Blender-style textFields

[lagarkane]

Hi!
I'd like to make custom textFields in the same style as Blender's. The idea is that I'll have custom widgets for specific datatypes, that would be grouped together by joining the edges of their fields, and rounding the corners of non-adjacent edges as seen in the following capture of blender's interface

I found some hack solutions online, using multiple Rectangles to set, say, the bottom corners square and the top ones rounded, but this would not look great if I add gradients, or worse, borders...

Did anyone try to do something similar already?

Thanks in advance!