Add support for Qt 6 alongside Qt 5

.github/workflows/ci.yml

@@ -21,6 +21,7 @@ jobs:
       fail-fast: false
       matrix:
         runs-on: ["ubuntu-latest"]
+        qt-major-version: [5, 6]
     steps:
       - uses: actions/checkout@9bb56186c3b09b4f86b1c65136769dd318469633 # v4.1.2
 
@@ -36,7 +37,8 @@ jobs:
       - name: Retrieve new lists of APT packages
         run: sudo apt-get update
 
-      - name: Install Qt
+      - name: Install Qt 5
+        if: ${{ matrix.qt-major-version == 5 }}
         run: |
           sudo apt-get install -y \
             qtbase5-dev \
@@ -50,17 +52,33 @@ jobs:
             libqt5x11extras5-dev \
             libxt-dev
 
-      - name: Install VTK
-        if: matrix.runs-on == 'ubuntu-latest'
+      - name: Install VTK (Qt 5)
+        if: ${{ matrix.runs-on == 'ubuntu-latest' && matrix.qt-major-version == 5 }}
         run: |
           sudo apt-get install -y \
             libvtk9-dev \
             libvtk9-qt-dev
 
+      - name: Install Qt 6
+        if: ${{ matrix.qt-major-version == 6 }}
+        run: |
+          sudo apt-get install -y \
+            qt6-base-dev \
+            qt6-base-private-dev \
+            qt6-5compat-dev \
+            qt6-multimedia-dev \
+            qt6-scxml-dev \
+            qt6-tools-dev \
+            qt6-tools-dev-tools \
+            qt6-svg-dev \
+            qt6-webengine-dev \
+            libqt6openglwidgets6 \
+            libxt-dev
+
       - name: Configure CTK
         run: |
           cmake \
-            -DCTK_QT_VERSION:STRING=5 \
+            -DCTK_QT_VERSION:STRING=${{ matrix.qt-major-version }} \
             -DCTK_ENABLE_Widgets:BOOL=ON \
             -DCTK_USE_SYSTEM_VTK:BOOL=$CTK_USE_VTK \
             -DCTK_LIB_Visualization/VTK/Widgets:BOOL=$CTK_USE_VTK \
@@ -81,11 +99,14 @@ jobs:
             -B CTK-build \
             -S .
         env:
-          CTK_USE_VTK: "${{ matrix.runs-on == 'ubuntu-latest' && 'ON' || 'OFF' }}"
+          CTK_USE_VTK: "${{ matrix.runs-on == 'ubuntu-latest' && matrix.qt-major-version == 5 && 'ON' || 'OFF' }}"
 
-      - name: Display Qt5_DIR
+      - name: Display Qt_DIR
         run: |
-          cat CTK-build/CMakeCache.txt | grep ^Qt5_DIR
+          echo "Qt5_DIR:"
+          cat CTK-build/CMakeCache.txt | grep '^Qt5_DIR' || true
+          echo "Qt6_DIR:"
+          cat CTK-build/CMakeCache.txt | grep '^Qt6_DIR' || true
 
       - name: Build CTK
         run: |

CMake/ctkFunctionGeneratePluginManifest.cmake

@@ -104,8 +104,8 @@ function(ctkFunctionGeneratePluginManifest MANIFEST_QRC_FILEPATH_VAR)
   if(MY_SKIP_QT5_ADD_RESOURCES)
     set(${MANIFEST_QRC_FILEPATH_VAR} ${_manifest_qrc_filepath} PARENT_SCOPE)
   else()
-    if(CTK_QT_VERSION VERSION_EQUAL "5")
-      QT5_ADD_RESOURCES(_qrc_src ${_manifest_qrc_filepath})
+    if(CTK_QT_VERSION MATCHES "^(5|6)$")
+      qt_add_resources(_qrc_src ${_manifest_qrc_filepath})
     else()
       message(FATAL_ERROR "Support for Qt${CTK_QT_VERSION} is not implemented")
     endif()

CMake/ctkMacroBuildPlugin.cmake

@@ -193,8 +193,8 @@ macro(ctkMacroBuildPlugin)
   if(MY_TRANSLATIONS)
     set_source_files_properties(${MY_TRANSLATIONS}
                                 PROPERTIES OUTPUT_LOCATION ${_translations_dir})
-  if(CTK_QT_VERSION VERSION_EQUAL "5")
-      qt5_create_translation(_plugin_qm_files ${MY_SRCS} ${MY_UI_FORMS} ${MY_TRANSLATIONS})
+  if(CTK_QT_VERSION MATCHES "^(5|6)$")
+      qt_create_translation(_plugin_qm_files ${MY_SRCS} ${MY_UI_FORMS} ${MY_TRANSLATIONS})
   else()
     message(FATAL_ERROR "Support for Qt${CTK_QT_VERSION} is not implemented")
   endif()

CMake/ctkMacroBuildQtPlugin.cmake

@@ -119,6 +119,8 @@ macro(ctkMacroBuildQtPlugin)
   set(compile_flags "-DQT_PLUGIN")
   if(CTK_QT_VERSION VERSION_EQUAL "5")
     set(compile_flags "${compile_flags} -DHAVE_QT5")
+  elseif(CTK_QT_VERSION VERSION_EQUAL "6")
+    set(compile_flags "${compile_flags} -DHAVE_QT6")
   else()
     message(FATAL_ERROR "Support for Qt${CTK_QT_VERSION} is not implemented")
   endif()
@@ -172,27 +174,29 @@ macro(ctkMacroBuildQtPlugin)
 endmacro()
 
 macro(ctkMacroBuildQtDesignerPlugin)
+  find_package(Qt${CTK_QT_VERSION} COMPONENTS Designer REQUIRED)
   if(CTK_QT_VERSION VERSION_EQUAL "5")
-    find_package(Qt5 COMPONENTS Designer REQUIRED)
+    # Variables like Qt*_DEFINITIONS may include generator expressions (genex) in newer Qt versions,
+    # which cannot be directly passed to "add_definitions()". For example, the list may include elements
+    # like "$<$<BOOL:$<TARGET_PROPERTY:QT_PLUGIN_CLASS_NAME>>:QDESIGNER_EXPORT_WIDGETS>". Stripping these using
+    # "string(GENEX_STRIP ...)" would result in an incomplete set of definitions.
+    # Therefore, we maintain the use of add_definitions()/include_directories() for Qt5 and encourage
+    # developers to rely on target usage requirements for newer versions.
     add_definitions(${Qt5Designer_DEFINITIONS})
     include_directories(${Qt5Designer_INCLUDE_DIRS})
   else()
-    message(FATAL_ERROR "Support for Qt${CTK_QT_VERSION} is not implemented")
+    # For newer Qt versions, use target usage requirements to handle definitions and include directories.
   endif()
   ctkMacroBuildQtPlugin(
     PLUGIN_DIR designer
     ${ARGN})
-  if(CTK_QT_VERSION VERSION_EQUAL "5")
-    cmake_parse_arguments(MY
-      "" # no options
-      "NAME;EXPORT_DIRECTIVE;FOLDER;PLUGIN_DIR" # one value args
-      "SRCS;MOC_SRCS;UI_FORMS;INCLUDE_DIRECTORIES;TARGET_LIBRARIES;RESOURCES" # multi value args
-      ${ARGN}
-      )
-    target_link_libraries(${MY_NAME} Qt5::Designer)
-  else()
-    message(FATAL_ERROR "Support for Qt${CTK_QT_VERSION} is not implemented")
-  endif()
+  cmake_parse_arguments(MY
+    "" # no options
+    "NAME;EXPORT_DIRECTIVE;FOLDER;PLUGIN_DIR" # one value args
+    "SRCS;MOC_SRCS;UI_FORMS;INCLUDE_DIRECTORIES;TARGET_LIBRARIES;RESOURCES" # multi value args
+    ${ARGN}
+    )
+  target_link_libraries(${MY_NAME} Qt${CTK_QT_VERSION}::Designer)
 endmacro()
 
 macro(ctkMacroBuildQtIconEnginesPlugin)

CMake/ctkMacroSetupPlugins.cmake

@@ -103,13 +103,13 @@ macro(ctkMacroSetupPlugins )
 
   # Set the variable QT_INSTALLED_LIBRARY_DIR that contains all
   # Qt shared libraries
-  if(CTK_QT_VERSION VERSION_EQUAL "5")
+  if(CTK_QT_VERSION MATCHES "^(5|6)$")
     if(WIN32)
-      get_target_property(_qt5_moc_executable Qt5::moc LOCATION)
-      get_filename_component(QT_INSTALLED_LIBRARY_DIR ${_qt5_moc_executable} PATH)
+      get_target_property(_qt_moc_executable Qt${CTK_QT_VERSION}::moc LOCATION)
+      get_filename_component(QT_INSTALLED_LIBRARY_DIR ${_qt_moc_executable} PATH)
     else()
-      get_target_property(_qt5_core_lib Qt5::Core LOCATION)
-      get_filename_component(QT_INSTALLED_LIBRARY_DIR ${_qt5_core_lib} PATH)
+      get_target_property(_qt_core_lib Qt${CTK_QT_VERSION}::Core LOCATION)
+      get_filename_component(QT_INSTALLED_LIBRARY_DIR ${_qt_core_lib} PATH)
     endif()
   else()
     message(FATAL_ERROR "Support for Qt${CTK_QT_VERSION} is not implemented")

CMake/ctkMacroSetupQt.cmake

@@ -21,12 +21,19 @@
 #! \ingroup CMakeUtilities
 macro(ctkMacroSetupQt)
 
-  if(CTK_QT_VERSION VERSION_EQUAL "5")
+  if(CTK_QT_VERSION MATCHES "^(5|6)$")
     cmake_minimum_required(VERSION 3.20.6)
-    find_package(Qt5 COMPONENTS Core)
+    find_package(Qt${CTK_QT_VERSION} COMPONENTS Core)
 
     set(CTK_QT_COMPONENTS Core)
 
+    if(CTK_QT_VERSION VERSION_GREATER "5")
+      list(APPEND CTK_QT_COMPONENTS
+        Core5Compat # For QRegExp used in "ctkCommandLineParser.cpp"
+        StateMachine # For QAbstractTransition used in "ctkWorkflowTransitions.h"
+        )
+    endif()
+
     # See https://github.com/commontk/CTK/wiki/Maintenance#updates-of-required-qt-components
 
     if(CTK_LIB_Widgets
@@ -46,7 +53,9 @@ macro(ctkMacroSetupQt)
       OR CTK_LIB_CommandLineModules/Core
       OR CTK_LIB_Scripting/Python/Core_PYTHONQT_WRAP_QTXMLPATTERNS
       )
-      list(APPEND CTK_QT_COMPONENTS XmlPatterns)
+      if(CTK_QT_VERSION VERSION_EQUAL "5")
+        list(APPEND CTK_QT_COMPONENTS XmlPatterns)
+      endif()
     endif()
 
     if(CTK_APP_ctkCommandLineModuleExplorer
@@ -82,6 +91,10 @@ macro(ctkMacroSetupQt)
 
     if(CTK_LIB_Widgets)
       list(APPEND CTK_QT_COMPONENTS OpenGL)
+
+      if(CTK_QT_VERSION VERSION_GREATER "5")
+        list(APPEND CTK_QT_COMPONENTS OpenGLWidgets)
+      endif()
     endif()
 
     if(CTK_APP_ctkCommandLineModuleExplorer
@@ -108,6 +121,10 @@ macro(ctkMacroSetupQt)
 
     if(CTK_BUILD_QTDESIGNER_PLUGINS)
       list(APPEND CTK_QT_COMPONENTS Designer)
+
+      if(CTK_QT_VERSION VERSION_GREATER "5")
+        list(APPEND CTK_QT_COMPONENTS DesignerComponentsPrivate)
+      endif()
     endif()
 
     if(CTK_LIB_XNAT/Core
@@ -118,18 +135,28 @@ macro(ctkMacroSetupQt)
       list(APPEND CTK_QT_COMPONENTS Network)
     endif()
 
-    find_package(Qt5 COMPONENTS ${CTK_QT_COMPONENTS} REQUIRED)
+    if(CTK_QT_VERSION VERSION_EQUAL "5")
+      find_package(Qt5 COMPONENTS ${CTK_QT_COMPONENTS} REQUIRED)
+      mark_as_superbuild(Qt5_DIR) # Qt 5
+
+      set(_major ${Qt5_VERSION_MAJOR})
+      set(_minor ${Qt5_VERSION_MINOR})
+      set(_patch ${Qt5_VERSION_PATCH})
 
-    mark_as_superbuild(Qt5_DIR) # Qt 5
+    elseif(CTK_QT_VERSION VERSION_EQUAL "6")
+      find_package(Qt6 COMPONENTS ${CTK_QT_COMPONENTS} REQUIRED)
+      mark_as_superbuild(Qt6_DIR) # Qt 6
+
+      set(_major ${Qt6_VERSION_MAJOR})
+      set(_minor ${Qt6_VERSION_MINOR})
+      set(_patch ${Qt6_VERSION_PATCH})
+    endif()
 
     # XXX Backward compatible way
     if(DEFINED CMAKE_PREFIX_PATH)
       mark_as_superbuild(CMAKE_PREFIX_PATH) # Qt 5
     endif()
 
-    set(_major ${Qt5_VERSION_MAJOR})
-    set(_minor ${Qt5_VERSION_MINOR})
-    set(_patch ${Qt5_VERSION_PATCH})
 
     ctk_list_to_string(", " "${CTK_QT_COMPONENTS}" comma_separated_module_list)
     message(STATUS "Configuring CTK with Qt ${_major}.${_minor}.${_patch} (using modules: ${comma_separated_module_list})")

CMakeLists.txt

@@ -105,10 +105,18 @@ mark_as_advanced(CTK_SUPERBUILD)
 #-----------------------------------------------------------------------------
 # Qt version
 #
-set(CTK_QT_VERSION "5" CACHE STRING "Expected Qt version")
+if(DEFINED Qt6_DIR)
+  set(_default_qt_major_version "6")
+else()
+  set(_default_qt_major_version "5")
+endif()
+set(CTK_QT_VERSION "${_default_qt_major_version}" CACHE STRING "Expected major Qt version")
 mark_as_advanced(CTK_QT_VERSION)
-set_property(CACHE CTK_QT_VERSION PROPERTY STRINGS 5)
+set_property(CACHE CTK_QT_VERSION PROPERTY STRINGS 5 6)
 mark_as_superbuild(CTK_QT_VERSION)
+if(NOT "${CTK_QT_VERSION}" MATCHES "^(5|6)$")
+  message(FATAL_ERROR "CTK_QT_VERSION must be 5 or 6.")
+endif()
 
 #-----------------------------------------------------------------------------
 # Output directories.
@@ -321,6 +329,14 @@ endif()
 #
 option(CTK_USE_QTTESTING "Enable/Disable QtTesting" OFF)
 mark_as_advanced(CTK_USE_QTTESTING)
+if(NOT CTK_QT_VERSION VERSION_EQUAL "5")
+  # Forcing to OFF as "QtTesting" depends on XmlPatterns Qt component not available with Qt 6
+  if(DEFINED CTK_USE_QTTESTING AND CTK_USE_QTTESTING)
+    unset(CTK_USE_QTTESTING CACHE)
+    set(CTK_USE_QTTESTING OFF)
+    message(WARNING "Forcing option [CTK_USE_QTTESTING] to OFF as QtTesting depends on XmlPatterns Qt component not available with Qt ${CTK_QT_VERSION}")
+  endif()
+endif()
 mark_as_superbuild(CTK_USE_QTTESTING)
 
 #-----------------------------------------------------------------------------
@@ -503,6 +519,7 @@ ctk_lib_option(Visualization/VTK/Core
 ctk_lib_option(Visualization/VTK/Widgets
                "Build the VTK Widgets library" OFF)
 
+if(CTK_QT_VERSION VERSION_EQUAL "5")
 ctk_lib_option(CommandLineModules/Core
                "Build the Command Line Module core library" OFF)
 
@@ -521,6 +538,16 @@ ctk_lib_option(CommandLineModules/Backend/LocalProcess
 ctk_lib_option(CommandLineModules/Backend/FunctionPointer
                "Build the Command Line Module back-end for function pointers" OFF)
 
+else()
+  # "CommandLineModules/Core" depends on XmlPatterns Qt component not available with Qt 6
+  set(CTK_LIB_CommandLineModules/Core OFF)
+  set(CTK_LIB_CommandLineModules/Frontend/QtWebKit OFF)
+  set(CTK_LIB_CommandLineModules/Frontend/QtGui OFF)
+  set(CTK_LIB_CommandLineModules/Backend/XMLChecker OFF)
+  set(CTK_LIB_CommandLineModules/Backend/LocalProcess OFF)
+  set(CTK_LIB_CommandLineModules/Backend/FunctionPointer OFF)
+endif()
+
 ctk_lib_option(XNAT/Core
                "Build the XNAT Core library" OFF)
 
@@ -574,6 +601,7 @@ ctk_app_option(ctkDICOMQueryRetrieve
                "Build the DICOM example application" OFF
                CTK_ENABLE_DICOM AND CTK_BUILD_EXAMPLES)
 
+if(CTK_QT_VERSION VERSION_EQUAL "5")
 ctk_app_option(ctkDICOMHost
                "Build the DICOM application host example application" OFF
                CTK_ENABLE_DICOMApplicationHosting AND CTK_BUILD_EXAMPLES)
@@ -585,6 +613,12 @@ ctk_app_option(ctkExampleHost
 ctk_app_option(ctkExampleHostedApp
                "Build the DICOM example application" OFF
                CTK_ENABLE_DICOMApplicationHosting AND CTK_BUILD_EXAMPLES)
+else()
+  # Host apps depends on "org.commontk.dah.core" which depends on QtSOAP not available with Qt 6
+  set(CTK_APP_ctkDICOMHost OFF)
+  set(CTK_APP_ctkExampleHost OFF)
+  set(CTK_APP_ctkExampleHostedApp OFF)
+endif()
 
 if(FALSE)
 # Since EventBusDemo depends on qxmlrpc that is lacking Qt5 support, it is excluded.
@@ -593,9 +627,14 @@ ctk_app_option(ctkEventBusDemo
                CTK_ENABLE_PluginFramework AND CTK_BUILD_EXAMPLES)
 endif()
 
+if(CTK_QT_VERSION VERSION_EQUAL "5")
 ctk_app_option(ctkCommandLineModuleExplorer
                "Build the Command Line Module Explorer" OFF
                CTK_BUILD_EXAMPLES)
+else()
+  # "ctkCommandLineModuleExplorer" depends on "CommandLineModules/Core" which depends on XmlPatterns Qt component not available with Qt 6
+  set(CTK_APP_ctkCommandLineModuleExplorer OFF)
+endif()
 
 # We use the CTKWidgets library together with the Qt Designer plug-in
 # in ctkCommandLineModuleExplorer, so enabling the options here.
@@ -672,6 +711,7 @@ ctk_plugin_option(org.commontk.plugingenerator.ui
                   CTK_APP_ctkPluginGenerator)
 
 # Plug-ins related to DICOM WG23 (Application Hosting)
+if(CTK_QT_VERSION VERSION_EQUAL "5")
 ctk_plugin_option(org.commontk.dah.core "Build the org.commontk.dah.core plugin." OFF)
 ctk_plugin_option(org.commontk.dah.hostedapp "Build the org.commontk.dah.hostedapp plugin." OFF
                   CTK_ENABLE_DICOMApplicationHosting)
@@ -681,14 +721,31 @@ ctk_plugin_option(org.commontk.dah.host "Build the org.commontk.dah.host plugin.
 ctk_plugin_option(org.commontk.dah.exampleapp
                   "Build the org.commontk.dah.exampleapp plugin." OFF
                   CTK_APP_ctkExampleHostedApp)
+else()
+  # "org.commontk.dah.core" and its dependent plugins depend on QtSOAP not available with Qt 6
+  set(CTK_PLUGIN_org.commontk.dah.core OFF)
+  set(CTK_PLUGIN_org.commontk.dah.hostedapp OFF)
+  set(CTK_PLUGIN_org.commontk.dah.host OFF)
+  set(CTK_PLUGIN_org.commontk.dah.exampleapp OFF)
+endif()
 
+if(CTK_QT_VERSION VERSION_EQUAL "5")
 ctk_plugin_option(org.commontk.dah.cmdlinemoduleapp
                   "Build the org.commontk.dah.cmdlinemoduleapp plugin." OFF
                   CTK_APP_ctkCommandLineModuleApp)
+else()
+  # "org.commontk.dah.cmdlinemoduleapp" depends on "CommandLineModules/Core" which depends on XmlPatterns Qt component not available with Qt 6
+  set(CTK_PLUGIN_org.commontk.dah.cmdlinemoduleapp OFF)
+endif()
 
+if(CTK_QT_VERSION VERSION_EQUAL "5")
 ctk_plugin_option(org.commontk.dah.examplehost
                   "Build the org.commontk.dah.examplehost plugin." OFF
                   CTK_APP_ctkExampleHost)
+else()
+  # "org.commontk.dah.examplehost" depends on "org.commontk.dah.core" which depends on QtSOAP not available with Qt 6
+  set(CTK_PLUGIN_org.commontk.dah.examplehost OFF)
+endif()
 
 # Plug-ins related to the EventBus demo application
 if(FALSE)