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EGLFS on Raspberry pi 4

  • Hi.

    I have installed archlinux on a raspberry pi.
    I followed the "" guide to use EGLFS with a dual screen.
    One of these screens is touchScreen and I have found that if I press anything on the 7 inch touch screen, it actually executes a command on the main HDMI screen.

    This is my json configuration.

    "hucursor": false,
    "buffers": true,
    "outputs": [
    "name": "HDMI-A-2",

    To launch the application I run:
    export QT_QPA_EGLFS_KMS_CONFIG = "/home/config.json"

    ./myApp --platform eglfs

    The output is:

    "Cannot fin EGLConfig, returning null config"

    The application starts anyway. But with the touch screen not working on the right screen.

  • Lifetime Qt Champion

    @LucaOlimpio said in EGLFS on Raspberry pi 4:

    "/ home / config.json"

    You have blanks in this path string

  • @jsulm sorry, just a spelling mistake.
    If I get the path wrong, I get another error like "Failed to open "wrong/path/file".
    Therefore this is not the case, but thanks for the reply

  • I found the mistake.

    In json file the names of the outputs were wrong.
    The real name is the name found by eglfs/kms.
    I found it from debug console of eglfs.
    I activate it with 'export QT_LOGGING_RULES="qt.qpa.*=true"
    The real name is "HDM1,HDM2".

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