Hi tmn,
Thank you for being patience.
The GridgroupingControl uses the GDI+ for drawing the text by default. To make use of the GDI for drawing the GridGDIPaint class can be used. The following is the demo sample, please try it and let us know if you need any further assistance.
Sample :
GGC_UseGDI.zipHave a nice day.
Best regards,
Madhan