The older versions of drawterm just map a large view to fill
the whole screen and then clip the view to the window size you’ve
selected.  When you drag the view it doesn’t resize the internal
rio content.  That meant that when taking a 1280x1024 window to
2560x1440 everything would stay the same and you’d just see the
extra space already allocated.  If you draw to the new areas and
then resize the window back to the smaller rect you lose easy
access to any rio windows created outside of the current clipping
rect.

The Cocoa version does proper resizing.  It’s just a lot of effort
to get the same features back into the X11 code base.