[Eloquent backport]: Allow the MapDisplay "Update Topic" to be changed. (#517)

[clalancette]

The major reason for this is so that the "Update Topic"
(and more importantly the QoS profile) is saved when clicking
"Save Config" in RViz2. The more minor reason is that a user
might want to use a different topic for this. We still
auto-populate this field with <topic_name>_updates by default,
but the user can now override it.

Signed-off-by: Chris Lalancette clalancette@openrobotics.org

[wjwwood]

I think this is fine.

One thing I was concerned with is if this change will cause any problems with existing .rviz files, since I think this change will affect the stored config structure. I didn't test for this case though.

[clalancette]

One thing I was concerned with is if this change will cause any problems with existing .rviz files, since I think this change will affect the stored config structure. I didn't test for this case though.

I don't believe it will.

In the existing Eloquent RViz, because this is marked as read-only, clicking "Save" in RViz won't actually save it. So for most "normal" uses of RViz, this is a straightforward addition.

If someone went ahead and and hand-typed the data into a saved RViz file, then in current Eloquent RViz it will be properly loaded in (I have a customer using that workaround right now). By changing this to not be read-only, that behavior is preserved, but it additionally allows us to save by clicking "Save" (and has the side-effect of allowing the user to set the "Update Topic" to an arbitrary value).

[wjwwood]

@mjcarroll if you want me to do a release into Eloquent let me know.