Qt Embedded for Linux. Keyboard layout switching

问题

I'm developing application with Qt Embedded and run it in linux framebuffer. I need a way to type non-US characters. Is it possible to change keyboard layout with Qt?

I tried to run it on Qt/X11. Layout switching and input are perfectly fine there. But when I compile it with Qt/Embedded and run it in framebuffer I cannot change layout.

I searched in the documentation and didn't find anything about layout switching.

I think it has something to do with qt keyboard driver as specified at the documentation. It seems that I should develop my own keyboard driver. But I'm using standard keyboard and I think there must be a standard way to change input language?

What would you suggest?

BTW, I'm using 4.5 version. Maybe 4.6 has something to solve this issue?

Exact the same problem here:

http://lists.trolltech.com/pipermail/qt-embedded-interest/2008-August/000034.html

http://lists.trolltech.com/qt-interest/2004-02/msg00570.html

回答1:

Version 4.6 has gained keymap support. Solution:

1. generate kmap file:

   ckbcomp -layout xx > xx.kmap

2. convert kmap to qmap

   kmap2qmap xx.kmap xx.qmap

3. load keymap either by

   1. specifying QWS_KEYBOARD environment variable:

      QWS_KEYBOARD="TTY:keymap=xx.qmap"

   2. or loading a keymap dynamically:

      QWSKeyboardHandler * currentKeyboardHandler =
          QKbdDriverFactory::create("TTY", "keymap=foo.qmap");
      

      Make sure that you delete created handler when you create a new one:

      delete currentKeyboardHandler;
      currentKeyboardHandler =
          QKbdDriverFactory::create("TTY", "keymap=bar.qmap");
      

Seems like Qt for Embedded linux is superseeded by Project Lighthouse. Not sure though, if it is production ready, neither I know how does it handle keyboard layout switching.

Update

Qt5 doesn't have QWS and all QWS-related APIs are removed. So you'll need some thirdparty solution. Or write a plugin for QPA.

回答2:

I need a way to type non-US characters

You can change qmap, but even in Qt 4.8.0 there is no way to switch between US and russian (for example). You need to patch kmap2qmap (add AltGr_Lock support), qkbd_qws.cpp (change testmods according to state of AltGr_Lock). It's looks like no one is used QtEmbedded with keyboard. Or all keeps final patches in secret place.

回答3:

Can't comment, so this is the answer to

You need to patch kmap2qmap (add AltGr_Lock support), qkbd_qws.cpp (change testmods according to state of AltGr_Lock).

This simple patch to qkbd_qws.cpp enables switch beteewn languages by the CapsLock button.

523,526c523,524
<             //if (d->m_locks[0] /*CapsLock*/ && (m->flags & QWSKeyboard::IsLetter))
<             //    testmods ^= QWSKeyboard::ModShift;
<             if (d->m_locks[0] /*CapsLock*/)
<                 testmods ^= QWSKeyboard::ModAltGr;
---
>             if (d->m_locks[0] /*CapsLock*/ && (m->flags & QWSKeyboard::IsLetter))
>                 testmods ^= QWSKeyboard::ModShift;

来源：https://stackoverflow.com/questions/2669464/qt-embedded-for-linux-keyboard-layout-switching