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>

1 files changed, 5 insertions, 1 deletions

diff --git a/mkspecs/features/create_cmake.prf b/mkspecs/features/create_cmake.prf
index 346fbf2467..63b4a73660 100644
--- a/mkspecs/features/create_cmake.prf
+++ b/mkspecs/features/create_cmake.prf
@@ -176,7 +176,7 @@ contains(CONFIG, plugin) {
         list_plugin_extends =
         for (p, PLUGIN_EXTENDS) {
             m = $$cmakeModuleName($$p)
-            list_plugin_extends += Qt5::$$m
+            list_plugin_extends += Qt::$$m
         }
         CMAKE_PLUGIN_EXTENDS = $$join(list_plugin_extends, ";")
     }
@@ -291,6 +291,10 @@ CMAKE_INTERFACE_MODULE_DEPS = $$join(aux_mod_deps, ";")
 CMAKE_INTERFACE_QT5_MODULE_DEPS = $$join(aux_lib_deps, ";")
 CMAKE_MODULE_PLUGIN_TYPES = $$join(QT.$${MODULE}.plugin_types, ";")
 
+# Interface libraries have to have all properties starting with "INTERFACE_".
+CMAKE_FEATURE_PROPERTY_PREFIX = ""
+equals(TEMPLATE, aux): CMAKE_FEATURE_PROPERTY_PREFIX = "INTERFACE_"
+
 mac {
     !isEmpty(CMAKE_STATIC_TYPE) {
         CMAKE_LIB_FILE_LOCATION_DEBUG = lib$${CMAKE_QT_STEM}_debug.a