Getting started with CMake▲

CMake is a group of tools that allow to build, test, and package applications. Just like Qt, it is available on all major development platforms. It is also supported by various IDE's, including Qt Creator.

In this section we will show the most basic way to use Qt in a CMake project. First, we create a basic console application. Then, we extend the project into a GUI application that uses Qt Widgets.

If you want to know how to build an existing CMake project with Qt, see the documentation on how to build projects with CMake on the command line.

Building a C++ console application▲

A CMake project is defined by files written in the CMake language. The main file is called CMakeLists.txt, and is usually placed in the same directory as the actual program sources.

Here is a typical CMakeLists.txt file for a console application written in C++ using Qt:

 
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cmake_minimum_required(VERSION 3.16)

project(helloworld VERSION 1.0.0 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(Qt6 REQUIRED COMPONENTS Core)
qt_standard_project_setup()

add_executable(helloworld
    main.cpp
)

target_link_libraries(helloworld PRIVATE Qt6::Core)

Let's go through the content.

 
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cmake_minimum_required(VERSION 3.16)

cmake_minimum_required() specifies the minimum CMake version that the application requires. Qt itself requires at least CMake version 3.16. If you use a Qt that was built statically - the default in Qt for iOS and Qt for WebAssembly - you need CMake 3.21.1 or newer.

 
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project(helloworld VERSION 1.0.0 LANGUAGES CXX)

project() sets a project name and the default project version. The LANGUAGES argument tells CMake that the program is written in C++.

 
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set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

Qt 6 requires a compiler supporting C++ version 17 or newer. Enforcing this by setting the CMAKE_CXX_STANDARD, CMAKE_CXX_STANDARD_REQUIRED variables will let CMake print an error if the compiler is too old.

 
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find_package(Qt6 REQUIRED COMPONENTS Core)

This tells CMake to look up Qt 6, and import the Core module. There is no point in continuing if CMake cannot locate the module, so we do set the REQUIRED flag to let CMake abort in this case.

If successful, the module will set some CMake variables documented in Module variables. It furthermore imports the Qt6::Core target that we use below.

For find_package to be successful, CMake must find the Qt installation. There are different ways you can tell CMake about Qt, but the most common and recommended approach is to set the CMake cache variable CMAKE_PREFIX_PATH to include the Qt 6 installation prefix. Note that Qt Creator will handle this transparently for you.

 
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qt_standard_project_setup()

The qt_standard_project_setup command sets project-wide defaults for a typical Qt application.

Among other things, this command sets the CMAKE_AUTOMOC variable to ON, which instructs CMake to automatically set up rules so that Qt's Meta-Object Compiler (moc) is called transparently, when required.

See qt_standard_project_setup's reference for details.

 
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add_executable(helloworld
    main.cpp
)

add_executable() tells CMake that we want to build an executable (so not a library) called helloworld as a target. The target should be built from the C++ source file main.cpp.

Note tha