How to build and include a 3rd party library in a ROS2 package?

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I have source code for a library (and test application) which I have written. I configure and compile it fine as a standalone application.

Now I would like to reference the library portion of it from a ros2 node that looks surprisingly similar to the publisher_member_function.cpp node documented here.

I suppose I could build my library manually, install it in the file system on my development host, and then add that as a dependency to the publisher node project... maybe I would need to invent a mylibConfig.cmake file, but there has got to be a better way than doing that.

I would prefer to check out my code into the src directory in my workspace, perhaps create a package.xml file for it, update CMakeLists.txt for the cpp_pubsub package, and have colcon make everything work like magic for me.

Is there a tutorial somewhere that explains how to do this? I can't seem to figure out the best keywords to plug into Google to find it myself, so I figured I would just ask.

Complicating matters somewhat... my library depends on somebody else's library (which probably, in turn, depends on one or more -dev packages installed on my build machine). I'm hoping that if I can figure out how to manage this custom dependency thing once, then I can make it apply recursively... but if there are any gotchas I should be aware of for this sort of dependency chain, it sure would be nice if I could learn that sooner rather than later.

Basically, I think I'm asking how to modify the CMakeLists.txt file and/or packages.xml file in the cpp_pubsub example to reference code in a directory parallel to the cpp_pubsub directory, and probably, what requirements, (such as the presence and contents of a package.xml file) are imposed on the project maintained in that parallel directory.

Answering some of my question... I was able to build the 3rd party library by putting it (sdbus-cpp) into its own directory adjacent to the cpp_pubsub directory and creating a package.xml file that looked like this:

<?xml version="1.0"?>
<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
<package format="3">
  <name>sdbus-cpp</name>
  <version>0.0.0</version>
  <description>sdbus-c++</description>
  <maintainer email="fill@in.later>wpd</maintainer>
  <license>Double Check This</license>

  <buildtool_depend>ament_cmake</buildtool_depend>
  <depend>libsystemd-dev</depend>

  <test_depend>ament_lint_auto</test_depend>
  <test_depend>ament_lint_common</test_depend>

  <export>
    <build_type>ament_cmake</build_type>
  </export>
</package>

With this in place, I could run

$ rosdep install -i --from-path src --rosdistro foxy -y

and install the libsystemd-dev dependency. Then I was able to run:

$ colcon install --packages-select sdbus-cpp

and build sdbus-cpp. Yay. Now I'm working on creating the package.xml file for my own library (which depends on sdbus-cpp), following the same procedure. That basically worked, except that I don't have the machinery in place to create and install the .cmake file(s) necessary to reference my library from ... (more)