Implement initial drag zoom control (shift + drag)

src/ol/control/dragzoom.js

@@ -0,0 +1,52 @@
+// FIXME draw drag box
+
+goog.provide('ol.control.DragZoom');
+
+goog.require('ol.Extent');
+goog.require('ol.MapBrowserEvent');
+goog.require('ol.control.Drag');
+
+
+/**
+ * @define {number} Hysterisis pixels.
+ */
+ol.DRAG_ZOOM_HYSTERESIS_PIXELS = 8;
+
+
+
+/**
+ * @constructor
+ * @extends {ol.control.Drag}
+ */
+ol.control.DragZoom = function() {
+  goog.base(this);
+};
+goog.inherits(ol.control.DragZoom, ol.control.Drag);
+
+
+/**
+ * @inheritDoc
+ */
+ol.control.DragZoom.prototype.handleDragEnd = function(mapBrowserEvent) {
+  if (this.deltaX * this.deltaX + this.deltaY * this.deltaY >=
+      ol.DRAG_ZOOM_HYSTERESIS_PIXELS * ol.DRAG_ZOOM_HYSTERESIS_PIXELS) {
+    var extent = ol.Extent.boundingExtent(
+        this.startCoordinate,
+        mapBrowserEvent.getCoordinate());
+    mapBrowserEvent.map.fitExtent(extent);
+  }
+};
+
+
+/**
+ * @inheritDoc
+ */
+ol.control.DragZoom.prototype.handleDragStart = function(mapBrowserEvent) {
+  var browserEventObject = mapBrowserEvent.getBrowserEventObject();
+  if (browserEventObject.shiftKey) {
+    browserEventObject.preventDefault();
+    return true;
+  } else {
+    return false;
+  }
+};