QT:: do we have a problem? (solved) - Page 1
Forum section: electronics / general

author: 0db
author_rank: Frequent Contributor
timestamp: August 14, 2020, 04:41:54 pm
content: "kalgebra" is a GPL-2 MathML-based 2D and 3D graph calculator made by KDE, seehere.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 thisQuoteNo idea what's wrong. I am running the application remotely through a SSH.edit:title+=(solved)

author: AntiProtonBoy
author_rank: Frequent Contributor
timestamp: August 14, 2020, 04:50:30 pm
content: maybe file a bug report with the software developers?

author: Nominal Animal
author_rank: Super Contributor
timestamp: August 14, 2020, 05:09:04 pm
content: 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 viaenv LIBGL_ALWAYS_SOFTWARE=true kalgebramobilefixes it.

author: 0db
author_rank: Frequent Contributor
timestamp: August 14, 2020, 05:19:47 pm
content: Quote from: Nominal Animal on August 14, 2020, 05:09:04 pmI had this suspicion, but I was not sure.Quote from: Nominal Animal on August 14, 2020, 05:09:04 pmI am running QT-* v5.14.2Quote from: Nominal Animal on August 14, 2020, 05:09:04 pmThanks 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.

author: Nominal Animal
author_rank: Super Contributor
timestamp: August 14, 2020, 05:45:33 pm
content: Is the qt.glx line the only error, or are there others? Could it beQTBUG-85869?

author: 0db
author_rank: Frequent Contributor
timestamp: August 14, 2020, 05:47:42 pm
content: Code:# kalgebramobileqt.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 GLXAbortedit looks qt.glx only

author: Nominal Animal
author_rank: Super Contributor
timestamp: August 14, 2020, 05:51:27 pm
content: 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 yourlocalmachine, 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 addingOption "IndirectGLX" "on"in aServerFlagssection 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 toxserver-command=X -core +iglxinstead, i.e. add the +iglx parameter.)

author: 0db
author_rank: Frequent Contributor
timestamp: August 15, 2020, 02:17:21 pm
content: Quote from: Nominal Animal on August 14, 2020, 05:51:27 pmYup. 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.aQuote from: Nominal Animal on August 14, 2020, 05:51:27 pmI am on a Windows10 machine through MobaXterm. I don't see an option to force "IndirectGLX"

author: Nominal Animal
author_rank: Super Contributor
timestamp: August 15, 2020, 03:36:40 pm
content: Quote from: 0db on August 15, 2020, 02:17:21 pmQuote from: 0db on August 15, 2020, 02:17:21 pmOk. What's the distro running on the Linux end?What do you get if you runssh -X you@linux glxgears? (It's usually part of mesa-utils package.)

author: 0db
author_rank: Frequent Contributor
timestamp: August 17, 2020, 12:10:47 am
content: Quote from: Nominal Animal on August 15, 2020, 03:36:40 pmbefore answering, I tried formatting and reinstalling two Linux distributions from scratch- Arch Linux- Gentoo LinuxAll the same result.Quote from: Nominal Animal on August 15, 2020, 03:36:40 pmCode:Error: couldn't get an RGB, Double-buffered visual

author: Nominal Animal
author_rank: Super Contributor
timestamp: August 17, 2020, 10:59:03 am
content: Quote from: 0db on August 17, 2020, 12:10:47 amThanks. This is odd, becauseit should work in MobaXterm. (Remember, I don't have a Windows machine, so I cannot check this myself.)Some reports say thatdisablinghardware 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.

author: 0db
author_rank: Frequent Contributor
timestamp: August 17, 2020, 03:42:40 pm
content: Quote from: Nominal Animal on August 17, 2020, 10:59:03 amI 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