Windows: QScreen::devicePixelRatio sometimes inaccurate results

#include <QApplication>
#include <QLabel>
#include <QScreen>
#include <QStyle>
#include <QSystemTrayIcon>

int main(int argc, char *argv[])
{
	QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
	QApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);

	QApplication app(argc, argv);
	app.setApplicationName("Qt cached pixel ratio bug");
	app.setQuitOnLastWindowClosed(false);

	QLabel window;
	window.resize({ 300, 100 });
	window.show();

	auto updateText = [&window]()
	{
		const qreal ratio = QGuiApplication::primaryScreen()->devicePixelRatio();
		window.setText(QString("Primary screen pixel ratio: %1").arg(ratio));
	};
	updateText();

	QScreen* screen = QGuiApplication::primaryScreen();
	QObject::connect(screen, &QScreen::logicalDotsPerInchChanged, updateText);
	QObject::connect(screen, &QScreen::physicalDotsPerInchChanged, updateText);

	QSystemTrayIcon icon;
	icon.setIcon(QApplication::style()->standardIcon(QStyle::SP_ComputerIcon));
	icon.show();

	// Not using a context menu here because opening the context menu creates
	// a long-lived HWND that will handle the WM_SETTINGCHANGED event. This
	// would cause the repro steps to work only once per session.
	QObject::connect(&icon, &QSystemTrayIcon::activated, [&](auto reason)
	{
		switch (reason)
		{
		case QSystemTrayIcon::DoubleClick:
			updateText();
			window.show();
			break;

		case QSystemTrayIcon::MiddleClick:
		case QSystemTrayIcon::Context:
			app.exit();
			break;

		default:
			break;
		}
	});

	return app.exec();
}