[QScintilla] Weird Eric4 Editor Font Spacing and Highlighting

[Christian Prinoth]

For what it is worth, the same "error" also appears in Spyder (another
python development environment which uses pyqt and qscintilla).

I noticed that the boxes are displayed correctly when using some font
sizes (10,20,25) but not with all the others. I only tried monospaced
fonts.

Another weird thing, that happens with font sizes <> 10 (yes I also
tried smaller fonts), is that highlighted braces (and colons), which
should only change color, also change size. In my experience, whatever
the font size I selected for the code, highlighted braces switch back
to size 10.

Cheers
Chris