Experiment: *scoped recomputes* - deal with slow editing of early features in large projects

[DeepSOIC]

@leoheck has been complaining to me about being unable to do anything because his massive project was stuck in a long recompute. I have had these issues too, sometimes.

This is not in mainline Part-o-magic yet. It is in a highly experimental branch mega-hack. Now in master!

Be warned. If Part-o-magic is a hack, this change is a much uglier hack. It replaces App.ActiveDocument with a proxy object, to hook onto recompute calls.

How to use:

• Part-o-magic, tick "enable Fake Document" and "enable scoped recomputes"
• It requires that project's recomputes are frozen. As a consequence, freezing recomputes is not possible anymore. Unfreezing (right-click the project in tree and untick "skip recomputes") mostly disables scoped recomputes.
• Objects in active container, and all dependencies (aka inputs) are recomputed. Objects dependent on stuff in active container are NOT recomputed.
• FreeCAD's Recompute button becomes scoped.
• Recompute button stays enabled after a scoped recompute. Because objects out of scope end up touched.
• To recompute everything, deactivate active container, then click Recompute.
• Automatic recomputes upon property edits in property editor are disabled (not intentionally, just couldn't get it to work)
• to get things back to normal, go to preferences. Disabling the observer (Stop button) will also disable scoped recomputes.

tested on:
FreeCAD Version: 1.0.0.39109 (Git) Conda

[DeepSOIC]

Might be interesting to also try an even harsher scoping: recompute only what's necessary for only what's currently visible.

[DeepSOIC]

I am likely to include this into mainline Part-o-magic soon, as an option that is not on by default.

[DeepSOIC]

in master!