Autogen: Documentation update

Closes #15254

Help/manual/cmake-qt.7.rst

@@ -63,20 +63,24 @@ 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.
+``<basename>.moc``, following the Qt conventions.  The ``<basename>.moc`` must
+be included by the user in the C++ implementation file with a preprocessor
+``#include``.
 
-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 generated ``moc_*.cpp`` and ``*.moc`` files are placed in the
+Included ``moc_*.cpp`` and ``*.moc`` files will be generated in the
 ``<CMAKE_CURRENT_BINARY_DIR>/<TARGETNAME>_autogen/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.)
 
+Not included ``moc_<basename>.cpp`` files will be generated in custom
+folders to avoid name collisions and included in a separate
+``<CMAKE_CURRENT_BINARY_DIR>/<TARGETNAME>_autogen/moc_compilation.cpp``
+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.
+
 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

Help/prop_tgt/AUTOMOC.rst

@@ -8,31 +8,41 @@ preprocessor automatically, i.e.  without having to use the
 :module:`QT4_WRAP_CPP() <FindQt4>` or QT5_WRAP_CPP() macro.  Currently Qt4 and Qt5 are
 supported.
 
-When this property is set ``ON``, CMake will scan the
+When this property is set ``ON``, CMake will scan the header and
 source files at build time and invoke moc accordingly.
 
-* If an ``#include`` statement like ``#include "moc_foo.cpp"`` is found,
-  the ``Q_OBJECT`` class declaration is expected in the header, and
-  ``moc`` is run on the header file.  A ``moc_foo.cpp`` file will be
-  generated from the source's header into the
-  ``<CMAKE_CURRENT_BINARY_DIR>/<TARGETNAME>_autogen/include``
-  directory which is automatically added to the target's
+* If an ``#include`` statement like ``#include "moc_<basename>.cpp"`` is found,
+  the ``Q_OBJECT`` or ``Q_GADGET`` macros are expected in an otherwise empty
+  line of the ``<basename>.h(xx)`` header file. ``moc`` is run on the header file to
+  generate ``moc_<basename>.cpp`` in the
+  ``<CMAKE_CURRENT_BINARY_DIR>/<TARGETNAME>_autogen/include`` directory
+  which is automatically added to the target's
   :prop_tgt:`INCLUDE_DIRECTORIES`.  This allows the compiler to find the
-  included ``moc_foo.cpp`` file regardless of the location the original source.
-  However, if multiple source files in different directories do this then their
-  generated moc files would collide.  In this case a diagnostic will be issued.
-
-* If an ``#include`` statement like ``#include "foo.moc"`` is found,
-  then a ``Q_OBJECT`` is expected in the current source file and ``moc``
-  is run on the file itself.  Additionally, header files with the same
-  base name (like ``foo.h``) or ``_p`` appended to the base name (like
-  ``foo_p.h``) are parsed for ``Q_OBJECT`` macros, and if found, ``moc``
-  is also executed on those files.  ``AUTOMOC`` checks multiple header
-  alternative extensions, such as ``hpp``, ``hxx`` etc when searching
-  for headers.  The resulting moc files, which are not included as shown
-  above in any of the source files are included in a generated
-  ``moc_compilation.cpp`` file, which is compiled as part of the
-  target.
+  included ``moc_<basename>.cpp`` file regardless of the location the
+  original source.
+
+* If an ``#include`` statement like ``#include "<basename>.moc"`` is found,
+  then ``Q_OBJECT`` or ``Q_GADGET`` macros are expected in the current source
+  file and ``moc`` is run on the source file itself.
+
+* Header files that are not included by an ``#include "moc_<basename>.cpp"``
+  statement are nonetheless scanned for ``Q_OBJECT`` or ``Q_GADGET`` macros.
+  The resulting ``moc_<basename>.cpp`` files are generated in custom
+  directories and automatically included in the generated
+  ``<CMAKE_CURRENT_BINARY_DIR>/<TARGETNAME>_autogen/moc_compilation.cpp`` file,
+  which is compiled as part of the target. The custom directories help to
+  avoid name collisions for moc files with the same ``<basename>``.
+
+* 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 parsed for ``Q_OBJECT`` or ``Q_GADGET`` macros,
+  and if found, ``moc`` is also executed on those files.
+
+* ``AUTOMOC`` always checks multiple header alternative extensions,
+  such as ``hpp``, ``hxx``, etc. when searching for headers.
+
+* ``AUTOMOC`` looks for the ``Q_PLUGIN_METADATA`` macro and reruns the
+  ``moc`` when the file addressed by the ``FILE`` argument of the macro changes.
 
 This property is initialized by the value of the :variable:`CMAKE_AUTOMOC`
 variable if it is set when a target is created.