Method contains

core/src/processing/core/PShape.java:2964–3004

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.

(float x, float y)

   * with PATH shapes or GROUP shapes that contain other GROUPs or PATHs.
   */
  public boolean contains(float x, float y) {
    if (family == PATH) {
      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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