Ubuntu Manpage: cmake-qt - CMake Qt Features Reference

NAME

       cmake-qt - CMake Qt Features Reference

INTRODUCTION

       CMake  can find and use Qt 4, Qt 5 and Qt 6 libraries. The Qt 4 libraries are found by the
       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 cmake-packages(7) for more
       information about CMake packages, and see the Qt cmake manual for your Qt version.

       Qt 4, Qt 5 and Qt 6 may be used together in the same CMake buildsystem:

          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 cmake(1) if the appropriate
conditions are met. The automatic tool invocation may be used with Qt version 4 to 6.

AUTOMOC
The AUTOMOC target property controls whether 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 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 INCLUDE_DIRECTORIES.

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

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

• See 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 AUTOGEN_BUILD_DIR.

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

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

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

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

AUTOUIC
The AUTOUIC target property controls whether 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 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 INCLUDE_DIRECTORIES.

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

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

• See AUTOGEN_BUILD_DIR.

The AUTOUIC target property may be pre-set for all following targets by setting the
CMAKE_AUTOUIC variable. The AUTOUIC_OPTIONS target property may be populated to set
options to pass to uic. The CMAKE_AUTOUIC_OPTIONS variable may be populated to pre-set
the options for all following targets. The 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 AUTOUIC_OPTIONS target property.

A target may populate the INTERFACE_AUTOUIC_OPTIONS target property with options that
should be used when invoking uic. This must be consistent with the AUTOUIC_OPTIONS target
property content of the depender target. The CMAKE_DEBUG_TARGET_PROPERTIES variable may
be used to track the origin target of such 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:

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 AUTOUIC, as a result of linking with the IMPORTED
target:

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 AUTOUIC processing by enabling SKIP_AUTOUIC or the
broader SKIP_AUTOGEN.

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

add_executable(myexe main.cpp resource_file.qrc)

The AUTORCC target property may be pre-set for all following targets by setting the
CMAKE_AUTORCC variable. The AUTORCC_OPTIONS target property may be populated to set
options to pass to rcc. The CMAKE_AUTORCC_OPTIONS variable may be populated to pre-set
the options for all following targets. The 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 AUTORCC_OPTIONS target property.

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

THE <ORIGIN>_AUTOGEN TARGET

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

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

THE <ORIGIN>_AUTOGEN_TIMESTAMP_DEPS TARGET

       If Qt 5.15 or later is used and the generator is either Ninja or Makefile Generators,  the
       <ORIGIN>_autogen_timestamp_deps   target   is   also   created  in  addition  to  the  The
       <ORIGIN>_autogen target 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 The
       <ORIGIN>_autogen target 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  Visual  Studio  generators,  CMake  generates a PRE_BUILD custom command
       instead of the The <ORIGIN>_autogen target custom target (for AUTOMOC and AUTOUIC).   This
       isn't  always  possible  though  and an The <ORIGIN>_autogen target custom target is used,
       when either

       • the <ORIGIN> target depends on GENERATED files which aren't excluded  from  AUTOMOC  and
         AUTOUIC by SKIP_AUTOMOC, SKIP_AUTOUIC, SKIP_AUTOGEN or CMP0071

       • AUTOGEN_TARGET_DEPENDS lists a source file

       • CMAKE_GLOBAL_AUTOGEN_TARGET is enabled

QTMAIN.LIB ON WINDOWS

       The Qt 4 and 5 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
       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.

          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)

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