QQmlContext

QQmlContext is a class in the Qt QML module that represents the execution context for QML code. It encapsulates the environment in which QML components run, including accessible properties, the base URL used for module imports, and a reference to the QQmlEngine that executes the code. Each QQmlContext can be part of a hierarchy, with a root context provided by the engine and optional child contexts to scope a separate set of properties for a component or subtree.

Key features include exposing C++ data to QML via context properties, retrieving property values by name, and controlling locale-related or import-related aspects of the context. A context maintains a map of named properties set with setContextProperty, which become globally accessible to QML code within that context. The engine provides a root context, and developers can create child contexts to supply per-component data or to isolate property sets for different parts of the QML scene.

Usage typically involves obtaining the engine's root context and adding properties or objects that QML code can access. Example: engine->rootContext()->setContextProperty("backend", &backendObject); In QML you can reference backend.someProperty or call backend methods. Child contexts can be created to isolate properties for a particular QML component, helping avoid name clashes and enabling per-instance data binding.

Notes: QQmlContext does not own exposed QObjects; the lifetime of exposed objects must be managed by the application. It is part of the QtQml module and interacts with QQmlEngine and QQmlComponent during QML loading and evaluation.