Hi all,

Today I installed kde neon on my desktop (AMD A10-6700 APU, asus F2A85-M PRO, 4GB RAM, 750 crucial ssd).
Windows of a few pre-installed softwares (VLC and Spectacle) are NOT visible. I can only preview them by KDE widgets for windows. They are running but invisible.
I manually install Chrome (simply clicking on .deb file) from https://www.google.it/chrome/browser/desktop/index.html and Chromium from KDE Discover. Both are invisible.

Firefox and other pre-installed software work fine.
I installed Okular and LibreOfffice (Writer, Calc, Draw, Impress). They work perfectly.

KDE Neon is really nice.
I have to say that KDE Discover is extremely slow and incomplete, compared to other Package Manager Yast, Synaptic, ... It crashes frequently, especially when upgrading packages.

Running google-chrome from konsole:

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maurizio@maurizio-desktop:~$ google-chrome
[4412:4412:0720/022015:ERROR:browser_main_loop.cc(249)] GTK theme error: Unable to locate theme engine in module_path: "adwaita",
[4412:4412:0720/022015:ERROR:browser_main_loop.cc(249)] GTK theme error: Unable to locate theme engine in module_path: "adwaita",
[4472:4472:0720/022016:ERROR:sandbox_linux.cc(334)] InitializeSandbox() called with multiple threads in process gpu-process

Running chromium-browser from konsole:

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maurizio@maurizio-desktop:~$ chromium-browser
[4537:4537:0720/022141:ERROR:browser_main_loop.cc(249)] GTK theme error: Unable to locate theme engine in module_path: "adwaita",
[4537:4537:0720/022141:ERROR:browser_main_loop.cc(249)] GTK theme error: Unable to locate theme engine in module_path: "adwaita",

Runing vlc from konsole:

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maurizio@maurizio-desktop:~$ vlc
VLC media player 2.2.2 Weatherwax (revision 2.2.2-0-g6259d80)
[0000000001627148] core libvlc: Esecuzione di vlc con l'interfaccia predefinita. Usa 'cvlc' per utilizzare vlc senza interfaccia.

Running spectacle from konsole:

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maurizio@maurizio-desktop:~$ spectacle
qrc:/JobDialog.qml:67: TypeError: Cannot read property 'Layout' of null
qrc:/JobDialog.qml:66: TypeError: Cannot read property 'Layout' of null

How can I see and use vlc, chrome, chromium, spectacle and maybe other software?

I've just installed kdenlive and its window are invisible too. I can't take a screenshoot or record a desktop screencast to show you better this serious issue because Spectacle and kdenlive are not visible.
But I took some photos:

Hi,

It seems like the Theming-Engine or Theming-Integration for GTK-Applications is broken or missing.

First I would try, would to (re)install it (run in shell):

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sudo apt install gnome-themes-standard

If this installes it, restart or UI and it should be fixed.

If not, you can try to fiddle around with the GTK+ Settings in System Settings.

Go to System Settings -> Application Style -> GNOME Application Style (GTK)
There, try changing GTK Themes. Please tell me, if some of these options are missing. Sometimes it helps, to just switch the GTK themes for GTK2 and 3 to something else, restart the UI, and then change it back to breeze (or whatever you desire).

If these options are missing or seem broken, I will tell you how to re-install and fix it.

In case all of that doesn't work, we could try cleaning the complete GTK-Configuration (generated by KDE) and let KDE re-generate it.

maurizioa wrote:I have to say that KDE Discover is extremely slow and incomplete, compared to other Package Manager Yast, Synaptic, ... It crashes frequently, especially when upgrading packages.

My personal sarcastic opinion about Discover: Not bad for a pre-alpha release.

Currently, I personally would not recommend to use it (at least in Debian/Ubuntu Distributions) yet, even if the distributions ship it pre-installed with KDE desktops. It's a nice approach, but it needs to be finished.

Best regards,
Martin

maurizioa wrote:I've just installed kdenlive and its window are invisible too. I can't take a screenshoot or record a desktop screencast to show you better this serious issue because Spectacle and kdenlive are not visible.

Since those are non-GTK applications, it sounds more like a general issue. Have you tried changing your KDE theme to something else and restart ui? (System Settings -> Application Style -> Widget Style and Window Decoration)

If it works then, some part of the theme is broken.

Something else you could try: System Settings -> Display and Monitor -> Compositor; Disable "Enable compositor on startup" and restart the User Interface. All desktop effects (semi transparent window features, shadows, etc.) should be disabled now. If things work out, you've got an issue with your graphic card. You could simply try to change the "Rendering backend" at these settings, or try to change your graphics driver (switch open vs. proprietary driver for example) in case it breaks OpenGL.

Best regards,
Martin

I solved the problem on "Display and Monitor" of "System and Settings" but in strange way.
I have VGA and DVI cables both connected to my sony monitor. Because the bios of my motherboard is visible only on VGA, not on DVI.
Both displays was enabled on Settings of KDE Neon. I've just disabled the VGA display and now Windows of the above mentioned softwares are completely visible.
Maybe I should try to use only VGA cable and test if it works in the same way.
On Ubuntu 14.04 LTS this problem didn't occur. I think it depends on the version of Linux Kernel.

Dear Martin, thank you very much for your help. Your help was essential.
Best Regards
Maurizio

P.S. Should I un-install Discover and install synaptic? or other? What is the best solution in your opinion?

maurizioa wrote:Dear Martin, thank you very much for your help. Your help was essential.

You're welcome

maurizioa wrote:P.S. Should I un-install Discover and install synaptic? or other? What is the best solution in your opinion?

Plasma-Discover is an essential dependency and you will probably not get rid of it easily. However, it doesn't use too much disk space and the anouncements in taskbar are still usefull.

You can install Synaptic in parallel ("apt install synaptic"), it should work well and doesn't interfere with other package management frontends.

Myself I prefer the shell commands (apt search / apt install / apt update / apt dist-upgrade).

Best regards,
Martin