Commit b55e5d66 authored by Sebastian Holtermann's avatar Sebastian Holtermann Committed by Brad King

Help: Autogen: Overhaul AUTOMOC target property documentation

- Rewrites and restructures the AUTOMOC target property documentation
- Remove the reference to the deprecated CMAKE_AUTOMOC_RELAXED_MODE

Fixes: #19167
parent fdab21f3
AUTOMOC
-------
Should the target be processed with automoc (for Qt projects).
Should the target be processed with auto-moc (for Qt projects).
:prop_tgt:`AUTOMOC` is a boolean specifying whether CMake will handle the Qt
``moc`` preprocessor automatically, i.e. without having to use the
:module:`QT4_WRAP_CPP() <FindQt4>` or QT5_WRAP_CPP() macro.
:module:`QT4_WRAP_CPP() <FindQt4>` or ``QT5_WRAP_CPP()`` macro.
Currently Qt4 and Qt5 are supported.
This property is initialized by the value of the :variable:`CMAKE_AUTOMOC`
variable if it is set when a target is created.
When this property is set ``ON``, CMake will scan the header and
source files at build time and invoke moc accordingly.
source files at build time and invoke ``moc`` accordingly.
* If an ``#include`` statement like ``#include "moc_<basename>.cpp"`` is found,
a macro from :prop_tgt:`AUTOMOC_MACRO_NAMES` is expected to appear in the
``<basename>.h(xx)`` header file. ``moc`` is run on the header
file to generate ``moc_<basename>.cpp`` in the
``<AUTOGEN_BUILD_DIR>/include`` directory which is automatically added
to the target's :prop_tgt:`INCLUDE_DIRECTORIES`.
This allows the compiler to find the included ``moc_<basename>.cpp`` file
regardless of the location the original source.
* For :prop_gbl:`multi configuration generators <GENERATOR_IS_MULTI_CONFIG>`,
the include directory is ``<AUTOGEN_BUILD_DIR>/include_<CONFIG>``.
Header file processing
^^^^^^^^^^^^^^^^^^^^^^
* See :prop_tgt:`AUTOGEN_BUILD_DIR`.
At configuration time, a list of header files that should be scanned by
:prop_tgt:`AUTOMOC` is computed from the target's sources.
* If an ``#include`` statement like ``#include "<basename>.moc"`` is found,
a macro from :prop_tgt:`AUTOMOC_MACRO_NAMES` is expected to appear in the
source file and ``moc`` is run on the source file itself.
- All header files in the target's sources are added to the scan list.
- For all C++ source files ``<source_base>.<source_extension>`` in the
target's sources, CMake searches for
* Header files that are not included by an ``#include "moc_<basename>.cpp"``
statement are nonetheless scanned for a macro out of
:prop_tgt:`AUTOMOC_MACRO_NAMES`.
The resulting ``moc_<basename>.cpp`` files are generated in custom
directories and automatically included in a generated
``<AUTOGEN_BUILD_DIR>/mocs_compilation.cpp`` file,
which is compiled as part of the target.
- a regular header with the same base name
(``<source_base>.<header_extention>``) and
- a private header with the same base name and a ``_p`` suffix
(``<source_base>_p.<header_extention>``)
* The custom directories with checksum
based names help to avoid name collisions for ``moc`` files with the same
``<basename>``.
and adds these to the scan list.
* See :prop_tgt:`AUTOGEN_BUILD_DIR`.
At build time, CMake scans each unknown or modified header file from the
list and searches for
* Additionally, header files with the same base name as a source file,
(like ``<basename>.h``) or ``_p`` appended to the base name (like
``<basename>_p.h``), are scanned for a macro out of
:prop_tgt:`AUTOMOC_MACRO_NAMES`, and if found, ``moc``
is also executed on those files.
- a Qt macro from :prop_tgt:`AUTOMOC_MACRO_NAMES`,
- additional file dependencies from the ``FILE`` argument of a
``Q_PLUGIN_METADATA`` macro and
- additional file dependencies detected by filters defined in
:prop_tgt:`AUTOMOC_DEPEND_FILTERS`.
* ``AUTOMOC`` always checks multiple header alternative extensions,
such as ``hpp``, ``hxx``, etc. when searching for headers.
If a Qt macro is found, then the header will be compiled by the ``moc`` to the
output file ``moc_<base_name>.cpp``. The complete output file path is
described in the section `Output file location`_.
* ``AUTOMOC`` looks for the ``Q_PLUGIN_METADATA`` macro and reruns the
``moc`` when the file addressed by the ``FILE`` argument of the macro changes.
The header will be ``moc`` compiled again if a file from the additional file
dependencies changes.
This property is initialized by the value of the :variable:`CMAKE_AUTOMOC`
variable if it is set when a target is created.
Header ``moc`` output files ``moc_<base_name>.cpp`` can be included in source
files. In the section `Including header moc files in sources`_ there is more
information on that topic.
Source file processing
^^^^^^^^^^^^^^^^^^^^^^
At build time, CMake scans each unknown or modified C++ source file from the
target's sources for
- a Qt macro from :prop_tgt:`AUTOMOC_MACRO_NAMES`,
- includes of header ``moc`` files
(see `Including header moc files in sources`_),
- additional file dependencies from the ``FILE`` argument of a
``Q_PLUGIN_METADATA`` macro and
- additional file dependencies detected by filters defined in
:prop_tgt:`AUTOMOC_DEPEND_FILTERS`.
If a Qt macro is found, then the C++ source file
``<base>.<source_extension>`` is expected to as well contain an include
statement
.. code-block:: c++
#include <<base>.moc> // or
#include "<base>.moc"
The source file then will be compiled by the ``moc`` to the output file
``<base>.moc``. A description of the complete output file path is in section
`Output file location`_.
The source will be ``moc`` compiled again if a file from the additional file
dependencies changes.
Including header moc files in sources
"""""""""""""""""""""""""""""""""""""
A source file can include the ``moc`` output file of a header
``<header_base>.<header_extension>`` by using an include statement of
the form
.. code-block:: c++
#include <moc_<header_base>.cpp> // or
#include "moc_<header_base>.cpp"
If the ``moc`` output file of a header is included by a source, it will
be generated in a different location than if it was not included. This is
described in the section `Output file location`_.
Output file location
^^^^^^^^^^^^^^^^^^^^
Included moc output files
"""""""""""""""""""""""""
``moc`` output files that are included by a source file will be generated in
- ``<AUTOGEN_BUILD_DIR>/include``
for single configuration generators or in
- ``<AUTOGEN_BUILD_DIR>/include_<CONFIG>``
for :prop_gbl:`multi configuration <GENERATOR_IS_MULTI_CONFIG>` generators.
Where ``<AUTOGEN_BUILD_DIR>`` is the value of the target property
:prop_tgt:`AUTOGEN_BUILD_DIR`.
The include directory is automatically added to the target's
:prop_tgt:`INCLUDE_DIRECTORIES`.
Not included moc output files
"""""""""""""""""""""""""""""
``moc`` output files that are not included in a source file will be generated
in
- ``<AUTOGEN_BUILD_DIR>/<SOURCE_DIR_CHECKSUM>``
for single configuration generators or in,
- ``<AUTOGEN_BUILD_DIR>/include_<CONFIG>/<SOURCE_DIR_CHECKSUM>``
for :prop_gbl:`multi configuration <GENERATOR_IS_MULTI_CONFIG>` generators.
Where ``<SOURCE_DIR_CHECKSUM>`` is a checksum computed from the relative
parent directory path of the ``moc`` input file. This scheme allows to have
``moc`` input files with the same name in different directories.
All not included ``moc`` output files will be included automatically by the
CMake generated file
- ``<AUTOGEN_BUILD_DIR>/mocs_compilation.cpp``,
which is added to the target's sources.
Qt version detection
^^^^^^^^^^^^^^^^^^^^
:prop_tgt:`AUTOMOC` enabled targets need to know the Qt major and minor
version they're working with. The major version usually is provided by the
``INTERFACE_QT_MAJOR_VERSION`` property of the ``Qt[45]Core`` library,
that the target links to. To find the minor version, CMake builds a list of
available Qt versions from
- ``Qt5Core_VERSION_MAJOR`` and ``Qt5Core_VERSION_MINOR`` variables
(usually set by ``find_package(Qt5...)``)
- ``Qt5Core_VERSION_MAJOR`` and ``Qt5Core_VERSION_MINOR`` directory properties
- ``QT_VERSION_MAJOR`` and ``QT_VERSION_MINOR`` variables
(usually set by ``find_package(Qt4...)``)
- ``QT_VERSION_MAJOR`` and ``QT_VERSION_MINOR`` directory properties
in the context of the :command:`add_executable` or :command:`add_library` call.
Assumed ``INTERFACE_QT_MAJOR_VERSION`` is a valid number, the first
entry in the list with a matching major version is taken. If no matching major
version was found, an error is generated.
If ``INTERFACE_QT_MAJOR_VERSION`` is not a valid number, the first
entry in the list is taken.
A ``find_package(Qt[45]...)`` call sets the ``QT/Qt5Core_VERSION_MAJOR/MINOR``
variables. If the call is in a different context than the
:command:`add_executable` or :command:`add_library` call, e.g. in a function,
then the version variables might not be available to the :prop_tgt:`AUTOMOC`
enabled target.
In that case the version variables can be forwarded from the
`find_package(Qt[45]...)` calling context to the :command:`add_executable`
or :command:`add_library` calling context as directory properties.
The following Qt5 example demonstrates the procedure.
.. code-block:: cmake
function (add_qt5_client)
find_package(Qt5 REQUIRED QUIET COMPONENTS Core Widgets)
...
set_property(DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
PROPERTY Qt5Core_VERSION_MAJOR "${Qt5Core_VERSION_MAJOR}")
set_property(DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
PROPERTY Qt5Core_VERSION_MINOR "${Qt5Core_VERSION_MAJOR}")
...
endfunction ()
...
add_qt5_client()
add_executable(myTarget main.cpp)
target_link_libraries(myTarget Qt5::QtWidgets)
set_property(TARGET myTarget PROPERTY AUTOMOC ON)
Modifiers
^^^^^^^^^
:prop_tgt:`AUTOMOC_EXECUTABLE`:
The ``moc`` executable will be detected automatically, but can be forced to
a certain binary using the :prop_tgt:`AUTOMOC_EXECUTABLE` property.
a certain binary using this target property.
Additional command line options for ``moc`` can be set via the
:prop_tgt:`AUTOMOC_MOC_OPTIONS` property.
:prop_tgt:`AUTOMOC_MOC_OPTIONS`:
Additional command line options for ``moc`` can be set in this target property.
By enabling the :variable:`CMAKE_AUTOMOC_RELAXED_MODE` variable the
rules for searching the files which will be processed by ``moc`` can be relaxed.
See the documentation for this variable for more details.
:prop_tgt:`AUTOMOC_MACRO_NAMES`:
This list of Qt macro names can be extended to search for additional macros in
headers and sources.
The global property :prop_gbl:`AUTOGEN_TARGETS_FOLDER` can be used to group the
automoc targets together in an IDE, e.g. in MSVS.
:prop_tgt:`AUTOMOC_DEPEND_FILTERS`:
``moc`` dependency file names can be extracted from headers or sources by
defining file name filters in this target property.
The global property :prop_gbl:`AUTOGEN_SOURCE_GROUP` can be used to group
files generated by :prop_tgt:`AUTOMOC` together in an IDE, e.g. in MSVS.
:prop_tgt:`AUTOMOC_COMPILER_PREDEFINES`:
Compiler pre definitions for ``moc`` are written to the ``moc_predefs.h`` file.
The generation of this file can be enabled or disabled in this target property.
Additional macro names to search for can be added to
:prop_tgt:`AUTOMOC_MACRO_NAMES`.
:prop_sf:`SKIP_AUTOMOC`:
Sources and headers can be excluded from :prop_tgt:`AUTOMOC` processing by
setting this source file property.
Additional ``moc`` dependency file names can be extracted from source code
by using :prop_tgt:`AUTOMOC_DEPEND_FILTERS`.
:prop_sf:`SKIP_AUTOGEN`:
Source files can be excluded from :prop_tgt:`AUTOMOC`,
:prop_tgt:`AUTOUIC` and :prop_tgt:`AUTORCC` processing by
setting this source file property.
Compiler pre definitions for ``moc`` are written to a ``moc_predefs.h`` file
which is controlled by :prop_tgt:`AUTOMOC_COMPILER_PREDEFINES`.
:prop_gbl:`AUTOGEN_SOURCE_GROUP`:
This global property can be used to group files generated by
:prop_tgt:`AUTOMOC` or :prop_tgt:`AUTORCC` together in an IDE, e.g. in MSVS.
Source C++ files can be excluded from :prop_tgt:`AUTOMOC` processing by
enabling :prop_sf:`SKIP_AUTOMOC` or the broader :prop_sf:`SKIP_AUTOGEN`.
:prop_gbl:`AUTOGEN_TARGETS_FOLDER`:
This global property can be used to group :prop_tgt:`AUTOMOC`,
:prop_tgt:`AUTOUIC` and :prop_tgt:`AUTORCC` targets together in an IDE,
e.g. in MSVS.
The number of parallel ``moc`` processes to start can be modified by
setting :prop_tgt:`AUTOGEN_PARALLEL`.
:variable:`CMAKE_GLOBAL_AUTOGEN_TARGET`:
A global ``autogen`` target, that depends on all :prop_tgt:`AUTOMOC` or
:prop_tgt:`AUTOUIC` generated ``<ORIGIN>_autogen`` targets in the project,
will be generated when this variable is ``ON``.
A global ``autogen`` target that depends on all :prop_tgt:`AUTOMOC` generated
``<ORIGIN>_autogen`` targets in the project can be generated by enabling
:variable:`CMAKE_GLOBAL_AUTOGEN_TARGET`.
:prop_tgt:`AUTOGEN_PARALLEL`:
This target property controls the number of ``moc`` or ``uic`` processes to
start in parallel during builds.
See the :manual:`cmake-qt(7)` manual for more information on using CMake
with Qt.
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