[bug] Cant add reference constraint to already defined circle/arc

[kisolre]

Take any fully defined arc/circle. While in defining constraints mode try to add radius/diameter constraint to it. Check the "Reference" checkbox while creating the constraint to try to create a reference one. Error is displayed on confirmation and a reference constraint is not created.
I remember experiencing this in the past but cant find forum thread about it.

Edit: I just tried and you can not add reference constraint by this method even to non defined arc/circle. It is created as a real one regardless of the checkbox state. Works for angles and length dimensions.

OS: Windows 8.1 Version 6.3 (Build 9600)
Word size of FreeCAD: 64-bit
Version: 0.20.24673 (Git)
Build type: Release
Branch: master
Hash: e66ed26769ce8affe0a4ed330ff0435f4802f05e
Python version: 3.8.6+
Qt version: 5.15.1
Coin version: 4.0.1
OCC version: 7.5.0
Locale: Bulgarian/Bulgaria (bg_BG)

[Bance]

confirmed on:-

OS: Linux Mint 20.1 (XFCE/xfce)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.
Build type: Release
Branch: unknown
Hash: 2599d67c2bd41a5f051b994b6da7890a2b4ecc4c
Python version: 3.8.5
Qt version: 5.12.8
Coin version: 4.0.0
OCC version: 7.5.1
Locale: English/United Kingdom (en_GB)
28.2.21

and on:-

OS: Linux Mint 20.1 (XFCE/xfce)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24276 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.19.1)
Hash: a88db11e0a908f6e38f92bfc5187b13ebe470438
Python version: 3.8.8
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: English/United Kingdom (en_GB)

[edwilliams16]

You can RMC on the constraint (in the task box) and toggle it to reference OK. You can also create the arc in construction mode, create the reference and then toggle the arc back to normal geometry. But otherwise as described.

[chrisb]

There is no ticket for this, so please create one.

My observations:
- It's independent from the arc's state, the issue remains if it is not or partially constrained. The checkbox in creation dialog doesn't work on radius.
- A workaround is to toggle the dimension tools: use while nothing is selected and then add the driven constraint.

[kisolre]

issue #4627

Ping

[openBrain]

My observations:
- It's independent from the arc's state, the issue remains if it is not or partially constrained. The checkbox in creation dialog doesn't work on radius.
- A workaround is to toggle the dimension tools: use while nothing is selected and then add the driven constraint.

As further observations :
- At dimension creation time, the 'Reference' checkbox seems to fail soon as clicking on it neither vary the DoFs nor trigger a recompute (which it does for other dimensions)
- The 'Reference' checkbox works correctly when the constraint is edited (double-click on existing dimension)

I'll try to have a look.

[openBrain]

OK, guys. After some investigations, the problem may be a bit weird.
Actually, radius/diameter constraint is processed a bit differently from other dimensional ones as it is allowed to select several arcs/circles before applying the constraint. It makes the code different from other constraints. For those who like history, it was introduced following issue #1633
BTW I wasn't aware of this (quite unique) behavior.
ATM, I see 3 possibilities that I'd like community's opinion :
1 - Make angle constraint as others : 'Reference' checkbox will work, but multi-selection before applying will be lost
2 - Remove 'Reference' checkbox when talking about radius/diameter
3 - Improve dimension dialog so it supports setting multiple constraints at a time : that will probably take quite a long time
---
Personal vote : 1
Rational :
- Multiselection makes radius/diameter inconsistent in behavior with other constraints
- This isn't so much time won when you're used to sketcher
- This encouraged bad sketch constraining (one of the offered option when multiselecting is to add a dimensional constraint on each arc/circle)

[Bance]

I like the multi-selection feature, but I could live without it

[openBrain]

I like the multi-selection feature, but I could live without it

Actually there could be a 1bis option. In case of multiselection, an equal constraint is added between all selected arcs/circles (no other option) and the dimensional is applied on the first (last TBD) selected one. Would that be OK?

[Bance]

Yes that would do nicely.

Thank you.