view_controller_chains does not work with example

[christophfroehlich]

Describe the bug
The output of view_controller_chains does not seem to work with the new example 12 of the demo repository.

To Reproduce
Steps to reproduce the behavior:

1. Checkout https://github.com/ros-controls/ros2_control_demos/
2. Run the example 12 as written in the doc
3. ros2 control view_controller_chains

Expected behavior
Some chain in the PDF.

Screenshots
But there are no links, just nodes:
controller_diagram.gv.pdf

Environment (please complete the following information):

• OS: Ubuntu 22.04
• Version: Rolling

Additional context
none

[christophfroehlich]

@pac48 could you please have a look on that if you find time?

[pac48]

I was able to reproduce the error that you mentioned. It seems that the Python library was changed from graphviz to pygraphviz in this PR #812 When I run with the old graphviz way, I get this output.

I am not too familiar with the differences between graphviz and pygraphviz, but it seems there is a difference in usage.

Is it possible to get a diagram of what the output should look like? The output above doesn't seem right.

[christophfroehlich]

I haven't seen the changes from your version, sorry. Maybe @sachinkum0009 can have a look?

@saikishor designed the example, imho the graph posted above isn't correct?

[bmagyar]

I believe the motivation for using a different graphviz python implementation was that the former isn't supported by rosdep