Blank screen on KDE with VirtualGL on EGL with NVIDIA

[ehfd]

Environment: Ubuntu 22.04 with KDE, using vglrun +wm startplasma-x11 with Xvfb with export VGL_DISPLAY="egl".

What I am supposed to see (In the exact same condition except when using Xorg with NVIDIA 515 drivers):

What I see:

Is there any other considerations for using QT desktop environments with VirtualGL?
I believe these issues may be affected by QT XCB.

[ehfd]

It works if the compositor is off, but when it's on, it doesn't work with or without +wm.

[dcommander]

Hard to say. Regular Qt applications work with VirtualGL, so I would need a better understanding of what Plasma is doing differently. Unfortunately, the odds that I will be able to look into this anytime soon are close to zero. TurboVNC doesn't officially support Plasma, so it falls into the category of "community support." That means that I am happy to integrate patches that fix issues with it, but diagnosing those issues isn't something I can do outside of the context of a paid support contract.

[ehfd]

I needed the compositor off anyways, so it will be kept that way for now...

[ehfd]

About how much would be the range of that paid contract, by the way? We have a potential sponsor.

[dcommander]

Contact me through e-mail:
https://virtualgl.org/About/Contact

[ehfd]

There is one way to use VirtualGL + KWin Compositing: Set Rendering Backend: XRender, both OpenGL 3.0 and 2.1 fails now.
Should be possible in command-line with something in the lines of kwriteconfig5 --file kwinrc --group Compositing --key ??? --type ???.

[ehfd]

XRender is not in Ubuntu 22.04.

Possible fix:

export QT_XCB_GL_INTEGRATION=xcb_egl
export KWIN_OPENGL_INTERFACE=egl

From https://linuxreviews.org/HOWTO_enable_10-bit_color_on_Linux#KDE_Plasma_5.x.x_And_The_Deepin_Desktop_Envionment_Won.27t_Start

I will tell you if it is successful, and if you should add that to the docs or not.

[ehfd]

It's still broken. The last time I made it work was through llvmpipe. I guess it's something with the pixmaps that must be supported.

[dcommander]

Is there a way to tell Qt to use GLX (QT_OPENGL=desktop)? I'm just wondering if this is another facet of #226, which also seems to be related to Qt trying and failing to use our new EGL/X11 front end.

[ehfd]

I'm just wondering if this is another facet of #226, which also seems to be related to Qt trying and failing to use our new EGL/X11 front end.

Possible, however the VLC issue arise additionally in 3.0.91. This issue is in 3.0.2 as well as 3.0.9x.

I am trying to make some time for reproducing this.

[ehfd]

Solved together with #226.

Nope, not solved.

Plus, an immense black border around Firefox.

[ehfd]

QT_OPENGL=desktop
changes nothing.

[dcommander]

Yeah, I personally observed the issue after the VLC issue was fixed, and that issue affected the EGL/X11 front end, whereas this issue affects the GLX front end with the EGL back end. I suspect that it's because the EGL back end doesn't yet implement GLX_EXT_texture_from_pixmap.

[ehfd]

What would be the steps needed for support?

[dcommander]

Contact me through e-mail:
https://virtualgl.org/About/Contact
We would first need to determine whether the addition of GLX_EXT_texture_from_pixmap would really solve the problem, then I can give you a formal estimate for the cost of developing it.

[dcommander]

Any news on this front? It might be worth trying the latest pre-release build, which includes a fix for the EGL back end that affected other applications.

[ehfd]

Hi, Darrell. Always a pleasure to converse with you.
I'll try it right away this weekend. So, this commit is in the latest dev build (in AWS S3), I assume?

[dcommander]

Lastest 3.1.x Stable build:

https://virtualgl.org/DeveloperInfo/PreReleases

[ehfd]

Unfortunately, basically the same issue. export QT_XCB_GL_INTEGRATION=xcb_egl and export KWIN_OPENGL_INTERFACE=egl shows the above.

With QT_OPENGL=desktop above.

Used the VirtualGL 3.1.1 PreRelease.

[ehfd]

I reproduce this situation with Chrome on KDE as well with compositing disabled.

[ehfd]

Related to: https://gitlab.gnome.org/GNOME/gtk/-/issues/4815

export KWIN_COMPOSE=N before invoking startplasma-x11 disables the compositor completely and doesn't result in the borders. Do not touch the KWin Compositor Settings post-invocation as that will activate the compositor and result in the black borders.