- it is a well-known and often feed-backed missing feature that SectionCuttings fails for intersecting objects.
To resolve this, the objects must be put int a BooleanFragments object.
- this PR adds this functionality as option.
- since a BooleanFragments objects has a specific color, the different colors of the objects cannot be preserved. Because of this disadvantage, the BooleanFragments option will not be the default.
- this PR also modernize all for loops
- a typical use-case is to open a document with an existing cut and only this cut is visible. When now opening the section cutting tool, the user got the fault message that there were no visible objects to be cut.
- the transparency for the cut was not explicitly set. Therefore the default transparency for new objects was used instead of the transparency of the objects to be cut.
- workaround for a graphics issue: when cutting objects intersection each other (only then), the transparency setting might be ignored. The fix is simply to change the default color slightly (By the way, this issue is independent on the color that is set in the Part preferences as color for new objects, seems to be a graphics driver or OCC issue.)
- besides this, avoid code duplication by using a lambda function
* [Part] feature to make persistent section cut views
* one aim is to have a feature to make real cuts, not hollow ones like with clipping
* the second one is to have a persistent view, so an object in the tree that can be further exported, meshed etc.
For a detailed description with examples see https://forum.freecadweb.org/viewtopic.php?f=17&t=52441
