Next/Prev wiping out any data inserted via paint.

[Cecil1999]

Expected/Wanted Behavior: Data inserted via .paint() should persist after using any navigation method.

Current Behavior: After using any navigation method, data inserted via .paint() resets back to the initial data with which the chart was initialized.

Install Method: CDN

Since this issue came up at my workplace, I'll provide an example shortly. However, here's a list of the steps taken to reproduce this issue.

1. The chart is initialized with no data.
2. The user sends a request for data via AJAX.
3. The AJAX request resolves and uses data from X to paint the heatmap.
4. The user presses the Next or Previous button, which calls cal.previous() or cal.next().
5. The data that was just painted disappears.

Is expected behavior? I haven't seen any related issues regarding missing data in the repo since 2013.

Currently, we have a refresh method, so this isn't a huge deal. However, I'd still like to see this as a feature.