Why external library includes require full qualified path?

[iqbal-h]

Hi,
When I add some header that is not part of webRTC, an error occurs at make.

For example, I want to add opencv in desktopcapturer.cpp.
In the CMakeList.txt, I added find_package(OpenCV REQUIRED). It successfully adds the path in CMakeCache.txt:

//The directory containing a CMake configuration file for OpenCV.
OpenCV_DIR:PATH=/usr/local/lib/cmake/opencv4

When I run make, following error occurs:

src/desktopcapturer.cpp:15: fatal error: opencv2/opencv.hpp: No such file or directory
    4 | #include <opencv2/opencv.hpp>

However, when I replace the include in desktopcapturer.cpp with #include "/usr/local/include/opencv4/opencv2/opencv.hpp", on make, it recognizes the include. However, it starts throwing error on the includes inside opencv.hpp:

/usr/local/include/opencv4/opencv2/opencv.hpp:48:10: fatal error: opencv2/opencv_modules.hpp: No such file or directory
   48 | #include "opencv2/opencv_modules.hpp"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is no end to fixing these fully qualified paths.
How to fix this?

[iqbal-h]

@mpromonet would really appeciate your thoughts?

[mpromonet]

Hi @iqbal-h

You need to add include path of opencv, something like include_directories( ${OpenCV_INCLUDE_DIRS} )

Best Regards,
Michel.

[iqbal-h]

Thanks