Details
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Bug
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Resolution: Unresolved
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P2: Important
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None
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6.5.3
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None
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Linux/Yocto
Description
I am experimenting with dual monitors setup with KMS backend by following this blog:
https://www.qt.io/blog/2016/09/19/qt-graphics-with-multiple-displays-on-embedded-linux
That is basically using a config file, specifying 2 output entries, and setting QT_QPA_EGLFS_KMS_CONFIG.
For simplicity, I use a minimal testing sample with some tweaks:
int main(int argc, char *argv[]) { qputenv("QT_QPA_EGLFS_KMS_CONFIG","kmsconfig.json"); QApplication a(argc, argv); QList<QScreen*> screenList = a.screens(); QQuickView w0; QQuickView w1; w0.setScreen(screenList.at(0)); w0.setGeometry(QRect(screenList.at(0)->availableGeometry().topLeft(), QSize(128, 128))); w1.setScreen(screenList.at(1)); w1.setGeometry(QRect(screenList.at(1)->availableGeometry().topLeft(), QSize(128, 128))); QTimer t0; QTimer t1; t0.setInterval(1000); t0.setSingleShot(true); t1.setInterval(1000); t1.setSingleShot(true); QObject::connect(&t0, &QTimer::timeout, &w0, [](){ qDebug() << "Message from screen 0"; }); QObject::connect(&t1, &QTimer::timeout, &w1, [](){ qDebug() << "Message from screen 1"; }); w0.showFullScreen(); w1.showFullScreen(); t0.start(); t1.start(); return a.exec(); }
It works as expected with QQuickView being set to each screen. Both are shown and QTimer also triggers output.
But it does not work for QWidget. One can replace both QQuickView with QWidget. The result is that only 1 QWidget is shown on the second screen. It seems to be only a display issue since both QTimer still times out normally.
I am testing with Raspberry Pi 4 + Boot2Qt 6.5.3. My config file is pretty standard:
{
"device": "/dev/dri/card0",
"outputs": [
{
"name": "HDMI1",
"mode": "1920x1080"
},
{
"name": "HDMI2",
"mode": "1920x1080"
}
]
}