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<?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 }
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</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 4.12.1 for X11</td><td align="center" width="50%">Copyright © <a href="http://www.riverbankcomputing.com">Riverbank Computing Ltd</a> and <a href="http://www.qt.io">The Qt Company</a> 2015</td><td align="right" width="25%">Qt 4.8.7</td></tr></table></div></address></body></html>
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