Comment # 14 on bug 1124508 from Stasiek Michalski

(In reply to Felix Miata from comment #13)
> The computer figures out how many pixels are needed to produce appropriate
> size instead of the designer choosing arbitrary px numbers that work for him
> on his display but become illegible on high density displays.

I really wanted to use em for stylesheets, but I can't do that, because of
```
However, Qt is limited to font sizes in pt and px and any other size must be in
px, em or ex.
```
From: http://doc.qt.io/qt-5/stylesheet-reference.html#length

That basically means that even if we change the fonts to use em, they will be
out of size compared to everything else (checkboxes, logos, scrollbars, arrows
for sliding widgets etc). Unfortunately the only way to keep that at least
somewhat consistent is to use px measurements. That is entirely Qt's fault, css
has long ago adapted to using em's for all the elements' sizing being possible.

I will take a look at font sizes soon, Source Sans Pro is in fact smaller than
previous Sans font we used for the interface, which is an issue.