Get started with CMake | Build with CMake 5.15.19

- Qt 5.15
- Build with CMake
- Get started with CMake
- Qt 5.15.19 Reference Documentation

Build with CMake ◦ CMake Variable Reference

# Get started with CMake

Start with `find_package` to locate the libraries and header files shipped with Qt. Then, you can use these libraries and header files with the `target_link_libraries` command to build Qt-based libraries and applications. This command automatically adds the appropriate include directories, compile definitions, the position-independent-code flag, and links to the `qtmain.lib` library on Windows, for example.

### Build a GUI executable

To build a helloworld GUI executable, you need the following:

     cmake_minimum_required(VERSION 3.1.0)

     project(helloworld VERSION 1.0.0 LANGUAGES CXX)

     set(CMAKE_CXX_STANDARD 11)
     set(CMAKE_CXX_STANDARD_REQUIRED ON)

     set(CMAKE_AUTOMOC ON)
     set(CMAKE_AUTORCC ON)
     set(CMAKE_AUTOUIC ON)

     if(CMAKE_VERSION VERSION_LESS "3.7.0")
         set(CMAKE_INCLUDE_CURRENT_DIR ON)
     endif()

     find_package(Qt5 COMPONENTS Widgets REQUIRED)

     add_executable(helloworld
         mainwindow.ui
         mainwindow.cpp
         main.cpp
         resources.qrc
     )

     target_link_libraries(helloworld Qt5::Widgets)

For `find_package` to be successful, `CMake` must find the Qt installation in one of the following ways:

1. Set your `CMAKE_PREFIX_PATH` environment variable to the Qt 5 installation prefix. This is the recommended way.
2. Set the `Qt5_DIR` in the `CMake` cache to the location of the `Qt5Config.cmake` file.

The `CMAKE_AUTOMOC` setting runs moc automatically when required. For more details, see CMake AUTOMOC documentation.

### Imported library targets

Each Qt module that is loaded defines a CMake library target. The target names start with `Qt5::`, followed by the module name. For example: `Qt5::Core`, `Qt5::Gui`. Pass the name of the library target to `target_link_libraries` to use the respective library.

Note: Since Qt 5.15, the CMake targets are also available as `Qt::Core`, `Qt::Gui`, and so on. This eases writing CMake code that can work with both Qt 5 and Qt 6.

Imported targets are created with the same configurations as when Qt was configured. That is:

- If Qt was configured with the `-debug` switch, an imported target with the DEBUG configuration is created.
- If Qt was configured with the `-release` switch, an imported target with the RELEASE configuration is created.
- If Qt was configured with the `-debug-and-release` switch, then imported targets are created with both RELEASE and DEBUG configurations.

If your project has custom `CMake` build configurations, you have to map your custom configuration to either the debug or the release Qt configuration.

     find_package(Qt5 COMPONENTS Core REQUIRED)

     set(CMAKE_CXX_FLAGS_COVERAGE "${CMAKE_CXX_FLAGS_RELEASE} -fprofile-arcs -ftest-coverage")

     # set up a mapping so that the Release configuration for the Qt imported target is
     # used in the COVERAGE CMake configuration.
     set_target_properties(Qt5::Core PROPERTIES MAP_IMPORTED_CONFIG_COVERAGE "RELEASE")

Build with CMake ◦ CMake Variable Reference