How should minimum size be handled on widgets with no actual minimum?

[Osspial]

There are a few widgets that don't have a logical minimum size (sliders and progress bars are good examples), but it doesn't make sense to cap them at zero. How should a default minimum size for these be figured out?

[scalarwaves]

Half the window size is usually a good starting point, or 40%, something like that...

[Osspial]

The solution I've come up with is to let the rendering engine figure out the minimum size based on sprite size, and let the widget know about its conclusions. However, getting that working requires some fairly significant overhauls to the rendering API (which I needed to do anyway since the one that's currently on master isn't great), which I've been working through slowly but surely.