qt_add_qml_module + singleton confusion

[RobertB]

TL;DR:

1. Do I need qmldir or will CMake generate it?
2. Do I need RESOURCE_PREFIX / in qt_add_qml_module() ?
3. Do I need to link against something after calling qt_add_qml_module() ?
4. When do I call qt_add_qml_module() ? Before or after qt_add_resources() ? Before or after qt_add_executable() ?
5. What is the correct way of importing?
   • import "FontAwesome"
   • import FontAwesome
   • import FontAwesome 1.0

The issue

I have a singleton QML file I am trying to add, it looks like:

pragma Singleton
import QtQuick

Object {
    FontLoader {
        id: regular
        source: "./fa-regular-400.otf"
    }

    property string fontFamily: regular.name
    property string addressBook : "\uf2b9"
}

So that I can do:

import FontAwesome

Text {
    text: FontAwesome.addressBook
}

I checked the documentation on qt_add_qml_module but unfortunately it seems to be written by a programmer, thus incomprehensible to regular humans.

I tried:

set_source_files_properties(FontAwesome.qml PROPERTIES QT_QML_SINGLETON_TYPE TRUE)

qt_add_qml_module(FontAwesome
    URI FontAwesome
    VERSION 1.0
    QML_FILES
      FontAwesome.qml
)

But when running the application I get:

[     0.268 warning] test default unknown - qrc:/app/qml/Main.qml:11:1: module "FontAwesome" is not installed 
     import FontAwesome 
     ^

Note: I can specify a filename that does not exist and it continues the configure step regardless. So I don't know if qt_add_qml_module() actually does anything...

Lets try to link against it because why not:

target_link_libraries(test PRIVATE
  Qt6::Core
  Qt6::Gui
[...]
  FontAwesomeplugin
)

But that yields in:

CMake Error at src/CMakeLists.txt:34 (target_link_libraries):
  Target "FontAwesomeplugin" of type MODULE_LIBRARY may not be linked into
  another target.  One may link only to INTERFACE, OBJECT, STATIC or SHARED
  libraries, or to executables with the ENABLE_EXPORTS property set.

How to proceed? Anyone have some tips?

[petero3]

Any luck?
Am having similar issues.
Am following this
https://wiki.qt.io/Qml_Styling#Approach_2:_Style_Singleton
and this
https://doc.qt.io/qt-6/qtqml-modules-qmldir.html#object-type-declaration
but those still leave the reader hanging re:
the CMake side and
if/why so much boilerplate is really needed (in the .qml and qmldir and CMake) just to make one style property accessible from other qml files.
Thank you.

[petero3]

And
https://www.qt.io/blog/qml-modules-in-qt-6.2

[Mesrine]

@RobertB said in qt_add_qml_module + singleton confusion:

FontAwesome

I believe what you are doing is mostly correct.
It would help if you linked to the FontAwesome target.
You link to the FontAwesomeplugin target if the FontAwsome library is static.
Sometimes the engine would not find your module FontAwsome
when is compiled as a shared library for that the module has to be loaded at runtime by setting the QML_IMPORT_PATH environment variable or as explained here.

To be safer try to not use the same name for the Singleton type and the module.

https://forum.qt.io/post/762513

[petero3]

The following works for me when running the app, however when trying to preview it under the Design view in Qt Creator, it doesn't display the expected color.

// CMakeLists.txt
...
qt_add_qml_module(appsingleton
URI singleton
VERSION 1.0
QML_FILES Main.qml
QML_FILES Shapes.qml
)

qt_add_qml_module(CustomStyles
URI CustomStyles
VERSION 1.0
QML_FILES CustomStyles/Style.qml
RESOURCES CustomStyles/qmldir
)
..

// CustomStyles/Style.qml
pragma Singleton
import QtQuick 2.15

QtObject {
property color color: "green"
}

// CustomStyles/qmldir
module CustomStyles
singleton Style 1.0 Style.qml

// Shapes.qml
import CustomStyles
...
color: Style.color

[petero3]

This post is deleted!

[petero3]

@RobertB
If you do
File | New Project | Qt Quick Application
x Creates a project that you can open in Qt Design Studio
that gives you a "working" starter project which uses a singleton Constants.qml
Well it works running, but also doesn't seem to work in Design mode of Qt Creator?