just for display, and any text entry will happen via some floating
text box, same as entering a dimension on the sketch.
Add the hover and selection mechanism, which now seems to work.
Still not clear how to do imported parts, for assemblies and
hierarchy. The handle formats may still have to change.
[git-p4: depot-paths = "//depot/solvespace/": change = 1662]
progress. I want to change the sketch.h stuff fairly significantly,
I think, before proceeding.
[git-p4: depot-paths = "//depot/solvespace/": change = 1657]