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, 65 insertions, 1 deletions

diff --git a/src/corelib/Qt5CoreMacros.cmake b/src/corelib/Qt5CoreMacros.cmake
index e298cf7de7..6c21470164 100644
--- a/src/corelib/Qt5CoreMacros.cmake
+++ b/src/corelib/Qt5CoreMacros.cmake
@@ -157,6 +157,16 @@ function(qt5_generate_moc infile outfile )
     qt5_create_moc_command(${abs_infile} ${_outfile} "${moc_flags}" "" "${moc_target}" "")
 endfunction()
 
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_generate_moc)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_generate_moc(${ARGV})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_generate_moc(${ARGV})
+        endif()
+    endfunction()
+endif()
+
 
 # qt5_wrap_cpp(outfiles inputfile ... )
 
@@ -184,6 +194,17 @@ function(qt5_wrap_cpp outfiles )
     set(${outfiles} ${${outfiles}} PARENT_SCOPE)
 endfunction()
 
+# This will override the CMake upstream command, because that one is for Qt 3.
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_wrap_cpp outfiles)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_wrap_cpp("${outfiles}" ${ARGN})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_wrap_cpp("${outfiles}" ${ARGN})
+        endif()
+        set("${outfiles}" "${${outfiles}}" PARENT_SCOPE)
+    endfunction()
+endif()
 
 
 # _qt5_parse_qrc_file(infile _out_depends _rc_depends)
@@ -255,6 +276,16 @@ function(qt5_add_binary_resources target )
     add_custom_target(${target} ALL DEPENDS ${rcc_destination})
 endfunction()
 
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_add_binary_resources)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_add_binary_resources(${ARGV})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_add_binary_resources(${ARGV})
+        endif()
+    endfunction()
+endif()
+
 
 # qt5_add_resources(outfiles inputfile ... )
 
@@ -293,6 +324,18 @@ function(qt5_add_resources outfiles )
     set(${outfiles} ${${outfiles}} PARENT_SCOPE)
 endfunction()
 
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_add_resources outfiles)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_add_resources("${outfiles}" ${ARGN})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_add_resources("${outfiles}" ${ARGN})
+        endif()
+        set("${outfiles}" "${${outfiles}}" PARENT_SCOPE)
+    endfunction()
+endif()
+
+
 # qt5_add_big_resources(outfiles inputfile ... )
 
 function(qt5_add_big_resources outfiles )
@@ -341,6 +384,18 @@ function(qt5_add_big_resources outfiles )
     set(${outfiles} ${${outfiles}} PARENT_SCOPE)
 endfunction()
 
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_add_big_resources outfiles)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_add_big_resources(${outfiles} ${ARGN})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_add_big_resources(${outfiles} ${ARGN})
+        endif()
+        set("${outfiles}" "${${outfiles}}" PARENT_SCOPE)
+    endfunction()
+endif()
+
+
 set(_Qt5_COMPONENT_PATH "${CMAKE_CURRENT_LIST_DIR}/..")
 
 macro(qt5_use_modules _target _link_type)
@@ -413,10 +468,19 @@ function(qt5_import_plugins TARGET_NAME)
             elseif(_doing STREQUAL "EXCLUDE_BY_TYPE")
                 string(REGEX REPLACE "[-/]" "_" _plugin_type "${_arg}")
                 set_property(TARGET ${TARGET_NAME} PROPERTY "QT_PLUGINS_${_plugin_type}" -)
-                set(_doing "")
             else()
                 message(FATAL_ERROR "Unexpected extra argument: \"${_arg}\"")
             endif()
         endif()
     endforeach()
 endfunction()
+
+if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
+    function(qt_import_plugins)
+        if(QT_DEFAULT_MAJOR_VERSION EQUAL 5)
+            qt5_import_plugins(${ARGV})
+        elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
+            qt6_import_plugins(${ARGV})
+        endif()
+    endfunction()
+endif()