<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- qgesturerecognizer.cpp --> <title>QGestureRecognizer Class | Qt Widgets 5.12.2</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.12</td><td ><a href="qtwidgets-index.html">Qt Widgets</a></td><td ><a href="qtwidgets-module.html">C++ Classes</a></td><td >QGestureRecognizer</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right"><a href="qtwidgets-index.html">Qt 5.12.2 Reference Documentation</a></td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#public-types">Public Types</a></li> <li class="level1"><a href="#public-functions">Public Functions</a></li> <li class="level1"><a href="#static-public-members">Static Public Members</a></li> <li class="level1"><a href="#details">Detailed Description</a></li> <li class="level2"><a href="#recognizing-gestures">Recognizing Gestures</a></li> <li class="level2"><a href="#supporting-new-gestures">Supporting New Gestures</a></li> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">QGestureRecognizer Class</h1> <!-- $$$QGestureRecognizer-brief --> <p>The <a href="qgesturerecognizer.html">QGestureRecognizer</a> class provides the infrastructure for gesture recognition. <a href="#details">More...</a></p> <!-- @@@QGestureRecognizer --> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QGestureRecognizer></span> </td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += widgets</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign"> Qt 4.6</td></tr></table></div><ul> <li><a href="qgesturerecognizer-members.html">List of all members, including inherited members</a></li> </ul> <a name="public-types"></a> <h2 id="public-types">Public Types</h2> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> flags </td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#ResultFlag-enum">Result</a></b></td></tr> <tr><td class="memItemLeft rightAlign topAlign"> enum </td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#ResultFlag-enum">ResultFlag</a></b> { Ignore, MayBeGesture, TriggerGesture, FinishGesture, CancelGesture, ConsumeEventHint }</td></tr> </table></div> <a name="public-functions"></a> <h2 id="public-functions">Public Functions</h2> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#QGestureRecognizer">QGestureRecognizer</a></b>()</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#dtor.QGestureRecognizer">~QGestureRecognizer</a></b>()</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> virtual QGesture *</td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#create">create</a></b>(QObject *<i>target</i>)</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> virtual QGestureRecognizer::Result </td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#recognize">recognize</a></b>(QGesture *<i>gesture</i>, QObject *<i>watched</i>, QEvent *<i>event</i>) = 0</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#reset">reset</a></b>(QGesture *<i>gesture</i>)</td></tr> </table></div> <a name="static-public-members"></a> <h2 id="static-public-members">Static Public Members</h2> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> Qt::GestureType </td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#registerRecognizer">registerRecognizer</a></b>(QGestureRecognizer *<i>recognizer</i>)</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qgesturerecognizer.html#unregisterRecognizer">unregisterRecognizer</a></b>(Qt::GestureType <i>type</i>)</td></tr> </table></div> <a name="details"></a> <!-- $$$QGestureRecognizer-description --> <div class="descr"> <h2 id="details">Detailed Description</h2> <p>The <a href="qgesturerecognizer.html">QGestureRecognizer</a> 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. <a href="qgesturerecognizer.html">QGestureRecognizer</a> 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 in Widgets and Graphics View</a> document.</p> <a name="recognizing-gestures"></a> <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 name="supporting-new-gestures"></a> <h3 >Supporting New Gestures</h3> <p>To add support for new gestures, you need to derive from <a href="qgesturerecognizer.html">QGestureRecognizer</a> 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 <a href="qgesturerecognizer.html">QGestureRecognizer</a> 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> </div> <p><b>See also </b><a href="qgesture.html">QGesture</a>.</p> <!-- @@@QGestureRecognizer --> <div class="types"> <h2>Member Type Documentation</h2> <!-- $$$ResultFlag$$$Ignore$$$MayBeGesture$$$TriggerGesture$$$FinishGesture$$$CancelGesture$$$ResultState_Mask$$$ConsumeEventHint$$$ResultHint_Mask --> <h3 class="flags" id="ResultFlag-enum"><a name="ResultFlag-enum"></a>enum QGestureRecognizer::<span class="name">ResultFlag</span><br/>flags QGestureRecognizer::<span class="name">Result</span></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> <div class="table"><table class="valuelist"><tr valign="top" class="odd"><th class="tblConst">Constant</th><th class="tblval">Value</th><th class="tbldscr">Description</th></tr> <tr><td class="topAlign"><code>QGestureRecognizer::Ignore</code></td><td class="topAlign tblval"><code>0x0001</code></td><td class="topAlign">The event does not change the state of the recognizer.</td></tr> <tr><td class="topAlign"><code>QGestureRecognizer::MayBeGesture</code></td><td class="topAlign tblval"><code>0x0002</code></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"><code>QGestureRecognizer::TriggerGesture</code></td><td class="topAlign tblval"><code>0x0004</code></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"><code>QGestureRecognizer::FinishGesture</code></td><td class="topAlign tblval"><code>0x0008</code></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"><code>QGestureRecognizer::CancelGesture</code></td><td class="topAlign tblval"><code>0x0010</code></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"><code>QGestureRecognizer::ConsumeEventHint</code></td><td class="topAlign tblval"><code>0x0100</code></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></div> <p>The Result type is a typedef for <a href="../qtcore/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> <!-- @@@ResultFlag --> </div> <div class="func"> <h2>Member Function Documentation</h2> <!-- $$$QGestureRecognizer[overload1]$$$QGestureRecognizer --> <h3 class="fn" id="QGestureRecognizer"><a name="QGestureRecognizer"></a>QGestureRecognizer::<span class="name">QGestureRecognizer</span>()</h3> <p>Constructs a new gesture recognizer object.</p> <!-- @@@QGestureRecognizer --> <!-- $$$~QGestureRecognizer[overload1]$$$~QGestureRecognizer --> <h3 class="fn" id="dtor.QGestureRecognizer"><a name="dtor.QGestureRecognizer"></a><code>[virtual] </code>QGestureRecognizer::<span class="name">~QGestureRecognizer</span>()</h3> <p>Destroys the gesture recognizer.</p> <!-- @@@~QGestureRecognizer --> <!-- $$$create[overload1]$$$createQObject* --> <h3 class="fn" id="create"><a name="create"></a><code>[virtual] </code><span class="type"><a href="qgesture.html">QGesture</a></span> *QGestureRecognizer::<span class="name">create</span>(<span class="type"><a href="../qtcore/qobject.html">QObject</a></span> *<i>target</i>)</h3> <p>This function is called by Qt to create a new <a href="qgesture.html">QGesture</a> object for the given <i>target</i> (<a href="qwidget.html">QWidget</a> or <a href="qgraphicsobject.html">QGraphicsObject</a>).</p> <p>Reimplement this function to create a custom <a href="qgesture.html">QGesture</a>-derived gesture object if necessary.</p> <p>The application takes ownership of the created gesture object.</p> <!-- @@@create --> <!-- $$$recognize[overload1]$$$recognizeQGesture*QObject*QEvent* --> <h3 class="fn" id="recognize"><a name="recognize"></a><code>[pure virtual] </code><span class="type"><a href="qgesturerecognizer.html#ResultFlag-enum">QGestureRecognizer::Result</a></span> QGestureRecognizer::<span class="name">recognize</span>(<span class="type"><a href="qgesture.html">QGesture</a></span> *<i>gesture</i>, <span class="type"><a href="../qtcore/qobject.html">QObject</a></span> *<i>watched</i>, <span class="type"><a href="../qtcore/qevent.html">QEvent</a></span> *<i>event</i>)</h3> <p>Handles the given <i>event</i> for the <i>watched</i> object, updating the state of the <i>gesture</i> object as required, and returns a suitable result for the current recognition step.</p> <p>This function is called by the framework to allow the recognizer to filter input events dispatched to <a href="qwidget.html">QWidget</a> or <a href="qgraphicsobject.html">QGraphicsObject</a> instances that it is monitoring.</p> <p>The result reflects how much of the gesture has been recognized. The state of the <i>gesture</i> object is set depending on the result.</p> <p><b>See also </b><a href="qgesturerecognizer.html#ResultFlag-enum">QGestureRecognizer::Result</a>.</p> <!-- @@@recognize --> <!-- $$$registerRecognizer[overload1]$$$registerRecognizerQGestureRecognizer* --> <h3 class="fn" id="registerRecognizer"><a name="registerRecognizer"></a><code>[static] </code><span class="type"><a href="../qtcore/qt.html#GestureType-enum">Qt::GestureType</a></span> QGestureRecognizer::<span class="name">registerRecognizer</span>(<span class="type"><a href="qgesturerecognizer.html#QGestureRecognizer">QGestureRecognizer</a></span> *<i>recognizer</i>)</h3> <p>Registers the given <i>recognizer</i> in the gesture framework and returns a gesture ID for it.</p> <p>The application takes ownership of the <i>recognizer</i> and returns the gesture type ID associated with it. For gesture recognizers which handle custom <a href="qgesture.html">QGesture</a> objects (i.e., those which return <a href="../qtcore/qt.html#GestureType-enum">Qt::CustomGesture</a> in a <a href="qgesture.html#gestureType-prop">QGesture::gestureType</a>() function) the return value is a generated gesture ID with the <a href="../qtcore/qt.html#GestureType-enum">Qt::CustomGesture</a> flag set.</p> <p><b>See also </b><a href="qgesturerecognizer.html#unregisterRecognizer">unregisterRecognizer</a>(), <a href="qgesturerecognizer.html#create">QGestureRecognizer::create</a>(), and <a href="qgesture.html">QGesture</a>.</p> <!-- @@@registerRecognizer --> <!-- $$$reset[overload1]$$$resetQGesture* --> <h3 class="fn" id="reset"><a name="reset"></a><code>[virtual] </code><span class="type">void</span> QGestureRecognizer::<span class="name">reset</span>(<span class="type"><a href="qgesture.html">QGesture</a></span> *<i>gesture</i>)</h3> <p>This function is called by the framework to reset a given <i>gesture</i>.</p> <p>Reimplement this function to implement additional requirements for custom <a href="qgesture.html">QGesture</a> objects. This may be necessary if you implement a custom <a href="qgesture.html">QGesture</a> whose properties need special handling when the gesture is reset.</p> <!-- @@@reset --> <!-- $$$unregisterRecognizer[overload1]$$$unregisterRecognizerQt::GestureType --> <h3 class="fn" id="unregisterRecognizer"><a name="unregisterRecognizer"></a><code>[static] </code><span class="type">void</span> QGestureRecognizer::<span class="name">unregisterRecognizer</span>(<span class="type"><a href="../qtcore/qt.html#GestureType-enum">Qt::GestureType</a></span> <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> <!-- @@@unregisterRecognizer --> </div> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2019 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br/> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br/> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. </p> </div> </body> </html>