DisplayRobotState: Add ability to hide any link

[simonschmeisser]

We implemented tool changers in our software Mikado by allowing collisions and hiding inactive tools. Currently we do this via toggling rviz properties. I'm currently reviewing some changes to it and it looks very painful ... it would be lovely if this could be solved on the publisher side.

Another use-case would be multi robot setups where you might want to hide all other arms when visualizing a goal or such.

If there is agreement to this I'll implement support for it in RobotStateDisplay and similar.

For us hiding whole groups would be even more convenient, so I added this as well but I'm open to discussion.

[v4hn]

At first glance I'm not a fan of this change, because it turns the message into a generic "here's the joint positions. now show any combination of links in Cartesian space in any color" and I would expect it to describe a complete robot state (that's the name).
That being said I'm not much opposed either.

It might be good if these fields just toggle rviz properties the user can override there to see the rest of the robot.

One other thing to say is that this patch also suggests more fields in the message to specify which groups/links should be shown when all others should be hidden.
Maybe the names could be mask_links/mask_groups to invert the behavior if hide == true?

[rhaschke]

Generally, I'm open for this approach. On the other hand, can't you simply hide links already now, by specifying a zero alpha channel in their highlight_links ObjectColor?

It might be good if these fields just toggle rviz properties the user can override there to see the rest of the robot.

This would have been my expectation. There are checkboxes to show/hide links in any rviz::Robot...

Maybe the names could be mask_links/mask_groups to invert the behavior if hide == true?

It like this idea very much.