When you go to full screen mode in a chart, sometimes if the chart is complex or if the connection is slow, it takes 10 seconds or even a bit more for the chart to show up in full screen. During that time, the screen would be blank and this is confusing the users and at times they refresh the page.
To avoid this, it would be good to show the loading icon or animation, until the chart is loaded in full screen mode (similar to the ones shown during the normal chart load)