Standalone kdl_parser library

[christian-rauch]

As proposed in #12, this PR makes catkin and rosconsole optional. I.e. plain CMake macros are used if catkin is not available and logging is done via std io streams if rosconsole is not available.

Since urdf itself depends on ROS for similar reasons, it has been replaced by urdfdom. This disables some of the functions like treeFromParam and treeFromXml, which use methods that are not present in urdfdom. In the log term it would be beneficial, if urdf also would be disentangled from ROS.

I copied FindTinyXML.cmake and FindTinyXML2.cmake from https://github.com/ros/cmake_modules into this repo, to not introduce another dependency.

[christian-rauch]

@sloretz Can you comment on this PR?

[sloretz]

Thanks for the PR, and your patience @christian-rauch . Comments are below.

[sloretz]

I was going to say it looks like this was copied from urdfdom, in which case this shouldn't be needed since find_package(urdfdom REQUIRED) is used in the CMakeLists.txt, but it looks like urdfdom is not find_packageing TinyXML in its <project>-config.cmake like it should

[sloretz]

ros/urdfdom#120

[sloretz]

I would rather keep the signature, but return False if the library was not built with urdf. That way a downstream package including kdl_parser.hpp doesn't have to define HAS_URDF themselves.

@clalancette thoughts?

[christian-rauch]

Thanks for coming back to this PR.

I discovered that the non-catkin version doesn't build any more.
The urdf lib version in ROS melodic (1.13) uses TinyXML2, i.e. initXml (const tinyxml2::XMLDocument *xml), while the Ubuntu repo (version 1.12) still uses TinyXML(1), i.e. initXml (TiXmlElement *xml), like in ROS kinetic.
I might have intended to base this PR on kinetic-devel instead of melodic-devel.

Anyway, should we maybe use urdf::parseURDF from (urdf_parser / liburdfdom-dev) instead of the manual XML loading and parsing?

[christian-rauch]

I went ahead and replaced most of the urdf library with urdfdom. The urdf library is basically only required if you want to read a URDF model from a ROS parameter. Maybe this could also replaced by ROS methods to remove the urdf library dependency completely.

[sloretz]

LGTM! @clalancette Mind taking a look at this one too?

I ran check_kdl_parser on test/pr2_desc.xml building with ROS and without. The only difference I see is how ROS_WARN/ROS_ERROR are output, which is fine.

When building with ROS ROS_WARN is output to stdout with formatting that includes a timestamp and console colors. When building without ROS the warning is sent to stderr and is just the text of the warning itself.

[christian-rauch]

@sloretz @clalancette Any news/feedback on this?

[sloretz]

ping @clalancette , ok to merge this one?

[clalancette]

One minor change, but I'll still approve.

[sloretz]

Thanks for the PR!