Allow using a function for mode (#258)

Allow using a function for `mode`

Author: davidswinegar

README.md

@@ -33,6 +33,11 @@ plugins: {
 
 			// Panning directions. Remove the appropriate direction to disable
 			// Eg. 'y' would only allow panning in the y direction
+			// A function that is called as the user is panning and returns the
+			// available directions can also be used:
+			//   mode: function({ chart }) {
+			//     return 'xy';
+			//   },
 			mode: 'xy',
 
 			rangeMin: {
@@ -69,6 +74,11 @@ plugins: {
 
 			// Zooming directions. Remove the appropriate direction to disable
 			// Eg. 'y' would only allow zooming in the y direction
+			// A function that is called as the user is zooming and returns the
+			// available directions can also be used:
+			//   mode: function({ chart }) {
+			//     return 'xy';
+			//   },
 			mode: 'xy',
 
 			rangeMin: {

src/plugin.js

@@ -73,6 +73,10 @@ function storeOriginalOptions(chart) {
 	});
 }
 
+/**
+ * @param {string} mode can be 'x', 'y' or 'xy'
+ * @param {string} dir can be 'x' or 'y'
+ */
 function directionEnabled(mode, dir) {
 	if (mode === undefined) {
 		return true;
@@ -195,7 +199,7 @@ function doZoom(chart, percentZoomX, percentZoomY, focalPoint, whichAxes) {
 	if (zoomOptions.enabled) {
 		storeOriginalOptions(chart);
 		// Do the zoom here
-		var zoomMode = zoomOptions.mode;
+		var zoomMode = typeof zoomOptions.mode === 'function' ? zoomOptions.mode({chart: chart}) : zoomOptions.mode;
 
 		// Which axe should be modified when figers were used.
 		var _whichAxes;
@@ -301,7 +305,7 @@ function doPan(chartInstance, deltaX, deltaY) {
 	storeOriginalOptions(chartInstance);
 	var panOptions = chartInstance.$zoom._options.pan;
 	if (panOptions.enabled) {
-		var panMode = panOptions.mode;
+		var panMode = typeof panOptions.mode === 'function' ? panOptions.mode({chart: chartInstance}) : panOptions.mode;
 
 		helpers.each(chartInstance.scales, function(scale) {
 			if (scale.isHorizontal() && directionEnabled(panMode, 'x') && deltaX !== 0) {