it did nothing when GenerateAll got called with an explicit range
(vs. with no args, to run on the dirty groups), so the emphasized
edges ended up out of date. I think this is better.
Also check in latest updates to manual.
[git-p4: depot-paths = "//depot/solvespace/": change = 1852]
theorem; it's evaluated as a surface integral over each triangle.
And don't regenerate the emphasized edges unless we have to;
specifically, don't do it when the only dirty group is the
drawing group.
[git-p4: depot-paths = "//depot/solvespace/": change = 1849]
Jonathan Westhues