Important: Please read the Qt Code of Conduct -

Keyboard layout switching in Qt, not just in Qt for embedded Linux

  • Hello everyone,

    I have the problem I described here:

    Basically I want to use qmap files without having to use Qt for Embedded Linux. Alternatively, if using qmaps is impossible, I'd like to use any other method for mapping the keyboard layout inside QML, apart from hand-typing huge QMap-objects. I searched the internet a lot, but to little to no avail. Can anyone help me?


  • Nobody at all?

  • Lifetime Qt Champion

    Hi and welcome to devnet,

    One question first, which version of Qt are you using ?

  • Thanks for the welcome.

    I am using Qt 4.7.4 (32 Bit) and QtCreator 2.4.1.
    I work on Ubuntu 12.04, 64 Bit on a Virtual Machine.

  • Lifetime Qt Champion

    There's something I'm not sure to follow. You wan't plug e.g. an QWERTZ keyboard and then change for e.g. an AZERTY and let Qt handle that ?

    Another question, what window manager will you be using ? Ubuntu's unity ?

  • Yes, I want to let Qt handle it. I would've liked to just call some qmap-handler-functions like you can apparently do if you use Qt for Embedded Linux, but for some reason it's not that easy in other Qt versions.

    The whole thing will run on a hardware with a specialized Linux-Kernel without Unity. The display is a permanent camera stream und Qt takes up a portion of the screen. I don't know how exactly this happens, but I can ask around if it's important.

  • Lifetime Qt Champion

    Because it's not useful outside Qt Embedded since it's done e.g. through Xorg. But that doesn't answer the main question: what do you use as graphic server ?

  • We have no graphic server. We use an Atmel SAM9G45 board. On the following pdf on page 1052 is a block diagram:

    The "DISPLAY IF" output is connected to a display.

  • Lifetime Qt Champion

    Seems like my last answer disappeared, did you got it ?

  • No, sorry, I didn't receive it. Can you post it again, please?

  • Lifetime Qt Champion

    The question was: what will you be using (software speaking) to draw the video and the Qt GUI ? Linux frame buffer ? Also what distribution will be running on the device ?

  • We use the Linux frame buffer. It's a self-compiled distribution based on kernel 2.6.38 armv5tejl GNU/Linux (with udev).

  • Lifetime Qt Champion

    Then if you don't have any graphic server/window manager and are using the linux frame buffer then you have to use Qt for Embedded Linux. Or there's something I'm missing

  • Ok, too bad. I guess we'll have to try to switch our Qt version after all.

    Thanks for the help!

  • Lifetime Qt Champion

    Before that, can you tell me what software setup you had planned ?

  • Can you elaborate on what you mean exactly?

  • Lifetime Qt Champion

    Simple what are the software architecture you want to use. Until now you wrote that your were using a self-built distribution with a custom kernel and not wanted to use Qt Embedded, but don't have any window manager nor graphic server.

    So what would your software stack be ?

  • I don't know the exact software stack, but our Atmel board has frame buffer support and that's what we use for the graphics.

  • Lifetime Qt Champion

    So all in all quick version: -> kernel -> busybox -> Qt Application ?

  • Yes, that's right.

  • Lifetime Qt Champion

    Well, then Qt for Embedded Linux is the only option. Why did you want to use it in the first place ?

  • Ok, we'll try that.

    Assuming you were asking: "Why did you not want to use it in the first place ?"
    Well, the project has been running for a few years now, requirements kept changing and keyboard layout switching was added to the specification just recently.

    I have a question about the tutorial on
    How do I switch between my two Qt versions? I use Qt Simulator for simulations and when compiling our stuff on the hardware, we use a makefile without QtCreator. Do I only have to change $PATH?
    If possible I'd like to keep the code working for both versions by using a #compileflag

  • Lifetime Qt Champion

    Indeed, the was a word missing :D

    Just create one kit for each Qt version and use both for you project, then you can switch at will from Qt Creator

  • Ok, but how? Is it enough to choose the corresponding qmake in the "Build Settings/General/Qt Version/Manage"? Qt Simulator doesn't allow me to change that one.

    And if I run a shell-script to compile everything together for the hardware, how does the system know which Qt to use if I change it only in QtCreator?

  • Lifetime Qt Champion

    Wait, Qt Simulator ? The one from the Nokia time ?

  • Yes, that one, but I can compile it in Desktop mode, too, if I have to. Qt simulator has the advantage of not being fullscreen (because it provides its own virtual screen), so I've used it until now. Though I don't mind abandoning it if it means getting those accursed keyboard layouts to work.

    But just switching qmake doesn't make a difference. I followed the tutorial on (but didn't setup the virtual frame buffer), so I'd expect that at least "QKbdDriverFactory::create" shouldn't be an undefined reference anymore. I know that I still need to do some other things to get it to run, like finding out where the QApplication object is that needs to be constructed with the QApplication::GuiServer type, but that shouldn't matter for the compiler, right?

  • Lifetime Qt Champion


    What I do when I have to develop for embedded is to build an embedded version for x86 that uses QVFB so I have the same set of libraries than the version from my target.

  • But even if I don't have the virtual frame buffer, the compiler should compile everything. But still the factory can't be found.

    Do I really only need to switch the qmake in the project settings?

  • Lifetime Qt Champion

    Are you sure you are doing an x86 embedded build ?

    If you are using Qt Creator, just switch from one kit to another one. Or if from the command line, use the correct qmake version.

  • I am not sure, that's why I'm asking if switching the qmake is enough or if more things are needed to make QtCreator use the other kit.

  • I am going to be on holidays for the next 3 weeks. Thanks for the help so far!

    Afterwards I will probably try to setup a new VM, install only Qt for Embedded Linux and see if it works better.

  • Lifetime Qt Champion

    The simplest way on the command line is to give the full path to the qmake corresponding to which version of Qt you want to compile with.

    On Qt Creator, you have to check your kits.

    Have a nice time

  • Hello again,

    I had a nice time indeed. I hope you're doing well, too.

    I finally tried to tackle Qt for Embedded Linux again, but I got another problem:
    I set up a new VM and installed only Qt for Embedded Linux SDK. When I found out that this SDK doesn't include QtCreator, I installed QtCreator version 3.2.1. Now I have the problem that it doesn't find any kits. I assumed when you install an SDK it would be registered in a place where QtCreator could find it, but apparently just extending PATH doesn't do the trick.

    Do I have to add it manually? I tried that, too, but the SDK doesn't have a GCC. I tried using RCC instead, but QtCreator says that this one is not able to compile the project. And unfortunately there doesn't seem to be a tutorial on that here. so I'd like to know

    1. how to properly register the SDK so QtCreator sees it and
    2. if that's not possible, how to link a kit manually


  • Also the SDK we're currently using for compiling (a custom-made arm SDK) has some functionality that's required as well, so if I switch all paths in our compile-scripts to the Qt for Embedded Linux SDK I get the error
    "configure: error: C compiler cannot create executables"

    So apparently I need some functionality from the current SDK, too. I guess that means I'd have to merge both SDKs, right? Is something like that even doable? I mean, obviously it's possible to customize an SDK, but the Qt for Embedded Linux one seems to be the only one capable of keyboard layout switching, so I'm expecting massive compatibility problems.

  • Lifetime Qt Champion

    You are mixing several things.

    To register a new version of Qt with Qt Creator you have to go the Build & Run panel of the Preferences, Qt Version and add it there. Qt doesn't provide gcc (or rather g++) you have to install these using your linux distribution package manager.

    Did you already cross-compiled Qt for arm ?

  • Yes, we've been cross-compiling the project for arm for quite some time now, but instead of QtCreator we use sh-scripts that call makefiles for that. QtCreator was used for simulation only.

    Incidentally I found out that "QKbdDriverFactory::create" throws its error only inside of QtCreator. When using the sh-scripts it compiles fine, even though as far as I can tell we're referencing the same SDK in both cases. Of course switching layouts doesn't work yet because I just tested invoking the create-function so far and I can't tell if it will work at all. Is there a working example somewhere? I've been searching for some time now, but to no avail. I do know roughly what to do but without an example I'd have to guess around a lot, without knowing if our custom SDK (and our current software architecture) can do it at all.

    About QtCreator:
    That problem is fairly minor now because if I switch to embedded SDK, some other arm-related things are missing, but thanks for the help. After going back to our original version of QtCreator (2.4.1) the Qt Kit tab is fortunately gone (so no more manually configuring a kit), so I did what you told me and now the kit is there, but in the SDK's qdeclarativeitem.h it doesn't like Q_REVISION. But since this is likely a dead-end unless I find out how to merge both SDKs this issue is not important anymore.

    And one more question:
    Can Qt for Embedded Linux SDK handle special things like when you're in Chinese and you type a bunch of characters they get combined into fewer characters? When I searched around for alternative solutions to using the embedded SDK and I read that xkbcommon can not do that I started wondering if the SDK can do it.

  • Lifetime Qt Champion

    Are you trying to build Qt from Qt Creator ?

    Kanji handling ? I don't know at all, the subject always intrigued me but I didn't take the time to investigate that.

  • Building Qt from Qt Creator? No, we installed a Qt SDK that included Qt Creator.

    So, do you know of a working example? The examples on don't have anything to do with keyboard layouts. I could test Kanji handling there.

Log in to reply