QPainter::drawText ignores increasing set of codepoints

Our project uses hand-crafted ttf fonts to display specific symbols. We traditionally use QPainter::drawText for drawing these, but it seems that Qt is increasingly blocking specific codepoints (painting empty space instead), which breaks previously working symbols.

It used to be that we needed to fix codepoint 0x09 (\t) during qt 4 series and rebuild our fonts, now qt 5 seem to break even more codepoints (quick check without claim of full set: 10 12 13 88 89).

It would be nice if qt allowed font to render whatever it wants or allowed to switch this behaviour or at least clearly declared in docs forbidden ranges which stay fixed so we don't need to redesign fonts for each version of Qt...

If there is already existing solution, please share it, thanks...