rclcpp file not found error for creating GUI user interface with ROS2 (Humble) using QT Creator

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Hi Willy,

I don't have any experience with "QT Creator 4.9.2 for ROS development", so maybe someone from that team (ROS-Industrial) can answer your questions about it.

However, I will try to answer your questions more directly:

1) Is the path correct ?

No, not in my opinion. Adding the compiler flags, e.g. manually setting the INCLUDEPATH and LIBS settings in Qt Creator, is really fragile, because if these settings change in ROS 2, your project will break.

There are many things you could do instead, but I think the easiest thing for you to do is to create a CMake based ROS package and have Qt Creator open it, which is something it can do:

https://doc-snapshots.qt.io/qtcreator...

This documentation gives you an overview on how to make a ROS 2 package:

http://docs.ros.org/en/humble/Tutoria...

It tells you how to build it using colcon, but you can build a single package without colcon, using the normal CMake procedure, i.e. cmake ..., cmake --build ..., etc., or using tools that understand CMake, like Qt Creator.

Now, after you setup a ROS 2 package using CMake, you still need to use Qt in your CMake project, which is detailed here:

https://doc.qt.io/qt-6/cmake-get-star...

I think between this Qt docs, the Qt docs about using CMake with Qt Creator, and the ROS 2 documentation on how to setup a new package that uses rclcpp and CMake, you should be able to build your application.

It's a bit complicated, but you can see an example of this in rviz2 which uses CMake, ROS 2, and Qt:

https://github.com/ros2/rviz/blob/rol...

Note, that also in your project you should include #include <rclcpp/rclcpp.hpp>, not having the extra rclcpp. More on that below.

2) How can I fix this error?

Like I said above I think a change in approach is the right solution.

However, you can fix your problem by changing your INCLUDEPATH to include /opt/ros/humble/include/rclcpp. This is because rclcpp nests its headers in a sub directory, for a variety of technical reasons. This is actually somewhat new in Humble (I think), but in the past what you are doing would have worked.

Unfortunately, this will just lead you to new errors of missing headers, because other packages also nest their headers, rather than putting them directly into /opt/ros/humble/include, so you'd also have to extend the INCLUDEPATH with things like /opt/ros/humble/include/rcl and /opt/ros/humble/include/rcutils, just to name a few.

This is why using CMake is better, because these settings are gathered automatically by the packages you're depending on. So you don't need to set your compiler flags manually.

Hope that helps.

I will also point you (and others) to this example of using "pure" CMake, in case you don't want to have a dependency on ament_cmake (ROS 2's cmake ... (more)