When running a Qt for Embedded Linux application, it either runs as a server or connects to an existing server. The keyboard driver is loaded by the server application when it starts running, using Qt's plugin system .
Internally in the client/server protocol, all system generated events, including key events, are passed to the server application which then propagates the event to the appropriate client. Note that key events do not always come from a keyboard device, they can can also be generated by the server process using input widgets.
| Input Widgets |
|---|
|
The server process may call the static
QWSServer::sendKeyEvent
() function at any time. Typically, this is done by popping up a widget that enables the user specify characters with the pointer device.
Note that the key input widget should not take focus since the server would then just send the key events back to the input widget. One way to make sure that the input widget never takes focus is to set the Qt::Tool widget flag in the QWidget 构造函数。 The Qt Extended environment contains various input widgets such as Handwriting Recognition and Virtual Keyboard. |
Qt for Embedded Linux
provides ready-made drivers for the console (TTY) and the standard Linux Input Subsystem (USB, PS/2, ...). Run the
configure
script to list the available drivers:
./configure -help
Note that only the console (TTY) keyboard driver handles console switching ( Ctrl+Alt+F1 , ..., Ctrl+Alt+F10 ) and termination ( Ctrl+Alt+Backspace ).
In the default Qt configuration, only the "TTY" driver is enabled. The various drivers can be enabled and disabled using the
configure
script. For example:
configure -qt-kbd-linuxinput
Custom keyboard drivers can be implemented by subclassing the QWSKeyboardHandler class and creating a keyboard driver plugin (derived from the QKbdDriverPlugin class). The default implementation of the QKbdDriverFactory class will automatically detect the plugin, loading the driver into the server application at run-time.
Starting with 4.6,
Qt for Embedded Linux
has gained support for user defined keymaps. Keymap handling is supported by the built-in keyboard drivers
TTY
and
LinuxInput
. Custom keyboard drivers can use the existing keymap handling code via
QWSKeyboardHandler::processKeycode
().
By default Qt will use an internal, compiled-in US keymap. See the options below for how to load a different keymap.
To specify which driver to use, set the QWS_KEYBOARD environment variable. For example (if the current shell is bash, ksh, zsh or sh):
export QWS_KEYBOARD=<driver>[:<driver specific options>]
The
<driver>
arguments are
TTY
,
LinuxInput
and
keys
identifying custom drivers, and the driver specific options are typically a device, e.g.,
/dev/tty0
.
Multiple keyboard drivers can be specified in one go:
export QWS_KEYBOARD="<driver>[:<driver specific options>] <driver>[:<driver specific options>] <driver>[:<driver specific options>]"
Input will be read from all specified drivers.
Currently the following options are supported by both the
TTY
and
LinuxInput
driver:
| 选项 | 描述 |
|---|---|
/dev/xxx
|
Open the specified device, instead of the driver's default device. |
repeat-delay=<d>
|
Time (in milliseconds) until auto-repeat kicks in. |
repeat-rate=<r>
|
Time (in milliseconds) specifying the interval between auto-repeats. |
keymap=xx.qmap
|
File name of a keymap file in Qt's
qmap
format. See
kmap2qmap
for instructions on how to create thoes files.
Note that the file name can of course also be the name of a QResource . |
disable-zap
|
Disable the QWS server "Zap" shortcut Ctrl+Alt+Backspace |
enable-compose
|
Activate Latin-1 composing features in the built-in US keymap. You can use the right
AltGr
or right
Alt
is used as a dead key modifier, while
AltGr+
. is the compose key. For example:
|
