HTML5 canvas charts not rendered using WebEngine

The graphs on sites like http://www.chartjs.org or home-assistant websites utilizing this library.

I have tried multiple browsers based on QWebEngine:

• qutebrowser
• falkon

It works with chromium, but not the ones above. Using qutebrowser or falkon and hovering above the all white canvas area, hints will eventually popup of a data point.

When unsetting:

• QT_DEVICE_PIXEL_RATIO
• QT_AUTO_SCREEN_SCALE_FACTOR{{}}

It eventually worked with qutebrowser.

Qt 5.10.1 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 7.3.1 20180312) on "xcb"
OS: Arch Linux [linux version 4.15.12-1-ARCH]

Architecture: x86_64; features: SSE2 SSE3 SSSE3 SSE4.1 SSE4.2 AVX AVX2

Environment:
QT_AUTO_SCREEN_SCALE_FACTOR="0.4"
QT_STYLE_OVERRIDE="GTK+"