There are many fonts which come with a set of variants like 'Light, Semilight, Bold, Semibold, Regular, etc...'
I would like to use some font as 'Semilight' throughout my entire applicaiton. How about adding an optional parameter to setDefaultSansSerifTypefaceName for the typeface style?
I guess you could set the typeface style in LookAndFeel::getTypefaceForFont. Just add f.setTypefaceStyle(defaultStyle), right after the 'setTypefaceName' line.
On a sidenote,
I have many fonts which act weird when are set as the default sans font and have their style untouched. Notably Microsoft's Segoe UI and Google's Open Sans.
When I set their style, even to 'Regular', the irregularities stop and the fonts are drawn fine.