Yep, known bug in Qt going back literally decades:
https://bugreports.qt.io/browse/QTBUG-51891
So doing it programmatically is out! I really do not want to rewrite our highly customized CodeViewEditor class as a QTextEdit class.
This is so silly of Qt.
The only options would be to:
1. Use a font specially modified ala BeckyEbook
2. Use Zoom which helps text readability in general but not line height
3. Use Mend and Prettify to double space text in CodeView then use Zoom to make things cleaner
I am leaning toward BeckyEbook's idea. Perhaps we can modify a set of fixed width fonts (Courier, et al ) and use FontForge to manually adjust the font metrics for 1.5 and double spacing and include them as optional fonts alongside Sigil.