[Interest] Running Qt application on Linux without screen

[Tomasz Olszak]

@Francisco

Perhaps it wold be possible to move non GUI code out from application and
create gui one connecting with backend.

@Tony
Sorry using word "service" was unfortunate. The app is just started from
systemd - that's all. It is GUI application using OpenGL, Qt Quick etc.
I noticed that it works ok with wayland headless-backend.so but by default
this backend does not render anything.

App works OK on odroid-c2(mali-fbdev) however odroid there are some
parameters passed from uboot to kernel that ensures HDMI reports as if it
is always connected.




2018-06-18 14:58 GMT+02:00 Tony Rietwyk <tony at rightsoft.com.au>:

> Hi Tomasz,
>
> I think in Windows, it simply is not possible for a service app to also
> run in desktop - they have separate desktops.  The usual solution is to
> move data and commands between the service and desktop app via some form of
> inter process communication - TCP, pipes, mailslots, etc.
>
> Can you use the same techniques in your app?  You should be able to easily
> split it, depending on how much data the desktop needs?
>
> Hope that helps, Tony
>
> On 18/06/2018 9:26 PM, Tomasz Olszak wrote:
>
> Hello,
>
> Has anyone of you needed to handle following use case?
>
>
> 1. Linux
> 2. Full screen GUI app -  fast as much as possible so no X, considered
> eglfs over drm and wayland
> 3. It starts as a service without screen
> 4. Screen can be connected at any time - app should be visible on screen
>
> 3 seems currently impossible with Qt 5.10 (is there a point updating it to
> 5.11).
>
> What I tried so far:
> 1. Eglfs app works ok with screen connected
> 2. Eglfs crashes when no screen connected in egl qpa
> 3. Eglfs work ok when I add in eglfs configuration file (
> QT_QPA_EGLFS_KMS_CONFIG) certain modeline string as mode. However when
> screen is connected there is no QGuiApplication::screenAdded signal so I
> can't show application on different screen.
> 4. on Qt Wayland app exits with "Running on a compositor with no screens
> is not supported". It comes from QWaylandIntegration::initialize() and
> compositor is weston
>
> Any ideas how to approach such case?
>
>
>
>
>
>
>
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