Start xinit with default font?

Question

I'm using Raspberry Pi and try to make it like kiosk. I've added my app as a service to the systemd /lib/systemd/system/app.service and it starts when system opened. Inside the app.service:

[Unit]
Description=Start the app

[Service]
Environment=DISPLAY=:0
Environment=XAUTHORITY=/home/pi/.Xauthority
ExecStart=xinit /home/pi/App/app -nocursor
Restart=always
RestartSec=2s
KillMode=process
TimeoutSec=infinity

[Install]
WantedBy=multi-user.target

But the problem is:

When I opened the app on xfce4, it runs perfectly.

When I run it as service on startup without window manager:

• Fonts are ugly (not uses default system font which I use in xfce)
• Qt's virtual keyboard is not working properly.
• etc...

How can I solve this? Thanks!