I'm completely ignorant about Qt, but I found a bug while using a web browser built on it (qutebrowser). I replicated it on another browser (Qupzilla).
In a really specific case part of the HTML gets stretched. I created a JSFiddle that reproduces it: https://jsfiddle.net/q67nc5nc/
And this is exactly what happens here: https://pasteboard.co/GSBtdSc.png
I'm on a Retina MacBook, please let me know if there's any other detail I can provide to help identifiyng this issue.