Using platform eglfs for two screens

beckseba

Hello,

I have several apps which are started separately from each other via a bash script. They are communicating via QtRemoteObjects. Two of them create a window which shall run on two different screens with a different resolution.

Now, I want to use eglfs with the following config:

app1

if (qEnvironmentVariableIsEmpty("QTGLESSTREAM_DISPLAY")) {
        qputenv("QT_QPA_EGLFS_PHYSICAL_WIDTH", QByteArray("1920"));
        qputenv("QT_QPA_EGLFS_PHYSICAL_HEIGHT", QByteArray("1080"));
        qputenv("QT_QPA_EGLFS_KMS_CONFIG", QByteArray("/etc/kms.conf"));
        qputenv("QT_QPA_EGLFS_INTEGRATION", QByteArray("eglfs_kms"));
        qputenv("QT_QPA_EGLFS_ALWAYS_SET_MODE", QByteArray("1"));
        qputenv("QT_LOGGING_RULES", QByteArray("qt.qpa.eglfs.kms=true"));

app2

if (qEnvironmentVariableIsEmpty("QTGLESSTREAM_DISPLAY")) {
        qputenv("QT_QPA_EGLFS_PHYSICAL_WIDTH", QByteArray("1366"));
        qputenv("QT_QPA_EGLFS_PHYSICAL_HEIGHT", QByteArray("512"));
        qputenv("QT_QPA_EGLFS_KMS_CONFIG", QByteArray("/etc/kms.conf"));
        qputenv("QT_QPA_EGLFS_INTEGRATION", QByteArray("eglfs_kms"));
        qputenv("QT_QPA_EGLFS_ALWAYS_SET_MODE", QByteArray("1"));
        qputenv("QT_LOGGING_RULES", QByteArray("qt.qpa.eglfs.kms=true"));

/etc/kms.conf

{
	"device": "/dev/dri/card0",
	"hwcursor": true,
	"pbuffers": false,
	"separateScreens": true,
	"outputs": [
		{ "name": "DP3", "mode": "1920x1080", "touchDevice": "/dev/input/mouse1", "primary": true, "virtualindex": 0 },
		{ "name": "DP2", "mode": "1366x512", "virtualindex": 1 }
	]
}

I start both apps consecutively:

./app1 -platform eglfs
./app2 -platform eglfs

App1 works very well, however, app2 reports "Could not set DRM mode for screen DP3". I need for both apps OpenGL. I have only one framebuffer (fb0) so that using QT_QPA_EGLFS_FB is not working.

In qml the screens are assigned via the screen property.

Thanks a lot.

SGaist

Hi,

Not a direct answer but wouldn't it be simpler to use Wayland as backend ?

beckseba

Hi,

thanks for the response. Of course wayland could be a potential solution, are there any options with eglfs?

In case of wayland: I have two physical screens - each screen is addressed by one application (app1 and app2). Now, do I have to implement a compositor additionally and run both apps as client? I have problems to transfer the example https://doc.qt.io/qt-5/qtwaylandcompositor-multi-screen-example.html to my use case. In general, the documention is very well in explaining the idea behind wayland but not in how to apply it for specific use cases.

SGaist

What happens if you use the same mode for both screens ?