perspective and parallel projections. Add a snap grid, for points
and for text comments. Draw text comments in the plane of their
workplane if they have one, otherwise always facing forward.
And fix a few nasty bugs: the possibility of an extremely long
animation onto a workplane, accidental use of the wrong style line
width for constraints, misplaced text box in style screen for
default styles, other little stuff.
[git-p4: depot-paths = "//depot/solvespace/": change = 2037]
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