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It allows to enable and disable a constraint in the constraint list.
When disabled, the constraints current value is shown, but its value is not enforced (it is driven by the other constraints and user interaction).
A disabled constraint can be enabled (as far as it is enforceable, see non-driving constraints to external geometry below).
The sketcher functionality has been extended to support non-driving constraints to external geometry elements. This were previously excluded from
the possibility of creating a constraint on them (as their values depend on other sketches and would be redundant with the unchanged value or conflicting when value is changed).
Now these constraints are created as non-driving, but as they are not enforceable, the UI does not allow you to make them driving.
The constraint filter has been extended to include a Non-Driving constraints category.
Thanks again to Werner for his continuous support, and specially in this case to DeepSOIC, as he pointed towards a much better implementation solution than my original idea.
Ex 1: User selects constraints from the list => right click => select "select elements" from the contextual menu => The elements (edges,vertex) involved in the constraint(s) are selected.
Ex 2: User selects (a) constraint(s) => Clicks button in toolbar (if included by the user) => The elements (edges,vertex) involved in the constraint(s) are selected.
Intended as visual aid to see which elements are being affected by a constraint.
Requested by Jim on thread:
http://forum.freecadweb.org/viewtopic.php?f=19&t=6875&start=10
Solving another Mantis ticket I can not find now.
