Provide ability to export all libraries and headers of theCore to use in external projects

[forGGe]

Suppose that someone needs to use theCore functionality, but he has already made project written using make/scons etc. Extracting headers and libraries in that case would be a problem.

Usually it done by simply building and installing dependency (theCore in our case) in some dir and then using contents of that dir when building top-level project.

install() cmake command can be used for such purpose.

Preprocessor definitions that are generated during theCore build can be exported to a header using configure_file() command It means that all preprocessor public definitions (i.e. such that used within public library headers) must be present in core_config_${library}.h rather than defined from command line

[forGGe]

install() has problems with exporting sources, instead following snippet can be used:

macro(theCore_export_target)
    cmake_parse_arguments(
        EXPORT
        "INTERFACE"
        "TARGET"
        ""
        ${ARGN}
    )


    set(CORE_EXPORT_INC_DIR ${CORE_BIN_DIR}/export/inc/)
    set(CORE_EXPORT_SRC_DIR ${CORE_BIN_DIR}/export/src/)

    file(MAKE_DIRECTORY ${CORE_EXPORT_INC_DIR} ${CORE_EXPORT_SRC_DIR})

    # TODO: take into account interface libraries

    if(EXPORT_INTERFACE)
        get_target_property(TARGET_INC ${EXPORT_TARGET} INTERFACE_INCLUDE_DIRECTORIES)
        message(">> ${TARGET_INC}")
        else()
        get_target_property(TARGET_SRCS ${EXPORT_TARGET} SOURCES)
        get_target_property(TARGET_INC ${EXPORT_TARGET} INCLUDE_DIRECTORIES)

        set(EXPORT_CMD
            COMMAND
                ${CMAKE_COMMAND} -E copy_if_different
                ${TARGET_SRCS}
                ${CORE_EXPORT_SRC_DIR}
            )
    endif()

    set(EXPORT_CMD ${EXPORT_CMD}
        COMMAND ${CMAKE_COMMAND} -E copy_directory
            ${TARGET_INC}
            ${CORE_EXPORT_INC_DIR}
        )

    add_custom_target(${EXPORT_TARGET}_export
        ${EXPORT_CMD}
        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
    )

    # Tie all exporting together
    add_dependencies(export ${EXPORT_TARGET}_export)
    add_dependencies(${EXPORT_TARGET}_export ${EXPORT_TARGET})

    unset(CORE_EXPORT_INC_DIR)
    unset(CORE_EXPORT_SRC_DIR)
endmacro()

It can be extended with additional parameters:

• ADD_INCLUDE_FILES - additional files to be exported as includes
• OVERRIDE_INCLUDE_FILES - only copy specified files as includes, do not export entire dir