When setting the scale factor of the primary screen to e.g. 100 % and the
scale factor of the second screen to something higher like 200 % the icons
appear too big on buttons and tabs. This is because icons are apparently
just rendered with the required size and the scale factor should therefore
not be applied.
This change adds overloads to specify a scale factor manually and uses a
scale factor of 1.0 for icons. The icons do not look blurry afterwards but
are also not too big anymore in the mentioned case. So this is probably how
it is supposed to be done.
Martchus