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<h1 class="title">QWSCalibratedMouseHandler Class Reference</h1>
<!-- $$$QWSCalibratedMouseHandler-brief -->
<p>The QWSCalibratedMouseHandler class provides mouse calibration and noise reduction in Qt for Embedded Linux. <a href="#details">More...</a></p>
<!-- @@@QWSCalibratedMouseHandler -->
<pre class="cpp"> <span class="preprocessor">#include <QWSCalibratedMouseHandler></span></pre><p><b>Inherits: </b><a href="qwsmousehandler.html">QWSMouseHandler</a>.</p>
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<li><a href="qwscalibratedmousehandler-members.html">List of all members, including inherited members</a></li>
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<a name="reimplemented-public-functions"></a>
<h2>Reimplemented Public Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qwscalibratedmousehandler.html#calibrate">calibrate</a></b> ( const QWSPointerCalibrationData * <i>data</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qwscalibratedmousehandler.html#clearCalibration">clearCalibration</a></b> ()</td></tr>
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<ul>
<li class="fn">9 public functions inherited from <a href="qwsmousehandler.html#public-functions">QWSMouseHandler</a></li>
</ul>
<a name="protected-functions"></a>
<h2>Protected Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qwscalibratedmousehandler.html#readCalibration">readCalibration</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qwscalibratedmousehandler.html#sendFiltered">sendFiltered</a></b> ( const QPoint & <i>position</i>, int <i>state</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qwscalibratedmousehandler.html#setFilterSize">setFilterSize</a></b> ( int <i>size</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QPoint </td><td class="memItemRight bottomAlign"><b><a href="qwscalibratedmousehandler.html#transform">transform</a></b> ( const QPoint & <i>position</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qwscalibratedmousehandler.html#writeCalibration">writeCalibration</a></b> ()</td></tr>
</table>
<a name="details"></a>
<!-- $$$QWSCalibratedMouseHandler-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QWSCalibratedMouseHandler class provides mouse calibration and noise reduction in Qt for Embedded Linux.</p>
<p>Note that this class is only available in <a href="qt-embedded-linux.html">Qt for Embedded Linux</a>.</p>
<p><a href="qt-embedded-linux.html">Qt for Embedded Linux</a> provides ready-made drivers for several mouse protocols, see the <a href="qt-embedded-pointer.html">pointer handling</a> documentation for details. In general, custom mouse drivers can be implemented by subclassing the <a href="qwsmousehandler.html">QWSMouseHandler</a> class. But when the system device does not have a fixed mapping between device and screen coordinates and/or produces noisy events (e.g., a touchscreen), you should derive from the QWSCalibratedMouseHandler class instead to take advantage of its calibration functionality. As always, you must also create a mouse driver plugin (derived from <a href="qmousedriverplugin.html">QMouseDriverPlugin</a>); the implementation of the <a href="qmousedriverfactory.html">QMouseDriverFactory</a> class will then automatically detect the plugin, and load the driver into the server application at run-time using Qt's <a href="plugins-howto.html">plugin system</a>.</p>
<p>QWSCalibratedMouseHandler provides an implementation of the <a href="qwscalibratedmousehandler.html#calibrate">calibrate</a>() function to update the calibration parameters based on coordinate mapping of the given calibration data. The calibration data is represented by an <a href="qwspointercalibrationdata.html">QWSPointerCalibrationData</a> object. The linear transformation between device coordinates and screen coordinates is performed by calling the <a href="qwscalibratedmousehandler.html#transform">transform</a>() function explicitly on the points passed to the <a href="qwsmousehandler.html#mouseChanged">QWSMouseHandler::mouseChanged</a>() function. Use the <a href="qwscalibratedmousehandler.html#clearCalibration">clearCalibration</a>() function to make the mouse driver return mouse events in raw device coordinates and not in screen coordinates.</p>
<p>The calibration parameters are recalculated whenever <a href="qwscalibratedmousehandler.html#calibrate">calibrate</a>() is called, and they can be stored using the <a href="qwscalibratedmousehandler.html#writeCalibration">writeCalibration</a>() function. Previously written parameters can be retrieved at any time using the <a href="qwscalibratedmousehandler.html#readCalibration">readCalibration</a>() function (calibration parameters are always read when the class is instantiated). Note that the calibration parameters is written to and read from the file currently specified by the <a href="qt-embedded-envvars.html#pointercal-file">POINTERCAL_FILE</a> environment variable; the default file is <tt>/etc/pointercal</tt>.</p>
<p>To achieve noise reduction, QWSCalibratedMouseHandler provides the <a href="qwscalibratedmousehandler.html#sendFiltered">sendFiltered</a>() function. Use this function instead of <a href="qwsmousehandler.html#mouseChanged">mouseChanged</a>() whenever a mouse event occurs. The filter's size can be manipulated using the <a href="qwscalibratedmousehandler.html#setFilterSize">setFilterSize</a>() function.</p>
</div>
<p><b>See also </b><a href="qwsmousehandler.html">QWSMouseHandler</a>, <a href="qwspointercalibrationdata.html">QWSPointerCalibrationData</a>, and <a href="qws-mousecalibration.html">Mouse Calibration Example</a>.</p>
<!-- @@@QWSCalibratedMouseHandler -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$calibrate[overload1]$$$calibrateconstQWSPointerCalibrationData* -->
<h3 class="fn"><a name="calibrate"></a><span class="type">void</span> QWSCalibratedMouseHandler::<span class="name">calibrate</span> ( const <span class="type"><a href="qwspointercalibrationdata.html">QWSPointerCalibrationData</a></span> * <i>data</i> )<tt> [virtual]</tt></h3>
<p>Reimplemented from <a href="qwsmousehandler.html#calibrate">QWSMouseHandler::calibrate</a>().</p>
<p>Updates the calibration parameters based on coordinate mapping of the given <i>data</i>.</p>
<p>Create an instance of the <a href="qwspointercalibrationdata.html">QWSPointerCalibrationData</a> class, fill in the device and screen coordinates and pass that object to the mouse driver using this function.</p>
<p><b>See also </b><a href="qwscalibratedmousehandler.html#clearCalibration">clearCalibration</a>() and <a href="qwscalibratedmousehandler.html#transform">transform</a>().</p>
<!-- @@@calibrate -->
<!-- $$$clearCalibration[overload1]$$$clearCalibration -->
<h3 class="fn"><a name="clearCalibration"></a><span class="type">void</span> QWSCalibratedMouseHandler::<span class="name">clearCalibration</span> ()<tt> [virtual]</tt></h3>
<p>Reimplemented from <a href="qwsmousehandler.html#clearCalibration">QWSMouseHandler::clearCalibration</a>().</p>
<p>Clears the current calibration, i.e., makes the mouse driver return mouse events in raw device coordinates instead of screen coordinates.</p>
<p><b>See also </b><a href="qwscalibratedmousehandler.html#calibrate">calibrate</a>().</p>
<!-- @@@clearCalibration -->
<!-- $$$readCalibration[overload1]$$$readCalibration -->
<h3 class="fn"><a name="readCalibration"></a><span class="type">void</span> QWSCalibratedMouseHandler::<span class="name">readCalibration</span> ()<tt> [protected]</tt></h3>
<p>Reads previously written calibration parameters which are stored in <tt>/etc/pointercal</tt> (separated by whitespace and in alphabetical order).</p>
<p>You can override the default <tt>/etc/pointercal</tt> by specifying another file using the <a href="qt-embedded-envvars.html#pointercal-file">POINTERCAL_FILE</a> environment variable.</p>
<p><b>See also </b><a href="qwscalibratedmousehandler.html#writeCalibration">writeCalibration</a>().</p>
<!-- @@@readCalibration -->
<!-- $$$sendFiltered[overload1]$$$sendFilteredconstQPoint&int -->
<h3 class="fn"><a name="sendFiltered"></a><span class="type">bool</span> QWSCalibratedMouseHandler::<span class="name">sendFiltered</span> ( const <span class="type"><a href="qpoint.html">QPoint</a></span> & <i>position</i>, <span class="type">int</span> <i>state</i> )<tt> [protected]</tt></h3>
<p>Notifies the system of a new mouse event <i>after</i> applying a noise reduction filter. Returns true if the filtering process is successful; otherwise returns false. Note that if the filtering process failes, the system is not notified about the event.</p>
<p>The given <i>position</i> is the global position of the mouse. The <i>state</i> parameter is a bitmask of the <a href="qt.html#MouseButton-enum">Qt::MouseButton</a> enum's values indicating which mouse buttons are pressed.</p>
<p>The noice is reduced by calculating an average position from a collection of mouse event positions and then calling the <a href="qwsmousehandler.html#mouseChanged">mouseChanged</a>() function with the new position. The number of positions that is used is determined by the filter size.</p>
<p><b>See also </b><a href="qwsmousehandler.html#mouseChanged">mouseChanged</a>() and <a href="qwscalibratedmousehandler.html#setFilterSize">setFilterSize</a>().</p>
<!-- @@@sendFiltered -->
<!-- $$$setFilterSize[overload1]$$$setFilterSizeint -->
<h3 class="fn"><a name="setFilterSize"></a><span class="type">void</span> QWSCalibratedMouseHandler::<span class="name">setFilterSize</span> ( <span class="type">int</span> <i>size</i> )<tt> [protected]</tt></h3>
<p>Sets the size of the filter used in noise reduction to the given <i>size</i>.</p>
<p>The <a href="qwscalibratedmousehandler.html#sendFiltered">sendFiltered</a>() function reduces noice by calculating an average position from a collection of mouse event positions. The filter size determines the number of positions that forms the basis for these calculations.</p>
<p><b>See also </b><a href="qwscalibratedmousehandler.html#sendFiltered">sendFiltered</a>().</p>
<!-- @@@setFilterSize -->
<!-- $$$transform[overload1]$$$transformconstQPoint& -->
<h3 class="fn"><a name="transform"></a><span class="type"><a href="qpoint.html">QPoint</a></span> QWSCalibratedMouseHandler::<span class="name">transform</span> ( const <span class="type"><a href="qpoint.html">QPoint</a></span> & <i>position</i> )<tt> [protected]</tt></h3>
<p>Transforms the given <i>position</i> from device coordinates to screen coordinates, and returns the transformed position.</p>
<p>This function is typically called explicitly on the points passed to the <a href="qwsmousehandler.html#mouseChanged">QWSMouseHandler::mouseChanged</a>() function.</p>
<p>This implementation is a linear transformation using 7 parameters (<tt>a</tt>, <tt>b</tt>, <tt>c</tt>, <tt>d</tt>, <tt>e</tt>, <tt>f</tt> and <tt>s</tt>) to transform the device coordinates (<tt>Xd</tt>, <tt>Yd</tt>) into screen coordinates (<tt>Xs</tt>, <tt>Ys</tt>) using the following equations:</p>
<pre class="cpp"> s<span class="operator">*</span>Xs <span class="operator">=</span> a<span class="operator">*</span>Xd <span class="operator">+</span> b<span class="operator">*</span>Yd <span class="operator">+</span> c
s<span class="operator">*</span>Ys <span class="operator">=</span> d<span class="operator">*</span>Xd <span class="operator">+</span> e<span class="operator">*</span>Yd <span class="operator">+</span> f</pre>
<p><b>See also </b><a href="qwsmousehandler.html#mouseChanged">mouseChanged</a>().</p>
<!-- @@@transform -->
<!-- $$$writeCalibration[overload1]$$$writeCalibration -->
<h3 class="fn"><a name="writeCalibration"></a><span class="type">void</span> QWSCalibratedMouseHandler::<span class="name">writeCalibration</span> ()<tt> [protected]</tt></h3>
<p>Saves the current calibration parameters in <tt>/etc/pointercal</tt> (separated by whitespace and in alphabetical order).</p>
<p>You can override the default <tt>/etc/pointercal</tt> by specifying another file using the <a href="qt-embedded-envvars.html#pointercal-file">POINTERCAL_FILE</a> environment variable.</p>
<p><b>See also </b><a href="qwscalibratedmousehandler.html#readCalibration">readCalibration</a>().</p>
<!-- @@@writeCalibration -->
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