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112 lines
5.6 KiB
112 lines
5.6 KiB
14 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/charinput-qws.doc:36 -->
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Character input in Qt/Embedded</title>
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<font color="#004faf">Home</font></a>
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<font color="#004faf">All Classes</font></a>
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<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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<p> Internally in the client/server protocol, each key press and key
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release is sent as a <tt>QWSKeyEvent</tt>. A QWSKeyEvent contains the
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following fields:
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<p> <center><table cellpadding="4" cellspacing="2" border="0">
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<tr bgcolor="#f0f0f0"> <td valign="top"><tt>unicode</tt>
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<td valign="top">Unicode value
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<tr bgcolor="#d0d0d0"> <td valign="top"><tt>keycode</tt>
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<td valign="top">Qt keycode value as defined in <a href="qnamespace-h.html">qnamespace.h</a>
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<tr bgcolor="#f0f0f0"> <td valign="top"><tt>modifier</tt>
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<td valign="top">A bitfield consisting of some of <a href="qt.html#ButtonState-enum">Qt::ShiftButton</a>,
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<a href="qt.html#ButtonState-enum">Qt::ControlButton</a>, and <a href="qt.html#ButtonState-enum">Qt::AltButton</a>.
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<tr bgcolor="#d0d0d0"> <td valign="top"><tt>is_press</tt>
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<td valign="top">TRUE if this is a key press, FALSE if it is a key release.
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<tr bgcolor="#f0f0f0"> <td valign="top"><tt>is_auto_repeat</tt>
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<td valign="top">TRUE if this event is caused by auto repeat.
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</table></center>
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<p> When the server receives a key event it is sent to each client process
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which is responsible for processing the key event and sending it to
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the right window, if any. Key events may come from several different
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sources.
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<p> <h2> Keyboard drivers
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</h2>
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<a name="1"></a><p> A keyboard driver reads data from a device and gives key events to the
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server.
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<p> Keyboard drivers can be compiled into the library or loaded as
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plugins. Running ./configure -help lists the available keyboard drivers.
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The "tty" driver is enabled in the default configuration.
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<p> The keyboard drivers all follow the same pattern. They read keyboard
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data from a device, find out which keys were pressed, and then call
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the static function QWSServer::processKeyEvent() with the key information.
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<p> At present, the console keyboard driver also handles console switching
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(<b>Ctrl+Alt-F1</b>...<b>Ctrl+Alt+F10</b>) and termination
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(<b>Ctrl+Alt+Backspace</b>).
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<p> To add a keyboard driver for a new device, subclasses of
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<a href="qwskeyboardhandler.html">QWSKeyboardHandler</a> and <a href="qkbddriverplugin.html">QKbdDriverPlugin</a> can be
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written and installed as plugins.
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<p> <h2> Key event filters (input methods)
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</h2>
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<a name="2"></a><p> When the server receives a key event from a keyboard driver, it first
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passes it through a filter.
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<p> This can be used to implement input methods, providing input of
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characters that are not on the keyboard.
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<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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the clients (using <a href="qwsserver.html#sendKeyEvent">QWSServer::sendKeyEvent</a>()). If <tt>filter()</tt> returns
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<tt>TRUE</tt>, the event will be stopped. To generate new key events, use
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QWSServer::sendKeyEvent(). (Do not use processKeyEvent(), since this
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will lead to infinite recursion.)
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<p> To install a keyboard event filter, use
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<a href="qwsserver.html#setKeyboardFilter">QWSServer::setKeyboardFilter</a>(). Currently, only one filter
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can be installed at a time.
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<p> Filtering must be done in the server process.
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<p> The launcher example contains an example of a simple input method,
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<tt>SimpleIM</tt> which reads a substitution table from a file.
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<p> <h2> Pen input
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</h2>
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<a name="3"></a><p> Key events do not need to come from a keyboard device. The server
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process may call QWSServer::sendKeyEvent() at any time.
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<p> Typically, this is done by popping up a widget, and letting the user
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specify characters with the pointer device.
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<p> <b>Note</b>: the key input widget should not take focus, since the
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server would then just send the key events back to the input widget.
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One way to make sure that the input widget never takes focus is to set
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the <tt>WStyle_Customize</tt> and <tt>WStyle_Tool</tt> widget flags in
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the <a href="qwidget.html">QWidget</a> constructor.
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<p> The <a href="http://www.trolltech.com/products/qtopia/">Qtopia</a>
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environment contains various input widgets such as
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Handwriting Recognition and Virtual Keyboard.
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<p>
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<!-- eof -->
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<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>Qt 3.3.8</div>
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</table></div></address></body>
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</html>
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