CMake: Restore qt5_use_modules() function

It appears that in the 5 years since we deprecated this function, people
have not stopped using it. The removal of qt5_use_modules() caused lots of
troubles in packages still using it when they were compiled against Qt 5.11.0.

Instead, let's revive this function and keep it for the Qt5 life time.

See discussion on qt-development mailing list:
  http://lists.qt-project.org/pipermail/development/2018-June/032837.html

Change-Id: Ic263e3bb6706268cb9ea38a0711665f166a3aa9e
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

5 files changed, 158 insertions, 0 deletions

diff --git a/src/corelib/Qt5CoreMacros.cmake b/src/corelib/Qt5CoreMacros.cmake
index 1627de4002..819b48f973 100644
--- a/src/corelib/Qt5CoreMacros.cmake
+++ b/src/corelib/Qt5CoreMacros.cmake
@@ -294,3 +294,54 @@ function(QT5_ADD_RESOURCES outfiles )
 endfunction()
 
 set(_Qt5_COMPONENT_PATH "${CMAKE_CURRENT_LIST_DIR}/..")
+
+if (NOT CMAKE_VERSION VERSION_LESS 2.8.9)
+    macro(qt5_use_modules _target _link_type)
+        if(NOT CMAKE_MINIMUM_REQUIRED_VERSION VERSION_LESS 2.8.11)
+            if(CMAKE_WARN_DEPRECATED)
+                set(messageType WARNING)
+            endif()
+            if(CMAKE_ERROR_DEPRECATED)
+                set(messageType FATAL_ERROR)
+            endif()
+            if(messageType)
+                message(${messageType} "The qt5_use_modules macro is obsolete. Use target_link_libraries with IMPORTED targets instead.")
+            endif()
+        endif()
+
+        if (NOT TARGET ${_target})
+            message(FATAL_ERROR "The first argument to qt5_use_modules must be an existing target.")
+        endif()
+        if ("${_link_type}" STREQUAL "LINK_PUBLIC" OR "${_link_type}" STREQUAL "LINK_PRIVATE" )
+            set(_qt5_modules ${ARGN})
+            set(_qt5_link_type ${_link_type})
+        else()
+            set(_qt5_modules ${_link_type} ${ARGN})
+        endif()
+
+        if ("${_qt5_modules}" STREQUAL "")
+            message(FATAL_ERROR "qt5_use_modules requires at least one Qt module to use.")
+        endif()
+
+        foreach(_module ${_qt5_modules})
+            if (NOT Qt5${_module}_FOUND)
+                find_package(Qt5${_module} PATHS "${_Qt5_COMPONENT_PATH}" NO_DEFAULT_PATH)
+                if (NOT Qt5${_module}_FOUND)
+                    message(FATAL_ERROR "Can not use \"${_module}\" module which has not yet been found.")
+                endif()
+            endif()
+            target_link_libraries(${_target} ${_qt5_link_type} ${Qt5${_module}_LIBRARIES})
+            set_property(TARGET ${_target} APPEND PROPERTY INCLUDE_DIRECTORIES ${Qt5${_module}_INCLUDE_DIRS})
+            set_property(TARGET ${_target} APPEND PROPERTY COMPILE_DEFINITIONS ${Qt5${_module}_COMPILE_DEFINITIONS})
+            set_property(TARGET ${_target} APPEND PROPERTY COMPILE_DEFINITIONS_RELEASE QT_NO_DEBUG)
+            set_property(TARGET ${_target} APPEND PROPERTY COMPILE_DEFINITIONS_RELWITHDEBINFO QT_NO_DEBUG)
+            set_property(TARGET ${_target} APPEND PROPERTY COMPILE_DEFINITIONS_MINSIZEREL QT_NO_DEBUG)
+            if (Qt5_POSITION_INDEPENDENT_CODE
+                    AND (CMAKE_VERSION VERSION_LESS 2.8.12
+                        AND (NOT CMAKE_CXX_COMPILER_ID STREQUAL "GNU"
+                        OR CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0)))
+                set_property(TARGET ${_target} PROPERTY POSITION_INDEPENDENT_CODE ${Qt5_POSITION_INDEPENDENT_CODE})
+            endif()
+        endforeach()
+    endmacro()
+endif()
diff --git a/tests/auto/cmake/CMakeLists.txt b/tests/auto/cmake/CMakeLists.txt
index f1d8657091..ec75ec7caf 100644
--- a/tests/auto/cmake/CMakeLists.txt
+++ b/tests/auto/cmake/CMakeLists.txt
@@ -47,6 +47,7 @@ find_package(Qt5Core REQUIRED)
 
 include("${_Qt5CTestMacros}")
 
+expect_pass(test_use_modules_function)
 expect_pass(test_umbrella_config)
 expect_pass(test_wrap_cpp_and_resources)
 if (NOT NO_WIDGETS)
diff --git a/tests/auto/cmake/test_use_modules_function/CMakeLists.txt b/tests/auto/cmake/test_use_modules_function/CMakeLists.txt
new file mode 100644
index 0000000000..be05c75054
--- /dev/null
+++ b/tests/auto/cmake/test_use_modules_function/CMakeLists.txt
@@ -0,0 +1,18 @@
+
+cmake_minimum_required(VERSION 2.8)
+
+project(test_use_modules_function)
+
+set(CMAKE_AUTOMOC ON)
+
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+add_executable(two two.cpp)
+add_executable(three three.cpp)
+
+find_package(Qt5Core)
+
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${Qt5Core_EXECUTABLE_COMPILE_FLAGS}")
+
+qt5_use_modules(two Test)
+qt5_use_modules(three Gui Test)
diff --git a/tests/auto/cmake/test_use_modules_function/three.cpp b/tests/auto/cmake/test_use_modules_function/three.cpp
new file mode 100644
index 0000000000..507cc8479d
--- /dev/null
+++ b/tests/auto/cmake/test_use_modules_function/three.cpp
@@ -0,0 +1,45 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Stephen Kelly <stephen.kelly@kdab.com>
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest>
+#include <QWindow>
+
+class Three : public QObject
+{
+    Q_OBJECT
+public:
+    Three(QObject *parent = 0)
+    {
+        QWindow *w = new QWindow;
+        w->show();
+    }
+};
+
+QTEST_MAIN(Three)
+
+#include "three.moc"
diff --git a/tests/auto/cmake/test_use_modules_function/two.cpp b/tests/auto/cmake/test_use_modules_function/two.cpp
new file mode 100644
index 0000000000..44eb7fe96e
--- /dev/null
+++ b/tests/auto/cmake/test_use_modules_function/two.cpp
@@ -0,0 +1,43 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Stephen Kelly <stephen.kelly@kdab.com>
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest>
+
+class Two : public QObject
+{
+    Q_OBJECT
+public:
+    Two(QObject *parent = 0)
+    {
+
+    }
+};
+
+QTEST_MAIN(Two)
+
+#include "two.moc"