How to migrate from Qt5 to Qt6 ?

[AndrzejB]

My program works with Qt5 and KF5
I change it to Qt6
my CMakeLists.txt

cmake_minimum_required(VERSION 3.5)

project(EdiQ VERSION 0.1 LANGUAGES CXX)

if(CMAKE_COMPILER_IS_GNUCXX)
    SET(GCC_COVERAGE_COMPILE_FLAGS "-Werror=return-type")
    add_definitions(${GCC_COVERAGE_COMPILE_FLAGS})
endif()

set(CMAKE_INCLUDE_CURRENT_DIR ON)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
# SingleApplication base class
set(QAPPLICATION_CLASS QApplication)
add_subdirectory(SingleApplication)

find_package(QT NAMES Qt6)
find_package(Qt6 REQUIRED COMPONENTS Widgets)

set(KF_LIB_SYNTAX KF6SyntaxHighlighting)

set(BOTAN_DIR "/usr/include/botan-2")
IF(NOT EXISTS ${BOTAN_DIR})
    message(FATAL_ERROR "Not found ${BOTAN_DIR}")
ELSE()
    message(STATUS "Found ${BOTAN_DIR}")
ENDIF()

set(PROJECT_SOURCES
        main.cpp
        mainwindow.cpp mainwindow.h
        CodeEditor.cpp CodeEditor.h
        IEditorFactory.h IEditor.h
        EditorFactory.cpp EditorFactory.h
        UntitledCounter.cpp UntitledCounter.h
        EdiException.h
        CodeEditorSidebar.cpp CodeEditorSidebar.h
        PlainTextEdit.h
        SearchBar.cpp SearchBar.h
        Popup.cpp Popup.h
        raise.cpp raise.h XRaise.cpp XRaise.h
        een.cpp een.h
        PlainTextEdit.cpp)

qt_add_executable(${PROJECT_NAME}
    MANUAL_FINALIZATION
        res/icons.qrc
    ${PROJECT_SOURCES}
)

target_include_directories(${PROJECT_NAME} PRIVATE
        ${BOTAN_DIR})

target_link_libraries(${PROJECT_NAME} PRIVATE Qt6::Widgets
        SingleApplication::SingleApplication
        ${KF_LIB_SYNTAX}
        X11 botan-2
        )

set_target_properties(${PROJECT_NAME} PROPERTIES
    MACOSX_BUNDLE_GUI_IDENTIFIER my.example.com
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

install(TARGETS ${PROJECT_NAME}
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

qt_finalize_executable(${PROJECT_NAME})

my SingleApplication/CMakeLists.txt

cmake_minimum_required(VERSION 3.12.0)

project(SingleApplication LANGUAGES CXX DESCRIPTION "Replacement for QtSingleApplication")

set(CMAKE_AUTOMOC ON)

add_library(${PROJECT_NAME} STATIC
    singleapplication.cpp
    singleapplication_p.cpp
)
add_library(${PROJECT_NAME}::${PROJECT_NAME} ALIAS ${PROJECT_NAME})

if(NOT QT_DEFAULT_MAJOR_VERSION)
    set(QT_DEFAULT_MAJOR_VERSION 5 CACHE STRING "Qt version to use (5 or 6), defaults to 5")
endif()

# Find dependencies
set(QT_COMPONENTS Core Network)
set(QT_LIBRARIES Qt6::Core Qt6::Network)

if(QAPPLICATION_CLASS STREQUAL QApplication)
    list(APPEND QT_COMPONENTS Widgets)
    list(APPEND QT_LIBRARIES Qt6::Widgets)
elseif(QAPPLICATION_CLASS STREQUAL QGuiApplication)
    list(APPEND QT_COMPONENTS Gui)
    list(APPEND QT_LIBRARIES Qt6::Gui)
else()
    set(QAPPLICATION_CLASS QCoreApplication)
endif()

find_package(Qt6 COMPONENTS ${QT_COMPONENTS} REQUIRED)

option(SINGLEAPPLICATION_DOCUMENTATION "Generate Doxygen documentation" OFF)
if(SINGLEAPPLICATION_DOCUMENTATION)
    find_package(Doxygen)
endif()

target_link_libraries(${PROJECT_NAME} PUBLIC ${QT_LIBRARIES})

if(WIN32)
    target_link_libraries(${PROJECT_NAME} PRIVATE advapi32)
endif()

target_compile_definitions(${PROJECT_NAME} PUBLIC QAPPLICATION_CLASS=${QAPPLICATION_CLASS})
target_include_directories(${PROJECT_NAME} PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
target_compile_definitions(${PROJECT_NAME} PRIVATE
    QT_NO_CAST_TO_ASCII
    QT_NO_CAST_FROM_ASCII
    QT_NO_URL_CAST_FROM_STRING
    QT_NO_CAST_FROM_BYTEARRAY
    QT_USE_QSTRINGBUILDER
    QT_NO_NARROWING_CONVERSIONS_IN_CONNECT
    QT_NO_KEYWORDS
    QT_NO_FOREACH
)

if(DOXYGEN_FOUND)
    # Doxygen theme
    include(FetchContent)
    FetchContent_Declare(DoxygenAwesome
        GIT_REPOSITORY https://github.com/jothepro/doxygen-awesome-css
        GIT_TAG 4cd62308d825fe0396d2f66ffbab45d0e247724c # 2.0.3
    )
    FetchContent_MakeAvailable(DoxygenAwesome)
    FetchContent_GetProperties(DoxygenAwesome SOURCE_DIR DoxygenAwesome_SOURCE_DIR)

    set(DOXYGEN_USE_MDFILE_AS_MAINPAGE README.md)
    set(DOXYGEN_GENERATE_TREEVIEW YES)
    set(DOXYGEN_HTML_HEADER ${DoxygenAwesome_SOURCE_DIR}/doxygen-custom/header.html)
    set(DOXYGEN_HTML_EXTRA_STYLESHEET ${DoxygenAwesome_SOURCE_DIR}/doxygen-awesome.css)
    set(DOXYGEN_HTML_EXTRA_FILES
        ${DoxygenAwesome_SOURCE_DIR}/doxygen-awesome-fragment-copy-button.js
        ${DoxygenAwesome_SOURCE_DIR}/doxygen-awesome-paragraph-link.js
        ${DoxygenAwesome_SOURCE_DIR}/doxygen-awesome-darkmode-toggle.js
    )

    doxygen_add_docs(${PROJECT_NAME}Documentation
        singleapplication.h
        CHANGELOG.md
        Windows.md
        README.md
    )
endif()

I have installed

sudo apt install qt6-base-dev

libqt6opengl6-dev is already installed:

$ aptitude search qt | grep opengl | grep 6
p  libqt5opengl5:i386 - Qt 5 OpenGL module
v  libqt5opengl5-desktop-dev:i386 - 
p  libqt5opengl5-dev:i386 - Qt 5 OpenGL library development files
i A libqt6opengl6 - Qt 6 OpenGL module
i A libqt6opengl6-dev - Qt 6 OpenGL library development files
i A libqt6openglwidgets6 - Qt 6 OpenGL widgets module
p  python3-pyqt5.qtopengl:i386 - Python 3 bindings for Qt5's OpenGL module

and libqt6gui6:

$ aptitude search qt | grep gui | grep 6
p  cmake-qt-gui:i386 - Qt based user interface for CMake (cmake-gui)
p  libqt5gui5:i386 - Qt 5 GUI module
i A libqt6gui6 - Qt 6 GUI module
p  linguist-qt6 - Qt 6 Linguist

but are errors:

CMake Warning at /home/andrzej/.local/share/JetBrains/Toolbox/apps/CLion/ch-0/232.8660.186/bin/cmake/linux/x64/share/cmake-3.26/Modules/CMakeFindDependencyMacro.cmake:76 (find_package):
  Found package configuration file:

    /usr/lib/x86_64-linux-gnu/cmake/Qt6Gui/Qt6GuiConfig.cmake

  but it set Qt6Gui_FOUND to FALSE so package "Qt6Gui" is considered to be
  NOT FOUND.  Reason given by package:

  Qt6Gui could not be found because dependency WrapOpenGL could not be found.

Call Stack (most recent call first):
  /usr/lib/x86_64-linux-gnu/cmake/Qt6/QtPublicDependencyHelpers.cmake:14 (find_dependency)
  /usr/lib/x86_64-linux-gnu/cmake/Qt6Widgets/Qt6WidgetsDependencies.cmake:96 (_qt_internal_find_dependencies)
  /usr/lib/x86_64-linux-gnu/cmake/Qt6Widgets/Qt6WidgetsConfig.cmake:50 (include)
  /usr/lib/x86_64-linux-gnu/cmake/Qt6/Qt6Config.cmake:219 (find_package)
  SingleApplication/CMakeLists.txt:31 (find_package)


CMake Warning at /usr/lib/x86_64-linux-gnu/cmake/Qt6/Qt6Config.cmake:219 (find_package):
  Found package configuration file:

    /usr/lib/x86_64-linux-gnu/cmake/Qt6Widgets/Qt6WidgetsConfig.cmake

  but it set Qt6Widgets_FOUND to FALSE so package "Qt6Widgets" is considered
  to be NOT FOUND.  Reason given by package:

  Qt6Widgets could not be found because dependency Qt6Gui could not be found.

Call Stack (most recent call first):
  SingleApplication/CMakeLists.txt:31 (find_package)


CMake Error at SingleApplication/CMakeLists.txt:31 (find_package):
  Found package configuration file:

    /usr/lib/x86_64-linux-gnu/cmake/Qt6/Qt6Config.cmake

  but it set Qt6_FOUND to FALSE so package "Qt6" is considered to be NOT
  FOUND.  Reason given by package:

  Failed to find Qt component "Widgets".

  Expected Config file at
  "/usr/lib/x86_64-linux-gnu/cmake/Qt6Widgets/Qt6WidgetsConfig.cmake" exists

Previously I only has been using Qt5, but I want move to Qt6.
KF5 also works with Qt6 since not packaged KF6?

Partial Solution:

sudo apt install libglvnd-dev

helps to satisfy cmake, also KF5 syntax highlighter do, but is runtime error - must be KF6 syntax highlighter (?)

[Christian Ehrlicher]

@AndrzejB said in How to migrate from Qt5 to Qt6 ?:

KF5 syntax highlighter do, but is runtime error - must be KF6 syntax highlighter (?)

You can not mix Qt5 and Qt6. Do yes you have to wait for KF6

[JoeCFD]

@AndrzejB said in How to migrate from Qt5 to Qt6 ?:

set(CMAKE_CXX_STANDARD 14)

set(CMAKE_CXX_STANDARD 17)