declare global property in QML for other QML files

Question

I want to declare a global property in a config file and use it in other files. for example declare mainbg in:

Style.qml:

Answer 1

Adding some contribute to @pixelgrease answer, I found another technique that doesn't require the path relative import ".", workarounding the bug QTBUG-34418. This is useful especially if one has qmldir and singleton class in a different place than the qml file where the singleton is used. The technique requires defining a proper module inside the tree structure: the module is then resolved by adding the parent path of the module to the QML engine with QmlEngine::addImportPath(moduleParentPath). For example:

qml/
├── /
│ ├── .qml
│ ├── qmldir

In main.cpp you have then:

QQmlApplicationEngine engine;
engine.addImportPath("qrc:/qml");    // Can be any directory
engine.load("qrc:/qml/main.qml");

If you use resources, qml.qrc:

 
      (...)
 qml/main.qml
 qml/MySingletons/MySingleton.qml
 qml/MySingletons/qmldir
 

In qmldir:

module MySingletons
singleton MySingleton 1.0 MySingleton.qml

In main.qml, or any other qml file in a different directory:

import MySingletons 1.0

Then you use MySingleton class as usual. I attached the example MySingletonWithModule.7z to bug QTBUG-34418 for reference.