QML and Qt Quick

The existing answers are correct, but to amend them: With qmlRegisterSingletonInstance, the same instance is shared by all engines (which can be somewhat problematic when there's more than one), whereas with qmlRegisterSingletonType, each engine will end up with its own instance. Please see also https://doc.qt.io/qt-6/qml-singleton.html , especially the sections on "Exposing an existing object as a singleton", "Imperative type registration" and "Guidelines for (not) using singletons".

Improperly explained problems lead to bad answers. I'm not sure I properly understand what you are asking so I probably won't answer it either and each time I read your question I understand a completely different thing of the previous read. I've read five times and I'm still unsure about what I should understand. If I'm understanding it right, you might be willing to instanciate an object outside a Loader, but be able to access it within it ? if yes then you need to use a binding. Item { id: rootItem SerialData { id: serialData } Loader { id: loader source: someCondition ? "page1.qml" : "page2.qml" } Binding { target: loader property: "serialData" // the property name as it will be available inside the loader WITHIN PARENTHESES value: data } } and inside your loader you can access your property classically via rootItem.serialData other option : you want to instantiate your SerialData component inside some component and make it accessible to it's parent. Then you can declare it as a property inside the component that instanciates it and thus make it available to the parent component. Doing this for data properties is fine, but injecting out an object is bad architecture. That's a very bad choice. It is much cleaner to create it in the main page and inject it into the subpages rather than creating it in a subpage and injecting it out to the main page and back to the siblings.

@JoeCFD Hi, Do you know of any sample code?

You're right, thanks. Running with paramter "-platform xcb" works. (Then, of course, it is no longer Wayland)

Hi all, The issue is now resolved. The project I was porting required glibc 2.29, whereas RHEL 8.10 only supports up to glibc 2.28. When I installed Qt using the online installer, it was expecting 2.29, rather than the system provided version. I couldn't find any precompiled Qt libraries for my version of RHEL, so I rebuilt Qt from source using the system provided version of glibc, and now there is no crash. Thanks for the responses!

you should import modules, not directories. Question : are those directories part of one single module ? Or different modules ? in first case, they all just should be declared in your CMakeLists.txt in the qt_add_qml_module directive, optionnaly a qmldir file in each directory if you load from source dir instead of resources (hot reloader for example) and you shouldn't have to import anything, as it's same module. in second case you have to import module in caller's CMakeLists.txt first via classically via target_link_directories and target_link_libraries before you can import in QML.

QTBUG-136489

The QML files and the qmldir file must be placed inside a module folder, e.g., qml/MyModule/. The qmldir file must be added to the .qrc resource file along with all the QML files it references. The qmldir file must include: A module declaration: module MyModule A list of all QML types with version and filename: Example: MyItem 1.0 MyItem.qml In C++, you must call engine.addImportPath("qrc:/qml"); This tells the QML engine to look for modules inside the .qrc resource system. In your qml.qrc, you must include all files in the correct relative path: <file>qml/MyModule/qmldir</file> <file>qml/MyModule/MyItem.qml</file> Use the module in QML with the correct name and version, as defined in qmldir: import MyModule 1.0 Filenames in qmldir must match exactly (case-sensitive) with the actual file names. CMake must include the .qrc file using qt5_add_resources() and link against Qt5::Qml and Qt5::Quick.

@Shankarlinga-M sorry for the late reply and thank you. Indeed, I found that the issue is related to the fact that the Screen.DevicePixelRatio is rounded up. When I set the display scaling to 120% the value of Screen.DevicePixelRatio is set to 2 instead of 1.2. Replacing Screen.DevicePixelRatio in the code with 1.2 makes the image look fine. I found also an other thread about this issue https://forum.qt.io/topic/160425/wayland-and-fractional-screen-scaling-reported-as-integer-by-wayland-info-and-q-screen/3

Please create a bugreport over at https://bugreports.qt.io

@Arpitha said in Facing issue in disabling up and down arrow buttons on user selecting 2 values, please hlep me to fix this.: console.info(" ARPITHA " +(flightsDataManager.selectedEffModel.getNavigationRestricted)) if NavigatioRestricted is defined inside selectedEffModel, the access is like the following console.info(" ARPITHA " + flightsDataManager.selectedEffModel. NavigatioRestricted ) //not sure how NavigatioRestricted is defined. and func getNavigationRestricted call is not needed. You need to show some code here and read some basic doc about binding of qml and c++ class.

perhaps this bug https://bugreports.qt.io/browse/QTBUG-131920 fixed in 6.8.2 / 6.9.0

I v solve this problem： insert this 2 line code in main.cpp before create QGuiApplication object: qputenv("QSG_RENDER_LOOP", "basic" ); QQuickWindow::setGraphicsApi(QSGRendererInterface::OpenGL);

@Groundbounce said in qmlRegisterType still usable?: How do you connect C++ and QML? Like explained in the documentation: https://doc.qt.io/qt-6/qtqml-cppintegration-overview.html QtCompany will for sure not ditch C++ as QML is only for UI and some logic in the UI. Everything else is still C++.

import QtQuick 2.15 import QtQuick.Window 2.15 import QtQuick.Controls 2.15 import QtQuick.Layouts 1.15 Window { id: mainWindow visible: true width: 850 height: 360 minimumWidth: 350 minimumHeight: 620 title: "Flight Plan Dashboard" color: "#1e2130" property bool isHorizontal: width >= 700 ColumnLayout { anchors.fill: parent anchors.margins: 10 spacing: 10 GridLayout { id: mainContentGrid Layout.fillWidth: true Layout.fillHeight: true flow: isHorizontal ? GridLayout.LeftToRight : GridLayout.TopToBottom columns: isHorizontal ? 3 : 1 rows: isHorizontal ? 1 : 3 // Flight Plan Panel Rectangle { Layout.fillWidth: !isHorizontal Layout.preferredWidth: isHorizontal ? mainWindow.width * 0.25 : -1 Layout.preferredHeight: isHorizontal ? mainWindow.height - 20 : 100 color: "#282c3e" radius: 5 ColumnLayout { anchors.fill: parent anchors.margins: 12 spacing: 6 Text { text: "Flight Plan 1.0" font.pixelSize: 14 font.bold: true color: "white" } Text { text: "26 Nov 06:43Z" font.pixelSize: 12 color: "#a0a0a0" } Text { text: "KRISTINA-SOLI" font.pixelSize: 14 font.bold: true color: "white" Layout.topMargin: 4 } Text { text: "4047154622*79502/0B" font.pixelSize: 12 color: "#a0a0a0" } Item { Layout.fillHeight: true } } } // Crew Panel Rectangle { Layout.fillWidth: !isHorizontal Layout.preferredWidth: isHorizontal ? mainWindow.width * 0.35 : -1 Layout.preferredHeight: isHorizontal ? mainWindow.height - 20 : 180 color: "#282c3e" radius: 5 ColumnLayout { anchors.fill: parent anchors.margins: 12 spacing: 6 Text { text: "Crew" font.pixelSize: 14 font.bold: true color: "white" } RowLayout { spacing: 6 Text { text: "Flight Deck" font.pixelSize: 12 color: "#a0a0a0" } Rectangle { Layout.preferredWidth: 20 Layout.preferredHeight: 20 radius: 10 color: "#4a5064" Text { anchors.centerIn: parent text: "2" color: "white" font.pixelSize: 10 } } Text { text: "Cabin" font.pixelSize: 12 color: "#a0a0a0" Layout.leftMargin: 8 } Rectangle { Layout.preferredWidth: 20 Layout.preferredHeight: 20 radius: 10 color: "#4a5064" Text { anchors.centerIn: parent text: "4" color: "white" font.pixelSize: 10 } } } Repeater { model: isHorizontal ? 2 : 3 delegate: Rectangle { Layout.fillWidth: true Layout.preferredHeight: 30 color: "transparent" border.color: "#444" border.width: 1 radius: 4 Layout.topMargin: 4 RowLayout { anchors.fill: parent anchors.margins: 6 spacing: 8 Rectangle { Layout.preferredWidth: 20 Layout.preferredHeight: 20 radius: 10 color: "#4a5064" Text { anchors.centerIn: parent text: "👤" color: "white" font.pixelSize: 12 } } Text { text: { if (index === 0) return "CRAIG M GIFFORD"; if (index === 1) return "COLIN P ZIMMERM..."; if (index === 2) return "CHRISTY L ALLEN"; return ""; } color: "white" font.pixelSize: 12 } } } } Item { Layout.fillHeight: true } } } // Aircraft Status Panel with FMS INIT & FA ColumnLayout { Layout.fillWidth: !isHorizontal Layout.preferredWidth: isHorizontal ? mainWindow.width * 0.4 - 30 : -1 Layout.preferredHeight: isHorizontal ? mainWindow.height - 20 : -1 spacing: 6 Rectangle { Layout.fillWidth: true Layout.preferredHeight: 200 color: "#282c3e" radius: 5 ColumnLayout { anchors.fill: parent anchors.margins: 12 spacing: 6 Text { text: "Aircraft Status" font.pixelSize: 14 font.bold: true color: "white" } Text { text: "N542DE / DL375" font.pixelSize: 14 font.bold: true color: "white" Layout.topMargin: 4 } Text { text: "A21N" font.pixelSize: 12 color: "#a0a0a0" } Item { Layout.fillHeight: true } } } RowLayout { Layout.fillWidth: true spacing: 10 Rectangle { Layout.fillWidth: true Layout.preferredHeight: (mainWindow.width * 0.4 - 50) / 3 color: "#343747" radius: 4 Text { anchors.centerIn: parent text: "FMS INIT" color: "white" font.pixelSize: 12 } } Rectangle { Layout.fillWidth: true Layout.preferredHeight: (mainWindow.width * 0.4 - 50) / 3 color: "#343747" radius: 4 Text { anchors.centerIn: parent text: "FA" color: "white" font.pixelSize: 12 } } } } } } }

Hi! This is my problrem too any advice? :(

Hi and welcome to devnet, Where are you using Qt in your system ? As per your code, I would say never so it would be better if you explained exactly what runs where and what exactly are you using.