CMake/Help/manual/cmake-qt.7.rst

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

cmake-qt(7)
***********

.. only:: html

   .. contents::

Introduction
============

CMake can find and use Qt 4 and Qt 5 libraries.  The Qt 4 libraries are found
by the :module:`FindQt4` find-module shipped with CMake, whereas the
Qt 5 libraries are found using "Config-file Packages" shipped with Qt 5. See
:manual:`cmake-packages(7)` for more information about CMake packages, and
see `the Qt cmake manual <http://qt-project.org/doc/qt-5/cmake-manual.html>`_
for your Qt version.

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

.. code-block:: cmake

  cmake_minimum_required(VERSION 3.0.0 FATAL_ERROR)

  project(Qt4And5)

  set(CMAKE_AUTOMOC ON)
  set(CMAKE_INCLUDE_CURRENT_DIR ON)

  find_package(Qt5Widgets REQUIRED)
  add_executable(publisher publisher.cpp)
  target_link_libraries(publisher Qt5::Widgets Qt5::DBus)

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

A CMake target may not link to both Qt 4 and Qt 5.  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 filesystem 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 both Qt 4 and Qt 5.

The tools are executed as part of a synthesized custom target generated by
CMake.  Target dependencies may be added to that custom target by adding them
to the :prop_tgt:`AUTOGEN_TARGET_DEPENDS` target property.

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 ``Q_OBJECT`` or ``Q_GADGET`` macro 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 ``moc file`` may be
included by the user in the C++ implementation file with a preprocessor
``#include``.  If it is not so included, it will be added to a separate file
which is compiled into the target.

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.

Generated ``moc_*.cpp`` and ``*.moc`` files are placed in the build directory
so it is convenient to set the :variable:`CMAKE_INCLUDE_CURRENT_DIR`
variable.  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.

.. _`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
``ui_<basename>.h``, and a ``<basename>.ui`` file exists, then ``uic`` will
be executed to generate the appropriate file.

Generated ``ui_*.h`` files are placed in the build directory so it is
convenient to set the :variable:`CMAKE_INCLUDE_CURRENT_DIR` variable.  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 Qt5::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
  )

.. _`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.

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)