Autogen: Process .hh headers based on new policy CMP0100 settings

Reintroduces .hh header processing in AUTOMOC and AUTOUIC based on the new
policy CMP0100 setting.

Fixes: #13904 CMAKE_AUTOMOC misses headers with ".hh" extension

3 files changed, 47 insertions, 0 deletions

diff --git a/Help/manual/cmake-policies.7.rst b/Help/manual/cmake-policies.7.rst
index 2118031..1fd49ed 100644
--- a/Help/manual/cmake-policies.7.rst
+++ b/Help/manual/cmake-policies.7.rst
@@ -57,6 +57,7 @@ Policies Introduced by CMake 3.17
 .. toctree::
    :maxdepth: 1
 
+   CMP0100: Let AUTOMOC and AUTOUIC process .hh header files. </policy/CMP0100>
    CMP0099: Link properties are transitive over private dependency on static libraries. </policy/CMP0099>
    CMP0098: FindFLEX runs flex in CMAKE_CURRENT_BINARY_DIR when executing. </policy/CMP0098>
 
diff --git a/Help/policy/CMP0100.rst b/Help/policy/CMP0100.rst
new file mode 100644
index 0000000..b24d013
--- /dev/null
+++ b/Help/policy/CMP0100.rst
@@ -0,0 +1,40 @@
+CMP0100
+-------
+
+Let :prop_tgt:`AUTOMOC` and :prop_tgt:`AUTOUIC` process
+header files that end with a ``.hh`` extension.
+
+Since version 3.17, CMake processes header files that end with a
+``.hh`` extension in :prop_tgt:`AUTOMOC` and :prop_tgt:`AUTOUIC`.
+In earlier CMake versions, these header files were ignored by
+:prop_tgt:`AUTOMOC` and :prop_tgt:`AUTOUIC`.
+
+This policy affects how header files that end with a ``.hh`` extension
+get treated in :prop_tgt:`AUTOMOC` and :prop_tgt:`AUTOUIC`.
+
+The ``OLD`` behavior for this policy is to ignore ``.hh`` header files
+in :prop_tgt:`AUTOMOC` and :prop_tgt:`AUTOUIC`.
+
+The ``NEW`` behavior for this policy is to process ``.hh`` header files
+in :prop_tgt:`AUTOMOC` and :prop_tgt:`AUTOUIC` just like other header files.
+
+.. note::
+
+  To silence the ``CMP0100`` warning source files can be excluded from
+  :prop_tgt:`AUTOMOC` and :prop_tgt:`AUTOUIC` processing by setting the
+  source file properties :prop_sf:`SKIP_AUTOMOC`, :prop_sf:`SKIP_AUTOUIC` or
+  :prop_sf:`SKIP_AUTOGEN`.
+
+  .. code-block:: cmake
+
+    # Source skip example:
+    set_property(SOURCE /path/to/file1.hh PROPERTY SKIP_AUTOMOC ON)
+    set_property(SOURCE /path/to/file2.hh PROPERTY SKIP_AUTOUIC ON)
+    set_property(SOURCE /path/to/file3.hh PROPERTY SKIP_AUTOGEN ON)
+
+This policy was introduced in CMake version 3.17.0.  CMake version
+|release| warns when the policy is not set and uses ``OLD`` behavior.
+Use the :command:`cmake_policy` command to set it to ``OLD`` or ``NEW``
+explicitly.
+
+.. include:: DEPRECATED.txt
diff --git a/Help/release/dev/autogen_hh_headers.rst b/Help/release/dev/autogen_hh_headers.rst
new file mode 100644
index 0000000..35ccd61
--- /dev/null
+++ b/Help/release/dev/autogen_hh_headers.rst
@@ -0,0 +1,6 @@
+autogen_hh_headers
+------------------
+
+* :prop_tgt:`AUTOMOC` and :prop_tgt:`AUTOUIC` learned to process headers with
+  a ``.hh`` extension.  The new behavior is enabled by policy
+  :policy:`CMP0100`.