Created attachment 139961 [details]
Incorrect rendering in preview video

SUMMARY

Overlapping characters in fonts (e.g. Pacifico [1]) are rendered as the background and not the font color.

This happens both in the preview video and in the rendered video. In the title editor, the font is rendered correctly.

This behavior was introduced in 20.12.3 (it is still present in 21.04.2). Version 20.12.2 renders the font correctly. Maybe this has something to do with the typewriter feature? However, the rendering is incorrect irrelevant whether typewriting is used or not.

Note that there has been a similar bug in Krita a couple of years ago [2].

[1] Pacifico font: https://fonts.google.com/specimen/Pacifico?query=pacifico
[2] Krita bug: https://bugs.kde.org/show_bug.cgi?id=361169

STEPS TO REPRODUCE
1. Install Pacifico [1] on your system (or any other overlapping font)
2. Create a new title
3. Write any text using the overlapping font (it is rendered correctly in the title editor)
4. Pull the title into a video lane. The preview video renders the font incorrectly.
5. Render the video. The font is rendered incorrectly in the output video.

OBSERVED RESULT
The overlapping area of characters is rendered in the background color.

EXPECTED RESULT
Font is rendered correctly in the preview video as well as the rendered video. Overlapping areas are rendered using the font color as well.

SOFTWARE/OS VERSIONS
Windows: -
macOS: -
Linux/KDE Plasma: ArchLinux, Kernel 5.12.13-zen1-1-zen
(available in About System)
KDE Plasma Version: n/a (using i3 without KDE)
KDE Frameworks Version: 
Qt Version: 5.15.2+kde+r207-1

ADDITIONAL INFORMATION