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| 6 | <title>Character input in Qt/Embedded</title>
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| 24 | <font color="#004faf">Main Classes</font></a>
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| 31 | </td>
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| 32 | <td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Character input in Qt/Embedded</h1>
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| 33 |
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| 34 |
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| 35 |
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| 36 | <p> Internally in the client/server protocol, each key press and key
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| 37 | release is sent as a <tt>QWSKeyEvent</tt>. A QWSKeyEvent contains the
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| 38 | following fields:
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| 39 | <p> <center><table cellpadding="4" cellspacing="2" border="0">
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| 40 | <tr bgcolor="#f0f0f0"> <td valign="top"><tt>unicode</tt>
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| 41 | <td valign="top">Unicode value
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| 42 | <tr bgcolor="#d0d0d0"> <td valign="top"><tt>keycode</tt>
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| 43 | <td valign="top">Qt keycode value as defined in <a href="qnamespace-h.html">qnamespace.h</a>
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| 44 | <tr bgcolor="#f0f0f0"> <td valign="top"><tt>modifier</tt>
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| 45 | <td valign="top">A bitfield consisting of some of <a href="qt.html#ButtonState-enum">Qt::ShiftButton</a>,
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| 46 | <a href="qt.html#ButtonState-enum">Qt::ControlButton</a>, and <a href="qt.html#ButtonState-enum">Qt::AltButton</a>.
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| 47 | <tr bgcolor="#d0d0d0"> <td valign="top"><tt>is_press</tt>
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| 48 | <td valign="top">TRUE if this is a key press, FALSE if it is a key release.
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| 49 | <tr bgcolor="#f0f0f0"> <td valign="top"><tt>is_auto_repeat</tt>
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| 50 | <td valign="top">TRUE if this event is caused by auto repeat.
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| 51 | </table></center>
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| 52 | <p> When the server receives a key event it is sent to each client process
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| 53 | which is responsible for processing the key event and sending it to
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| 54 | the right window, if any. Key events may come from several different
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| 55 | sources.
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| 56 | <p> <h2> Keyboard drivers
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| 57 | </h2>
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| 58 | <a name="1"></a><p> A keyboard driver reads data from a device and gives key events to the
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| 59 | server.
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| 60 | <p> Keyboard drivers can be compiled into the library or loaded as
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| 61 | plugins. Running ./configure -help lists the available keyboard drivers.
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| 62 | The "tty" driver is enabled in the default configuration.
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| 63 | <p> The keyboard drivers all follow the same pattern. They read keyboard
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| 64 | data from a device, find out which keys were pressed, and then call
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| 65 | the static function QWSServer::processKeyEvent() with the key information.
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| 66 | <p> At present, the console keyboard driver also handles console switching
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| 67 | (<b>Ctrl+Alt-F1</b>...<b>Ctrl+Alt+F10</b>) and termination
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| 68 | (<b>Ctrl+Alt+Backspace</b>).
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| 69 | <p> To add a keyboard driver for a new device, subclasses of
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| 70 | <a href="qwskeyboardhandler.html">QWSKeyboardHandler</a> and <a href="qkbddriverplugin.html">QKbdDriverPlugin</a> can be
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| 71 | written and installed as plugins.
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| 72 | <p> <h2> Key event filters (input methods)
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| 73 | </h2>
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| 74 | <a name="2"></a><p> When the server receives a key event from a keyboard driver, it first
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| 75 | passes it through a filter.
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| 76 | <p> This can be used to implement input methods, providing input of
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| 77 | characters that are not on the keyboard.
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| 78 | <p> To make an input method, subclass QWSServer::KeyboardFilter (in <tt>src/kernel/qwindowsystem_qws.h</tt>) and implement the virtual function <tt>filter()</tt>. If <tt>filter()</tt> returns <tt>FALSE</tt>, the event will be sent to
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| 79 | the clients (using <a href="qwsserver.html#sendKeyEvent">QWSServer::sendKeyEvent</a>()). If <tt>filter()</tt> returns
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| 80 | <tt>TRUE</tt>, the event will be stopped. To generate new key events, use
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| 81 | QWSServer::sendKeyEvent(). (Do not use processKeyEvent(), since this
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| 82 | will lead to infinite recursion.)
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| 83 | <p> To install a keyboard event filter, use
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| 84 | <a href="qwsserver.html#setKeyboardFilter">QWSServer::setKeyboardFilter</a>(). Currently, only one filter
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| 85 | can be installed at a time.
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| 86 | <p> Filtering must be done in the server process.
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| 87 | <p> The launcher example contains an example of a simple input method,
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| 88 | <tt>SimpleIM</tt> which reads a substitution table from a file.
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| 89 | <p> <h2> Pen input
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| 90 | </h2>
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| 91 | <a name="3"></a><p> Key events do not need to come from a keyboard device. The server
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| 92 | process may call QWSServer::sendKeyEvent() at any time.
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| 93 | <p> Typically, this is done by popping up a widget, and letting the user
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| 94 | specify characters with the pointer device.
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| 95 | <p> <b>Note</b>: the key input widget should not take focus, since the
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| 96 | server would then just send the key events back to the input widget.
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| 97 | One way to make sure that the input widget never takes focus is to set
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| 98 | the <tt>WStyle_Customize</tt> and <tt>WStyle_Tool</tt> widget flags in
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| 99 | the <a href="qwidget.html">QWidget</a> constructor.
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| 100 | <p> The <a href="http://www.trolltech.com/products/qtopia/">Qtopia</a>
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| 101 | environment contains various input widgets such as
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| 102 | Handwriting Recognition and Virtual Keyboard.
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| 103 | <p>
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| 104 | <!-- eof -->
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| 105 | <p><address><hr><div align=center>
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| 106 | <table width=100% cellspacing=0 border=0><tr>
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| 107 | <td>Copyright © 2007
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| 108 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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| 109 | <td align=right><div align=right>Qt 3.3.8</div>
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| 110 | </table></div></address></body>
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