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High-DPI Support in Qt Labs Controls

Qt Labs Controls support Qt's cross-platform high-DPI scaling introduced in Qt 5.6. The feature is opt-in, and can be enabled by setting the Qt::AA_EnableHighDpiScaling application attribute in C++ before QGuiApplication is constructed:

#include <QGuiApplication>
#include <QQmlApplicationEngine>

int main(int argc, char *argv[])
{
    QGuiApplication::setAttribute(Qt::AA_EnableHighDpiScaling); // <--
    QGuiApplication app(argc, argv);
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    return app.exec();
}

Alternatively, an environment variable QT_AUTO_SCREEN_SCALE_FACTOR=1 can be set to enable automatic high-DPI scaling.

Warning: Qt Quick Controls 1.x are not compatible with Qt's automatic high-DPI scaling. There is currently no available solution for high-DPI support in applications wishing to mix Qt Quick Controls and Qt Labs Controls.

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