][1]-vertices[i][Y]) +
                vertices[i][X])) {
          c = !c;
        }
      }
      return c;

    } else if (family == GROUP) {
      // If this is a group, loop through children until we find one that
      // contains the supplied coordinates. If a child does not support
      // contains() throw a warning and continue.
      for (int i = 0; i < childCount; i++) {
        if (children[i].contains(x, y)) return true;
      }
      return false;

    } else {
      // https://github.com/processing/processing/issues/1280
      throw new IllegalArgumentException("The contains() method is only implemented for paths.");
    }
  }


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