The Gantt Chart in Jaspersoft - Widget Pro does not render the special characters for any language other than English
The Gantt chart is rendered correctly in the preview section, but when exported as PDF/PPT the special characters get rendered as escaped unicode values e.g. \u0107 -> "ć" ->
Release : 16.0.2
This issue has been log as Defect JSS-3050 (Tibco Jaspersoft) - open for Gantt chart where it does not support localization.
As of now we do not have any ETA,