QT:: do we have a problem? (solved)

[0db]

"kalgebra" is a GPL-2 MathML-based 2D and 3D graph calculator made by KDE, see here.

It uses QT, and it has dependencies with qt-declarative, qt-gui, qt-printsupport, qt-webengine, qt-widgets as well as with the kde framework.

When I launch it, I get this

# kalgebramobile

qt.glx: qglx_findConfig: Failed to finding matching FBConfig for QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize -1, redBufferSize 1, greenBufferSize 1, blueBufferSize 1, alphaBufferSize -1, stencilBufferSize -1, samples -1, swapBehavior QSurfaceFormat::SingleBuffer, swapInterval 1, colorSpace QSurfaceFormat::DefaultColorSpace, profile  QSurfaceFormat::NoProfile)

No idea what's wrong. I am running the application remotely through a SSH.

edit:
title+=(solved)

[AntiProtonBoy]

maybe file a bug report with the software developers?

[Nominal Animal]

Qt cannot get an accelerated (glx) OpenGL surface for your remote display.

I'm not sure if this is a known Qt bug fixed in 5.13.0, or if running it via env LIBGL_ALWAYS_SOFTWARE=true kalgebramobile fixes it.

[0db]

Qt cannot get an accelerated (glx) OpenGL surface for your remote display

I had this suspicion, but I was not sure.

I'm not sure if this is a known Qt bug fixed in 5.13.0

I am running QT-* v5.14.2

or if running it via env LIBGL_ALWAYS_SOFTWARE=true kalgebramobile fixes it.

Thanks for the trick. Unfortunately it doesn't fir the issue.

I am thinking about recompling QT-libraries without glx. I don't know if it's possible of it will break some application. I also need avidemux3/qt5, which is surprisingly working at the moment.

[Nominal Animal]

Is the qt.glx line the only error, or are there others?  Could it be QTBUG-85869?

[0db]

Code: [Select]

# kalgebramobile

qt.glx: qglx_findConfig: Failed to finding matching FBConfig for QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize -1, redBufferSize 1, greenBufferSize 1, blueBufferSize 1, alphaBufferSize -1, stencilBufferSize -1, samples -1, swapBehavior QSurfaceFormat::SingleBuffer, swapInterval 1, colorSpace QSurfaceFormat::DefaultColorSpace, profile  QSurfaceFormat::NoProfile)
qt.glx: qglx_findConfig: Failed to finding matching FBConfig for QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize -1, redBufferSize 1, greenBufferSize 1, blueBufferSize 1, alphaBufferSize -1, stencilBufferSize -1, samples -1, swapBehavior QSurfaceFormat::SingleBuffer, swapInterval 1, colorSpace QSurfaceFormat::DefaultColorSpace, profile  QSurfaceFormat::NoProfile)
qt.glx: qglx_findConfig: Failed to finding matching FBConfig for QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize -1, redBufferSize 1, greenBufferSize 1, blueBufferSize 1, alphaBufferSize -1, stencilBufferSize -1, samples -1, swapBehavior QSurfaceFormat::SingleBuffer, swapInterval 1, colorSpace QSurfaceFormat::DefaultColorSpace, profile  QSurfaceFormat::NoProfile)
Could not initialize GLX
Aborted

it looks qt.glx only 

[Nominal Animal]

Can you install libgl1-mesa-glx and libgl1-mesa-dri packages, and see if that fixes the issue?  I don't think it does, but if you can install them painlessly and check, it would help.

The solution, I suspect, is to force Qt to not use GLX.  I'll check if we can do that easily, without recompiling Qt.

Edit: Actually, if you can enable indirect GLX contexts on your local machine, that could also fix the issue.  If your local machine (the one your display is physically connected to, not the remote machine running KAlgebraMobile) is also running Linux, then adding Option "IndirectGLX" "on" in a ServerFlags section in local /etc/X11/Xorg.conf (which might not even exist) should solve it.  Otherwise, check the local X server options, to see if it supports indirect GLX contexts.

(If your local machine is running some Ubuntu derivative, and you have /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf, just change the xserver-command line to xserver-command=X -core +iglx instead, i.e. add the +iglx parameter.)

[0db]

The solution, I suspect, is to force Qt to not use GLX.  I'll check if we can do that easily, without recompiling Qt.

Yup. What I don't actually understand is why the qtgui v5.14.2 is only configured with "xcb-glx", which triggers  to (re)compile /usr/lib/libQt5GlxSupport.a

Actually, if you can enable indirect GLX contexts on your local machine, that could also fix the issue.  If your local machine (the one your display is physically connected to, not the remote machine running KAlgebraMobile) is also running Linux, then adding Option "IndirectGLX" "on" in a ServerFlags section in local /etc/X11/Xorg.conf (which might not even exist) should solve it.  Otherwise, check the local X server options, to see if it supports indirect GLX contexts.

I am on a Windows10 machine through MobaXterm. I don't see an option to force "IndirectGLX" 

[Nominal Animal]

Yup. What I don't actually understand is why the qtgui v5.14.2 is only configured with "xcb-glx", which triggers  to (re)compile /usr/lib/libQt5GlxSupport.a

I am on a Windows10 machine through MobaXterm. I don't see an option to force "IndirectGLX" 

Ok.  What's the distro running on the Linux end?

What do you get if you run ssh -X you@linux glxgears ? (It's usually part of mesa-utils package.)

[0db]

What's the distro running on the Linux end?

before answering, I tried formatting and reinstalling two Linux distributions from scratch
- Arch Linux
- Gentoo Linux
All the same result.

What do you get if you run ssh -X you@linux glxgears ? (It's usually part of mesa-utils package.)

Code: [Select]

Error: couldn't get an RGB, Double-buffered visual


[Nominal Animal]

Code: [Select]

Error: couldn't get an RGB, Double-buffered visual


Thanks.  This is odd, because it should work in MobaXterm.  (Remember, I don't have a Windows machine, so I cannot check this myself.)

Some reports say that disabling hardware acceleration in MobaXterm lets GLX work.  Could you try that?  The X11 tab in the Global Settings are also crucial here, but the mobatek documentation doesn't document them properly, nor even show a screenshot.  You need to fix your MobaXterm settings, until glxgears works; then the Qt applications should also Just Work without recompiling etc.

[0db]

Some reports say that disabling hardware acceleration in MobaXterm lets GLX work. 

I downloaded and installed the latest version, mobaxterm v20.3.
I disabled GLX hardware acceleration, and set GLX software acceleration. But it didn't work.

Digging deeper I recompiled everything without "glvnd".

Affected were
- mesalib
- x11lib-extension
- QT-*

Results:
Arch now works!
Gentoo now works!

I am happy