[SOLVED] How to rotate a Qt5 application using the linux framebuffer?

How to rotate a Qt5 application using the linux framebuffer?

I have an embedded linux application running directly on the linux framebuffer (no x-Windows). We now have to physically rotate the display 180 degrees. How do I get my Qt application to rotate so it doesn't appear upside down? I saw reference to using the following option:

 -platform linuxfb:fb=/dev/fb0:rotation:180

However, the rotation option seems to be ignored.

Using Qt 5.9.2 on Ubuntu server 16.04.6

Solution

You could handle it on application level. With QML thats easy, but with QWidgets the best I could come up with is to render the Widget on a QGraphicsScene and rotate it like this:

#include "mainwindow.h"
#include <QApplication>

#include <QGraphicsScene>
#include <QGraphicsView>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;

    QGraphicsScene *scene = new QGraphicsScene();
    QGraphicsView *view = new QGraphicsView();
    view->setGeometry(w.geometry());
    view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    view->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    scene->addWidget(&w);
    view->setScene(scene);
    view->show();
    view->rotate(180);

    //w.show();

    return a.exec();
}

It seems a bit glitchy, but you could give it a try.

Also I think the correct syntax is -platform linuxfb:fb=/dev/fb0:rotation=180 note the = instead of : Edit: but that did not make a difference for me either.