Tab favicons should only be aligned to the left if the text is overflowing

[jurf]

Right now it's always aligned to the left, whereas in Adwaita it's aligned to the text if it's not overflowing. Also the spacing between them should be a bit larger.

Web:

Otter:

qTox:

[MartinBriza]

Might do this in the future. Currently, it's just too much hassle, as all of the tab layout stuff is done in QCommonStylePrivate::tabLayout - would need to reimplement everything regarding tab rendering.