Adapt build system for building against qt6

(cherry picked from commit c886b918151a4e07008c39fec0f115691890b9e0)

CMakeLists.txt

@@ -24,7 +24,10 @@ include(ECMAddQch)
 
 set(KMIME_LIB_VERSION ${PIM_VERSION})
 set(QT_REQUIRED_VERSION "5.15.2")
-find_package(Qt5 ${QT_REQUIRED_VERSION} CONFIG REQUIRED Core)
+find_package(Qt${QT_MAJOR_VERSION} ${QT_REQUIRED_VERSION} CONFIG REQUIRED Core)
+if (QT_MAJOR_VERSION STREQUAL "6")
+    find_package(Qt6Core5Compat)
+endif()
 
 ecm_setup_version(PROJECT VARIABLE_PREFIX KMIME
                         VERSION_HEADER "${CMAKE_CURRENT_BINARY_DIR}/kmime_version.h"
@@ -80,7 +83,7 @@ install(EXPORT KF5MimeTargets
 
 install(FILES
     ${KMime_BINARY_DIR}/kmime_version.h
-    DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5}
+    DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}
     COMPONENT Devel
     )
 

KF5MimeConfig.cmake.in

 @PACKAGE_INIT@
 include(CMakeFindDependencyMacro)
-find_dependency(Qt5Core @QT_REQUIRED_VERSION@)
+find_dependency(Qt@QT_MAJOR_VERSION@Core @QT_REQUIRED_VERSION@)
 find_dependency(KF5Codecs @KF5_MIN_VERSION@)
 
 include("${CMAKE_CURRENT_LIST_DIR}/KF5MimeTargets.cmake")

autotests/CMakeLists.txt

 include(ECMMarkAsTest)
 
-find_package(Qt5Test ${QT_REQUIRED_VERSION} CONFIG REQUIRED)
+find_package(Qt${QT_MAJOR_VERSION}Test ${QT_REQUIRED_VERSION} CONFIG REQUIRED)
 
 # Turn exceptions on
 kde_enable_exceptions()
@@ -18,9 +18,12 @@ macro(ADD_KMIME_TEST)
     add_test(NAME kmime-${_testName} COMMAND ${_testName})
     target_link_libraries(${_testName}
       KF5Mime
-      Qt::Test
+      Qt${QT_MAJOR_VERSION}::Test
       KF5::Codecs
     )
+    if (TARGET Qt6::Core5Compat)
+        target_link_libraries(${_testName} Qt6::Core5Compat) # QTextCodec
+    endif()
     set_target_properties(${_testName} PROPERTIES COMPILE_FLAGS -DTEST_DATA_DIR="\\"${CMAKE_CURRENT_SOURCE_DIR}/data\\"" )
     ecm_mark_as_test(${_testName})
     set_tests_properties(kmime-${_testName} PROPERTIES ENVIRONMENT "LANG=C")

includes/CMakeLists.txt

@@ -16,5 +16,5 @@ set(KMime_HEADERS
 
 install(FILES
         ${KMime_HEADERS}
-        DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5}/KMime/KMime COMPONENT Devel
+        DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}/KMime/KMime COMPONENT Devel
 )

src/CMakeLists.txt

@@ -52,7 +52,7 @@ if (COMPILE_WITH_UNITY_CMAKE_SUPPORT)
 endif()
 generate_export_header(KF5Mime BASE_NAME KMime)
 
-target_include_directories(KF5Mime INTERFACE "$<INSTALL_INTERFACE:${KDE_INSTALL_INCLUDEDIR_KF5}/KMime>")
+target_include_directories(KF5Mime INTERFACE "$<INSTALL_INTERFACE:${KDE_INSTALL_INCLUDEDIR_KF}/KMime>")
 target_include_directories(KF5Mime PUBLIC "$<BUILD_INTERFACE:${KMime_SOURCE_DIR}/src;${KMime_BINARY_DIR}/src;${KMime_BINARY_DIR}>")
 
 if (WIN32)
@@ -61,12 +61,15 @@ endif()
 
 target_link_libraries(KF5Mime
 PUBLIC
-    Qt::Core
+    Qt${QT_MAJOR_VERSION}::Core
 PRIVATE
     KF5::I18n
     KF5::Codecs
     ${_kmime_extra_libs}
 )
+if (TARGET Qt6::Core5Compat)
+    target_link_libraries(KF5Mime PRIVATE Qt6::Core5Compat) # QTextCodec
+endif()
 
 set_target_properties(KF5Mime PROPERTIES
     VERSION ${KMIME_VERSION}
@@ -102,7 +105,7 @@ install(FILES
          kmime_dateformatter.h
          kmime_util.h
          kmime_types.h
-         DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5}/KMime/kmime COMPONENT Devel
+         DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF}/KMime/kmime COMPONENT Devel
 )
 
 if (BUILD_QCH)
@@ -130,5 +133,5 @@ endif()
 
 ecm_qt_install_logging_categories(EXPORT KMIME FILE kmime.categories DESTINATION ${KDE_INSTALL_LOGGINGCATEGORIESDIR})
 
-ecm_generate_pri_file(BASE_NAME KMime LIB_NAME KF5Mime DEPS "" FILENAME_VAR PRI_FILENAME INCLUDE_INSTALL_DIR ${KDE_INSTALL_INCLUDEDIR_KF5}/KMime)
+ecm_generate_pri_file(BASE_NAME KMime LIB_NAME KF5Mime DEPS "" FILENAME_VAR PRI_FILENAME INCLUDE_INSTALL_DIR ${KDE_INSTALL_INCLUDEDIR_KF}/KMime)
 install(FILES ${PRI_FILENAME} DESTINATION ${ECM_MKSPECS_INSTALL_DIR})