Another TF implementation suggestion

[gaya-]

Major differences:

• All common interfaces / utilities for CL_TF and CL_TF2 are in CL_TRANSFORMS_STAMPED (previously CL_TF_DATATYPES) now
• There is no CAN-TRANSFORM anymore, one needs to call LOOKUP-TRANSFORM and check for NIL
• In CL-TF2:BUFFER-CLIENT each LOOKUP-TRANSFORM always calls ACTIONLIB:WAIT-FOR-SERVER due to unstable actionlib server. This is a TODO point.
• CL-TF2:BUFFER-CLIENT, just as CL-TF:TRANSFORMER or CL-TF:TRANSFORM-LISTENER implements a TRANSFORM-POSE-STAMPED and TRANSFORM-POINT-STAMPED now, analogous to the TRANSFORM-POSE and TRANSFORM-POINT in APIs in other languages.

[gaya-]

Oh, GitHub even remembered the old discussions, nice.

[airballking]

@gaya- With the SAPHARI review over, I will look into this this week. Is this PR still current? I'll see about this merge conflict that github is reporting.

[gaya-]

Oh, wow, I didn't notice the merge conflict, it's something new I guess. The PR is current, I've been testing this for some time now.

[gaya-]

The conflict is because of the last commit on the master branch from 8 days ago. The file corresponding to cl_tf2/src/message-conversions.lisp is cl_transforms_stamped/src/ros-message.lisp in this PR. I'll leave the merging to you then as you're the author of the commit.

[gaya-]

No conflicts.

[gaya-]

Will need to merge https://github.com/ros/roslisp_common/pull/32 first though (for the sake of cleanness).

[airballking]

@gaya- Thanks for unifying the two interface. Obviously, I have done this differently. But I think we can also continue with your suggestion. Thanks for putting in the work!

[gaya-]

Thanks for merging this PR.

Here is a final summary of what changed for those interested.

The point of the Pull Request was to create a unified interface for the two TF implementations - cl_tf and cl_tf2 for TF and TF2 correspondingly - such that the user code could be independent of the actual implementation. That is, the user writes their code using the interface (implemented mostly through generic functions) and later runs the code using a specific instance of TF.

• The cl_tf_datatypes package got renamed into cl_transforms_stamped. cl_tf_datatypes contained the definitions of stamped datatypes pose-stamped, point-stamped, and stamped-transform. The name of the package was chosen analogous to cl_transforms package, which only contained the row pose, point datatypes etc.
• stamped-transform datatype got deprecated in favor of trnasforms-stamped for the sake of consistency
• Functions of cl_tf for converting Lisp datatypes to/from ROS messages got merged with the corresponding functions from cl_tf2 and were moved to cl_transforms_stamped. The functions you should use now are to-msg and from-msg if the conversion is unambiguous. Otherwise, there are specific functions. There is also restamp-msg to change the stamp in the header.
• The error types from cl_tf and cl_tf2 got merged and put into cl_transforms_stamped.
• lookup_transform function now has a new parameter, timeout, which is the time for which to wait for a transform to become available.
• There are no cl-tf2:can-transform or cl-tf:wait-for-transform functions anymore. The timeout should be used to wait for a long enough period or 0.0 timeout can be used to check if a transform is available at the moment.
• The old callback mechanism of cl-tf:transformer that issued callbacks whenever a new transform was added got little name changes and is only available in cl_tf but not cl_tf2 due to conceptual differences in the two implementations.
• cl-tf:transform-pose and cl-tf:trnasform-point functions got renamed into transform-pose-stamped and transform-point-stamped and moved up into the interface package. Now cl_tf2 also implements these functions. The renaming was done to avoid the confusion between these functions and the cl-transforms:transform-pose/point.
• Both cl-tf and cl-tf2 export all the symbols from cl-transforms-stamped as their own symbols so if you don't want your code to be independent of the TF implementation and definitely want to use, say, cl-tf2, you can use it as if cl-transforms-stamped didn't exist: cl-tf2:lookup-transform, cl-tf2:to-msg etc.
• ensure-transform-available and ensure-pose-stamped-transformed got removed now that there is a timeout parameter in lookup-transform and transform-pose/point.