Qt 5 embedded screen rotation

[Dr.V]

@tsaG There does not seem to be any easy way – unless you are using QML.

However, it is possible that your platform supports rotation. For example, Raspberry Pi (kind of) supports rotation as a boot-up option. The rotation occurs then at a lower level (i.e. below the OpenGL layer). Other embedded platforms may provide similar functionality.

I actually tested both methods (with RPi/EGLFS). Using the QML rotation is relatively fast, at least I did not notice any significant speed difference between landscape and portrait orientations. Using the platform-specific rotation was slow, but that result cannot be generalized to other platforms. (RPi seems to fall into some sort of soft OpenGL when rotated by 90° or 270°.)

Of course, X11 or Wayland may provide a solution here, but at the same time the performance will suffer both at startup and during run time. YMMV.

This is a strange omission indeed, as screen rotation is not uncommon with embedded devices.

[Peder]

I found a solution that works for single touch. First I rotate the display:

sudo nano /boot/config.txt

Add this at the end for a 90 degree rotation:

display_rotate=1

Restart unit.

Then I Just catch the touch event, transforms the coordinate and then send a mouse event instead.

Creating a new class:

myguiapplication.h

#ifndef MYGUIAPPLICATION_H
#define MYGUIAPPLICATION_H

#include <QGuiApplication>
#include <QEvent>

class MyGuiApplication : public QGuiApplication
{
    Q_OBJECT
public:
    MyGuiApplication(int &argc, char **argv);
    virtual bool notify(QObject*, QEvent*);
};

#endif // MYGUIAPPLICATION_H

myguiapplication.c

#include "myguiapplication.h"
#include <QTouchEvent>
#include <QMouseEvent>
#include <QDebug>

MyGuiApplication::MyGuiApplication(int &argc, char **argv) : QGuiApplication(argc, argv)
{

}

bool MyGuiApplication::notify(QObject* target, QEvent* event)
{
    try {
        switch (event->type())
        {
        case QEvent::TouchBegin:
        case QEvent::TouchUpdate:
        case QEvent::TouchEnd:
        {
            QTouchEvent* te = static_cast<QTouchEvent*>(event);

            if (te->device()->type() == QTouchDevice::TouchScreen)
            {
                QList<QTouchEvent::TouchPoint> tps = te->touchPoints();

                if(tps.count() != 1)
                {
                    qDebug() << "Touch points != 1";
                    return true;
                }

                qreal tx = tps.first().pos().x();
                qreal ty = tps.first().pos().y();

                qreal mx = 480.0/800 * ty;
                qreal my = 800 - 800.0/480 * tx;

                qDebug() << tx << "," << ty << " => " << mx << "," << my;

                QPointF mp(mx, my);

                switch (event->type())
                {
                case QEvent::TouchBegin:
                {
                    qDebug() << "BEGIN";
                    QMouseEvent ee(QEvent::MouseButtonPress, mp, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
                    QCoreApplication::sendEvent(target, &ee);
                    break;
                }
                case QEvent::TouchUpdate:
                {
                    qDebug() << "UPDATE";
                    QMouseEvent ee(QEvent::MouseMove, mp, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
                    QCoreApplication::sendEvent(target, &ee);
                    break;
                }
                case QEvent::TouchEnd:
                {
                    qDebug() << "END";
                    QMouseEvent ee(QEvent::MouseButtonRelease, mp, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
                    QCoreApplication::sendEvent(target, &ee);
                    break;
                }
                default:
                    qDebug() << "Unhandled touch event";
                    return true;
                }

                return true;
            }
            break;
        }
        case QEvent::MouseButtonPress:
        {
            QMouseEvent *k = (QMouseEvent *)event;
            qDebug() << "MouseButtonPress:" << k->pos();
            break;
        }
        case QEvent::MouseMove:
        {
            QMouseEvent *k = (QMouseEvent *)event;
            qDebug() << "MouseMove:" << k->pos();
            break;
        }
        case QEvent::MouseButtonRelease:
        {
            QMouseEvent *k = (QMouseEvent *)event;
            qDebug() << "MouseButtonRelease:" << k->pos();
            break;
        }
        default:
            ;
        }
    } catch (...) {
    }

    return QGuiApplication::notify(target, event);
 }

And then using my new class instead of QGuiApplication:

#include "myguiapplication.h"
#include <QQmlApplicationEngine>
#include <QQmlContext>
int main(int argc, char *argv[])
{
    MyGuiApplication app(argc, argv);
    //...
}

[katd]

Has anyone found a suitable solution for an embedded device on eglfs? I want to use a natively portrait display in landscape orientation, for displaying Qt5 Widget applications