Why not adhere to the copy-on-write scheme for forms in Morphic? That’s how it was designed.
E.g. when you make a green-handle copy of a SystemWindow, why would you want to deep-copy all the icons?
I don't. I want to deepCopy the form bits when I invoke the green-halo it on a SketchMorph, not a SystemWindow. That's what Morph-cmm.1096 does, without affecting it when copying SystemWindows or anything else besides a SketchMorph.
But you said the problem with that is that Etoys students are putting their behaviors directly on SketchMorphs instead of something more abstract like a PlayerMorph. With a PlayerMorph they could set his #fillStyle to some Form which would still share on veryDeepCopy, and yet with my #veryDeepFixup: in SketchMorph, the green-halo would ALSO work properly when invoked directly on a SketchMorph -- the best of both worlds.
But we have to break this common use-case so that this design choice to use SketchMorphs everywhere, will be more memory-efficient.. Sigh..
Instead, before you modify a form (which is an extremely rare operation compared to all uses of forms), make a copy of it.
As I said, that's exactly what I did -- or thought I was doing. I just did it via the green halo because I expected it to behave as it does on all other Morphs -- to make a meaningfully separate copy.