buildsystem - improvements for building statemachineviewer plugin

add_subdirectory(statemachineviewer) if:
 * Qt5
or
 * Qt6 and QtStateMachine

CMakeLists.txt

@@ -476,6 +476,9 @@ find_package(Qt${QT_VERSION_MAJOR}IviCore 1.1 NO_MODULE QUIET) # 1.1 is based on
 find_package(Qt${QT_VERSION_MAJOR}IviVehicleFunctions 1.1 NO_MODULE QUIET)
 find_package(Qt${QT_VERSION_MAJOR}IviMedia 1.1 NO_MODULE QUIET)
 find_package(Qt${QT_VERSION_MAJOR}Scxml 5.8 NO_MODULE QUIET)
+if(QT_VERSION_MAJOR GREATER_EQUAL 6)
+    find_package(Qt${QT_VERSION_MAJOR}StateMachine NO_MODULE QUIET)
+endif()
 
 # if translation/doc host tools are missing, the Qt5 cmake config files throw errors...
 if(GAMMARAY_BUILD_DOCS)
@@ -493,9 +496,6 @@ if(QT_VERSION_MAJOR GREATER_EQUAL 6)
         # prevent 'file too big' and 'too many sections' errors with Qt6
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wa,-mbig-obj")
     endif()
-    find_package(Qt${QT_VERSION_MAJOR}StateMachine NO_MODULE QUIET)
-else()
-    find_package(Qt${QT_VERSION_MAJOR}Scxml 5.8 NO_MODULE QUIET)
 endif()
 
 # these need to included after the last Qt-related find_package() call

plugins/CMakeLists.txt

@@ -9,7 +9,11 @@
 if(TARGET Qt5::Core)
     add_subdirectory(codecbrowser)
 endif()
-add_subdirectory(statemachineviewer)
+if((QT_VERSION_MAJOR EQUAL 5) OR (QT_VERSION_MAJOR EQUAL 6 AND TARGET Qt6::StateMachine))
+    add_subdirectory(statemachineviewer)
+else()
+    message(STATUS "WARNING: Skipping the statemachineviewer plugin since Qt6StateMachine was not found")
+endif()
 add_subdirectory(eventmonitor)
 add_subdirectory(fontbrowser)
 add_subdirectory(kjobtracker)

plugins/statemachineviewer/CMakeLists.txt

@@ -83,7 +83,7 @@ if(GAMMARAY_BUILD_UI AND ${KDSME_PACKAGE_NAME}_FOUND)
         gammaray_ui
     )
 
-    if(QT_VERSION_MAJOR GREATER_EQUAL 6)
+    if(TARGET Qt6::StateMachine)
         target_link_libraries(gammaray_statemachineviewer_ui_plugin Qt6::StateMachine)
     endif()
 endif()