Wayland/weston, Qt and RDP connection...

Marius Vlad marius.vlad at collabora.com
Fri Jan 13 14:05:17 UTC 2023

On Fri, Jan 13, 2023 at 12:13:41PM +0000, Matti Ristimäki wrote:
> Hi,
> Any tips, where/how to debug RDP related problem with Wayland/Weston. Not kind of sure if this is Weston problem or Qt problem...
> Goal:
> Trying to create a RDP connection to a Qt GUI-application.
What do you mean exactly?  Don't you mean the other way around?

Weston starts with the RDP backend and you connect to it with a client
that knows about the RDP protocol. Who is the client and who's the
server in your case? It is no clear what you are trying to achieve.
> [Service]
> # Requires systemd-notify.so Weston plugin.
> Type=notify
> EnvironmentFile=/etc/default/weston
> ExecStart=/usr/bin/weston --log=${XDG_RUNTIME_DIR}/weston.log --modules=systemd-notify.so --modules=screen.share.so
This might be a long shot but it is screen-share.so (hyphen).
> Problem:
> Seems, that the Qt application doesn't start after adding the "--modules=screen.share.so" to services. And it doesn't start:
Yeah, same issue here.
> root at sm2s-imx8mp:~# journalctl -u cpx.service
> -- Journal begins at Fri 2023-01-13 08:19:03 CET, ends at Fri 2023-01-13 10:26:26 CET. --
> Jan 13 08:20:06 sm2s-imx8mp systemd[1]: Started CPX Control Panel.
> Jan 13 08:20:06 sm2s-imx8mp cpx.sh[769]: qt.core.logging: Loading "logging.ini" ...
> Jan 13 08:20:06 sm2s-imx8mp cpx.sh[769]: Failed to create wl_display (No such file or directory)
> Jan 13 08:20:06 sm2s-imx8mp cpx.sh[769]: EGL: Warning: No default display support on wayland
> Jan 13 08:20:06 sm2s-imx8mp cpx.sh[769]: qt.qpa.wayland: EGL not available
> Jan 13 08:20:06 sm2s-imx8mp cpx.sh[769]: qt.qpa.plugin: Could not load the Qt platform plugin "wayland-egl" in "" even though it was found.
> Jan 13 08:20:06 sm2s-imx8mp cpx.sh[769]: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the app>
> Jan 13 08:20:06 sm2s-imx8mp cpx.sh[769]: Available platform plugins are: wayland, offscreen, vnc, minimal, minimalegl, vkkhrdisplay, eglfs, waylan>
> Jan 13 08:20:06 sm2s-imx8mp cpx.sh[764]: /opt/cpx/cpx.sh: line 84:   769 Aborted                 ./cpx --display=LVDS-1 --rotate=0 "$@"
> Jan 13 08:20:06 sm2s-imx8mp systemd[1]: cpx.service: Main process exited, code=exited, status=134/n/a
> Jan 13 08:20:06 sm2s-imx8mp systemd[1]: cpx.service: Failed with result 'exit-code'.
This kind of sounds like there's no Wayland compositor to connect to.
Maybe weston is failing to start because it can't find that module. 

Printing that weston is saying maybe useful. Maybe journalctl -t weston
says something?
> Basic overview:
> Running "first" weston with...
> drm-backend
> screen-share
> Qt-application (CPX Control Panel is the Qt application)
So basically your Qt application is a simple Qt application after all.
> ...and when the screen.share.so starts the "second" Weston, a RDP command is executed from weston.ini*
> rdp-backend
> fullscreen-shell
> *=weston.ini will run the rdp-backend.so
> [screen-share]
> command=@bindir@/weston --backend=rdp-backend.so --rdp-tls-cert=/data/etc/ssh/tls.crt --rdp-tls-key=/data/etc/ssh/tls.key --shell=fullscreen-shell.so --no-clients-resize --no-config
> start-on-startup=true
Right, if you use the screen-share module that would basically run that
command and in turn what would start another weston instance which you
can connect to it with a RDP client. It scrapes off the content and it sends 
it over RDP.
> More about platform(iMX8, Poky (Yocto Project Reference Distro)) and Qt debug print can be found at:
> https://forum.qt.io/topic/142178/qt-qpa-plugin-could-not-load-the-qt-platform-plugin-wayland-egl-in-even-though-it-was-found
> BR,
> -Matti
> Matti Ristimäki
> Test Engineer
> Dental Care Units & CAD/CAM Division
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