cmake Custom Build-Steps Running a Custom Target

Example

You can also create a custom target to run when you want to perform a particular task. These are typically executables that you run to do different things. Something that may be of particular use is to run Doxygen to generate documentation for your project. To do this you can do the following in your CMakeLists.txt (for the sake of simplicity we'll contiue our Qt5 project example):

cmake_minimum_required(VERSION 3.0)
project(MyQtProj LANGUAGES C CXX)
find_package(Qt5 COMPONENTS Core Gui Widgets)
#...set up your project

add_executable(MyQtProj ${PROJ_SOURCES} ${PROJ_HEADERS})
    
add_custom_command(TARGET MyQtProj POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E copy_if_different $<TARGET_FILE:Qt5::Core> $<TARGET_FILE_DIR:MyQtProj>
    COMMAND ${CMAKE_COMMAND} -E copy_if_different $<TARGET_FILE:Qt5::Gui> $<TARGET_FILE_DIR:MyQtProj>
    COMMAND ${CMAKE_COMMAND} -E copy_if_different $<TARGET_FILE:Qt5::Widgets> $<TARGET_FILE_DIR:MyQtProj>
    )

#Add target to build documents from visual studio.
set(DOXYGEN_INPUT ${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile)
#set the output directory of the documentation
set(DOXYGEN_OUTPUT_DIR ${CMAKE_CURRENT_SOURCE_DIR}/docs)
# sanity check...
message("Doxygen Output ${DOXYGEN_OUTPUT_DIR}")
find_package(Doxygen)

if(DOXYGEN_FOUND)
    # create the output directory where the documentation will live
    file(MAKE_DIRECTORY ${DOXYGEN_OUTPUT_DIR})
    # configure our Doxygen configuration file. This will be the input to the doxygen
    # executable
    configure_file(${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile.in
    ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile @ONLY)

# now add the custom target. This will create a build target called 'DOCUMENTATION' 
# in your project
ADD_CUSTOM_TARGET(DOCUMENTATION
  COMMAND ${CMAKE_COMMAND} -E echo_append "Building API Documentation..."
  COMMAND ${CMAKE_COMMAND} -E make_directory ${DOXYGEN_OUTPUT_DIR}
  COMMAND ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile
    WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
  COMMAND ${CMAKE_COMMAND} -E echo "Done."
  WORKING_DIRECTORY ${DOXYGEN_OUTPUT_DIR})

endif(DOXYGEN_FOUND)

Now when we create our solution (again assuming you're using Visual Studio), you'll have a build target called DOCUMENTATION that you can build to regenerate your project's documentation.