Visualize chained controllers with graphviz

[pac48]

This change depends on this PR. It adds a new command line option ros2 control view_controller_chains, which generates an image using Graphviz.

[codecov-commenter]

Codecov Report

Merging #763 (c023416) into master (925f5f3) will decrease coverage by 1.92%.
The diff coverage is 36.60%.

@@            Coverage Diff             @@
##           master     #763      +/-   ##
==========================================
- Coverage   34.61%   32.69%   -1.93%     
==========================================
  Files          52       90      +38     
  Lines        2981     8620    +5639     
  Branches     1855     5765    +3910     
==========================================
+ Hits         1032     2818    +1786     
- Misses        310      673     +363     
- Partials     1639     5129    +3490     

Flag	Coverage Δ
unittests	32.69% <36.60%> (-1.93%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
controller_manager/src/realtime.cpp	0.00% <0.00%> (ø)
controller_manager/src/ros2_control_node.cpp	0.00% <0.00%> (ø)
..._interface/include/hardware_interface/actuator.hpp	100.00% <ø> (ø)
...re_interface/include/hardware_interface/sensor.hpp	100.00% <ø> (ø)
...re_interface/include/hardware_interface/system.hpp	100.00% <ø> (ø)
hardware_interface/src/resource_manager.cpp	50.09% <ø> (-3.53%)	⬇️
hardware_interface/src/sensor.cpp	50.52% <ø> (ø)
hardware_interface/src/system.cpp	55.45% <ø> (ø)
...rface/test/mock_components/test_generic_system.cpp	8.62% <ø> (ø)
...dware_interface/test/test_component_interfaces.cpp	32.44% <ø> (+4.25%)	⬆️
... and 106 more

[destogl]

This looks very cool! What do you think that we create a rqt plugin for that?

[pac48]

This looks very cool! What do you think that we create a rqt plugin for that?

I was taking inspiration from ros2 run tf2_tools view_frames.py described here, but I think an rqt_plugin would also be a good idea. I will investigate the rqt plugin.

[ejalaa12]

That is a very cool feature indeed.
In general a plugin that displays the state of each controller(active, inactive, hardware interface claimed) with features like the one that existed in rqt in Ros1 would be very useful.

[pac48]

That is a very cool feature indeed. In general a plugin that displays the state of each controller(active, inactive, hardware interface claimed) with features like the one that existed in rqt in Ros1 would be very useful.

What if I make the lines dashed if the interface is not claimed and solid if it is? And what if I put the controller status (active, inactive) underneath the name at the top of each node?

[ejalaa12]

What if I make the lines dashed if the interface is not claimed and solid if it is? And what if I put the controller status (active, inactive) underneath the name at the top of each node?

Agreed for the dashed lines.
I would add a either a small circle (red for inactive, green for active) on the side, or just change the text color, this would be more readable than having an additional text to tell if it is active inactive.

[mergify]

This pull request is in conflict. Could you fix it @pac48?

[bmagyar]

Minor cleanup