Merge pull request #4 from maxpaj/master

Added support for ChartJS draw plugins

Author: sedouard

README.md

@@ -63,3 +63,28 @@ method to release the native resources or you may leak memory:
 ```
 chartNode.destroy();
 ```
+
+## Adding draw plugins
+
+To use draw plugins, simply use the ``options`` object to add your plugins, like so:
+```
+var myChartOptions = {
+    plugins: {
+        afterDraw: function (chart, easing) {
+            var self = chart.config;    /* Configuration object containing type, data, options */
+            var ctx = chart.chart.ctx;  /* Canvas context used to draw with */
+            ...
+        }
+    }
+}
+
+var chartJsOptions = {
+    type: 'pie',
+    data: myChartData,
+    options: myChartOptions
+}
+```
+
+[Read here](http://www.chartjs.org/docs/#advanced-usage-creating-plugins) to see what plugins you can write. In the context of drawing static images, ``beforeDraw`` and/or ``afterDraw`` methods makes most sense to implement.
+
+[Read here](https://developer.mozilla.org/en/docs/Web/API/CanvasRenderingContext2D) to see which methods are available for the ``ctx`` object.

index.js

@@ -49,6 +49,9 @@ class ChartjsNode {
             global.document = window.document;
             global.window = window;
             const Chartjs = require('chart.js');
+            if(configuration.options.plugins) {
+                Chartjs.pluginService.register(configuration.options.plugins);
+            }
             this._window = window;
             debug('got window');
             this._disableDynamicChartjsSettings(configuration);