Run Qt Widget program on remote VPS with minimal Xorg installed

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I want to run on my VPS simple Qt program which uses QWidget so it's visual (not console) program. So I Installed XOrg packages and also Fluxbox to have some minimalistic VM. To have abiliti to connect to my server I installed x11vnc. Up to this point everything works without problem. I started X with startx and as I see it implicitly starts Fluxbox. I can connect to the server with VNC client also without problem. But when I run test Qt program I get lots of errors:
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QWidget::paintEngine: Should no longer be called
QPainter::begin: Paint device returned engine == 0, type: 1
QWidget::paintEngine: Should no longer be called
QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::save: Painter not active
...
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So what I do wrong and how can I run my Qt program?