I have incorporated a copy of the Gantt Chart Visualization into my dashboard, and it shows up and works great. However, if I schedule the dashboard for emailing a PDF, the Gantt Chart is not on the PDF. The titles for the panel are there, but no graphics. I find that this same behavior exists in the Gantt Chart Visualization Sample page with the documentation as well. Any ideas?
I'm afraid that's a problem common to all the Splunk custom visualizations, you can see it as well in Splunk's Dashboard Examples app (https://splunkbase.splunk.com/app/1603/).
I'll open a support request to see if there's something that can be done about this. I'm not sure there will be, though, as the graphs are generated on the client side through Javascript.
I still haven't really gotten Support to acknowledge the problem, so I don't really expect this to be implemented anytime soon...
I would like to see a general solution for this problem, too!