RCC Warning When Using CMake

oa_flo

Hi, first of all thanks for looking at this post, any help is appreciated. I encountered this problem with a larger project but I have been able to reproduce it with a simple project.

When I import QtQuick.Controls, I get the following warning:

Warning: QtQuick.Controls uses optional imports which are not supported. Some types might not be found. [import]

My goal is to solve this warning. Note that the application runs fine. But in a large project, the warnings add a lot of noise.

Setup
I am using:

Qt 6.5.0
CMake 3.22.3
QtCreator 10.0.1
Ubuntu 22

I am using a simple project that I created with QtCreator's wizard and modified it to reproduce the issue.

CMakeLists.txt:

cmake_minimum_required(VERSION 3.16)

project(test_qt6 VERSION 0.1 LANGUAGES CXX)

set(CMAKE_CXX_STANDARD_REQUIRED ON)

# find_package(Qt6 6.5 REQUIRED COMPONENTS Quick)
find_package(QT NAMES Qt6 COMPONENTS Qml Quick QuickControls2)
find_package(Qt6 REQUIRED COMPONENTS Core Qml Quick QuickControls2)

qt_standard_project_setup(REQUIRES 6.5)

set(QUICK_CONTROLS "QtQuick.Controls.Basic")

set_source_files_properties(
        TestSingleton.qml PROPERTIES
        QT_QML_SINGLETON_TYPE TRUE)

qt_add_executable(apptest_qt6
    main.cpp
)

qt_add_qml_module(apptest_qt6
    URI test_qt6
    VERSION 1.0
    IMPORTS ${QUICK_CONTROLS}
    QML_FILES Main.qml TestSingleton.qml
)

set_target_properties(apptest_qt6 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
)

target_link_libraries(apptest_qt6
    PRIVATE Qt6::Core Qt6::Quick
)

install(TARGETS apptest_qt6
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)

Main.qml:

import QtQuick
import QtQuick.Controls
import QtQuick.Window

Window {
    visible: true
    width: 801
    height: 1280
    Item {
        anchors.fill: parent
        Rectangle {
            id: rectangle
            anchors.fill: parent
            color: "red"

            Button {
                text: "TEST ME"
                anchors.verticalCenter: parent.verticalCenter
                anchors.horizontalCenter: parent.horizontalCenter
            }
        }
    }
}

main.cpp:

#include <QGuiApplication>
#include <QQmlApplicationEngine>


int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreationFailed,
        &app, []() { QCoreApplication::exit(-1); },
        Qt::QueuedConnection);
    engine.loadFromModule("test_qt6", "Main");

    return app.exec();
}

When I compile I get the warning posted earlier. Here is the full compile output (I removed sensitive info):

13:01:38: Running steps for project test_qt6...
13:01:38: Starting: "/usr/local/bin/cmake" --build /home/*****/qt_projects/build-test_qt6-Desktop_Qt_6_5_0_GCC_64bit-Debug --target all
[1/7 163.2/sec] Generating test_qt6/Main.qml
[2/7 40.2/sec] Running qmlimportscanner for apptest_qt6
[3/7 55.1/sec] Running rcc for resource apptest_qt6_raw_qml_0
[4/7 30.0/sec] Generating .rcc/qmlcache/apptest_qt6_Main_qml.cpp
Warning: Main.qml:2:1: Warnings occurred while importing module "QtQuick.Controls": [import]
import QtQuick.Controls
^^^^^^
---
Warning: QtQuick.Controls uses optional imports which are not supported. Some types might not be found. [import]
---

Info: Main.qml:2:1: Unused import [unused-imports]
import QtQuick.Controls
^^^^^^
[5/7 32.1/sec] Building CXX object CMakeFiles/apptest_qt6.dir/.rcc/qrc_apptest_qt6_raw_qml_0.cpp.o
[6/7 3.4/sec] Building CXX object CMakeFiles/apptest_qt6.dir/.rcc/qmlcache/apptest_qt6_Main_qml.cpp.o
[7/7 3.2/sec] Linking CXX executable apptest_qt6
13:01:40: The process "/usr/local/bin/cmake" exited normally.
13:01:40: Elapsed time: 00:02.

I found this blog post, but it did not seam to work in my case.

In my larger project, I have several other warnings that appear to comme from RCC. One of my guess is that RCC is missing info that I should maybe set from CMake, but it is only a guess.

Any help is greatly appreciated. Thanks.

mzimmers

@oa_flo have you tried adding:

set(CMAKE_AUTORCC ON)

To your CMakeList.txt file?

KH-219Design

I am still "stuck" (for the time being) on projects using Qt5 and not Qt6. So everything I say here is nothing more than educated guessing.

From the looks of it, it seems you cannot avoid that warning unless you can remove your reliance on QtQuick.Controls.

The warning is coming from here:
https://github.com/qt/qtdeclarative/blob/dev/src/qmlcompiler/qqmljsimporter.cpp#L304

Which was added here (with lots of discussion, but between Qt developers that have a lot more shared understanding of QML and legacy issues):
https://codereview.qt-project.org/c/qt/qtdeclarative/+/394363

It seems to have something to do with the migration/refactoring from Qt5 to Qt6, and the fact that QtQuick.Controls is "old."

You might be able to chase down more information if you keep following the breadcrumbs. I'd be interested to hear if you get a resolution. (I'll watch this forum thread.)