From email: The ganttproject toolbar text becomes garbled, after i choose another fonts

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I install the ganttproject software, and i change the text setting and fonts become garbled.
I have remove the software from win10 and delete the folder in C:\Program Files (x86). After i re-install again, the software toolbar text is still garbled.
What can i do then?

You need to remove .ganttproject file from your home directory. Your home directory on Windows is something like C:\Users\<your username>. Pay attention that there is a dot in the file name. Some file managers may hide such files.