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The checkboxes enable a constraint to swap virtual space.
If checked the constraint is visible in the selected space and hidden in the other space (Real Space or Virtual Space).
If unchecked the constraint is visible in the other space and hidden in the selected space.
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The constraint class has been extended so that every constraint knows and serializes whether it is in virtual space or in normal real space.
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Block constraint is naturally redundant/conflicting with almost any other constraint applied to an edge (certainly with constraints operating only on that element).
As such, a block constraint will have very little applicability in absence of a way to handle this redundancy/conflicting. For example, in the case of a BSpline all its
internal geometry (construction circles on poles and its constraints) would have to be removed before locking. This would mean that it is not possible to define the BSpline shape
and then block it, as when removing the internal geometry the shape would be lost. In other cases, like temporally blocking to avoid that a part of the sketch moves while performing some
operation with the idea of afterwards unblocking it, it would mean removing all constraints, to add the block constraint, then perform the action, then remove the block constraint and manually
constraint it again.
Handling this situation in a user expected way means ignoring certain constraints (those causing the redundancy/conflicting), so that the solver is not aware of them and does not complain. However,
generally ignoring those constraints has a negative effect, in that constraints applied by the user on already blocked geometry, or constraints that otherwise lead to a conflicting or redundant
situation as a consequence of actions (further constraining) after the Block constrain is applied are ignored, thereby not properly informing the user of this situation, which is undesirable.
This new mechanism takes account on the position of the constraints relative to the involved blocked constraint(s). As such, redundant/conflicting constraints that were added before the Block
constraint are ignored, whereas those constraints that lead to a redundant/conflicting situation and added AFTER the block constraint was already in place, those are not ignored and are reported
accordingly.
