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<td >Qt 5.9</td><td ><a href="qtcore-index.html">Qt Core</a></td><td ><a href="qtcore-module.html">C++ Classes</a></td><td >QLoggingCategory</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td>
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<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="#macros">Macros</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
<li class="level2"><a href="#creating-category-objects">Creating Category Objects</a></li>
<li class="level2"><a href="#checking-category-configuration">Checking Category Configuration</a></li>
<li class="level2"><a href="#default-category-configuration">Default Category Configuration</a></li>
<li class="level2"><a href="#configuring-categories">Configuring Categories</a></li>
<li class="level2"><a href="#printing-the-category">Printing the Category</a></li>
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<h1 class="title">QLoggingCategory Class</h1>
<!-- $$$QLoggingCategory-brief -->
<p>The <a href="qloggingcategory.html">QLoggingCategory</a> class represents a category, or 'area' in the logging infrastructure. <a href="#details">More...</a></p>
<!-- @@@QLoggingCategory -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QLoggingCategory></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"> Since:</td><td class="memItemRight bottomAlign"> Qt 5.2</td></tr></table></div><ul>
<li><a href="qloggingcategory-members.html">List of all members, including inherited members</a></li>
</ul>
<p><b>Note:</b> All functions in this class are thread-safe.</p>
<a name="public-types"></a>
<h2 id="public-types">Public Types</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> typedef </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#CategoryFilter-typedef">CategoryFilter</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="qloggingcategory.html#QLoggingCategory">QLoggingCategory</a></b>(const char *<i>category</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#QLoggingCategory-1">QLoggingCategory</a></b>(const char *<i>category</i>, QtMsgType <i>enableForLevel</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#dtor.QLoggingCategory">~QLoggingCategory</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const char *</td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#categoryName">categoryName</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#isCriticalEnabled">isCriticalEnabled</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#isDebugEnabled">isDebugEnabled</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#isEnabled">isEnabled</a></b>(QtMsgType <i>msgtype</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#isInfoEnabled">isInfoEnabled</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#isWarningEnabled">isWarningEnabled</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#setEnabled">setEnabled</a></b>(QtMsgType <i>type</i>, bool <i>enable</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QLoggingCategory &</td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#operator-28-29">operator()</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const QLoggingCategory &</td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#operator-28-29-1">operator()</a></b>() const</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"> QLoggingCategory *</td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#defaultCategory">defaultCategory</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> CategoryFilter </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#installFilter">installFilter</a></b>(CategoryFilter <i>filter</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#setFilterRules">setFilterRules</a></b>(const QString &<i>rules</i>)</td></tr>
</table></div>
<a name="macros"></a>
<h2 id="macros">Macros</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#Q_DECLARE_LOGGING_CATEGORY">Q_DECLARE_LOGGING_CATEGORY</a></b>(<i>name</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#Q_LOGGING_CATEGORY">Q_LOGGING_CATEGORY</a></b>(<i>name</i>, <i>string</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#Q_LOGGING_CATEGORY-1">Q_LOGGING_CATEGORY</a></b>(<i>name</i>, <i>string</i>, <i>msgType</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#qCCritical">qCCritical</a></b>(<i>category</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#qCCritical-1">qCCritical</a></b>(<i>category</i>, const char *<i>message</i>, <i>...</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#qCDebug">qCDebug</a></b>(<i>category</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#qCDebug-1">qCDebug</a></b>(<i>category</i>, const char *<i>message</i>, <i>...</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#qCInfo">qCInfo</a></b>(<i>category</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#qCInfo-1">qCInfo</a></b>(<i>category</i>, const char *<i>message</i>, <i>...</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#qCWarning">qCWarning</a></b>(<i>category</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qloggingcategory.html#qCWarning-1">qCWarning</a></b>(<i>category</i>, const char *<i>message</i>, <i>...</i>)</td></tr>
</table></div>
<a name="details"></a>
<!-- $$$QLoggingCategory-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qloggingcategory.html">QLoggingCategory</a> class represents a category, or 'area' in the logging infrastructure.</p>
<p><a href="qloggingcategory.html">QLoggingCategory</a> represents a certain logging category - identified by a string - at runtime. A category can be configured to enable or disable logging of messages per message type. Whether a message type is enabled or not can be checked with the <a href="qloggingcategory.html#isDebugEnabled">isDebugEnabled</a>(), <a href="qloggingcategory.html#isInfoEnabled">isInfoEnabled</a>(), <a href="qloggingcategory.html#isWarningEnabled">isWarningEnabled</a>(), and <a href="qloggingcategory.html#isCriticalEnabled">isCriticalEnabled</a>() methods.</p>
<p>All objects are meant to be configured by a common registry (see also <a href="qloggingcategory.html#configuring-categories">Configuring Categories</a>). Different objects can also represent the same category. It is therefore not recommended to export objects across module boundaries, nor to manipulate the objects directly, nor to inherit from <a href="qloggingcategory.html">QLoggingCategory</a>.</p>
<a name="creating-category-objects"></a>
<h3 >Creating Category Objects</h3>
<p>The <a href="qloggingcategory.html#Q_DECLARE_LOGGING_CATEGORY">Q_DECLARE_LOGGING_CATEGORY</a>() and <a href="qloggingcategory.html#Q_LOGGING_CATEGORY">Q_LOGGING_CATEGORY</a>() macros conveniently declare and create <a href="qloggingcategory.html">QLoggingCategory</a> objects:</p>
<pre class="cpp">
<span class="comment">// in a header</span>
Q_DECLARE_LOGGING_CATEGORY(driverUsb)
<span class="comment">// in one source file</span>
Q_LOGGING_CATEGORY(driverUsb<span class="operator">,</span> <span class="string">"driver.usb"</span>)
</pre>
<p><b>Note: </b>Category names are free text. However, to allow easy configuration of the categories using <a href="qloggingcategory.html#logging-rules">Logging Rules</a> the names should follow some rules:</p><ul>
<li>Use letters and numbers only.</li>
<li>Further structure categories into common areas by using dots.</li>
<li>Avoid the category names <code>debug</code>, <code>info</code>, <code>warning</code>, and <code>critical</code>.</li>
<li>Category names starting with <code>qt</code> are reserved for Qt modules.</li>
</ul>
<p><a href="qloggingcategory.html">QLoggingCategory</a> objects implicitly defined by <a href="qloggingcategory.html#Q_LOGGING_CATEGORY">Q_LOGGING_CATEGORY</a>() are created on first use in a thread-safe manner.</p>
<a name="checking-category-configuration"></a>
<h3 >Checking Category Configuration</h3>
<p><a href="qloggingcategory.html">QLoggingCategory</a> provides <a href="qloggingcategory.html#isDebugEnabled">isDebugEnabled</a>(), <a href="qloggingcategory.html#isInfoEnabled">isInfoEnabled</a>(), <a href="qloggingcategory.html#isWarningEnabled">isWarningEnabled</a>(), <a href="qloggingcategory.html#isCriticalEnabled">isCriticalEnabled</a>(), as well as <a href="qloggingcategory.html#isEnabled">isEnabled</a>() to check whether messages for the given message type should be logged.</p>
<p><b>Note: </b>The <a href="qloggingcategory.html#qCDebug">qCDebug</a>(), <a href="qloggingcategory.html#qCWarning">qCWarning</a>(), <a href="qloggingcategory.html#qCCritical">qCCritical</a>() macros prevent arguments from being evaluated if the respective message types are not enabled for the category, so explicit checking is not needed:</p><pre class="cpp">
<span class="comment">// usbEntries() will only be called if driverUsb category is enabled</span>
qCDebug(driverUsb) <span class="operator"><</span><span class="operator"><</span> <span class="string">"devices: "</span> <span class="operator"><</span><span class="operator"><</span> usbEntries();
</pre>
<a name="default-category-configuration"></a>
<h3 >Default Category Configuration</h3>
<p>Both the <a href="qloggingcategory.html">QLoggingCategory</a> constructor and the <a href="qloggingcategory.html#Q_LOGGING_CATEGORY">Q_LOGGING_CATEGORY</a>() macro accept an optional <a href="qtglobal.html#QtMsgType-enum">QtMsgType</a> argument, which disables all message types with a lower severity. That is, a category declared with</p>
<pre class="cpp">
Q_LOGGING_CATEGORY(driverUsbEvents<span class="operator">,</span> <span class="string">"driver.usb.events"</span><span class="operator">,</span> <span class="type"><a href="qtglobal.html#QtMsgType-enum">QtWarningMsg</a></span>)
</pre>
<p>will log messages of type <code>QtWarningMsg</code>, <code>QtCriticalMsg</code>, <code>QtFatalMsg</code>, but will ignore messages of type <code>QtDebugMsg</code> and <code>QtInfoMsg</code>.</p>
<p>If no argument is passed, all messages will be logged.</p>
<a name="configuring-categories"></a>
<h3 >Configuring Categories</h3>
<p>The default configuration of categories can be overridden either by setting logging rules, or by installing a custom filter.</p>
<a name="logging-rules"></a>
<h4 >Logging Rules</h4>
<p>Logging rules allow logging for categories to be enabled or disabled in a flexible way. Rules are specified in text, where every line must have the format</p>
<pre class="cpp">
<span class="operator"><</span>category<span class="operator">></span><span class="operator">[</span><span class="operator">.</span><span class="operator"><</span>type<span class="operator">></span><span class="operator">]</span> <span class="operator">=</span> <span class="keyword">true</span><span class="operator">|</span><span class="keyword">false</span>
</pre>
<p><code><category></code> is the name of the category, potentially with <code>*</code> as a wildcard symbol as the first or last character (or at both positions). The optional <code><type></code> must be either <code>debug</code>, <code>info</code>, <code>warning</code>, or <code>critical</code>. Lines that do not fit this scheme are ignored.</p>
<p>Rules are evaluated in text order, from first to last. That is, if two rules apply to a category/type, the rule that comes later is applied.</p>
<p>Rules can be set via <a href="qloggingcategory.html#setFilterRules">setFilterRules</a>(). Since Qt 5.3, logging rules can also be set in the <code>QT_LOGGING_RULES</code> environment variable, and are automatically loaded from the <code>[Rules]</code> section of a logging configuration file. Such configuration files are looked up in the QtProject configuration directory, or explicitly set in a <code>QT_LOGGING_CONF</code> environment variable:</p>
<pre class="cpp">
<span class="operator">[</span>Rules<span class="operator">]</span>
<span class="operator">*</span><span class="operator">.</span>debug<span class="operator">=</span><span class="keyword">false</span>
driver<span class="operator">.</span>usb<span class="operator">.</span>debug<span class="operator">=</span><span class="keyword">true</span>
</pre>
<p>Rules set by <a href="qloggingcategory.html#setFilterRules">setFilterRules</a>() take precedence over rules specified in the QtProject configuration directory, and can, in turn, be overwritten by rules from the configuration file specified by <code>QT_LOGGING_CONF</code>, and rules set by <code>QT_LOGGING_RULES</code>.</p>
<p>Since Qt 5.6, <code>QT_LOGGING_RULES</code> may contain multiple rules separated by semicolons:</p>
<pre class="cpp">
QT_LOGGING_RULES<span class="operator">=</span><span class="string">"*.debug=false;driver.usb.debug=true"</span>
</pre>
<p>Order of evaluation:</p>
<ul>
<li>[<a href="qlibraryinfo.html#LibraryLocation-enum">QLibraryInfo::DataPath</a>]/qtlogging.ini</li>
<li>QtProject/qtlogging.ini</li>
<li><a href="qloggingcategory.html#setFilterRules">setFilterRules</a>()</li>
<li><code>QT_LOGGING_CONF</code></li>
<li><code>QT_LOGGING_RULES</code></li>
</ul>
<p>The <code>QtProject/qtlogging.ini</code> file is looked up in all directories returned by <a href="qstandardpaths.html#StandardLocation-enum">QStandardPaths::GenericConfigLocation</a>, e.g.</p>
<ul>
<li>on macOS and iOS: <code>~/Library/Preferences</code></li>
<li>on Unix: <code>~/.config</code>, <code>/etc/xdg</code></li>
<li>on Windows: <code>%LOCALAPPDATA%</code>, <code>%ProgramData%</code>, <a href="qcoreapplication.html#applicationDirPath">QCoreApplication::applicationDirPath</a>(), <a href="qcoreapplication.html#applicationDirPath">QCoreApplication::applicationDirPath</a>() + <code>"/data"</code></li>
</ul>
<p>Set the <code>QT_LOGGING_DEBUG</code> environment variable to see from where logging rules are loaded.</p>
<a name="installing-a-custom-filter"></a>
<h4 >Installing a Custom Filter</h4>
<p>As a lower-level alternative to the text rules, you can also implement a custom filter via <a href="qloggingcategory.html#installFilter">installFilter</a>(). All filter rules are ignored in this case.</p>
<a name="printing-the-category"></a>
<h3 >Printing the Category</h3>
<p>Use the <code>%{category}</code> placeholder to print the category in the default message handler:</p>
<pre class="cpp">
<a href="qtglobal.html#qSetMessagePattern">qSetMessagePattern</a>(<span class="string">"%{category} %{message}"</span>);
</pre>
</div>
<!-- @@@QLoggingCategory -->
<div class="types">
<h2>Member Type Documentation</h2>
<!-- $$$CategoryFilter -->
<h3 class="fn" id="CategoryFilter-typedef"><a name="CategoryFilter-typedef"></a>typedef QLoggingCategory::<span class="name">CategoryFilter</span></h3>
<p>This is a typedef for a pointer to a function with the following signature:</p>
<pre class="cpp">
<span class="type">void</span> myCategoryFilter(<span class="type"><a href="qloggingcategory.html#QLoggingCategory">QLoggingCategory</a></span> <span class="operator">*</span>);
</pre>
<p>A function with this signature can be installed with <a href="qloggingcategory.html#installFilter">installFilter</a>().</p>
<!-- @@@CategoryFilter -->
</div>
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QLoggingCategory[overload1]$$$QLoggingCategoryconstchar* -->
<h3 class="fn" id="QLoggingCategory"><a name="QLoggingCategory"></a>QLoggingCategory::<span class="name">QLoggingCategory</span>(const <span class="type">char</span> *<i>category</i>)</h3>
<p>Constructs a <a href="qloggingcategory.html">QLoggingCategory</a> object with the provided <i>category</i> name. All message types for this category are enabled by default.</p>
<p>If <i>category</i> is <code>0</code>, the category name is changed to <code>"default"</code>.</p>
<!-- @@@QLoggingCategory -->
<!-- $$$QLoggingCategory$$$QLoggingCategoryconstchar*QtMsgType -->
<h3 class="fn" id="QLoggingCategory-1"><a name="QLoggingCategory-1"></a>QLoggingCategory::<span class="name">QLoggingCategory</span>(const <span class="type">char</span> *<i>category</i>, <span class="type"><a href="qtglobal.html#QtMsgType-enum">QtMsgType</a></span> <i>enableForLevel</i>)</h3>
<p>Constructs a <a href="qloggingcategory.html">QLoggingCategory</a> object with the provided <i>category</i> name, and enables all messages with types more severe or equal than <i>enableForLevel</i>.</p>
<p>If <i>category</i> is <code>0</code>, the category name is changed to <code>"default"</code>.</p>
<p>This function was introduced in Qt 5.4.</p>
<!-- @@@QLoggingCategory -->
<!-- $$$~QLoggingCategory[overload1]$$$~QLoggingCategory -->
<h3 class="fn" id="dtor.QLoggingCategory"><a name="dtor.QLoggingCategory"></a>QLoggingCategory::<span class="name">~QLoggingCategory</span>()</h3>
<p>Destructs a <a href="qloggingcategory.html">QLoggingCategory</a> object.</p>
<!-- @@@~QLoggingCategory -->
<!-- $$$categoryName[overload1]$$$categoryName -->
<h3 class="fn" id="categoryName"><a name="categoryName"></a>const <span class="type">char</span> *QLoggingCategory::<span class="name">categoryName</span>() const</h3>
<p>Returns the name of the category.</p>
<!-- @@@categoryName -->
<!-- $$$defaultCategory[overload1]$$$defaultCategory -->
<h3 class="fn" id="defaultCategory"><a name="defaultCategory"></a><code>[static] </code><span class="type"><a href="qloggingcategory.html#QLoggingCategory">QLoggingCategory</a></span> *QLoggingCategory::<span class="name">defaultCategory</span>()</h3>
<p>Returns a pointer to the global category <code>"default"</code> that is used e.g. by <a href="qtglobal.html#qDebug">qDebug</a>(), <a href="qtglobal.html#qInfo">qInfo</a>(), <a href="qtglobal.html#qWarning">qWarning</a>(), <a href="qtglobal.html#qCritical">qCritical</a>(), <a href="qtglobal.html#qFatal">qFatal</a>().</p>
<p><b>Note: </b>The returned pointer may be null during destruction of static objects.</p><p><b>Note: </b>Ownership of the category is not transferred, do not <code>delete</code> the returned pointer.</p><!-- @@@defaultCategory -->
<!-- $$$installFilter[overload1]$$$installFilterCategoryFilter -->
<h3 class="fn" id="installFilter"><a name="installFilter"></a><code>[static] </code><span class="type"><a href="qloggingcategory.html#CategoryFilter-typedef">CategoryFilter</a></span> QLoggingCategory::<span class="name">installFilter</span>(<span class="type"><a href="qloggingcategory.html#CategoryFilter-typedef">CategoryFilter</a></span> <i>filter</i>)</h3>
<p>Installs a function <i>filter</i> that is used to determine which categories and message types should be enabled. Returns a pointer to the previous installed filter.</p>
<p>Every <a href="qloggingcategory.html">QLoggingCategory</a> object created is passed to the filter, and the filter is free to change the respective category configuration with <a href="qloggingcategory.html#setEnabled">setEnabled</a>().</p>
<p>The filter might be called from different threads, but never concurrently. The filter shall not call any static functions of <a href="qloggingcategory.html">QLoggingCategory</a>.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html#QLoggingCategory">QLoggingCategory</a></span><span class="operator">::</span>CategoryFilter oldCategoryFilter;
<span class="type">void</span> myCategoryFilter(<span class="type"><a href="qloggingcategory.html#QLoggingCategory">QLoggingCategory</a></span> <span class="operator">*</span>category)
{
<span class="comment">// configure driver.usb category here, otherwise forward to to default filter.</span>
<span class="keyword">if</span> (qstrcmp(category<span class="operator">-</span><span class="operator">></span>categoryName()<span class="operator">,</span> <span class="string">"driver.usb"</span>) <span class="operator">=</span><span class="operator">=</span> <span class="number">0</span>)
category<span class="operator">-</span><span class="operator">></span>setEnabled(<span class="type"><a href="qtglobal.html#QtMsgType-enum">QtDebugMsg</a></span><span class="operator">,</span> <span class="keyword">true</span>);
<span class="keyword">else</span>
oldCategoryFilter(category);
}
</pre>
<p>An alternative way of configuring the default filter is via <a href="qloggingcategory.html#setFilterRules">setFilterRules</a>().</p>
<!-- @@@installFilter -->
<!-- $$$isCriticalEnabled[overload1]$$$isCriticalEnabled -->
<h3 class="fn" id="isCriticalEnabled"><a name="isCriticalEnabled"></a><span class="type">bool</span> QLoggingCategory::<span class="name">isCriticalEnabled</span>() const</h3>
<p>Returns <code>true</code> if critical messages should be shown for this category. Returns <code>false</code> otherwise.</p>
<p><b>Note: </b>The <a href="qloggingcategory.html#qCCritical">qCCritical</a>() macro already does this check before executing any code. However, calling this method may be useful to avoid expensive generation of data that is only used for debug output.</p><!-- @@@isCriticalEnabled -->
<!-- $$$isDebugEnabled[overload1]$$$isDebugEnabled -->
<h3 class="fn" id="isDebugEnabled"><a name="isDebugEnabled"></a><span class="type">bool</span> QLoggingCategory::<span class="name">isDebugEnabled</span>() const</h3>
<p>Returns <code>true</code> if debug messages should be shown for this category. Returns <code>false</code> otherwise.</p>
<p><b>Note: </b>The <a href="qloggingcategory.html#qCDebug">qCDebug</a>() macro already does this check before executing any code. However, calling this method may be useful to avoid expensive generation of data that is only used for debug output.</p><!-- @@@isDebugEnabled -->
<!-- $$$isEnabled[overload1]$$$isEnabledQtMsgType -->
<h3 class="fn" id="isEnabled"><a name="isEnabled"></a><span class="type">bool</span> QLoggingCategory::<span class="name">isEnabled</span>(<span class="type"><a href="qtglobal.html#QtMsgType-enum">QtMsgType</a></span> <i>msgtype</i>) const</h3>
<p>Returns <code>true</code> if a message of type <i>msgtype</i> for the category should be shown. Returns <code>false</code> otherwise.</p>
<!-- @@@isEnabled -->
<!-- $$$isInfoEnabled[overload1]$$$isInfoEnabled -->
<h3 class="fn" id="isInfoEnabled"><a name="isInfoEnabled"></a><span class="type">bool</span> QLoggingCategory::<span class="name">isInfoEnabled</span>() const</h3>
<p>Returns <code>true</code> if informational messages should be shown for this category. Returns <code>false</code> otherwise.</p>
<p><b>Note: </b>The <a href="qloggingcategory.html#qCInfo">qCInfo</a>() macro already does this check before executing any code. However, calling this method may be useful to avoid expensive generation of data that is only used for debug output.</p><p>This function was introduced in Qt 5.5.</p>
<!-- @@@isInfoEnabled -->
<!-- $$$isWarningEnabled[overload1]$$$isWarningEnabled -->
<h3 class="fn" id="isWarningEnabled"><a name="isWarningEnabled"></a><span class="type">bool</span> QLoggingCategory::<span class="name">isWarningEnabled</span>() const</h3>
<p>Returns <code>true</code> if warning messages should be shown for this category. Returns <code>false</code> otherwise.</p>
<p><b>Note: </b>The <a href="qloggingcategory.html#qCWarning">qCWarning</a>() macro already does this check before executing any code. However, calling this method may be useful to avoid expensive generation of data that is only used for debug output.</p><!-- @@@isWarningEnabled -->
<!-- $$$setEnabled[overload1]$$$setEnabledQtMsgTypebool -->
<h3 class="fn" id="setEnabled"><a name="setEnabled"></a><span class="type">void</span> QLoggingCategory::<span class="name">setEnabled</span>(<span class="type"><a href="qtglobal.html#QtMsgType-enum">QtMsgType</a></span> <i>type</i>, <span class="type">bool</span> <i>enable</i>)</h3>
<p>Changes the message type <i>type</i> for the category to <i>enable</i>.</p>
<p>This method is meant to be used only from inside a filter installed by <a href="qloggingcategory.html#installFilter">installFilter</a>(). See <a href="qloggingcategory.html#configuring-categories">Configuring Categories</a> for an overview on how to configure categories globally.</p>
<p><b>Note: </b><code>QtFatalMsg</code> cannot be changed. It will always remain <code>true</code>.</p><p><b>See also </b><a href="qloggingcategory.html#isEnabled">isEnabled</a>().</p>
<!-- @@@setEnabled -->
<!-- $$$setFilterRules[overload1]$$$setFilterRulesconstQString& -->
<h3 class="fn" id="setFilterRules"><a name="setFilterRules"></a><code>[static] </code><span class="type">void</span> QLoggingCategory::<span class="name">setFilterRules</span>(const <span class="type"><a href="qstring.html">QString</a></span> &<i>rules</i>)</h3>
<p>Configures which categories and message types should be enabled through a a set of <i>rules</i>.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html#QLoggingCategory">QLoggingCategory</a></span><span class="operator">::</span>setFilterRules(<span class="type"><a href="qstring.html#QStringLiteral">QStringLiteral</a></span>(<span class="string">"driver.usb.debug=true"</span>));
</pre>
<p><b>Note: </b>The rules might be ignored if a custom category filter is installed with <a href="qloggingcategory.html#installFilter">installFilter</a>(), or if the user defined <code>QT_LOGGING_CONF</code> or <code>QT_LOGGING_RULES</code> environment variable.</p><!-- @@@setFilterRules -->
<!-- $$$operator()[overload1]$$$operator() -->
<h3 class="fn" id="operator-28-29"><a name="operator-28-29"></a><span class="type"><a href="qloggingcategory.html#QLoggingCategory">QLoggingCategory</a></span> &QLoggingCategory::<span class="name">operator()</span>()</h3>
<p>Returns the object itself. This allows both a <a href="qloggingcategory.html">QLoggingCategory</a> variable, and a factory method returning a <a href="qloggingcategory.html">QLoggingCategory</a>, to be used in <a href="qloggingcategory.html#qCDebug">qCDebug</a>(), <a href="qloggingcategory.html#qCWarning">qCWarning</a>(), <a href="qloggingcategory.html#qCCritical">qCCritical</a>() macros.</p>
<!-- @@@operator() -->
<!-- $$$operator()$$$operator() -->
<h3 class="fn" id="operator-28-29-1"><a name="operator-28-29-1"></a>const <span class="type"><a href="qloggingcategory.html#QLoggingCategory">QLoggingCategory</a></span> &QLoggingCategory::<span class="name">operator()</span>() const</h3>
<p>Returns the object itself. This allows both a <a href="qloggingcategory.html">QLoggingCategory</a> variable, and a factory method returning a <a href="qloggingcategory.html">QLoggingCategory</a>, to be used in <a href="qloggingcategory.html#qCDebug">qCDebug</a>(), <a href="qloggingcategory.html#qCWarning">qCWarning</a>(), <a href="qloggingcategory.html#qCCritical">qCCritical</a>() macros.</p>
<!-- @@@operator() -->
</div>
<div class="macros">
<h2>Macro Documentation</h2>
<!-- $$$Q_DECLARE_LOGGING_CATEGORY[overload1]$$$Q_DECLARE_LOGGING_CATEGORY -->
<h3 class="fn" id="Q_DECLARE_LOGGING_CATEGORY"><a name="Q_DECLARE_LOGGING_CATEGORY"></a><span class="name">Q_DECLARE_LOGGING_CATEGORY</span>(<i>name</i>)</h3>
<p>Declares a logging category <i>name</i>. The macro can be used to declare a common logging category shared in different parts of the program.</p>
<p>This macro must be used outside of a class or method.</p>
<p>This function was introduced in Qt 5.2.</p>
<p><b>See also </b><a href="qloggingcategory.html#Q_LOGGING_CATEGORY">Q_LOGGING_CATEGORY</a>().</p>
<!-- @@@Q_DECLARE_LOGGING_CATEGORY -->
<!-- $$$Q_LOGGING_CATEGORY[overload1]$$$Q_LOGGING_CATEGORY -->
<h3 class="fn" id="Q_LOGGING_CATEGORY"><a name="Q_LOGGING_CATEGORY"></a><span class="name">Q_LOGGING_CATEGORY</span>(<i>name</i>, <i>string</i>)</h3>
<p>Defines a logging category <i>name</i>, and makes it configurable under the <i>string</i> identifier. By default, all message types are enabled.</p>
<p>Only one translation unit in a library or executable can define a category with a specific name. The implicitly defined <a href="qloggingcategory.html">QLoggingCategory</a> object is created on first use, in a thread-safe manner.</p>
<p>This macro must be used outside of a class or method.</p>
<p>This function was introduced in Qt 5.2.</p>
<p><b>See also </b><a href="qloggingcategory.html#Q_DECLARE_LOGGING_CATEGORY">Q_DECLARE_LOGGING_CATEGORY</a>().</p>
<!-- @@@Q_LOGGING_CATEGORY -->
<!-- $$$Q_LOGGING_CATEGORY$$$Q_LOGGING_CATEGORY -->
<h3 class="fn" id="Q_LOGGING_CATEGORY-1"><a name="Q_LOGGING_CATEGORY-1"></a><span class="name">Q_LOGGING_CATEGORY</span>(<i>name</i>, <i>string</i>, <i>msgType</i>)</h3>
<p>Defines a logging category <i>name</i>, and makes it configurable under the <i>string</i> identifier. By default, messages of <a href="qtglobal.html#QtMsgType-enum">QtMsgType</a> <i>msgType</i> and more severe are enabled, types with a lower severity are disabled.</p>
<p>Only one translation unit in a library or executable can define a category with a specific name. The implicitly defined <a href="qloggingcategory.html">QLoggingCategory</a> object is created on first use, in a thread-safe manner.</p>
<p>This macro must be used outside of a class or method. It is only defined if variadic macros are supported.</p>
<p>This function was introduced in Qt 5.4.</p>
<p><b>See also </b><a href="qloggingcategory.html#Q_DECLARE_LOGGING_CATEGORY">Q_DECLARE_LOGGING_CATEGORY</a>().</p>
<!-- @@@Q_LOGGING_CATEGORY -->
<!-- $$$qCCritical[overload1]$$$qCCritical -->
<h3 class="fn" id="qCCritical"><a name="qCCritical"></a><span class="name">qCCritical</span>(<i>category</i>)</h3>
<p>Returns an output stream for critical messages in the logging category <i>category</i>.</p>
<p>The macro expands to code that checks whether <a href="qloggingcategory.html#isCriticalEnabled">QLoggingCategory::isCriticalEnabled</a>() evaluates to <code>true</code>. If so, the stream arguments are processed and sent to the message handler.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html">QLoggingCategory</a></span> category(<span class="string">"driver.usb"</span>);
qCCritical(category) <span class="operator"><</span><span class="operator"><</span> <span class="string">"a critical message"</span>;
</pre>
<p><b>Note: </b>Arguments are not processed if critical output for the category is not enabled, so do not rely on any side effects.</p><p><b>Note: </b>Using the macro is thread-safe.</p><p><b>Note:</b> This function is thread-safe.</p>
<p>This function was introduced in Qt 5.2.</p>
<p><b>See also </b><a href="qtglobal.html#qCritical">qCritical</a>().</p>
<!-- @@@qCCritical -->
<!-- $$$qCCritical$$$qCCriticalconstchar*... -->
<h3 class="fn" id="qCCritical-1"><a name="qCCritical-1"></a><span class="name">qCCritical</span>(<i>category</i>, const <span class="type">char</span> *<i>message</i>, <i>...</i>)</h3>
<p>Logs a critical message <i>message</i> in the logging category <i>category</i>. <i>message</i> might contain place holders that are replaced by additional arguments, similar to the C printf() function.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html">QLoggingCategory</a></span> category(<span class="string">"driver.usb"</span>);
qCCritical(category<span class="operator">,</span> <span class="string">"a critical message logged into category %s"</span><span class="operator">,</span> category<span class="operator">.</span>categoryName());
</pre>
<p><b>Note: </b>Arguments might not be processed if critical output for the category is not enabled, so do not rely on any side effects.</p><p><b>Note: </b>Using the macro is thread-safe.</p><p><b>Note:</b> This function is thread-safe.</p>
<p>This function was introduced in Qt 5.3.</p>
<p><b>See also </b><a href="qtglobal.html#qCritical">qCritical</a>().</p>
<!-- @@@qCCritical -->
<!-- $$$qCDebug[overload1]$$$qCDebug -->
<h3 class="fn" id="qCDebug"><a name="qCDebug"></a><span class="name">qCDebug</span>(<i>category</i>)</h3>
<p>Returns an output stream for debug messages in the logging category <i>category</i>.</p>
<p>The macro expands to code that checks whether <a href="qloggingcategory.html#isDebugEnabled">QLoggingCategory::isDebugEnabled</a>() evaluates to <code>true</code>. If so, the stream arguments are processed and sent to the message handler.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html">QLoggingCategory</a></span> category(<span class="string">"driver.usb"</span>);
qCDebug(category) <span class="operator"><</span><span class="operator"><</span> <span class="string">"a debug message"</span>;
</pre>
<p><b>Note: </b>Arguments are not processed if debug output for the category is not enabled, so do not rely on any side effects.</p><p><b>Note: </b>Using the macro is thread-safe.</p><p><b>Note:</b> This function is thread-safe.</p>
<p>This function was introduced in Qt 5.2.</p>
<p><b>See also </b><a href="qtglobal.html#qDebug">qDebug</a>().</p>
<!-- @@@qCDebug -->
<!-- $$$qCDebug$$$qCDebugconstchar*... -->
<h3 class="fn" id="qCDebug-1"><a name="qCDebug-1"></a><span class="name">qCDebug</span>(<i>category</i>, const <span class="type">char</span> *<i>message</i>, <i>...</i>)</h3>
<p>Logs a debug message <i>message</i> in the logging category <i>category</i>. <i>message</i> might contain place holders that are replaced by additional arguments, similar to the C printf() function.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html">QLoggingCategory</a></span> category(<span class="string">"driver.usb"</span>);
qCDebug(category<span class="operator">,</span> <span class="string">"a debug message logged into category %s"</span><span class="operator">,</span> category<span class="operator">.</span>categoryName());
</pre>
<p><b>Note: </b>Arguments might not be processed if debug output for the category is not enabled, so do not rely on any side effects.</p><p><b>Note: </b>Using the macro is thread-safe.</p><p><b>Note:</b> This function is thread-safe.</p>
<p>This function was introduced in Qt 5.3.</p>
<p><b>See also </b><a href="qtglobal.html#qDebug">qDebug</a>().</p>
<!-- @@@qCDebug -->
<!-- $$$qCInfo[overload1]$$$qCInfo -->
<h3 class="fn" id="qCInfo"><a name="qCInfo"></a><span class="name">qCInfo</span>(<i>category</i>)</h3>
<p>Returns an output stream for informational messages in the logging category <i>category</i>.</p>
<p>The macro expands to code that checks whether <a href="qloggingcategory.html#isInfoEnabled">QLoggingCategory::isInfoEnabled</a>() evaluates to <code>true</code>. If so, the stream arguments are processed and sent to the message handler.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html">QLoggingCategory</a></span> category(<span class="string">"driver.usb"</span>);
qCInfo(category) <span class="operator"><</span><span class="operator"><</span> <span class="string">"an informational message"</span>;
</pre>
<p><b>Note: </b>Arguments are not processed if debug output for the category is not enabled, so do not rely on any side effects.</p><p><b>Note: </b>Using the macro is thread-safe.</p><p><b>Note:</b> This function is thread-safe.</p>
<p>This function was introduced in Qt 5.5.</p>
<p><b>See also </b><a href="qtglobal.html#qInfo">qInfo</a>().</p>
<!-- @@@qCInfo -->
<!-- $$$qCInfo$$$qCInfoconstchar*... -->
<h3 class="fn" id="qCInfo-1"><a name="qCInfo-1"></a><span class="name">qCInfo</span>(<i>category</i>, const <span class="type">char</span> *<i>message</i>, <i>...</i>)</h3>
<p>Logs an informational message <i>message</i> in the logging category <i>category</i>. <i>message</i> might contain place holders that are replaced by additional arguments, similar to the C printf() function.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html">QLoggingCategory</a></span> category(<span class="string">"driver.usb"</span>);
qCInfo(category<span class="operator">,</span> <span class="string">"an informational message logged into category %s"</span><span class="operator">,</span> category<span class="operator">.</span>categoryName());
</pre>
<p><b>Note: </b>Arguments might not be processed if debug output for the category is not enabled, so do not rely on any side effects.</p><p><b>Note: </b>Using the macro is thread-safe.</p><p><b>Note:</b> This function is thread-safe.</p>
<p>This function was introduced in Qt 5.5.</p>
<p><b>See also </b><a href="qtglobal.html#qInfo">qInfo</a>().</p>
<!-- @@@qCInfo -->
<!-- $$$qCWarning[overload1]$$$qCWarning -->
<h3 class="fn" id="qCWarning"><a name="qCWarning"></a><span class="name">qCWarning</span>(<i>category</i>)</h3>
<p>Returns an output stream for warning messages in the logging category <i>category</i>.</p>
<p>The macro expands to code that checks whether <a href="qloggingcategory.html#isWarningEnabled">QLoggingCategory::isWarningEnabled</a>() evaluates to <code>true</code>. If so, the stream arguments are processed and sent to the message handler.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html">QLoggingCategory</a></span> category(<span class="string">"driver.usb"</span>);
qCWarning(category) <span class="operator"><</span><span class="operator"><</span> <span class="string">"a warning message"</span>;
</pre>
<p><b>Note: </b>Arguments are not processed if warning output for the category is not enabled, so do not rely on any side effects.</p><p><b>Note: </b>Using the macro is thread-safe.</p><p><b>Note:</b> This function is thread-safe.</p>
<p>This function was introduced in Qt 5.2.</p>
<p><b>See also </b><a href="qtglobal.html#qWarning">qWarning</a>().</p>
<!-- @@@qCWarning -->
<!-- $$$qCWarning$$$qCWarningconstchar*... -->
<h3 class="fn" id="qCWarning-1"><a name="qCWarning-1"></a><span class="name">qCWarning</span>(<i>category</i>, const <span class="type">char</span> *<i>message</i>, <i>...</i>)</h3>
<p>Logs a warning message <i>message</i> in the logging category <i>category</i>. <i>message</i> might contain place holders that are replaced by additional arguments, similar to the C printf() function.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qloggingcategory.html">QLoggingCategory</a></span> category(<span class="string">"driver.usb"</span>);
qCWarning(category<span class="operator">,</span> <span class="string">"a warning message logged into category %s"</span><span class="operator">,</span> category<span class="operator">.</span>categoryName());
</pre>
<p><b>Note: </b>Arguments might not be processed if warning output for the category is not enabled, so do not rely on any side effects.</p><p><b>Note: </b>Using the macro is thread-safe.</p><p><b>Note:</b> This function is thread-safe.</p>
<p>This function was introduced in Qt 5.3.</p>
<p><b>See also </b><a href="qtglobal.html#qWarning">qWarning</a>().</p>
<!-- @@@qCWarning -->
</div>
</div>
</div>
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<acronym title="Copyright">©</acronym> 2017 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
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