Provide modern CMake FindMraa.cmake

[AndreasAZiegler]

Please provide a modern CMake interface as explained in https://pabloariasal.github.io/2018/02/19/its-time-to-do-cmake-right/.

[alext-mkrs]

@AndreasAZiegler, why exactly would you need that and what doesn't work for you in the current setup?

[AndreasAZiegler]

@alext-mkrs Because it is best practice and quite troublesome if someone want to use modern CMake and has to work with ugly work-arounds because the library maintainer don't provide the required CMake interface.

I wrote the following Findmraa.cmake but actually library maintainers should provide the corresponding Config.cmake e.g. mraaConfig.cmake.

# FindMraa.cmake
#
# Finds the rapidjson library
#
# This will define the following variables
#
#    Mraa_FOUND
#    Mraa_INCLUDE_DIRS
#    Mraa_LIBRARIES
#
# and the following imported targets
#
#     mraa::mraa
#
# Author: Andreas Ziegler - a.ziegler@mt-robot.com

find_package(PkgConfig)
pkg_check_modules(MRAA mraa)

find_path(Mraa_INCLUDE_DIR
    NAMES mraa.h
    PATHS ${PC_Mraa_INCLUDE_DIRS} /usr/include 
)

find_library(Mraa_LIBRARY
  NAMES libmraa.so
  PATHS ${PC_Mraa_LIBRARY_DIRS} /usr/lib
)

set(Mraa_VERSION ${Mraa_VERSION})

mark_as_advanced(Mraa_FOUND Mraa_INCLUDE_DIR Mraa_VERSION Mraa_LIBRARY)

include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(Mraa
    REQUIRED_VARS Mraa_INCLUDE_DIR
    REQUIRED_VARS Mraa_LIBRARY
    VERSION_VAR Mraa_VERSION
)

if(Mraa_FOUND)
  set(Mraa_INCLUDE_DIRS ${Mraa_INCLUDE_DIR})
  set(Mraa_LIBRARIES ${Mraa_LIBRARY})
endif()

if(Mraa_FOUND AND NOT TARGET mraa::mraa)
    add_library(mraa::mraa UNKNOWN IMPORTED)
    set_target_properties(mraa::mraa PROPERTIES
        INTERFACE_INCLUDE_DIRECTORIES "${Mraa_INCLUDE_DIRS}"
        IMPORTED_LOCATION "${Mraa_LIBRARIES}"
    )
endif()