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.. cmake-manual-description: CMake Qt Features Reference

cmake-qt(7)

.. only:: html

.. contents::

Introduction

CMake can find and use Qt 4, Qt 5 and Qt 6 libraries. The Qt 4 libraries are found by the :module:FindQt4 find-module shipped with CMake, whereas the Qt 5 and Qt 6 libraries are found using "Config-file Packages" shipped with Qt 5 and Qt 6. See :manual:cmake-packages(7) for more information about CMake packages, and see the Qt cmake manual_ for your Qt version.

.. _the Qt cmake manual: https://doc.qt.io/qt-6/cmake-manual.html

Qt 4, Qt 5 and Qt 6 may be used together in the same :manual:CMake buildsystem <cmake-buildsystem(7)>:

.. code-block:: cmake

cmake_minimum_required(VERSION 3.16 FATAL_ERROR)

project(Qt4_5_6)

set(CMAKE_AUTOMOC ON)

find_package(Qt6 COMPONENTS Widgets DBus REQUIRED) add_executable(publisher publisher.cpp) target_link_libraries(publisher Qt6::Widgets Qt6::DBus)

find_package(Qt5 COMPONENTS Gui DBus REQUIRED) add_executable(subscriber1 subscriber1.cpp) target_link_libraries(subscriber1 Qt5::Gui Qt5::DBus)

find_package(Qt4 REQUIRED) add_executable(subscriber2 subscriber2.cpp) target_link_libraries(subscriber2 Qt4::QtGui Qt4::QtDBus)

A CMake target may not link to more than one Qt version. A diagnostic is issued if this is attempted or results from transitive target dependency evaluation.

Qt Build Tools

Qt relies on some bundled tools for code generation, such as moc for meta-object code generation, uic for widget layout and population, and rcc for virtual file system content generation. These tools may be automatically invoked by :manual:cmake(1) if the appropriate conditions are met. The automatic tool invocation may be used with Qt version 4 to 6.

.. _Qt AUTOMOC:

AUTOMOC ^^^^^^^

The :prop_tgt:AUTOMOC target property controls whether :manual:cmake(1) inspects the C++ files in the target to determine if they require moc to be run, and to create rules to execute moc at the appropriate time.

If a macro from :prop_tgt:AUTOMOC_MACRO_NAMES is found in a header file, moc will be run on the file. The result will be put into a file named according to moc_<basename>.cpp. If the macro is found in a C++ implementation file, the moc output will be put into a file named according to <basename>.moc, following the Qt conventions. The <basename>.moc must be included by the user in the C++ implementation file with a preprocessor #include.

Included moc_*.cpp and *.moc files will be generated in the <AUTOGEN_BUILD_DIR>/include directory which is automatically added to the target's :prop_tgt:INCLUDE_DIRECTORIES.

  • This differs from CMake 3.7 and below; see their documentation for details.

  • For :prop_gbl:multi configuration generators <GENERATOR_IS_MULTI_CONFIG>, the include directory is <AUTOGEN_BUILD_DIR>/include_<CONFIG>.

  • See :prop_tgt:AUTOGEN_BUILD_DIR.

Not included moc_<basename>.cpp files will be generated in custom folders to avoid name collisions and included in a separate file which is compiled into the target, named either <AUTOGEN_BUILD_DIR>/mocs_compilation.cpp or <AUTOGEN_BUILD_DIR>/mocs_compilation_$<CONFIG>.cpp.

  • See :prop_tgt:AUTOGEN_BUILD_DIR.

The moc command line will consume the :prop_tgt:COMPILE_DEFINITIONS and :prop_tgt:INCLUDE_DIRECTORIES target properties from the target it is being invoked for, and for the appropriate build configuration.

The :prop_tgt:AUTOMOC target property may be pre-set for all following targets by setting the :variable:CMAKE_AUTOMOC variable. The :prop_tgt:AUTOMOC_MOC_OPTIONS target property may be populated to set options to pass to moc. The :variable:CMAKE_AUTOMOC_MOC_OPTIONS variable may be populated to pre-set the options for all following targets.

Additional macro names to search for can be added to :prop_tgt:AUTOMOC_MACRO_NAMES.

Additional moc dependency file names can be extracted from source code by using :prop_tgt:AUTOMOC_DEPEND_FILTERS.

Source C++ files can be excluded from :prop_tgt:AUTOMOC processing by enabling :prop_sf:SKIP_AUTOMOC or the broader :prop_sf:SKIP_AUTOGEN.

.. _Qt AUTOUIC:

AUTOUIC ^^^^^^^

The :prop_tgt:AUTOUIC target property controls whether :manual:cmake(1) inspects the C++ files in the target to determine if they require uic to be run, and to create rules to execute uic at the appropriate time.

If a preprocessor #include directive is found which matches <path>ui_<basename>.h, and a <basename>.ui file exists, then uic will be executed to generate the appropriate file. The <basename>.ui file is searched for in the following places

  1. <source_dir>/<basename>.ui
  2. <source_dir>/<path><basename>.ui
  3. <AUTOUIC_SEARCH_PATHS>/<basename>.ui
  4. <AUTOUIC_SEARCH_PATHS>/<path><basename>.ui

where <source_dir> is the directory of the C++ file and :prop_tgt:AUTOUIC_SEARCH_PATHS is a list of additional search paths.

The generated generated ui_*.h files are placed in the <AUTOGEN_BUILD_DIR>/include directory which is automatically added to the target's :prop_tgt:INCLUDE_DIRECTORIES.

  • This differs from CMake 3.7 and below; see their documentation for details.

  • For :prop_gbl:multi configuration generators <GENERATOR_IS_MULTI_CONFIG>, the include directory is <AUTOGEN_BUILD_DIR>/include_<CONFIG>.

  • See :prop_tgt:AUTOGEN_BUILD_DIR.

The :prop_tgt:AUTOUIC target property may be pre-set for all following targets by setting the :variable:CMAKE_AUTOUIC variable. The :prop_tgt:AUTOUIC_OPTIONS target property may be populated to set options to pass to uic. The :variable:CMAKE_AUTOUIC_OPTIONS variable may be populated to pre-set the options for all following targets. The :prop_sf:AUTOUIC_OPTIONS source file property may be set on the <basename>.ui file to set particular options for the file. This overrides options from the :prop_tgt:AUTOUIC_OPTIONS target property.

A target may populate the :prop_tgt:INTERFACE_AUTOUIC_OPTIONS target property with options that should be used when invoking uic. This must be consistent with the :prop_tgt:AUTOUIC_OPTIONS target property content of the depender target. The :variable:CMAKE_DEBUG_TARGET_PROPERTIES variable may be used to track the origin target of such :prop_tgt:INTERFACE_AUTOUIC_OPTIONS. This means that a library which provides an alternative translation system for Qt may specify options which should be used when running uic:

.. code-block:: cmake

add_library(KI18n klocalizedstring.cpp) target_link_libraries(KI18n Qt6::Core)

KI18n uses the tr2i18n() function instead of tr(). That function is

declared in the klocalizedstring.h header.

set(autouic_options -tr tr2i18n -include klocalizedstring.h )

set_property(TARGET KI18n APPEND PROPERTY INTERFACE_AUTOUIC_OPTIONS ${autouic_options} )

A consuming project linking to the target exported from upstream automatically uses appropriate options when uic is run by :prop_tgt:AUTOUIC, as a result of linking with the :prop_tgt:IMPORTED target:

.. code-block:: cmake

set(CMAKE_AUTOUIC ON)

Uses a libwidget.ui file:

add_library(LibWidget libwidget.cpp) target_link_libraries(LibWidget KF5::KI18n Qt5::Widgets )

Source files can be excluded from :prop_tgt:AUTOUIC processing by enabling :prop_sf:SKIP_AUTOUIC or the broader :prop_sf:SKIP_AUTOGEN.

.. _Qt AUTORCC:

AUTORCC ^^^^^^^

The :prop_tgt:AUTORCC target property controls whether :manual:cmake(1) creates rules to execute rcc at the appropriate time on source files which have the suffix .qrc.

.. code-block:: cmake

add_executable(myexe main.cpp resource_file.qrc)

The :prop_tgt:AUTORCC target property may be pre-set for all following targets by setting the :variable:CMAKE_AUTORCC variable. The :prop_tgt:AUTORCC_OPTIONS target property may be populated to set options to pass to rcc. The :variable:CMAKE_AUTORCC_OPTIONS variable may be populated to pre-set the options for all following targets. The :prop_sf:AUTORCC_OPTIONS source file property may be set on the <name>.qrc file to set particular options for the file. This overrides options from the :prop_tgt:AUTORCC_OPTIONS target property.

Source files can be excluded from :prop_tgt:AUTORCC processing by enabling :prop_sf:SKIP_AUTORCC or the broader :prop_sf:SKIP_AUTOGEN.

.. _<ORIGIN>_autogen:

The <ORIGIN>_autogen target

The moc and uic tools are executed as part of a synthesized <ORIGIN>_autogen :command:custom target <add_custom_target> generated by CMake. By default, that <ORIGIN>_autogen target inherits the dependencies of the <ORIGIN> target (see :prop_tgt:AUTOGEN_ORIGIN_DEPENDS). Target dependencies may be added to the <ORIGIN>_autogen target by adding them to the :prop_tgt:AUTOGEN_TARGET_DEPENDS target property.

.. note:: If Qt 5.15 or later is used and the generator is either :generator:Ninja or :ref:Makefile Generators, see :ref:<ORIGIN>_autogen_timestamp_deps.

.. _<ORIGIN>_autogen_timestamp_deps:

The <ORIGIN>_autogen_timestamp_deps target

If Qt 5.15 or later is used and the generator is either :generator:Ninja or :ref:Makefile Generators, the <ORIGIN>_autogen_timestamp_deps target is also created in addition to the :ref:<ORIGIN>_autogen <<ORIGIN>_autogen> target. This target does not have any sources or commands to execute, but it has dependencies that were previously inherited by the pre-Qt 5.15 :ref:<ORIGIN>_autogen <<ORIGIN>_autogen> target. These dependencies will serve as a list of order-only dependencies for the custom command, without forcing the custom command to re-execute.

Visual Studio Generators

When using the :ref:Visual Studio Generators, CMake generates a PRE_BUILD :command:custom command <add_custom_command> instead of the :ref:<ORIGIN>_autogen <<ORIGIN>_autogen> :command:custom target <add_custom_target> (for :prop_tgt:AUTOMOC and :prop_tgt:AUTOUIC). This isn't always possible though and an :ref:<ORIGIN>_autogen <<ORIGIN>_autogen> :command:custom target <add_custom_target> is used, when either

  • the <ORIGIN> target depends on :prop_sf:GENERATED files which aren't excluded from :prop_tgt:AUTOMOC and :prop_tgt:AUTOUIC by :prop_sf:SKIP_AUTOMOC, :prop_sf:SKIP_AUTOUIC, :prop_sf:SKIP_AUTOGEN or :policy:CMP0071
  • :prop_tgt:AUTOGEN_TARGET_DEPENDS lists a source file
  • :variable:CMAKE_GLOBAL_AUTOGEN_TARGET is enabled

qtmain.lib on Windows

The Qt 4 and 5 :prop_tgt:IMPORTED targets for the QtGui libraries specify that the qtmain.lib static library shipped with Qt will be linked by all dependent executables which have the :prop_tgt:WIN32_EXECUTABLE enabled.

To disable this behavior, enable the Qt5_NO_LINK_QTMAIN target property for Qt 5 based targets or QT4_NO_LINK_QTMAIN target property for Qt 4 based targets.

.. code-block:: cmake

add_executable(myexe WIN32 main.cpp) target_link_libraries(myexe Qt4::QtGui)

add_executable(myexe_no_qtmain WIN32 main_no_qtmain.cpp) set_property(TARGET main_no_qtmain PROPERTY QT4_NO_LINK_QTMAIN ON) target_link_libraries(main_no_qtmain Qt4::QtGui)