The application I am referring to might be "plasmaboard", not kvkbd. I just know it shows up in the list as "Virtuelle Tastatur" in german.

After having pressed the "Shift" key, the keyboard should adapt to the new layout. I don't know currently how to get a "layout changed" event so that the relabeling can be done automatically.

I assume you are referring to a version of KDE later than 4.5_rc3 and this was implemented just recently?
I am using 4.5_rc3, and just tried again with all display-layouts of the virtual keyboard: None of them displays arabic letters after I change my keyboard-layout using the keyboard-layout plasmoid. Even after pressing the shift key.

Maybe I lost the feature in the redesign for kde 4.5. Is the keyboard able to display arabic keyboards at all if you start it with that layout?

I set the keyboard layout to arabic using the layout-switching plasmoid, then added the keyboard-display plasmoid. It will still display the original german layout. The same is true when selecting de-neo2 via the plasmoid.

It probably receives the information which layout is active from a source that is not updated when the active layout is changed during runtime.

The keyboard does the mapping directly by the X-Server - it should know the layout :)
My question remains: Can plasmaboard display arabic layouts at all? I never tested...

Well, when switching layouts using the kde layout-switching plasmoid, the virtual-keyboard plasmoid never shows anything but the original layout KDE was started with. So far I did not try starting KDE with another layout.

Please try it for me :)

Well, I tried it myself now. Actually you don't have to restart kde but only plasma.
Anyway, for me everything works fine with the shift-trick. I immediately had arabic characters on the keyboard after using such a layout. It does not work with every layout - had a chinese one that didn't touch the english layout. Don't know the reason.

In "systemsettings -> input devices -> keyboard -> [layouts]-tab" I have enabled ~"activate layout display" ("Belegungsanzeige aktivieren" in german). This is the layout-switching "plasmoid" I talked about earlier.

I tried it now:
systemsettings -> input devices -> keyboard -> [layouts]-tab: Change the order so that arabic is first.
- restart kde
- input is in arabic
- adding a virtual-keyboard plasmoid to the panel will display with an arabic layout (very ugly rendered glyphs, but it works)

When I now switch the layout using the icon in the systray, the virtual-keyboard still displays the arabic layout.

When I change the order of layouts in "systemsettings -> input devices -> keyboard -> [layouts]-tab" so that the german layout is first, your "shift trick" will work, and the virtual-keyboard displays a german layout.

Summary: There are two issues:
1) virtual-keyboard does not notice when the layout is switched, but needs the "shift trick".
2) It uses the *first* keyboard layout, instead of the *active* one.

Okay, confirming this. KDE's layout management must add a layer on top of the X-server which plasmaboard misses.

I wonder whether this can be read/changed via Solid. That'd seem like the right place to change such hardware properties.

Thanks for reporting and investigating, this is fixed in trunk revision 1166313. The patch is backported to the 4.5 branch, so the problem should disappear with KDE 4.5.1

SVN commit 1166310 by ruberg:

BUG: 245184
Made plasmaboard display the keyboard layout that is selected by the layout switcher



 M  +5 -1      Helpers.h  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1166310

SVN commit 1211316 by ruberg:

BUG: 245184
Widget now uses a new dbus signal when the keyboard layout is changed to automatically adjust to it



 M  +6 -2      widget.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1211316

It seems to me the bug persists in KDE 4.5.3, installed on Ubuntu 10.10.

Symptoms:
1. I need to press the shift key to update the keyboard layout in the Virtual Keyboard widget

2. This only works as long as no more than 2 keyboard layouts are installed. Third layout displays wrong, and the fourth displays a lot of special characters, and triangles.

The layout changes automatically with KDE 4.6. That bug is solved. 
But the keyboard gets confused as soon as more than two key mappings are configured. I have no clue why. When someone with xkbd knowledge wants to look into it, the code is in Helpers.h

Seem to be related to (or duplicated by?) Bug #309138

Created attachment 84157 [details]
Plasma Keyboard widget when Arabic layout is selected

Screenshot: Plasma Keyboard widget when Arabic layout is selected

Using KDE 4.11.2, so this particular bug wasn't fixed in 4.5.x.

Workaround: Change the Keyboard layouts so that Arabic is first. This makes Plasma Keyboard Widget work "correctly" for Arabic (only), but is not ideal. So the 2nd and rest of layouts will still be incorrect.

Hello!

This feature request was filed for KDE Plasma 4, which reached end-of-support status in August 2015. KDE Plasma 5's desktop shell has been almost completely rewritten for better performance and usability, so it is likely that this feature request is already implemented in Plasma 5, or is no longer applicable.

Accordingly, we hope you understand why we must close this feature request. If the requested feature is still desired but not implemented in KDE Plasma 5.12 or later, please feel free to open a new ticket in the "plasmashell" product after reading https://community.kde.org/Get_Involved/Bug_Reporting

If you would like to get involved in KDE's bug triaging effort so that future mass bug closes like this are less likely, please read https://community.kde.org/Get_Involved#Bug_Triaging

Thanks for your understanding!

Nate Graham