From 321b1f72adf130e31409db1726dd60abd5cd448c Mon Sep 17 00:00:00 2001
From: Axel Utech <axel.utech@gmail.com>
Date: Fri, 9 Dec 2016 18:02:36 +0100
Subject: [PATCH] add an option to make the pinchZoom constrain zoom levels to
 integers

Changes the default behavior of ol.interaction.PinchZoom to keep
the fractional zoom level after the gesture.
The old behavior of zooming to the next whole-number level can be
enforced with the new parameter `constrainResolution`.
---
 externs/olx.js                  |  9 ++++++++-
 src/ol/interaction/pinchzoom.js | 22 +++++++++++++++-------
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/externs/olx.js b/externs/olx.js
index 5d9bd288f5..178ffc19f2 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -3104,6 +3104,13 @@ olx.interaction.PinchZoomOptions;
  */
 olx.interaction.PinchZoomOptions.prototype.duration;
 
+/**
+ * Zoom to the closest integer zoom level after the pinch gesture ends. Default is `false`.
+ * @type {boolean|undefined}
+ * @api
+ */
+olx.interaction.PinchZoomOptions.prototype.constrainResolution;
+
 
 /**
  * @typedef {{handleDownEvent: (function(ol.MapBrowserPointerEvent):boolean|undefined),
@@ -7613,7 +7620,7 @@ olx.view.FitOptions.prototype.maxZoom;
 
 
 /**
- * The duration of the animation in milliseconds. By default, there is no 
+ * The duration of the animation in milliseconds. By default, there is no
  * animations.
  * @type {number|undefined}
  * @api
diff --git a/src/ol/interaction/pinchzoom.js b/src/ol/interaction/pinchzoom.js
index ac0bc45f3a..412cc7ce12 100644
--- a/src/ol/interaction/pinchzoom.js
+++ b/src/ol/interaction/pinchzoom.js
@@ -27,6 +27,12 @@ ol.interaction.PinchZoom = function(opt_options) {
 
   var options = opt_options ? opt_options : {};
 
+  /**
+   * @private
+   * @type {boolean}
+   */
+  this.constrainResolution_ = options.constrainResolution || false;
+
   /**
    * @private
    * @type {ol.Coordinate}
@@ -111,13 +117,15 @@ ol.interaction.PinchZoom.handleUpEvent_ = function(mapBrowserEvent) {
     var map = mapBrowserEvent.map;
     var view = map.getView();
     view.setHint(ol.View.Hint.INTERACTING, -1);
-    var resolution = view.getResolution();
-    // Zoom to final resolution, with an animation, and provide a
-    // direction not to zoom out/in if user was pinching in/out.
-    // Direction is > 0 if pinching out, and < 0 if pinching in.
-    var direction = this.lastScaleDelta_ - 1;
-    ol.interaction.Interaction.zoom(map, view, resolution,
-        this.anchor_, this.duration_, direction);
+    if (this.constrainResolution_) {
+      var resolution = view.getResolution();
+      // Zoom to final resolution, with an animation, and provide a
+      // direction not to zoom out/in if user was pinching in/out.
+      // Direction is > 0 if pinching out, and < 0 if pinching in.
+      var direction = this.lastScaleDelta_ - 1;
+      ol.interaction.Interaction.zoom(map, view, resolution,
+          this.anchor_, this.duration_, direction);
+    }
     return false;
   } else {
     return true;