Additional fixes for listener setup (#254)

Author: benmccann

src/plugin.js

@@ -42,12 +42,14 @@ function resolveOptions(chart, options) {
 	// We also want to make sure listeners aren't always on. E.g. if you're scrolling down a page
 	// and the mouse goes over a chart you don't want it intercepted unless the plugin is enabled
 	var node = props._node;
-	if (!(options.zoom && options.zoom.drag)) {
+	var zoomEnabled = options.zoom && options.zoom.enabled;
+	var dragEnabled = options.zoom.drag;
+	if (zoomEnabled && !dragEnabled) {
 		node.addEventListener('wheel', props._wheelHandler);
 	} else {
 		node.removeEventListener('wheel', props._wheelHandler);
 	}
-	if (options.zoom && options.zoom.drag) {
+	if (zoomEnabled && dragEnabled) {
 		node.addEventListener('mousedown', props._mouseDownHandler);
 		node.ownerDocument.addEventListener('mouseup', props._mouseUpHandler);
 	} else {