From 8b900c78220c792c35b9b304409308cfcc31689d Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Mon, 30 Jul 2012 00:09:47 +0200
Subject: [PATCH] Add ol.control.ShiftDragRotate

---
 src/ol/control/shiftdragrotate.js | 57 +++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 src/ol/control/shiftdragrotate.js

diff --git a/src/ol/control/shiftdragrotate.js b/src/ol/control/shiftdragrotate.js
new file mode 100644
index 0000000000..ec013a6b96
--- /dev/null
+++ b/src/ol/control/shiftdragrotate.js
@@ -0,0 +1,57 @@
+goog.provide('ol.control.ShiftDragRotate');
+
+goog.require('ol.MapBrowserEvent');
+goog.require('ol.control.Drag');
+
+
+
+/**
+ * @constructor
+ * @extends {ol.control.Drag}
+ */
+ol.control.ShiftDragRotate = function() {
+  goog.base(this);
+};
+goog.inherits(ol.control.ShiftDragRotate, ol.control.Drag);
+
+
+/**
+ * @private
+ * @type {number}
+ */
+ol.control.ShiftDragRotate.prototype.startRotation_;
+
+
+/**
+ * @inheritDoc
+ */
+ol.control.ShiftDragRotate.prototype.handleDrag = function(mapBrowserEvent) {
+  var browserEvent = mapBrowserEvent.browserEvent;
+  var map = mapBrowserEvent.map;
+  var size = map.getSize();
+  var theta = Math.atan2(
+      size.height / 2 - browserEvent.offsetY,
+      browserEvent.offsetX - size.width / 2);
+  map.setRotation(this.startRotation_ - theta);
+};
+
+
+/**
+ * @inheritDoc
+ */
+ol.control.ShiftDragRotate.prototype.handleDragStart =
+    function(mapBrowserEvent) {
+  var browserEvent = mapBrowserEvent.browserEvent;
+  var map = mapBrowserEvent.map;
+  if (map.canRotate() && browserEvent.shiftKey) {
+    var size = map.getSize();
+    var theta = Math.atan2(
+        size.height / 2 - browserEvent.offsetY,
+        browserEvent.offsetX - size.width / 2);
+    this.startRotation_ = (map.getRotation() || 0) + theta;
+    browserEvent.preventDefault();
+    return true;
+  } else {
+    return false;
+  }
+};