<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- qeventloop.cpp --> <title>QEventLoop Class | Qt Core 5.12.6</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="qtcore-index.html">Qt Core</a></td><td ><a href="qtcore-module.html">C++ Classes</a></td><td >QEventLoop</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right"><a href="qtcore-index.html">Qt 5.12.6 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="#reimplemented-public-functions">Reimplemented Public Functions</a></li> <li class="level1"><a href="#public-slots">Public Slots</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> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">QEventLoop Class</h1> <!-- $$$QEventLoop-brief --> <p>The <a href="qeventloop.html">QEventLoop</a> class provides a means of entering and leaving an event loop. <a href="#details">More...</a></p> <!-- @@@QEventLoop --> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QEventLoop></span> </td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += core</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Inherits:</td><td class="memItemRight bottomAlign"> <a href="qobject.html">QObject</a></td></tr></table></div><ul> <li><a href="qeventloop-members.html">List of all members, including inherited members</a></li> <li><a href="qeventloop-obsolete.html">Obsolete 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"> enum </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#ProcessEventsFlag-enum">ProcessEventsFlag</a></b> { AllEvents, ExcludeUserInputEvents, ExcludeSocketNotifiers, WaitForMoreEvents }</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> flags </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#ProcessEventsFlag-enum">ProcessEventsFlags</a></b></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="qeventloop.html#QEventLoop">QEventLoop</a></b>(QObject *<i>parent</i> = nullptr)</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#dtor.QEventLoop">~QEventLoop</a></b>()</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#exec">exec</a></b>(QEventLoop::ProcessEventsFlags <i>flags</i> = AllEvents)</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#exit">exit</a></b>(int <i>returnCode</i> = 0)</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#isRunning">isRunning</a></b>() const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#processEvents">processEvents</a></b>(QEventLoop::ProcessEventsFlags <i>flags</i> = AllEvents)</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#processEvents-1">processEvents</a></b>(QEventLoop::ProcessEventsFlags <i>flags</i>, int <i>maxTime</i>)</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#wakeUp">wakeUp</a></b>()</td></tr> </table></div> <a name="reimplemented-public-functions"></a> <h2 id="reimplemented-public-functions">Reimplemented Public Functions</h2> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> virtual bool </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#event">event</a></b>(QEvent *<i>event</i>) override</td></tr> </table></div> <ul> <li class="fn">32 public functions inherited from <a href="qobject.html#public-functions">QObject</a></li> </ul> <a name="public-slots"></a> <h2 id="public-slots">Public Slots</h2> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#quit">quit</a></b>()</td></tr> </table></div> <ul> <li class="fn">1 public slot inherited from <a href="qobject.html#public-slots">QObject</a></li> </ul> <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"> const QMetaObject </td><td class="memItemRight bottomAlign"><b><a href="qeventloop.html#staticMetaObject-var">staticMetaObject</a></b></td></tr> </table></div> <ul> <li class="fn">10 static public members inherited from <a href="qobject.html#static-public-members">QObject</a></li> </ul> <h3>Additional Inherited Members</h3> <ul> <li class="fn">1 property inherited from <a href="qobject.html#properties">QObject</a></li> <li class="fn">2 signals inherited from <a href="qobject.html#signals">QObject</a></li> <li class="fn">9 protected functions inherited from <a href="qobject.html#protected-functions">QObject</a></li> </ul> <a name="details"></a> <!-- $$$QEventLoop-description --> <div class="descr"> <h2 id="details">Detailed Description</h2> <p>The <a href="qeventloop.html">QEventLoop</a> class provides a means of entering and leaving an event loop.</p> <p>At any time, you can create a <a href="qeventloop.html">QEventLoop</a> object and call <a href="qeventloop.html#exec">exec</a>() on it to start a local event loop. From within the event loop, calling <a href="qeventloop.html#exit">exit</a>() will force <a href="qeventloop.html#exec">exec</a>() to return.</p> </div> <p><b>See also </b><a href="qabstracteventdispatcher.html">QAbstractEventDispatcher</a>.</p> <!-- @@@QEventLoop --> <div class="types"> <h2>Member Type Documentation</h2> <!-- $$$ProcessEventsFlag$$$AllEvents$$$ExcludeUserInputEvents$$$ExcludeSocketNotifiers$$$WaitForMoreEvents$$$X11ExcludeTimers$$$EventLoopExec$$$DialogExec --> <h3 class="flags" id="ProcessEventsFlag-enum"><a name="ProcessEventsFlag-enum"></a>enum QEventLoop::<span class="name">ProcessEventsFlag</span><br/>flags QEventLoop::<span class="name">ProcessEventsFlags</span></h3> <p>This enum controls the types of events processed by the <a href="qeventloop.html#processEvents">processEvents</a>() functions.</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>QEventLoop::AllEvents</code></td><td class="topAlign tblval"><code>0x00</code></td><td class="topAlign">All events. Note that <a href="qevent.html#Type-enum">DeferredDelete</a> events are processed specially. See <a href="qobject.html#deleteLater">QObject::deleteLater</a>() for more details.</td></tr> <tr><td class="topAlign"><code>QEventLoop::ExcludeUserInputEvents</code></td><td class="topAlign tblval"><code>0x01</code></td><td class="topAlign">Do not process user input events, such as ButtonPress and KeyPress. Note that the events are not discarded; they will be delivered the next time <a href="qeventloop.html#processEvents">processEvents</a>() is called without the ExcludeUserInputEvents flag.</td></tr> <tr><td class="topAlign"><code>QEventLoop::ExcludeSocketNotifiers</code></td><td class="topAlign tblval"><code>0x02</code></td><td class="topAlign">Do not process socket notifier events. Note that the events are not discarded; they will be delivered the next time <a href="qeventloop.html#processEvents">processEvents</a>() is called without the ExcludeSocketNotifiers flag.</td></tr> <tr><td class="topAlign"><code>QEventLoop::WaitForMoreEvents</code></td><td class="topAlign tblval"><code>0x04</code></td><td class="topAlign">Wait for events if no pending events are available.</td></tr> </table></div> <p>The ProcessEventsFlags type is a typedef for <a href="qflags.html">QFlags</a><ProcessEventsFlag>. It stores an OR combination of ProcessEventsFlag values.</p> <p><b>See also </b><a href="qeventloop.html#processEvents">processEvents</a>().</p> <!-- @@@ProcessEventsFlag --> </div> <div class="func"> <h2>Member Function Documentation</h2> <!-- $$$QEventLoop[overload1]$$$QEventLoopQObject* --> <h3 class="fn" id="QEventLoop"><a name="QEventLoop"></a>QEventLoop::<span class="name">QEventLoop</span>(<span class="type"><a href="qobject.html#QObject">QObject</a></span> *<i>parent</i> = nullptr)</h3> <p>Constructs an event loop object with the given <i>parent</i>.</p> <!-- @@@QEventLoop --> <!-- $$$~QEventLoop[overload1]$$$~QEventLoop --> <h3 class="fn" id="dtor.QEventLoop"><a name="dtor.QEventLoop"></a><code>[virtual] </code>QEventLoop::<span class="name">~QEventLoop</span>()</h3> <p>Destroys the event loop object.</p> <!-- @@@~QEventLoop --> <!-- $$$event[overload1]$$$eventQEvent* --> <h3 class="fn" id="event"><a name="event"></a><code>[override virtual] </code><span class="type">bool</span> QEventLoop::<span class="name">event</span>(<span class="type"><a href="qevent.html">QEvent</a></span> *<i>event</i>)</h3> <p>Reimplemented from <a href="qobject.html#event">QObject::event</a>().</p> <!-- @@@event --> <!-- $$$exec[overload1]$$$execQEventLoop::ProcessEventsFlags --> <h3 class="fn" id="exec"><a name="exec"></a><span class="type">int</span> QEventLoop::<span class="name">exec</span>(<span class="type"><a href="qeventloop.html#ProcessEventsFlag-enum">QEventLoop::ProcessEventsFlags</a></span> <i>flags</i> = AllEvents)</h3> <p>Enters the main event loop and waits until <a href="qeventloop.html#exit">exit</a>() is called. Returns the value that was passed to <a href="qeventloop.html#exit">exit</a>().</p> <p>If <i>flags</i> are specified, only events of the types allowed by the <i>flags</i> will be processed.</p> <p>It is necessary to call this function to start event handling. The main event loop receives events from the window system and dispatches these to the application widgets.</p> <p>Generally speaking, no user interaction can take place before calling exec(). As a special case, modal widgets like <a href="../qtwidgets/qmessagebox.html">QMessageBox</a> can be used before calling exec(), because modal widgets use their own local event loop.</p> <p>To make your application perform idle processing (i.e. executing a special function whenever there are no pending events), use a <a href="qtimer.html">QTimer</a> with 0 timeout. More sophisticated idle processing schemes can be achieved using <a href="qeventloop.html#processEvents">processEvents</a>().</p> <p><b>See also </b><a href="qcoreapplication.html#quit">QCoreApplication::quit</a>(), <a href="qeventloop.html#exit">exit</a>(), and <a href="qeventloop.html#processEvents">processEvents</a>().</p> <!-- @@@exec --> <!-- $$$exit[overload1]$$$exitint --> <h3 class="fn" id="exit"><a name="exit"></a><span class="type">void</span> QEventLoop::<span class="name">exit</span>(<span class="type">int</span> <i>returnCode</i> = 0)</h3> <p>Tells the event loop to exit with a return code.</p> <p>After this function has been called, the event loop returns from the call to <a href="qeventloop.html#exec">exec</a>(). The <a href="qeventloop.html#exec">exec</a>() function returns <i>returnCode</i>.</p> <p>By convention, a <i>returnCode</i> of 0 means success, and any non-zero value indicates an error.</p> <p>Note that unlike the C library function of the same name, this function <i>does</i> return to the caller -- it is event processing that stops.</p> <p><b>See also </b><a href="qcoreapplication.html#quit">QCoreApplication::quit</a>(), <a href="qeventloop.html#quit">quit</a>(), and <a href="qeventloop.html#exec">exec</a>().</p> <!-- @@@exit --> <!-- $$$isRunning[overload1]$$$isRunning --> <h3 class="fn" id="isRunning"><a name="isRunning"></a><span class="type">bool</span> QEventLoop::<span class="name">isRunning</span>() const</h3> <p>Returns <code>true</code> if the event loop is running; otherwise returns false. The event loop is considered running from the time when <a href="qeventloop.html#exec">exec</a>() is called until <a href="qeventloop.html#exit">exit</a>() is called.</p> <p><b>See also </b><a href="qeventloop.html#exec">exec</a>() and <a href="qeventloop.html#exit">exit</a>().</p> <!-- @@@isRunning --> <!-- $$$processEvents[overload1]$$$processEventsQEventLoop::ProcessEventsFlags --> <h3 class="fn" id="processEvents"><a name="processEvents"></a><span class="type">bool</span> QEventLoop::<span class="name">processEvents</span>(<span class="type"><a href="qeventloop.html#ProcessEventsFlag-enum">QEventLoop::ProcessEventsFlags</a></span> <i>flags</i> = AllEvents)</h3> <p>Processes pending events that match <i>flags</i> until there are no more events to process. Returns <code>true</code> if pending events were handled; otherwise returns <code>false</code>.</p> <p>This function is especially useful if you have a long running operation and want to show its progress without allowing user input; i.e. by using the <a href="qeventloop.html#ProcessEventsFlag-enum">ExcludeUserInputEvents</a> flag.</p> <p>This function is simply a wrapper for <a href="qabstracteventdispatcher.html#processEvents">QAbstractEventDispatcher::processEvents</a>(). See the documentation for that function for details.</p> <!-- @@@processEvents --> <!-- $$$processEvents$$$processEventsQEventLoop::ProcessEventsFlagsint --> <h3 class="fn" id="processEvents-1"><a name="processEvents-1"></a><span class="type">void</span> QEventLoop::<span class="name">processEvents</span>(<span class="type"><a href="qeventloop.html#ProcessEventsFlag-enum">QEventLoop::ProcessEventsFlags</a></span> <i>flags</i>, <span class="type">int</span> <i>maxTime</i>)</h3> <p>Process pending events that match <i>flags</i> for a maximum of <i>maxTime</i> milliseconds, or until there are no more events to process, whichever is shorter. This function is especially useful if you have a long running operation and want to show its progress without allowing user input, i.e. by using the <a href="qeventloop.html#ProcessEventsFlag-enum">ExcludeUserInputEvents</a> flag.</p> <p><b>Notes:</b></p> <ul> <li>This function does not process events continuously; it returns after all available events are processed.</li> <li>Specifying the <a href="qeventloop.html#ProcessEventsFlag-enum">WaitForMoreEvents</a> flag makes no sense and will be ignored.</li> </ul> <!-- @@@processEvents --> <!-- $$$quit[overload1]$$$quit --> <h3 class="fn" id="quit"><a name="quit"></a><code>[slot] </code><span class="type">void</span> QEventLoop::<span class="name">quit</span>()</h3> <p>Tells the event loop to exit normally.</p> <p>Same as exit(0).</p> <p><b>See also </b><a href="qcoreapplication.html#quit">QCoreApplication::quit</a>() and <a href="qeventloop.html#exit">exit</a>().</p> <!-- @@@quit --> <!-- $$$wakeUp[overload1]$$$wakeUp --> <h3 class="fn" id="wakeUp"><a name="wakeUp"></a><span class="type">void</span> QEventLoop::<span class="name">wakeUp</span>()</h3> <p>Wakes up the event loop.</p> <p><b>See also </b><a href="qabstracteventdispatcher.html#wakeUp">QAbstractEventDispatcher::wakeUp</a>().</p> <!-- @@@wakeUp --> </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>