Add ResolveConstraints logic to JointSliders (=> ModelVisualizer)

[RussTedrake]

Updates JointSliders to have discrete state (previously it was
stateless). Additionally, if the new ResolveConstraints logic is
active, we publish the (rounded) resolved constraints back to Meshcat,
so that the other sliders are updated.

Since ModelVisualizer uses JointSliders, now ModelVisualizer also
satisfies the multibody constraints.

Resolves #18917.

Deprecates JointSliders::SetPositions(q), which has been replaced with
JointSliders::SetPositions(context, q).

Screen.Recording.2025-01-19.at.2.44.09.PM.mov

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This change is 

[RussTedrake]

+@jwnimmer-tri for feature review, please.

This PR contains #22495 as a first commit...; the request here is to review the second commit.

Reviewable status: LGTM missing from assignee jwnimmer-tri(platform), needs at least two assigned reviewers, commits need curation (https://drake.mit.edu/reviewable.html#curated-commits) (waiting on @RussTedrake)

[jwnimmer-tri]

Just a high-level skim for now ...

Reviewed 13 of 13 files at r1, 2 of 10 files at r2, all commit messages.
Reviewable status: 6 unresolved discussions, LGTM missing from assignee jwnimmer-tri(platform), needs at least two assigned reviewers, commits need curation (https://drake.mit.edu/reviewable.html#curated-commits) (waiting on @RussTedrake)

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multibody/meshcat/joint_sliders.h line 199 at r2 (raw file):

  systems::DiscreteStateIndex constrained_values_index_;
  systems::DiscreteStateIndex result_index_;
  mutable solvers::MathematicalProgram prog_;

This use of prog_ is not thread safe. We could either guard it with a mutex, place it into the context as a scratch value, or Clone the const program in ResolveConstraints (which would also then simplify the scope-cleanup logic).

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multibody/meshcat/joint_sliders.h line 201 at r2 (raw file):

  mutable solvers::MathematicalProgram prog_;
  solvers::VectorXDecisionVariable q_;
  std::unique_ptr<solvers::SolverInterface> solver_{};

nit The missing const here was very confusing (when evaluating thread-safety of the callbacks).

Suggestion:

std::unique_ptr<const solvers::SolverInterface> solver_{};

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multibody/meshcat/joint_sliders.h line 203 at r2 (raw file):

  std::unique_ptr<solvers::SolverInterface> solver_{};
  std::unique_ptr<systems::Context<double>> plant_context_{};
  std::unique_ptr<MultibodyPlant<double>> owned_plant_{};

BTW The owned_plant_ could be done away with by changing plant_ into a shared_ptr<const MbP> which can store both an owned or unowned plant depending on how the shared_ptr is constructed.

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multibody/inverse_kinematics/add_multibody_plant_constraints.h line 35 at r2 (raw file):

*/
std::vector<solvers::Binding<solvers::Constraint>> AddMultibodyPlantConstraints(
    const MultibodyPlant<double>& plant,

The plant must be passed by const pointer, since the function captures it. Actually a shared_ptr<const MbP> would even more clearly communicate what's happening, without requiring a special warning in the docs. The python
bindings also seem like they are missing the lifetime annotation.

I'll prepare a separate pull request with those fixes.

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multibody/meshcat/joint_sliders.cc line 81 at r2 (raw file):

      if (joint.num_positions() > 1) {
        description =
            fmt::format("{}_{}", joint.name(), joint.position_suffix(j));

BTW I'll open a new PR to enable clang-format in this directory in a moment. We'll either need to merge that change ahead of this PR, or else you'll need to revert the unrelated clang re-formatting here.

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multibody/meshcat/joint_sliders.cc line 288 at r2 (raw file):

  solvers::Binding<solvers::QuadraticCost> cost =
      prog_.AddQuadraticErrorCost(1.0, target_values, q_);
  std::vector<solvers::Binding<solvers::Constraint>> constraints;

As soon as we've declared constraints, we should use https://github.com/RobotLocomotion/drake/blob/master/common/scope_exit.h to arm the "remove from program" cleanup logic, so that if there are any exceptions our invariants will still hold.

Or in the alternative, clone the program into a local variable, mutate it in place, and then just throw it away when we're done. MP cloning is shallow, so should be pretty fast.

[jwnimmer-tri]

Reviewable status: 6 unresolved discussions, LGTM missing from assignee jwnimmer-tri(platform), needs at least two assigned reviewers, commits need curation (https://drake.mit.edu/reviewable.html#curated-commits) (waiting on @RussTedrake)

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multibody/inverse_kinematics/add_multibody_plant_constraints.h line 35 at r2 (raw file):

Previously, jwnimmer-tri (Jeremy Nimmer) wrote…

The plant must be passed by const pointer, since the function captures it. Actually a shared_ptr<const MbP> would even more clearly communicate what's happening, without requiring a special warning in the docs. The python
bindings also seem like they are missing the lifetime annotation.

I'll prepare a separate pull request with those fixes.

=> #22502

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multibody/meshcat/joint_sliders.cc line 81 at r2 (raw file):

Previously, jwnimmer-tri (Jeremy Nimmer) wrote…

BTW I'll open a new PR to enable clang-format in this directory in a moment. We'll either need to merge that change ahead of this PR, or else you'll need to revert the unrelated clang re-formatting here.

=> #22501

[jwnimmer-tri]

Reviewable status: 5 unresolved discussions, LGTM missing from assignee jwnimmer-tri(platform), needs at least two assigned reviewers, commits need curation (https://drake.mit.edu/reviewable.html#curated-commits) (waiting on @RussTedrake)

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multibody/meshcat/joint_sliders.cc line 81 at r2 (raw file):

Previously, jwnimmer-tri (Jeremy Nimmer) wrote…

=> #22501

Done.

[jwnimmer-tri]

Reviewable status: 5 unresolved discussions, LGTM missing from assignee jwnimmer-tri(platform), needs at least two assigned reviewers, commits need curation (https://drake.mit.edu/reviewable.html#curated-commits) (waiting on @RussTedrake)

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multibody/inverse_kinematics/add_multibody_plant_constraints.h line 35 at r2 (raw file):
Actually if you want to just remove this newly-added sentence ...

The plant must stay alive for the lifetime of the added constraints.

... from this PR, then we can decouple the two changes.

[RussTedrake]

i'll rebase and finish addressing your comments as soon as #22502 lands.

Reviewable status: 4 unresolved discussions, LGTM missing from assignee jwnimmer-tri(platform), needs at least two assigned reviewers, commits need curation (https://drake.mit.edu/reviewable.html#curated-commits)

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multibody/inverse_kinematics/add_multibody_plant_constraints.h line 35 at r2 (raw file):

Previously, jwnimmer-tri (Jeremy Nimmer) wrote…

=> #22502

Thank you.