From 95030cd838c2e2d56cab90d843d090bda52d494d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89ric=20Lemoine?= <eric.lemoine@gmail.com>
Date: Tue, 25 Aug 2015 13:53:13 +0200
Subject: [PATCH] Add ol.interaction.Draw#extend

This commit adds an `extend` method to the draw interaction. This method makes it possible to extend (continue drawing) an existing line string feature. It only works on line string features, where this functionality makes the most sense.

Here's an example on how to use `extend`:

```js
var vectorSource = vectorLayer.getSource();
vectroSource.removeFeature(feature);
drawInteraction.extend(feature);
```
---
 src/ol/interaction/drawinteraction.js         | 27 ++++++++++++++++
 .../ol/interaction/drawinteraction.test.js    | 31 +++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/src/ol/interaction/drawinteraction.js b/src/ol/interaction/drawinteraction.js
index 07b217a4cf..4b025dec09 100644
--- a/src/ol/interaction/drawinteraction.js
+++ b/src/ol/interaction/drawinteraction.js
@@ -714,6 +714,33 @@ ol.interaction.Draw.prototype.abortDrawing_ = function() {
 };
 
 
+/**
+ * Extend an existing geometry by adding additional points. This only works
+ * on features with `LineString` geometries, where the interaction will
+ * extend lines by adding points to the end of the coordinates array.
+ * @param {!ol.Feature} feature Feature to be extended.
+ * @api
+ */
+ol.interaction.Draw.prototype.extend = function(feature) {
+  var geometry = feature.getGeometry();
+  goog.asserts.assert(this.mode_ == ol.interaction.DrawMode.LINE_STRING,
+      'interaction mode must be "line"');
+  goog.asserts.assert(goog.isDefAndNotNull(geometry),
+      'feature must have a geometry');
+  goog.asserts.assert(geometry.getType() == ol.geom.GeometryType.LINE_STRING,
+      'feature geometry must be a line string');
+  var lineString = /** @type {ol.geom.LineString} */ (geometry);
+  this.sketchFeature_ = feature;
+  this.sketchCoords_ = lineString.getCoordinates();
+  var last = this.sketchCoords_[this.sketchCoords_.length - 1];
+  this.finishCoordinate_ = last.slice();
+  this.sketchCoords_.push(last.slice());
+  this.updateSketchFeatures_();
+  this.dispatchEvent(new ol.interaction.DrawEvent(
+      ol.interaction.DrawEventType.DRAWSTART, this.sketchFeature_));
+};
+
+
 /**
  * @inheritDoc
  */
diff --git a/test/spec/ol/interaction/drawinteraction.test.js b/test/spec/ol/interaction/drawinteraction.test.js
index b8aec5fe5d..e46d26287d 100644
--- a/test/spec/ol/interaction/drawinteraction.test.js
+++ b/test/spec/ol/interaction/drawinteraction.test.js
@@ -781,12 +781,43 @@ describe('ol.interaction.Draw', function() {
       expect(coordinates[0][0][1]).to.roughlyEqual(20, 1e-9);
     });
   });
+
+  describe('extend an existing feature', function() {
+    var draw;
+    var feature;
+
+    beforeEach(function() {
+      draw = new ol.interaction.Draw({
+        source: source,
+        type: ol.geom.GeometryType.LINE_STRING
+      });
+      map.addInteraction(draw);
+      feature = new ol.Feature(
+          new ol.geom.LineString([[0, 0], [1, 1], [2, 0]]));
+    });
+
+    it('sets the initial state', function() {
+      draw.extend(feature);
+      expect(draw.sketchCoords_).to.have.length(4);
+      expect(draw.sketchCoords_).to.eql([[0, 0], [1, 1], [2, 0], [2, 0]]);
+      expect(draw.finishCoordinate_).to.eql([2, 0]);
+    });
+
+    it('dispatches a drawstart event', function() {
+      var spy = sinon.spy();
+      goog.events.listen(draw, ol.interaction.DrawEventType.DRAWSTART, spy);
+      draw.extend(feature);
+      expect(spy.callCount).to.be(1);
+    });
+
+  });
 });
 
 goog.require('goog.dispose');
 goog.require('goog.events');
 goog.require('goog.events.BrowserEvent');
 goog.require('goog.style');
+goog.require('ol.Feature');
 goog.require('ol.Map');
 goog.require('ol.MapBrowserPointerEvent');
 goog.require('ol.View');