[Solved]-Highcharts CSS styling missing in exporting context button-Highcharts

Sorry I just figured out. I will required to add highcharts.css file in my header.

After googling and trying code samples for a good many hours, I finally find this post which describes the exact issue (It seems few people have this issue) and have the correct solution (add the highcharts.css file).

The tricky point is that I was thinking highchart does not have that css file included in project but only 3 css files under themes. What happened was Intellij "intelligently" grouped and collapsed that css file under the highcharts.scss file.

And also all the online demo and documents seem not to include that css file at all.