<?xml version="1.0" encoding="iso-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "DTD/xhtml1-strict.dtd"> <html><head><title>QGestureRecognizer Class Reference</title><style>h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm } a:link { color: #004faf; text-decoration: none } a:visited { color: #672967; text-decoration: none } td.postheader { font-family: sans-serif } tr.address { font-family: sans-serif } body { background: #ffffff; color: black; } </style></head><body><table border="0" cellpadding="0" cellspacing="0" width="100%"><tr /><td align="left" valign="top" width="32"><img align="left" border="0" height="32" src="images/rb-logo.png" width="32" /></td><td width="1">  </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a> · <a href="classes.html"><font color="#004faf">All Classes</font></a> · <a href="modules.html"><font color="#004faf">Modules</font></a></td></table><h1 align="center">QGestureRecognizer Class Reference<br /><sup><sup>[<a href="qtgui.html">QtGui</a> module]</sup></sup></h1><p>The QGestureRecognizer class provides the infrastructure for gesture recognition. <a href="#details">More...</a></p> <h3>Types</h3><ul><li><div class="fn" />class <b><a href="qgesturerecognizer-result.html">Result</a></b></li><li><div class="fn" />enum <b><a href="qgesturerecognizer.html#ResultFlag-enum">ResultFlag</a></b> { Ignore, MayBeGesture, TriggerGesture, FinishGesture, CancelGesture, ConsumeEventHint }</li></ul><h3>Methods</h3><ul><li><div class="fn" /><b><a href="qgesturerecognizer.html#QGestureRecognizer">__init__</a></b> (<i>self</i>)</li><li><div class="fn" /><b><a href="qgesturerecognizer.html#QGestureRecognizer-2">__init__</a></b> (<i>self</i>, QGestureRecognizer)</li><li><div class="fn" />QGesture <b><a href="qgesturerecognizer.html#create">create</a></b> (<i>self</i>, QObject <i>target</i>)</li><li><div class="fn" />Result <b><a href="qgesturerecognizer.html#recognize">recognize</a></b> (<i>self</i>, QGesture <i>state</i>, QObject <i>watched</i>, QEvent <i>event</i>)</li><li><div class="fn" /><b><a href="qgesturerecognizer.html#reset">reset</a></b> (<i>self</i>, QGesture <i>state</i>)</li></ul><h3>Static Methods</h3><ul><li><div class="fn" />Qt.GestureType <b><a href="qgesturerecognizer.html#registerRecognizer">registerRecognizer</a></b> (QGestureRecognizer <i>recognizer</i>)</li><li><div class="fn" /><b><a href="qgesturerecognizer.html#unregisterRecognizer">unregisterRecognizer</a></b> (Qt.GestureType <i>type</i>)</li></ul><a name="details" /><hr /><h2>Detailed Description</h2><p>The QGestureRecognizer class provides the infrastructure for gesture recognition.</p> <p>Gesture recognizers are responsible for creating and managing <a href="qgesture.html">QGesture</a> objects and monitoring input events sent to <a href="qwidget.html">QWidget</a> and <a href="qgraphicsobject.html">QGraphicsObject</a> subclasses. QGestureRecognizer is the base class for implementing custom gestures.</p> <p>Developers that only need to provide gesture recognition for standard gestures do not need to use this class directly. Instances will be created behind the scenes by the framework.</p> <p>For an overview of gesture handling in Qt and information on using gestures in your applications, see the <a href="gestures-overview.html">Gestures Programming</a> document.</p> <a id="recognizing-gestures" name="recognizing-gestures" /> <h3>Recognizing Gestures</h3> <p>The process of recognizing gestures involves filtering input events sent to specific objects, and modifying the associated <a href="qgesture.html">QGesture</a> objects to include relevant information about the user's input.</p> <p>Gestures are created when the framework calls <a href="qgesturerecognizer.html#create">create</a>() to handle user input for a particular instance of a <a href="qwidget.html">QWidget</a> or <a href="qgraphicsobject.html">QGraphicsObject</a> subclass. A <a href="qgesture.html">QGesture</a> object is created for each widget or item that is configured to use gestures.</p> <p>Once a <a href="qgesture.html">QGesture</a> has been created for a target object, the gesture recognizer will receive events for it in its <a href="qgesturerecognizer.html#recognize">recognize</a>() handler function.</p> <p>When a gesture is canceled, the <a href="qgesturerecognizer.html#reset">reset</a>() function is called, giving the recognizer the chance to update the appropriate properties in the corresponding <a href="qgesture.html">QGesture</a> object.</p> <a id="supporting-new-gestures" name="supporting-new-gestures" /> <h3>Supporting New Gestures</h3> <p>To add support for new gestures, you need to derive from QGestureRecognizer to create a custom recognizer class, construct an instance of this class, and register it with the application by calling <a href="qgesturerecognizer.html#registerRecognizer">QGestureRecognizer.registerRecognizer</a>(). You can also subclass <a href="qgesture.html">QGesture</a> to create a custom gesture class, or rely on dynamic properties to express specific details of the gesture you want to handle.</p> <p>Your custom QGestureRecognizer subclass needs to reimplement the <a href="qgesturerecognizer.html#recognize">recognize</a>() function to handle and filter the incoming input events for <a href="qwidget.html">QWidget</a> and <a href="qgraphicsobject.html">QGraphicsObject</a> subclasses. Although the logic for gesture recognition is implemented in this function, you can store persistent information about the state of the recognition process in the <a href="qgesture.html">QGesture</a> object supplied. The <a href="qgesturerecognizer.html#recognize">recognize</a>() function must return a value of <a href="qgesturerecognizer.html#ResultFlag-enum">QGestureRecognizer.Result</a> that indicates the state of recognition for a given gesture and target object. This determines whether or not a gesture event will be delivered to a target object.</p> <p>If you choose to represent a gesture by a custom <a href="qgesture.html">QGesture</a> subclass, you will need to reimplement the <a href="qgesturerecognizer.html#create">create</a>() function to construct instances of your gesture class. Similarly, you may need to reimplement the <a href="qgesturerecognizer.html#reset">reset</a>() function if your custom gesture objects need to be specially handled when a gesture is canceled.</p> <hr /><h2>Type Documentation</h2><h3 class="fn"><a name="ResultFlag-enum" />QGestureRecognizer.ResultFlag</h3><p>This enum describes the result of the current event filtering step in a gesture recognizer state machine.</p> <p>The result consists of a state value (one of Ignore, MayBeGesture, TriggerGesture, FinishGesture, CancelGesture) and an optional hint (ConsumeEventHint).</p> <table class="valuelist"> <tr class="odd" valign="top"> <th class="tblConst">Constant</th> <th class="tblval">Value</th> <th class="tbldscr">Description</th> </tr> <tr> <td class="topAlign"><tt>QGestureRecognizer.Ignore</tt></td> <td class="topAlign"><tt>0x0001</tt></td> <td class="topAlign">The event does not change the state of the recognizer.</td> </tr> <tr> <td class="topAlign"><tt>QGestureRecognizer.MayBeGesture</tt></td> <td class="topAlign"><tt>0x0002</tt></td> <td class="topAlign">The event changed the internal state of the recognizer, but it isn't clear yet if it is a gesture or not. The recognizer needs to filter more events to decide. Gesture recognizers in the MayBeGesture state may be reset automatically if they take too long to recognize gestures.</td> </tr> <tr> <td class="topAlign"> <tt>QGestureRecognizer.TriggerGesture</tt></td> <td class="topAlign"><tt>0x0004</tt></td> <td class="topAlign">The gesture has been triggered and the appropriate <a href="qgesture.html">QGesture</a> object will be delivered to the target as a part of a <a href="qgestureevent.html">QGestureEvent</a>.</td> </tr> <tr> <td class="topAlign"> <tt>QGestureRecognizer.FinishGesture</tt></td> <td class="topAlign"><tt>0x0008</tt></td> <td class="topAlign">The gesture has been finished successfully and the appropriate <a href="qgesture.html">QGesture</a> object will be delivered to the target as a part of a <a href="qgestureevent.html">QGestureEvent</a>.</td> </tr> <tr> <td class="topAlign"> <tt>QGestureRecognizer.CancelGesture</tt></td> <td class="topAlign"><tt>0x0010</tt></td> <td class="topAlign">The event made it clear that it is not a gesture. If the gesture recognizer was in GestureTriggered state before, then the gesture is canceled and the appropriate <a href="qgesture.html">QGesture</a> object will be delivered to the target as a part of a <a href="qgestureevent.html">QGestureEvent</a>.</td> </tr> <tr> <td class="topAlign"> <tt>QGestureRecognizer.ConsumeEventHint</tt></td> <td class="topAlign"><tt>0x0100</tt></td> <td class="topAlign">This hint specifies that the gesture framework should consume the filtered event and not deliver it to the receiver.</td> </tr> </table> <p>The Result type is a typedef for <a href="qflags.html">QFlags</a><ResultFlag>. It stores an OR combination of ResultFlag values.</p> <p><b>See also</b> <a href="qgesturerecognizer.html#recognize">QGestureRecognizer.recognize</a>().</p> <hr /><h2>Method Documentation</h2><h3 class="fn"><a name="QGestureRecognizer" />QGestureRecognizer.__init__ (<i>self</i>)</h3><p>Constructs a new gesture recognizer object.</p> <h3 class="fn"><a name="QGestureRecognizer-2" />QGestureRecognizer.__init__ (<i>self</i>, <a href="qgesturerecognizer.html">QGestureRecognizer</a>)</h3><h3 class="fn"><a name="create" /><a href="qgesture.html">QGesture</a> QGestureRecognizer.create (<i>self</i>, <a href="qobject.html">QObject</a> <i>target</i>)</h3><p>This function is called by Qt to create a new <a href="qgesture.html">QGesture</a> object for the given <i>target</i> (<a href="qwidget.html">QWidget</a> or <a href="qgraphicsobject.html">QGraphicsObject</a>).</p> <p>Reimplement this function to create a custom <a href="qgesture.html">QGesture</a>-derived gesture object if necessary.</p> <p>The application takes ownership of the created gesture object.</p> <h3 class="fn"><a name="recognize" /><a href="qgesturerecognizer-result.html">Result</a> QGestureRecognizer.recognize (<i>self</i>, <a href="qgesture.html">QGesture</a> <i>state</i>, <a href="qobject.html">QObject</a> <i>watched</i>, <a href="qevent.html">QEvent</a> <i>event</i>)</h3><p>This method is abstract and should be reimplemented in any sub-class.</p><p>Handles the given <i>event</i> for the <i>watched</i> object, updating the state of the <i>gesture</i> object as required, and returns a suitable result for the current recognition step.</p> <p>This function is called by the framework to allow the recognizer to filter input events dispatched to <a href="qwidget.html">QWidget</a> or <a href="qgraphicsobject.html">QGraphicsObject</a> instances that it is monitoring.</p> <p>The result reflects how much of the gesture has been recognized. The state of the <i>gesture</i> object is set depending on the result.</p> <p><b>See also</b> <a href="qgesturerecognizer.html#ResultFlag-enum">QGestureRecognizer.Result</a>.</p> <h3 class="fn"><a name="registerRecognizer" /><a href="qt.html#GestureType-enum">Qt.GestureType</a> QGestureRecognizer.registerRecognizer (<a href="qgesturerecognizer.html">QGestureRecognizer</a> <i>recognizer</i>)</h3><p>The <i>recognizer</i> argument has it's ownership transferred to Qt.</p><p>Registers the given <i>recognizer</i> in the gesture framework and returns a gesture ID for it.</p> <p>The application takes ownership of the <i>recognizer</i> and returns the gesture type ID associated with it. For gesture recognizers which handle custom <a href="qgesture.html">QGesture</a> objects (i.e., those which return <a href="qt.html#GestureType-enum">Qt.CustomGesture</a> in a <a href="qgesture.html#gestureType-prop">QGesture.gestureType</a>() function) the return value is a generated gesture ID with the <a href="qt.html#GestureType-enum">Qt.CustomGesture</a> flag set.</p> <p><b>See also</b> <a href="qgesturerecognizer.html#unregisterRecognizer">unregisterRecognizer</a>(), <a href="qgesturerecognizer.html#create">QGestureRecognizer.create</a>(), and <a href="qgesture.html">QGesture</a>.</p> <h3 class="fn"><a name="reset" />QGestureRecognizer.reset (<i>self</i>, <a href="qgesture.html">QGesture</a> <i>state</i>)</h3><p>This function is called by the framework to reset a given <i>gesture</i>.</p> <p>Reimplement this function to implement additional requirements for custom <a href="qgesture.html">QGesture</a> objects. This may be necessary if you implement a custom <a href="qgesture.html">QGesture</a> whose properties need special handling when the gesture is reset.</p> <h3 class="fn"><a name="unregisterRecognizer" />QGestureRecognizer.unregisterRecognizer (<a href="qt.html#GestureType-enum">Qt.GestureType</a> <i>type</i>)</h3><p>Unregisters all gesture recognizers of the specified <i>type</i>.</p> <p><b>See also</b> <a href="qgesturerecognizer.html#registerRecognizer">registerRecognizer</a>().</p> <address><hr /><div align="center"><table border="0" cellspacing="0" width="100%"><tr class="address"><td align="left" width="25%">PyQt 4.10.3 for X11</td><td align="center" width="50%">Copyright © <a href="http://www.riverbankcomputing.com">Riverbank Computing Ltd</a> and <a href="http://www.qtsoftware.com">Nokia</a> 2012</td><td align="right" width="25%">Qt 4.8.5</td></tr></table></div></address></body></html>