Qt doesn't render vector graphics when QT_SCALE_FACTOR is set

Qt doesn't render vector graphics when QT_SCALE_FACTOR is set - it only scale its previous bitmap render. It is look awful!

What I try to do:

I want zoom user interface with QT_SCALE_FACTOR=1.2. I do it success fully. But the only problem is with images. I use to have bitmaps (*.png), but they are scaled awfully. So I was thinking I should to use vector graphics in order to scale them smoothly. But I failed with this - they are rendered to bitmaps at the beginning and display shows only scaled these bitmaps.

Please fix this or give me a hit how to workaround these awful problem.