Singleton and QML in QT 6.3

[JKSH]

@RangerQT said in Singleton and QML in QT 6.3:

I have set qmldir as below

Since you are using Qt 6.3, don't create qmldir files manually. Use qt_add_qml_module() instead. See https://www.qt.io/blog/introduction-to-the-qml-cmake-api

import "../styles"

This syntax is for importing a folder from disk. But you don't have a QML folder deployed with your application -- the Qt 6 CMake API is designed to build your QML code into a library (which is statically linked to your application, ideally)

Set a URI in qt_add_qml_module() and import that URI instead.

[RangerQT]

Hmm. I'm trying to get my head around this <G>. The last time I used Qt was Qt 5 with pro files. I will read that article - again for the nth time!

You mention static linking so I assume Qt 6 CMake does that for me and I don't have to tell it to do a static library.
Thank you.

1). Do I understand we do not need import statements anymore in QML since the qt_add_qml_module should pull them all in so I can access properties, etc without the import statement in my qml files. When would I have a QML folder deployed. I guess I thought that is what the ui and styles were - folders to import but from what you say the CMakeLists.txt should handle that.
So I do import FlightLog which is my URI (no quotes around FlightLog) and that should work. Yes, that works so I just do FlightLog which is my URI instead of the import "somedir".

2). Do I need a CMakeLists.txt in each subdirectory or is the one CMakeLists.txt at the project level okay. I assume not but I see examples with CMakeLIsts.txt in subdirectories but then they have cpp and h files in them.

3). I have this in CMakeLists.txt so should this be okay to include all my *.qml files? I am assuming it's okay to do something like ui/AppWindow.qml and styles/Style.qml in the QML_FILES list.

qt_add_executable(FlightLogbook
    main.cpp
)


# QML and other files
qt_add_qml_module(FlightLogbook
    URI FlightLog
    VERSION 1.0
    QML_FILES
        main.qml
        ui/AppWindow.qml
        ui/MainMenu.qml
        ui/MainMenuList.qml
        styles/Style.qml
    SOURCES
        import/import.h
        import/import.cpp
)

4). Do I need the set_source_files_properties(Style.qml PROPERTIES QT_SINGLETON_TYPE TRUE) in my CMakeLists.txt?

5.) I can do color: "orange" in the Rectangle but if I try color: Style.menubgColor the app builds, starts, but no window comes up. Style is recognized and when I hit the . it gives me the properties in the file so for some reason it must not like how I am using it to color the rectangle. This is with and without the pragma statement.

[RangerQT]

A followup to this. First I like the cmake process a lot and how things are handled in Qt6 vs Qt5 so far.

I still can not get a property defined in one qml file used in another. I get a unable to assign [undefined] to QColor. However, if I define the property in this file.

// Qt Imports
import QtQuick

// Our Imports
import FlightLog

Item {
    id: root

    property string currentItemName: mainMenuList.currentItemName

    signal menuItemClicked(var name)

    Rectangle {
        id: mainmenuColorFill
        width: parent.width
        height: rootWindow.height
        color: CustomStyles.menubgColor //  "orange"
        MainMenuList {
            id:mainMenuList
            anchors.centerIn: parent
        }

    } // End Rectangle mainMenuColorFill

} // End Item root

The CustomStyles.qml file is

// Qt Imports
import QtQuick

// Our Imports
//import FlightLog

QtObject {
    id: customStyles
    property string menubgColor: "purple"
}

However, if I define a property string testcolor: "purple" in main.qml I can use mainqlmwindowid.testcolor and it works.

I did try customStyles.menubgcolor in the MainMenu.qml file and it fails also.

Given it works with the definition in main.qml I assume it means the build did not include the CustomStyles.qml.

[thomaso]

Hi @RangerQT , did you find a solution to your question? I am fighting with something similar (but using qmake, not cmake yet)

[RangerQT]

@thomaso said in Singleton and QML in QT 6.3:

Hi @RangerQT , did you find a solution to your question? I am fighting with something similar (but using qmake, not cmake yet)

I never did and stopped pursuing that. Right now I'm working on getting other parts of my application working and then I'll revisit Singletons since I do need them.

[blues-breaker]

Is set_source_files_properties(styles/Style.qml PROPERTIES QT_SINGLETON_TYPE TRUE) before the qt_add_qml_module line in your CMakeLists.txt?

Also in your set_source_files_properties call you posted above you seem to be omitting the styles/ prefix from the file name which may also be the issue .

I suspect the generated qmldir is not marking your Style.qml file as a singleton which can be easily checked by inspecting the generated file. I also encountered this issue and for me it was caused by incorrect ordering in the CMakeLists.txt file like I mentioned above.

[RangerQT]

@blues-breaker
Thanks for that. I'll give it a try.

[IAlexI]

I've been looking for a solution for a long time, but finally figured it out: you have a typo in your source file property name, it is QT_QML_SINGLETON_TYPE, not QT_SINGLETON_TYPE . If you add

set_source_files_properties(Style.qml PROPERTIES QT_QML_SINGLETON_TYPE TRUE)

Before qt_add_qml_modules, the singleton works without any manual qmldir or c++ code

[RangerQT]

@IAlexI
Arrgh. So simple! And where to put it is another part of the puzzle. Thank you all.

[DrSnowLabs]

Hi all.

Just to help out anyone else who get into singleton issues, I also found out that having singletons in a sub-directory doesn't work using set_source_files_properties.

Please take a look at this thread.

[kaushikv]

@DrSnowLabs @IAlexI
I am also running into this issue.

I have several custom component in a separate directly which is like a common library for example myTextBox.qml , myTextFiled.qml

and i have a Style.qml file at the same location.

I have added Style.qml in CMAKE:

This sets up the singleton module Style to be used across the application

set_source_files_properties(Style.qml PROPERTIES
QT_QML_SINGLETON_TYPE TRUE
)

but still I can' access Style.properties inside the same directory or from another library which uses these common custom components.

any ideas to resolve this issue?

[ekkescorner]

@DrSnowLabs also take a look at https://www.qt.io/blog/implicit-imports-vs.-qml-modules-in-qt-6