CMake: Add Qt6 forward compatible CMake API and targets

Create Qt:: versionless targets for libraries and tools. So
Qt::Core will link to Qt5::Core.

Add additional feature properties to targets, with the same name
they have in Qt6: QT_ENABLED_PUBLIC_FEATURES,
QT_DISABLED_PUBLIC_FEATURES, QT_ENABLED_PRIVATE_FEATURES,
QT_DISABLED_PRIVATE_FEATURES, to be forward-compatible with Qt6.
Prefix properties with INTERFACE_ for interface libraries.

Create functions with no major version in their prefix, so qt_foo
instead of qt5_foo.
The non-versioned functions will call the versioned functions,
depending on the value of QT_DEFAULT_MAJOR_VERSION, which can be
set by an application developer before finding the Qt package.

Set QT_DEFAULT_MAJOR_VERSION to 5 if the value has not been defined
in the current scope.

Application developers can set QT_NO_CREATE_VERSIONLESS_FUNCTIONS to
TRUE before calling find_package(Qt5) to suppress creation of the
non-versioned functions.

Application developers can set QT_NO_CREATE_VERSIONLESS_TARGETS to
TRUE before calling find_package(Qt5) to suppress creation of the
non-versioned targets.

Setting these can be useful when both find_package(Qt5) and
find_package(Qt6) are in the same project.
If none of these are set by the user, then the first find_package(Qt5)
will create versionless targets with the major version being "5",
which means the second find_package(Qt6) will not create versionless
targets.

Handle versionless plugin names in qt_import_plugins, so both
Qt::QCocoaIntegrationPlugin and Qt5/6::QCocoaIntegrationPlugin
are recognized by the function.

Allow specifying multiple types in EXCLUDE_BY_TYPE in
qt_import_plugins, to be consitent with the Qt 6 version.

Make sure to set the QT_PLUGIN_CLASS_NAME property to compatible with
Qt 6.

Task-number: QTBUG-74137
Task-number: QTBUG-80477
Change-Id: Ib89d090ea6f7794d7debd64f03f29da963a17ca7
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

2 files changed, 54 insertions, 0 deletions

diff --git a/src/dbus/Qt5DBusConfigExtras.cmake.in b/src/dbus/Qt5DBusConfigExtras.cmake.in
index 1d947159e2..a814678f7b 100644
--- a/src/dbus/Qt5DBusConfigExtras.cmake.in
+++ b/src/dbus/Qt5DBusConfigExtras.cmake.in
@@ -31,3 +31,14 @@ endif()
 
 set(Qt5DBus_QDBUSCPP2XML_EXECUTABLE Qt5::qdbuscpp2xml)
 set(Qt5DBus_QDBUSXML2CPP_EXECUTABLE Qt5::qdbusxml2cpp)
+
+# Create versionless tool targets.
+foreach(__qt_tool qdbuscpp2xml qdbusxml2cpp)
+    if(NOT \"${QT_NO_CREATE_VERSIONLESS_TARGETS}\" AND NOT TARGET Qt::${__qt_tool}
+       AND TARGET Qt5::${__qt_tool})
+        add_executable(Qt::${__qt_tool} IMPORTED)
+        get_target_property(__qt_imported_location Qt5::${__qt_tool} IMPORTED_LOCATION)
+        set_target_properties(Qt::${__qt_tool}
+                              PROPERTIES IMPORTED_LOCATION \"${__qt_imported_location}\")
+    endif()
+endforeach()
diff --git a/src/dbus/Qt5DBusMacros.cmake b/src/dbus/Qt5DBusMacros.cmake
index 9b69e77dc7..1cacccdddd 100644
--- a/src/dbus/Qt5DBusMacros.cmake
+++ b/src/dbus/Qt5DBusMacros.cmake
@@ -70,6 +70,17 @@ function(qt5_add_dbus_interface _sources _interface _basename)
     set(${_sources} ${${_sources}} PARENT_SCOPE)
 endfunction()
 
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_add_dbus_interface sources)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_add_dbus_interface("${sources}" ${ARGN})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_add_dbus_interface("${sources}" ${ARGN})
+        endif()
+        set("${sources}" "${${sources}}" PARENT_SCOPE)
+    endfunction()
+endif()
+
 
 function(qt5_add_dbus_interfaces _sources)
     foreach(_current_FILE ${ARGN})
@@ -83,6 +94,17 @@ function(qt5_add_dbus_interfaces _sources)
     set(${_sources} ${${_sources}} PARENT_SCOPE)
 endfunction()
 
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_add_dbus_interfaces sources)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_add_dbus_interfaces("${sources}" ${ARGN})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_add_dbus_interfaces("${sources}" ${ARGN})
+        endif()
+        set("${sources}" "${${sources}}" PARENT_SCOPE)
+    endfunction()
+endif()
+
 
 function(qt5_generate_dbus_interface _header) # _customName OPTIONS -some -options )
     set(options)
@@ -116,6 +138,16 @@ function(qt5_generate_dbus_interface _header) # _customName OPTIONS -some -optio
     )
 endfunction()
 
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_generate_dbus_interface)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_generate_dbus_interface(${ARGV})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_generate_dbus_interface(${ARGV})
+        endif()
+    endfunction()
+endif()
+
 
 function(qt5_add_dbus_adaptor _sources _xml_file _include _parentClass) # _optionalBasename _optionalClassName)
     get_filename_component(_infile ${_xml_file} ABSOLUTE)
@@ -152,3 +184,14 @@ function(qt5_add_dbus_adaptor _sources _xml_file _include _parentClass) # _optio
     list(APPEND ${_sources} "${_impl}" "${_header}" "${_moc}")
     set(${_sources} ${${_sources}} PARENT_SCOPE)
 endfunction()
+
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_add_dbus_adaptor sources)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_add_dbus_adaptor("${sources}" ${ARGN})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_add_dbus_adaptor("${sources}" ${ARGN})
+        endif()
+        set("${sources}" "${${sources}}" PARENT_SCOPE)
+    endfunction()
+endif()