# all files / ol/geom/flat/ orientflatgeom.js

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100% Branches 32/32
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     goog.provide('ol.geom.flat.orient');

    goog.require('ol');
    goog.require('ol.geom.flat.reverse');

    /**
     * @param {Array.<number>} flatCoordinates Flat coordinates.
     * @param {number} offset Offset.
     * @param {number} end End.
     * @param {number} stride Stride.
     * @return {boolean} Is clockwise.
     */
    ol.geom.flat.orient.linearRingIsClockwise =
        function(flatCoordinates, offset, end, stride) {
      // http://tinyurl.com/clockwise-method
      // https://github.com/OSGeo/gdal/blob/trunk/gdal/ogr/ogrlinearring.cpp
      var edge = 0;
      var x1 = flatCoordinates[end - stride];
      var y1 = flatCoordinates[end - stride + 1];
      for (; offset < end; offset += stride) {
        var x2 = flatCoordinates[offset];
        var y2 = flatCoordinates[offset + 1];
        edge += (x2 - x1) * (y2 + y1);
        x1 = x2;
        y1 = y2;
      }
      return edge > 0;
    };

    /**
     * Determines if linear rings are oriented.  By default, left-hand orientation
     * is tested (first ring must be clockwise, remaining rings counter-clockwise).
     * To test for right-hand orientation, use the `opt_right` argument.
     *
     * @param {Array.<number>} flatCoordinates Flat coordinates.
     * @param {number} offset Offset.
     * @param {Array.<number>} ends Array of end indexes.
     * @param {number} stride Stride.
     * @param {boolean=} opt_right Test for right-hand orientation
     *     (counter-clockwise exterior ring and clockwise interior rings).
     * @return {boolean} Rings are correctly oriented.
     */
    ol.geom.flat.orient.linearRingsAreOriented =
        function(flatCoordinates, offset, ends, stride, opt_right) {
      var right = opt_right !== undefined ? opt_right : false;
      var i, ii;
      for (i = 0, ii = ends.length; i < ii; ++i) {
        var end = ends[i];
        var isClockwise = ol.geom.flat.orient.linearRingIsClockwise(
            flatCoordinates, offset, end, stride);
        if (i === 0) {
          if ((right && isClockwise) || (!right && !isClockwise)) {
            return false;
          }
        } else {
          if ((right && !isClockwise) || (!right && isClockwise)) {
            return false;
          }
        }
        offset = end;
      }
      return true;
    };

    /**
     * Determines if linear rings are oriented.  By default, left-hand orientation
     * is tested (first ring must be clockwise, remaining rings counter-clockwise).
     * To test for right-hand orientation, use the `opt_right` argument.
     *
     * @param {Array.<number>} flatCoordinates Flat coordinates.
     * @param {number} offset Offset.
     * @param {Array.<Array.<number>>} endss Array of array of end indexes.
     * @param {number} stride Stride.
     * @param {boolean=} opt_right Test for right-hand orientation
     *     (counter-clockwise exterior ring and clockwise interior rings).
     * @return {boolean} Rings are correctly oriented.
     */
    ol.geom.flat.orient.linearRingssAreOriented =
        function(flatCoordinates, offset, endss, stride, opt_right) {
      var i, ii;
      for (i = 0, ii = endss.length; i < ii; ++i) {
        if (!ol.geom.flat.orient.linearRingsAreOriented(
            flatCoordinates, offset, endss[i], stride, opt_right)) {
          return false;
        }
      }
      return true;
    };

    /**
     * Orient coordinates in a flat array of linear rings.  By default, rings
     * are oriented following the left-hand rule (clockwise for exterior and
     * counter-clockwise for interior rings).  To orient according to the
     * right-hand rule, use the `opt_right` argument.
     *
     * @param {Array.<number>} flatCoordinates Flat coordinates.
     * @param {number} offset Offset.
     * @param {Array.<number>} ends Ends.
     * @param {number} stride Stride.
     * @param {boolean=} opt_right Follow the right-hand rule for orientation.
     * @return {number} End.
     */
    ol.geom.flat.orient.orientLinearRings =
        function(flatCoordinates, offset, ends, stride, opt_right) {
      var right = opt_right !== undefined ? opt_right : false;
      var i, ii;
      for (i = 0, ii = ends.length; i < ii; ++i) {
        var end = ends[i];
        var isClockwise = ol.geom.flat.orient.linearRingIsClockwise(
            flatCoordinates, offset, end, stride);
        var reverse = i === 0 ?
            (right && isClockwise) || (!right && !isClockwise) :
            (right && !isClockwise) || (!right && isClockwise);
        if (reverse) {
          ol.geom.flat.reverse.coordinates(flatCoordinates, offset, end, stride);
        }
        offset = end;
      }
      return offset;
    };

    /**
     * Orient coordinates in a flat array of linear rings.  By default, rings
     * are oriented following the left-hand rule (clockwise for exterior and
     * counter-clockwise for interior rings).  To orient according to the
     * right-hand rule, use the `opt_right` argument.
     *
     * @param {Array.<number>} flatCoordinates Flat coordinates.
     * @param {number} offset Offset.
     * @param {Array.<Array.<number>>} endss Array of array of end indexes.
     * @param {number} stride Stride.
     * @param {boolean=} opt_right Follow the right-hand rule for orientation.
     * @return {number} End.
     */
    ol.geom.flat.orient.orientLinearRingss =
        function(flatCoordinates, offset, endss, stride, opt_right) {
      var i, ii;
      for (i = 0, ii = endss.length; i < ii; ++i) {
        offset = ol.geom.flat.orient.orientLinearRings(
            flatCoordinates, offset, endss[i], stride, opt_right);
      }
      return offset;
    };