Allow SheetMetal to take advantage of the new upstream 'feature preview' functionality

[pierreporte]

Describe the feature

FreeCAD/FreeCAD#17249 introduced transparent previews, and they are now everywhere in Part Design workbench. Having them in sheet metal would improve consistency with the main program.

Additional context

No response

Would you like to work on this issue?

None

[shaise]

That would be great indeed. I do not know if there is a python API for that though. Need to investigate.

[pierreporte]

@kadet1090

[luzpaz]

@maxwxyz could you kindly weigh-in here ?

[maxwxyz]

@kadet1090

[luzpaz]

Other addons would benefit from this as well.

[luzpaz]

@chennes sorry if this is an imposition, is there an API for kadet's feature preview that 3rd party addon devs can integrate ?

[kadet1090]

Not right now, working on it - will be available soon ™️

[kadet1090]

Just so happened that I started to do it today just before that comment - FreeCAD/FreeCAD#29641 - here is PR with implementation, and here: FreeCAD/FreeCAD@c90bc54 commit with example.

@shaise if you have comments or would need help, please ping me. I'll try to write something useful for the developers handbook but it will take some time.