Merge pull request #3673 from ahocevar/draw-regular-polygon

More control over ol.interaction.Draw, to allow e.g. square drawing
2015-05-20 12:08:15 +02:00
parent 3580cdc823 100020fd59
commit 4be106d014
9 changed files with 394 additions and 110 deletions
--- a/changelog/upgrade-notes.md
+++ b/changelog/upgrade-notes.md
@@ -2,6 +2,10 @@

 ### v3.6.0

+#### `ol.interaction.Draw` changes
+
+* The `minPointsPerRing` config option has been renamed to `minPoints`. It is now also available for linestring drawing, not only for polygons.
+
 #### `ol.tilegrid` changes

 * The `ol.tilegrid.XYZ` constructor has been replaced by a static `ol.tilegrid.createXYZ()` function. The `ol.tilegrid.createXYZ()` function takes the same arguments as the previous `ol.tilegrid.XYZ` constructor, but returns an `ol.tilegrid.TileGrid` instance.
--- a/examples/draw-features.html
+++ b/examples/draw-features.html
@@ -6,7 +6,10 @@ docs: >
  Example of using the Draw interaction. Select a geometry type from the
  dropdown above to start drawing. To finish drawing, click the last
  point. To activate freehand drawing for lines and polygons, hold the `Shift`
-  key.
+  key. Square drawing is achieved by using Circle mode with a `geometryFunction`
+  that creates a 4-sided regular polygon instead of a circle. Box drawing uses a
+  custom `geometryFunction` that takes start and end point of a line with 2
+  points and creates a rectangular box.
 tags: "draw, edit, freehand, vector"
 ---
 <div class="row-fluid">
@@ -20,6 +23,8 @@ tags: "draw, edit, freehand, vector"
        <option value="LineString">LineString</option>
        <option value="Polygon">Polygon</option>
        <option value="Circle">Circle</option>
+        <option value="Square">Square</option>
+        <option value="Box">Box</option>
      </select>
    </form>
  </div>
--- a/examples/draw-features.js
+++ b/examples/draw-features.js
@@ -1,5 +1,6 @@
 goog.require('ol.Map');
 goog.require('ol.View');
+goog.require('ol.geom.Polygon');
 goog.require('ol.interaction.Draw');
 goog.require('ol.layer.Tile');
 goog.require('ol.layer.Vector');
@@ -51,9 +52,30 @@ var draw; // global so we can remove it later
 function addInteraction() {
  var value = typeSelect.value;
  if (value !== 'None') {
+    var geometryFunction, maxPoints;
+    if (value === 'Square') {
+      value = 'Circle';
+      geometryFunction = ol.interaction.Draw.createRegularPolygon(4);
+    } else if (value === 'Box') {
+      value = 'LineString';
+      maxPoints = 2;
+      geometryFunction = function(coordinates, geometry) {
+        if (!geometry) {
+          geometry = new ol.geom.Polygon(null);
+        }
+        var start = coordinates[0];
+        var end = coordinates[1];
+        geometry.setCoordinates([
+          [start, [start[0], end[1]], end, [end[0], start[1]], start]
+        ]);
+        return geometry;
+      };
+    }
    draw = new ol.interaction.Draw({
      source: source,
-      type: /** @type {ol.geom.GeometryType} */ (value)
+      type: /** @type {ol.geom.GeometryType} */ (value),
+      geometryFunction: geometryFunction,
+      maxPoints: maxPoints
    });
    map.addInteraction(draw);
  }
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -2357,8 +2357,10 @@ olx.interaction.DragZoomOptions.prototype.style;
 *     source: (ol.source.Vector|undefined),
 *     snapTolerance: (number|undefined),
 *     type: ol.geom.GeometryType,
- *     minPointsPerRing: (number|undefined),
+ *     maxPoints: (number|undefined),
+ *     minPoints: (number|undefined),
 *     style: (ol.style.Style|Array.<ol.style.Style>|ol.style.StyleFunction|undefined),
+ *     geometryFunction: (ol.interaction.Draw.GeometryFunctionType|undefined),
 *     geometryName: (string|undefined),
 *     condition: (ol.events.ConditionType|undefined),
 *     freehandCondition: (ol.events.ConditionType|undefined)}}
@@ -2393,7 +2395,7 @@ olx.interaction.DrawOptions.prototype.snapTolerance;

 /**
 * Drawing type ('Point', 'LineString', 'Polygon', 'MultiPoint',
- * 'MultiLineString', or 'MultiPolygon').
+ * 'MultiLineString', 'MultiPolygon' or 'Circle').
 * @type {ol.geom.GeometryType}
 * @api
 */
@@ -2401,12 +2403,21 @@ olx.interaction.DrawOptions.prototype.type;


 /**
- * The number of points that must be drawn before a polygon ring can be finished.
- * Default is `3`.
+ * The number of points that can be drawn before a polygon ring or line string
+ * is finished. The default is no restriction.
 * @type {number|undefined}
 * @api
 */
-olx.interaction.DrawOptions.prototype.minPointsPerRing;
+olx.interaction.DrawOptions.prototype.maxPoints;
+
+
+/**
+ * The number of points that must be drawn before a polygon ring or line string
+ * can be finished. Default is `3` for polygon rings and `2` for line strings.
+ * @type {number|undefined}
+ * @api
+ */
+olx.interaction.DrawOptions.prototype.minPoints;


 /**
@@ -2417,6 +2428,14 @@ olx.interaction.DrawOptions.prototype.minPointsPerRing;
 olx.interaction.DrawOptions.prototype.style;


+/**
+ * Function that is called when a geometry's coordinates are updated.
+ * @type {ol.interaction.Draw.GeometryFunctionType|undefined}
+ * @api
+ */
+olx.interaction.DrawOptions.prototype.geometryFunction;
+
+
 /**
 * Geometry name to use for features created by the draw interaction.
 * @type {string|undefined}
--- a/src/ol/geom/polygon.js
+++ b/src/ol/geom/polygon.js
@@ -2,6 +2,7 @@ goog.provide('ol.geom.Polygon');

 goog.require('goog.array');
 goog.require('goog.asserts');
+goog.require('goog.math');
 goog.require('ol.extent');
 goog.require('ol.geom.GeometryLayout');
 goog.require('ol.geom.GeometryType');
@@ -422,3 +423,53 @@ ol.geom.Polygon.fromExtent = function(extent) {
      ol.geom.GeometryLayout.XY, flatCoordinates, [flatCoordinates.length]);
  return polygon;
 };
+
+
+/**
+ * Create a regular polygon from a circle.
+ * @param {ol.geom.Circle} circle Circle geometry.
+ * @param {number=} opt_sides Number of sides of the polygon. Default is 32.
+ * @param {number=} opt_angle Start angle for the first vertex of the polygon in
+ *     radians. Default is 0.
+ * @return {ol.geom.Polygon} Polygon geometry.
+ * @api
+ */
+ol.geom.Polygon.fromCircle = function(circle, opt_sides, opt_angle) {
+  var sides = goog.isDef(opt_sides) ? opt_sides : 32;
+  var stride = circle.getStride();
+  var layout = circle.getLayout();
+  var polygon = new ol.geom.Polygon(null, layout);
+  var flatCoordinates = goog.array.repeat(0, stride * (sides + 1));
+  var ends = [flatCoordinates.length];
+  polygon.setFlatCoordinates(layout, flatCoordinates, ends);
+  ol.geom.Polygon.makeRegular(
+      polygon, circle.getCenter(), circle.getRadius(), opt_angle);
+  return polygon;
+};
+
+
+/**
+ * Modify the coordinates of a polygon to make it a regular polygon.
+ * @param {ol.geom.Polygon} polygon Polygon geometry.
+ * @param {ol.Coordinate} center Center of the regular polygon.
+ * @param {number} radius Radius of the regular polygon.
+ * @param {number=} opt_angle Start angle for the first vertex of the polygon in
+ *     radians. Default is 0.
+ */
+ol.geom.Polygon.makeRegular = function(polygon, center, radius, opt_angle) {
+  var flatCoordinates = polygon.getFlatCoordinates();
+  var layout = polygon.getLayout();
+  var stride = polygon.getStride();
+  var ends = polygon.getEnds();
+  goog.asserts.assert(ends.length === 1, 'only 1 ring is supported');
+  var sides = flatCoordinates.length / stride - 1;
+  var startAngle = goog.isDef(opt_angle) ? opt_angle : 0;
+  var angle, coord, offset;
+  for (var i = 0; i <= sides; ++i) {
+    offset = i * stride;
+    angle = startAngle + (goog.math.modulo(i, sides) * 2 * Math.PI / sides);
+    flatCoordinates[offset] = center[0] + (radius * Math.cos(angle));
+    flatCoordinates[offset + 1] = center[1] + (radius * Math.sin(angle));
+  }
+  polygon.setFlatCoordinates(layout, flatCoordinates, ends);
+};
--- a/src/ol/geom/simplegeometry.js
+++ b/src/ol/geom/simplegeometry.js
@@ -98,6 +98,12 @@ ol.geom.SimpleGeometry.prototype.computeExtent = function(extent) {
 };


+/**
+ * @return {Array} Coordinates.
+ */
+ol.geom.SimpleGeometry.prototype.getCoordinates = goog.abstractMethod;
+
+
 /**
 * Return the first coordinate of the geometry.
 * @return {ol.Coordinate} First coordinate.
@@ -209,6 +215,13 @@ ol.geom.SimpleGeometry.prototype.setFlatCoordinatesInternal =
 };


+/**
+ * @param {Array} coordinates Coordinates.
+ * @param {ol.geom.GeometryLayout=} opt_layout Layout.
+ */
+ol.geom.SimpleGeometry.prototype.setCoordinates = goog.abstractMethod;
+
+
 /**
 * @param {ol.geom.GeometryLayout|undefined} layout Layout.
 * @param {Array} coordinates Coordinates.
--- a/src/ol/interaction/drawinteraction.js
+++ b/src/ol/interaction/drawinteraction.js
@@ -12,6 +12,7 @@ goog.require('ol.FeatureOverlay');
 goog.require('ol.MapBrowserEvent');
 goog.require('ol.MapBrowserEvent.EventType');
 goog.require('ol.Object');
+goog.require('ol.coordinate');
 goog.require('ol.events.condition');
 goog.require('ol.geom.Circle');
 goog.require('ol.geom.GeometryType');
@@ -21,6 +22,7 @@ goog.require('ol.geom.MultiPoint');
 goog.require('ol.geom.MultiPolygon');
 goog.require('ol.geom.Point');
 goog.require('ol.geom.Polygon');
+goog.require('ol.geom.SimpleGeometry');
 goog.require('ol.interaction.InteractionProperty');
 goog.require('ol.interaction.Pointer');
 goog.require('ol.source.Vector');
@@ -126,15 +128,6 @@ ol.interaction.Draw = function(options) {
  this.snapTolerance_ = goog.isDef(options.snapTolerance) ?
      options.snapTolerance : 12;

-  /**
-   * The number of points that must be drawn before a polygon ring can be
-   * finished.  The default is 3.
-   * @type {number}
-   * @private
-   */
-  this.minPointsPerRing_ = goog.isDef(options.minPointsPerRing) ?
-      options.minPointsPerRing : 3;
-
  /**
   * Geometry type.
   * @type {ol.geom.GeometryType}
@@ -149,6 +142,77 @@ ol.interaction.Draw = function(options) {
   */
  this.mode_ = ol.interaction.Draw.getMode_(this.type_);

+  /**
+   * The number of points that must be drawn before a polygon ring or line
+   * string can be finished.  The default is 3 for polygon rings and 2 for
+   * line strings.
+   * @type {number}
+   * @private
+   */
+  this.minPoints_ = goog.isDef(options.minPoints) ?
+      options.minPoints :
+      (this.mode_ === ol.interaction.DrawMode.POLYGON ? 3 : 2);
+
+  /**
+   * The number of points that can be drawn before a polygon ring or line string
+   * is finished. The default is no restriction.
+   * @type {number}
+   * @private
+   */
+  this.maxPoints_ = goog.isDef(options.maxPoints) ?
+      options.maxPoints : Infinity;
+
+  var geometryFunction = options.geometryFunction;
+  if (!goog.isDef(geometryFunction)) {
+    if (this.type_ === ol.geom.GeometryType.CIRCLE) {
+      /**
+       * @param {ol.Coordinate|Array.<ol.Coordinate>|Array.<Array.<ol.Coordinate>>} coordinates
+       * @param {ol.geom.SimpleGeometry=} opt_geometry
+       * @return {ol.geom.SimpleGeometry}
+       */
+      geometryFunction = function(coordinates, opt_geometry) {
+        var circle = goog.isDef(opt_geometry) ? opt_geometry :
+            new ol.geom.Circle([NaN, NaN]);
+        goog.asserts.assertInstanceof(circle, ol.geom.Circle,
+            'geometry must be an ol.geom.Circle');
+        var squaredLength = ol.coordinate.squaredDistance(
+            coordinates[0], coordinates[1]);
+        circle.setCenterAndRadius(coordinates[0], Math.sqrt(squaredLength));
+        return circle;
+      };
+    } else {
+      var Constructor;
+      var mode = this.mode_;
+      if (mode === ol.interaction.DrawMode.POINT) {
+        Constructor = ol.geom.Point;
+      } else if (mode === ol.interaction.DrawMode.LINE_STRING) {
+        Constructor = ol.geom.LineString;
+      } else if (mode === ol.interaction.DrawMode.POLYGON) {
+        Constructor = ol.geom.Polygon;
+      }
+      /**
+       * @param {ol.Coordinate|Array.<ol.Coordinate>|Array.<Array.<ol.Coordinate>>} coordinates
+       * @param {ol.geom.SimpleGeometry=} opt_geometry
+       * @return {ol.geom.SimpleGeometry}
+       */
+      geometryFunction = function(coordinates, opt_geometry) {
+        var geometry = opt_geometry;
+        if (goog.isDef(geometry)) {
+          geometry.setCoordinates(coordinates);
+        } else {
+          geometry = new Constructor(coordinates);
+        }
+        return geometry;
+      };
+    }
+  }
+
+  /**
+   * @type {ol.interaction.Draw.GeometryFunctionType}
+   * @private
+   */
+  this.geometryFunction_ = geometryFunction;
+
  /**
   * Finish coordinate for the feature (first point for polygons, last point for
   * linestrings).
@@ -171,6 +235,13 @@ ol.interaction.Draw = function(options) {
   */
  this.sketchPoint_ = null;

+  /**
+   * Sketch coordinates. Used when drawing a line or polygon.
+   * @type {ol.Coordinate|Array.<ol.Coordinate>|Array.<Array.<ol.Coordinate>>}
+   * @private
+   */
+  this.sketchCoords_ = null;
+
  /**
   * Sketch line. Used when drawing polygon.
   * @type {ol.Feature}
@@ -179,11 +250,11 @@ ol.interaction.Draw = function(options) {
  this.sketchLine_ = null;

  /**
-   * Sketch polygon. Used when drawing polygon.
-   * @type {Array.<Array.<ol.Coordinate>>}
+   * Sketch line coordinates. Used when drawing a polygon or circle.
+   * @type {Array.<ol.Coordinate>}
   * @private
   */
-  this.sketchPolygonCoords_ = null;
+  this.sketchLineCoords_ = null;

  /**
   * Squared tolerance for handling up events.  If the squared distance
@@ -362,20 +433,15 @@ ol.interaction.Draw.prototype.handlePointerMove_ = function(event) {
 ol.interaction.Draw.prototype.atFinish_ = function(event) {
  var at = false;
  if (!goog.isNull(this.sketchFeature_)) {
-    var geometry = this.sketchFeature_.getGeometry();
    var potentiallyDone = false;
    var potentiallyFinishCoordinates = [this.finishCoordinate_];
    if (this.mode_ === ol.interaction.DrawMode.LINE_STRING) {
-      goog.asserts.assertInstanceof(geometry, ol.geom.LineString,
-          'geometry should be an ol.geom.LineString');
-      potentiallyDone = geometry.getCoordinates().length > 2;
+      potentiallyDone = this.sketchCoords_.length > this.minPoints_;
    } else if (this.mode_ === ol.interaction.DrawMode.POLYGON) {
-      goog.asserts.assertInstanceof(geometry, ol.geom.Polygon,
-          'geometry should be an ol.geom.Polygon');
-      potentiallyDone = geometry.getCoordinates()[0].length >
-          this.minPointsPerRing_;
-      potentiallyFinishCoordinates = [this.sketchPolygonCoords_[0][0],
-        this.sketchPolygonCoords_[0][this.sketchPolygonCoords_[0].length - 2]];
+      potentiallyDone = this.sketchCoords_[0].length >
+          this.minPoints_;
+      potentiallyFinishCoordinates = [this.sketchCoords_[0][0],
+        this.sketchCoords_[0][this.sketchCoords_[0].length - 2]];
    }
    if (potentiallyDone) {
      var map = event.map;
@@ -425,23 +491,22 @@ ol.interaction.Draw.prototype.createOrUpdateSketchPoint_ = function(event) {
 ol.interaction.Draw.prototype.startDrawing_ = function(event) {
  var start = event.coordinate;
  this.finishCoordinate_ = start;
-  var geometry;
  if (this.mode_ === ol.interaction.DrawMode.POINT) {
-    geometry = new ol.geom.Point(start.slice());
+    this.sketchCoords_ = start.slice();
+  } else if (this.mode_ === ol.interaction.DrawMode.POLYGON) {
+    this.sketchCoords_ = [[start.slice(), start.slice()]];
+    this.sketchLineCoords_ = this.sketchCoords_[0];
  } else {
-    if (this.mode_ === ol.interaction.DrawMode.LINE_STRING) {
-      geometry = new ol.geom.LineString([start.slice(), start.slice()]);
-    } else if (this.mode_ === ol.interaction.DrawMode.POLYGON) {
-      this.sketchLine_ = new ol.Feature(new ol.geom.LineString([start.slice(),
-            start.slice()]));
-      this.sketchPolygonCoords_ = [[start.slice(), start.slice()]];
-      geometry = new ol.geom.Polygon(this.sketchPolygonCoords_);
-    } else if (this.mode_ === ol.interaction.DrawMode.CIRCLE) {
-      geometry = new ol.geom.Circle(start.slice(), 0);
-      this.sketchLine_ = new ol.Feature(new ol.geom.LineString([start.slice(),
-            start.slice()]));
+    this.sketchCoords_ = [start.slice(), start.slice()];
+    if (this.mode_ === ol.interaction.DrawMode.CIRCLE) {
+      this.sketchLineCoords_ = this.sketchCoords_;
    }
  }
+  if (!goog.isNull(this.sketchLineCoords_)) {
+    this.sketchLine_ = new ol.Feature(
+        new ol.geom.LineString(this.sketchLineCoords_));
+  }
+  var geometry = this.geometryFunction_(this.sketchCoords_);
  goog.asserts.assert(goog.isDef(geometry), 'geometry should be defined');
  this.sketchFeature_ = new ol.Feature();
  if (goog.isDef(this.geometryName_)) {
@@ -462,60 +527,50 @@ ol.interaction.Draw.prototype.startDrawing_ = function(event) {
 ol.interaction.Draw.prototype.modifyDrawing_ = function(event) {
  var coordinate = event.coordinate;
  var geometry = this.sketchFeature_.getGeometry();
-  var coordinates, last, sketchLineGeom;
+  goog.asserts.assertInstanceof(geometry, ol.geom.SimpleGeometry,
+      'geometry should be ol.geom.SimpleGeometry or subclass');
+  var coordinates, last;
  if (this.mode_ === ol.interaction.DrawMode.POINT) {
-    goog.asserts.assertInstanceof(geometry, ol.geom.Point,
-        'geometry should be an ol.geom.Point');
-    last = geometry.getCoordinates();
-    last[0] = coordinate[0];
-    last[1] = coordinate[1];
-    geometry.setCoordinates(last);
-  } else {
-    if (this.mode_ === ol.interaction.DrawMode.LINE_STRING) {
-      goog.asserts.assertInstanceof(geometry, ol.geom.LineString,
-          'geometry should be an ol.geom.LineString');
-      coordinates = geometry.getCoordinates();
-    } else if (this.mode_ === ol.interaction.DrawMode.POLYGON) {
-      goog.asserts.assertInstanceof(geometry, ol.geom.Polygon,
-          'geometry should be an ol.geom.Polygon');
-      coordinates = this.sketchPolygonCoords_[0];
-    } else if (this.mode_ === ol.interaction.DrawMode.CIRCLE) {
-      goog.asserts.assertInstanceof(geometry, ol.geom.Circle,
-          'geometry should be an ol.geom.Circle');
-      coordinates = geometry.getCenter();
-    }
+    last = this.sketchCoords_;
+  } else if (this.mode_ === ol.interaction.DrawMode.POLYGON) {
+    coordinates = this.sketchCoords_[0];
+    last = coordinates[coordinates.length - 1];
    if (this.atFinish_(event)) {
      // snap to finish
      coordinate = this.finishCoordinate_.slice();
    }
+  } else {
+    coordinates = this.sketchCoords_;
+    last = coordinates[coordinates.length - 1];
+  }
+  last[0] = coordinate[0];
+  last[1] = coordinate[1];
+  goog.asserts.assert(!goog.isNull(this.sketchCoords_),
+      'sketchCoords_ must not be null');
+  this.geometryFunction_(this.sketchCoords_, geometry);
+  if (!goog.isNull(this.sketchPoint_)) {
    var sketchPointGeom = this.sketchPoint_.getGeometry();
    goog.asserts.assertInstanceof(sketchPointGeom, ol.geom.Point,
        'sketchPointGeom should be an ol.geom.Point');
    sketchPointGeom.setCoordinates(coordinate);
-    last = coordinates[coordinates.length - 1];
-    last[0] = coordinate[0];
-    last[1] = coordinate[1];
-    if (this.mode_ === ol.interaction.DrawMode.LINE_STRING) {
-      goog.asserts.assertInstanceof(geometry, ol.geom.LineString,
-          'geometry should be an ol.geom.LineString');
-      geometry.setCoordinates(coordinates);
-    } else if (this.mode_ === ol.interaction.DrawMode.POLYGON) {
-      sketchLineGeom = this.sketchLine_.getGeometry();
-      goog.asserts.assertInstanceof(sketchLineGeom, ol.geom.LineString,
-          'sketchLineGeom should be an ol.geom.LineString');
-      sketchLineGeom.setCoordinates(coordinates);
-      goog.asserts.assertInstanceof(geometry, ol.geom.Polygon,
-          'geometry should be an ol.geom.Polygon');
-      geometry.setCoordinates(this.sketchPolygonCoords_);
-    } else if (this.mode_ === ol.interaction.DrawMode.CIRCLE) {
-      goog.asserts.assertInstanceof(geometry, ol.geom.Circle,
-          'geometry should be an ol.geom.Circle');
-      sketchLineGeom = this.sketchLine_.getGeometry();
-      goog.asserts.assertInstanceof(sketchLineGeom, ol.geom.LineString,
-          'sketchLineGeom should be an ol.geom.LineString');
-      sketchLineGeom.setCoordinates([geometry.getCenter(), coordinate]);
-      geometry.setRadius(sketchLineGeom.getLength());
+  }
+  var sketchLineGeom;
+  if (geometry instanceof ol.geom.Polygon &&
+      this.mode_ !== ol.interaction.DrawMode.POLYGON) {
+    if (goog.isNull(this.sketchLine_)) {
+      this.sketchLine_ = new ol.Feature(new ol.geom.LineString(null));
    }
+    var ring = geometry.getLinearRing(0);
+    sketchLineGeom = this.sketchLine_.getGeometry();
+    goog.asserts.assertInstanceof(sketchLineGeom, ol.geom.LineString,
+        'sketchLineGeom must be an ol.geom.LineString');
+    sketchLineGeom.setFlatCoordinates(
+        ring.getLayout(), ring.getFlatCoordinates());
+  } else if (!goog.isNull(this.sketchLineCoords_)) {
+    sketchLineGeom = this.sketchLine_.getGeometry();
+    goog.asserts.assertInstanceof(sketchLineGeom, ol.geom.LineString,
+        'sketchLineGeom must be an ol.geom.LineString');
+    sketchLineGeom.setCoordinates(this.sketchLineCoords_);
  }
  this.updateSketchFeatures_();
 };
@@ -529,21 +584,29 @@ ol.interaction.Draw.prototype.modifyDrawing_ = function(event) {
 ol.interaction.Draw.prototype.addToDrawing_ = function(event) {
  var coordinate = event.coordinate;
  var geometry = this.sketchFeature_.getGeometry();
+  goog.asserts.assertInstanceof(geometry, ol.geom.SimpleGeometry,
+      'geometry must be an ol.geom.SimpleGeometry');
+  var done;
  var coordinates;
  if (this.mode_ === ol.interaction.DrawMode.LINE_STRING) {
    this.finishCoordinate_ = coordinate.slice();
-    goog.asserts.assertInstanceof(geometry, ol.geom.LineString,
-        'geometry should be an ol.geom.LineString');
-    coordinates = geometry.getCoordinates();
+    coordinates = this.sketchCoords_;
    coordinates.push(coordinate.slice());
-    geometry.setCoordinates(coordinates);
+    done = coordinates.length > this.maxPoints_;
+    this.geometryFunction_(coordinates, geometry);
  } else if (this.mode_ === ol.interaction.DrawMode.POLYGON) {
-    this.sketchPolygonCoords_[0].push(coordinate.slice());
-    goog.asserts.assertInstanceof(geometry, ol.geom.Polygon,
-        'geometry should be an ol.geom.Polygon');
-    geometry.setCoordinates(this.sketchPolygonCoords_);
+    coordinates = this.sketchCoords_[0];
+    coordinates.push(coordinate.slice());
+    done = coordinates.length > this.maxPoints_;
+    if (done) {
+      this.finishCoordinate_ = coordinates[0];
+    }
+    this.geometryFunction_(this.sketchCoords_, geometry);
  }
  this.updateSketchFeatures_();
+  if (done) {
+    this.finishDrawing();
+  }
 };


@@ -557,29 +620,21 @@ ol.interaction.Draw.prototype.finishDrawing = function() {
  var sketchFeature = this.abortDrawing_();
  goog.asserts.assert(!goog.isNull(sketchFeature),
      'sketchFeature should not be null');
-  var coordinates;
+  var coordinates = this.sketchCoords_;
  var geometry = sketchFeature.getGeometry();
-  if (this.mode_ === ol.interaction.DrawMode.POINT) {
-    goog.asserts.assertInstanceof(geometry, ol.geom.Point,
-        'geometry should be an ol.geom.Point');
-    coordinates = geometry.getCoordinates();
-  } else if (this.mode_ === ol.interaction.DrawMode.LINE_STRING) {
-    goog.asserts.assertInstanceof(geometry, ol.geom.LineString,
-        'geometry should be an ol.geom.LineString');
-    coordinates = geometry.getCoordinates();
+  goog.asserts.assertInstanceof(geometry, ol.geom.SimpleGeometry,
+      'geometry must be an ol.geom.SimpleGeometry');
+  if (this.mode_ === ol.interaction.DrawMode.LINE_STRING) {
    // remove the redundant last point
    coordinates.pop();
-    geometry.setCoordinates(coordinates);
+    this.geometryFunction_(coordinates, geometry);
  } else if (this.mode_ === ol.interaction.DrawMode.POLYGON) {
-    goog.asserts.assertInstanceof(geometry, ol.geom.Polygon,
-        'geometry should be an ol.geom.Polygon');
    // When we finish drawing a polygon on the last point,
    // the last coordinate is duplicated as for LineString
    // we force the replacement by the first point
-    this.sketchPolygonCoords_[0].pop();
-    this.sketchPolygonCoords_[0].push(this.sketchPolygonCoords_[0][0]);
-    geometry.setCoordinates(this.sketchPolygonCoords_);
-    coordinates = geometry.getCoordinates();
+    coordinates[0].pop();
+    coordinates[0].push(coordinates[0][0]);
+    this.geometryFunction_(coordinates, geometry);
  }

  // cast multi-part geometries
@@ -660,6 +715,44 @@ ol.interaction.Draw.prototype.updateState_ = function() {
 };


+/**
+ * Create a `geometryFunction` for `mode: 'Circle'` that will create a regular
+ * polygon with a user specified number of sides and start angle instead of an
+ * `ol.geom.Circle` geometry.
+ * @param {number=} opt_sides Number of sides of the regular polygon. Default is
+ *     32.
+ * @param {number=} opt_angle Angle of the first point in radians. 0 means East.
+ *     Default is the angle defined by the heading from the center of the
+ *     regular polygon to the current pointer position.
+ * @return {ol.interaction.Draw.GeometryFunctionType} Function that draws a
+ *     polygon.
+ * @api
+ */
+ol.interaction.Draw.createRegularPolygon = function(opt_sides, opt_angle) {
+  return (
+      /**
+       * @param {ol.Coordinate|Array.<ol.Coordinate>|Array.<Array.<ol.Coordinate>>} coordinates
+       * @param {ol.geom.SimpleGeometry=} opt_geometry
+       * @return {ol.geom.SimpleGeometry}
+       */
+      function(coordinates, opt_geometry) {
+        var center = coordinates[0];
+        var end = coordinates[1];
+        var radius = Math.sqrt(
+            ol.coordinate.squaredDistance(center, end));
+        var geometry = goog.isDef(opt_geometry) ? opt_geometry :
+            ol.geom.Polygon.fromCircle(new ol.geom.Circle(center), opt_sides);
+        goog.asserts.assertInstanceof(geometry, ol.geom.Polygon,
+            'geometry must be a polygon');
+        var angle = goog.isDef(opt_angle) ? opt_angle :
+            Math.atan((end[1] - center[1]) / (end[0] - center[0]));
+        ol.geom.Polygon.makeRegular(geometry, center, radius, angle);
+        return geometry;
+      }
+  );
+};
+
+
 /**
 * Get the drawing mode.  The mode for mult-part geometries is the same as for
 * their single-part cousins.
@@ -686,6 +779,19 @@ ol.interaction.Draw.getMode_ = function(type) {
 };


+/**
+ * Function that takes coordinates and an optional existing geometry as
+ * arguments, and returns a geometry. The optional existing geometry is the
+ * geometry that is returned when the function is called without a second
+ * argument.
+ * @typedef {function(!(ol.Coordinate|Array.<ol.Coordinate>|
+ *     Array.<Array.<ol.Coordinate>>), ol.geom.SimpleGeometry=):
+ *     ol.geom.SimpleGeometry}
+ * @api
+ */
+ol.interaction.Draw.GeometryFunctionType;
+
+
 /**
 * Draw mode.  This collapses multi-part geometry types with their single-part
 * cousins.
--- a/test/spec/ol/geom/polygon.test.js
+++ b/test/spec/ol/geom/polygon.test.js
@@ -436,10 +436,44 @@ describe('ol.geom.Polygon', function() {
    });
  });

+  describe('ol.geom.Polygon.fromCircle', function() {
+
+    it('creates a regular polygon', function() {
+      var circle = new ol.geom.Circle([0, 0, 0], 1, ol.geom.GeometryLayout.XYZ);
+      var polygon = ol.geom.Polygon.fromCircle(circle);
+      var coordinates = polygon.getLinearRing(0).getCoordinates();
+      expect(coordinates[0].length).to.eql(3);
+      expect(coordinates[0][2]).to.eql(0);
+      expect(coordinates[32]).to.eql(coordinates[0]);
+      // east
+      expect(coordinates[0][0]).to.roughlyEqual(1, 1e-9);
+      expect(coordinates[0][1]).to.roughlyEqual(0, 1e-9);
+      // south
+      expect(coordinates[8][0]).to.roughlyEqual(0, 1e-9);
+      expect(coordinates[8][1]).to.roughlyEqual(1, 1e-9);
+      // west
+      expect(coordinates[16][0]).to.roughlyEqual(-1, 1e-9);
+      expect(coordinates[16][1]).to.roughlyEqual(0, 1e-9);
+      // north
+      expect(coordinates[24][0]).to.roughlyEqual(0, 1e-9);
+      expect(coordinates[24][1]).to.roughlyEqual(-1, 1e-9);
+    });
+
+    it('creates a regular polygon with custom sides and angle', function() {
+      var circle = new ol.geom.Circle([0, 0], 1);
+      var polygon = ol.geom.Polygon.fromCircle(circle, 4, Math.PI / 2);
+      var coordinates = polygon.getLinearRing(0).getCoordinates();
+      expect(coordinates[4]).to.eql(coordinates[0]);
+      expect(coordinates[0][0]).to.roughlyEqual(0, 1e-9);
+      expect(coordinates[0][1]).to.roughlyEqual(1, 1e-9);
+    });
+  });
+
 });


 goog.require('ol.extent');
+goog.require('ol.geom.Circle');
 goog.require('ol.geom.GeometryLayout');
 goog.require('ol.geom.LinearRing');
 goog.require('ol.geom.Polygon');
--- a/test/spec/ol/interaction/drawinteraction.test.js
+++ b/test/spec/ol/interaction/drawinteraction.test.js
@@ -708,6 +708,36 @@ describe('ol.interaction.Draw', function() {

    });
  });
+
+  describe('ol.interaction.Draw.createRegularPolygon', function() {
+    it('creates a regular polygon in Circle mode', function() {
+      var draw = new ol.interaction.Draw({
+        source: source,
+        type: ol.geom.GeometryType.CIRCLE,
+        geometryFunction:
+            ol.interaction.Draw.createRegularPolygon(4, Math.PI / 4)
+      });
+      map.addInteraction(draw);
+
+      // first point
+      simulateEvent('pointermove', 0, 0);
+      simulateEvent('pointerdown', 0, 0);
+      simulateEvent('pointerup', 0, 0);
+
+      // finish on second point
+      simulateEvent('pointermove', 20, 20);
+      simulateEvent('pointerdown', 20, 20);
+      simulateEvent('pointerup', 20, 20);
+
+      var features = source.getFeatures();
+      var geometry = features[0].getGeometry();
+      expect(geometry).to.be.a(ol.geom.Polygon);
+      var coordinates = geometry.getCoordinates();
+      expect(coordinates[0].length).to.eql(5);
+      expect(coordinates[0][0][0]).to.roughlyEqual(20, 1e-9);
+      expect(coordinates[0][0][1]).to.roughlyEqual(20, 1e-9);
+    });
+  });
 });

 goog.require('goog.dispose');