Settings QML Type

The Settings type provides persistent platform-independent application settings.

Users normally expect an application to remember its settings (window sizes and positions, options, etc.) across sessions. The Settings type enables you to save and restore such application settings with the minimum of effort.

Individual setting values are specified by declaring properties within a Settings element. All basic type properties are supported. The recommended approach is to use property aliases in order to get automatic property updates both ways. The following example shows how to use Settings to store and restore the geometry of a window.

import QtQuick.Window 2.1
import Qt.labs.settings 1.0

Window {
    id: window

    width: 800
    height: 600

    Settings {
        property alias x: window.x
        property alias y: window.y
        property alias width: window.width
        property alias height: window.height
    }
}

At first application startup, the window gets default dimensions specified as 800x600. Notice that no default position is specified - we let the window manager handle that. Later when the window geometry changes, new values will be automatically stored to the persistent settings. The second application run will get initial values from the persistent settings, bringing the window back to the previous position and size.

A fully declarative syntax, achieved by using property aliases, comes at the cost of storing persistent settings whenever the values of aliased properties change. Normal properties can be used to gain more fine-grained control over storing the persistent settings. The following example illustrates how to save a setting on component destruction.

import QtQuick 2.1
import Qt.labs.settings 1.0

Item {
    id: page

    state: settings.state

    states: [
        State {
            name: "active"
            // ...
        },
        State {
            name: "inactive"
            // ...
        }
    ]

    Settings {
        id: settings
        property string state: "active"
    }

    Component.onDestruction: {
        settings.state = page.state
    }
}

Notice how the default value is now specified in the persistent setting property, and the actual property is bound to the setting in order to get the initial value from the persistent settings.

Application Identifiers▲

#include <QGuiApplication>
#include <QQmlApplicationEngine>

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
    app.setOrganizationName("Some Company");
    app.setOrganizationDomain("somecompany.com");
    app.setApplicationName("Amazing Application");

    QQmlApplicationEngine engine("main.qml");
    return app.exec();
}