Create unusual horizontal layout with QWidgets

[Suares]

Hello, guys!
I have a little example where green, orange and red labels:

MainWindow::MainWindow(QWidget *parent) :
	QMainWindow(parent)
{
	setMinimumSize(640, 480);

	QWidget* centralWgt = new QWidget{ this };
	setCentralWidget(centralWgt);

	QHBoxLayout* mainLayout = new QHBoxLayout;

	QLabel* leftLbl = new QLabel{ this };
	leftLbl->setStyleSheet("background-color: green;");
	leftLbl->setFixedWidth(100);
	mainLayout->addWidget(leftLbl);
	mainLayout->addStretch();

	QLabel* centerLbl = new QLabel{ this };
	centerLbl->setStyleSheet("background-color: orange;");
	centerLbl->setFixedWidth(100);
	mainLayout->addWidget(centerLbl);
	mainLayout->addStretch();

	QLabel* rightLbl = new QLabel{ this };
	rightLbl->setStyleSheet("background-color: red;");
	rightLbl->setFixedWidth(200);
	mainLayout->addWidget(rightLbl);

	centralWidget()->setLayout(mainLayout);
}

Independent from the main window size and label sizes I want to show the centerLbl always in the center of the central widget whereas the leftLbl move to the left side and the rightLbl always move to the right side.
I know how to do this in QML:

Window {
    minimumWidth: 640; minimumHeight: 480;
    visible: true

    Rectangle {
        id: leftId;
        height: parent.height;
        width: 100;
        anchors.left: parent.left;
        color: "green";
        visible: true;
    }

    Rectangle {
        id: centerId;
        width: 50; height: parent.height;
        anchors.centerIn: parent;
        color: "orange";
        visible: true;
    }

    Rectangle {
        id: rightId;
        width: 200; height: parent.height;
        anchors.right: parent.right;
        color: "red";
        visible: true;
    }
}

But I must avoid QML in this case.
Could you please give me an advise how to do the same with QWidgets?

Thanks for help!

[A Former User]

Hi! I've found a solution but I'm not sure if it meets your demands :-) It behaves the way you described above but only if the elements do not collide. I've made a screenshot:

[Suares]

Hello, @Wieland!

This is exactly what I want.
Thank you! :)

[A Former User]

@Suares Great :-)