FEM: Homogenize/update selection dialogues in FEM WB

[FreeCAD-Bug-Importer]

Issue imported from https://tracker.freecad.org/view.php?id=4395

• Reporter: @HoWilgh
• Date submitted: 6/30/2020
• FreeCAD version:
• Category: Feature
• Status: assigned
• Tags: boundary conditions, FEM, highlighting, selection

Original report text

Selection dialogues in FEM for e.g. boundary conditions like "ConstraintFixed" and e.g. "ConstraintElectrostaticPotential" have different features like highlighting of the selected element in the "Select Faces -> Add-> Remove" task panel.
This is probably due to the fact that some of them like the fixed-constraint are programmed in c++ while the others are used in python?

The attached screenshots do show that e.g. for the constraint ElectrostaticPotential no face is highlighted when there is an entry selected in the task panel.

See also
https://github.com/HoWilgh/FreeCAD/blob/femelmeresforce/src/Mod/Fem/femguiobjects/_ViewProviderFemConstraintElectrostaticPotential.py

https://github.com/HoWilgh/FreeCAD/blob/femelmeresforce/src/Mod/Fem/femguiobjects/ViewProviderFemConstraint.py
https://github.com/HoWilgh/FreeCAD/blob/femelmeresforce/src/Mod/Fem/Gui/TaskFemConstraintFixed.ui
https://github.com/HoWilgh/FreeCAD/blob/femelmeresforce/src/Mod/Fem/Gui/TaskFemConstraintFixed.h

Steps to reproduce

Create a solid cube in Part-wb
Create a analysis in FEM-wb
Add a Model->Mechanical constraints->Fixed constraints and enter it by doubleclicking it in the combo-view/tree-view
Select a face and 'Add' the face into the list of elements in the "FEM constraint parameters" dialogue
Click somewhere else to de-select the face and than click the element in the "FEM constraint parameters" list -> the selected face gets highlighted again!

Other bug information

• Priority: normal
• Severity: tweak
• Category: Feature
• Updated: 2/6/2021

[luzpaz]

CC @HoWilgh

[jedbrown]

A related concern is that the current selection mode is not adequate for large structures, such as the interior of pneumatic actuators (where a pressure BC needs to be applied). In this forum discussion we worked out a macro to do "seed selection" (select a seed surface and bounding edges, apply macro to expand the seed to all neighboring surfaces that don't cross the bounding edges). This can't be used for face selection or mesh groups through the usual modal dialog.

A workaround is to go back into this manual edit dialog, use seed-select, then manually delete the bounding edges that got picked up in the process.

This bypasses error checking and isn't a viable solution for users. How hard would it be to allow selecting the faces first and then pressing Add? This could preserve current functionality if the users presses Add when no faces are selected. (And let me know if I should shift this discussion elsewhere.)