[trac_ik_python]: Add suport for ROS 2

[SteveNguyen]

trac_ik_python bindings:

• used the catkin-to-ament script to convert the CMakeLists, plus some tinkering
• changed from rospy to rclpy
• removed the reading of robot_description from parameters

I now stumble upon a SWIG error:
This warning: "trac_ik/trac_ik_python/swig/trac_ik_wrap.i:298: Warning 303: %extend defined for an undeclared class TRAC_IK::TRAC_IK."
probably leads to the cascade of errors I got:
"build/trac_ik_python/CMakeFiles/_trac_ik_wrap.dir/trac_ik_wrapPYTHON_wrap.c:13463:24: error: ‘temp’ was not declared in this scope
13463 | TRAC_IK_PUBLIC * temp;" ...
My understanding is that SWIG does not find the TRAC_IK class, maybe due to a namespace problem?

I tried with a very basic trac_ik_wrap.i with just the include to expose the class and got the same error.

[aprotyas]

Thanks for opening this PR! I have some minimal progress in #4 that I can fold into this too, do you mind if I push commits to this branch?

About the actual problem you're facing, I should have some time to investigate into this over the next couple of days. I will report back once I understand how SWIG actually works. I suspect the problem is something to do with the trac_ik class changing? But that's just a hunch...

[SteveNguyen]

Well, I experimented a little bit and it seems that the include: "%include <trac_ik/trac_ik.hpp>" in trac_ik_wrap.i already confuses swig. If I comment this line I can get the package compile but of course, the wrapper is incomplete.

[aprotyas]

I wonder whether it's because I didn't export things correctly on the trac_ik_lib end, but that would manifest as a problem earlier through trac_ik_examples anyway. Any clue what's happening?

[SteveNguyen]

Ok so I have tried some various things and it seems that the TRAC_IK namespace may be a problem (https://stackoverflow.com/questions/15778870/swig-namespace-error-not-a-valid-base-class) a namespace with the same name as the class may create problems.
Secondly, it seems that the TRAC_IK_PUBLIC macros in trac_ik_lib visibility_control.hpp also breaks stuff.
But I still did not find something working...

[aprotyas]

Apologies for the lack of activity here.

Namespacing

Wasn't it always like this though? As in, even in the ROS 1 package, the namespace was still like this no? I'm not sure what would cause a regression here. 😕

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Visibility control

Yes, the visibility control macros were introduced because ROS 2 treats the Windows platform as a first class citizen, so I wanted this package to be cross-platform.

Do you mind checking if this recommendation is actionable and/or relevant for the swig stuff happening in this package? https://sourceforge.net/p/swig/mailman/message/35356996/

I will also be looking at it over the weekend hopefully, so don't feel pressed!