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<li class="level1"><a href="#public-types">Public Types</a></li>
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<h1 class="title">QPixmapCache Class Reference</h1>
<!-- $$$QPixmapCache-brief -->
<p>The QPixmapCache class provides an application-wide cache for pixmaps. <a href="#details">More...</a></p>
<!-- @@@QPixmapCache -->
<pre class="cpp"> <span class="preprocessor">#include <QPixmapCache></span></pre><ul>
<li><a href="qpixmapcache-members.html">List of all members, including inherited members</a></li>
<li><a href="qpixmapcache-obsolete.html">Obsolete members</a></li>
</ul>
<a name="public-types"></a>
<h2>Public Types</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> class </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache-key.html">Key</a></b></td></tr>
</table>
<a name="static-public-members"></a>
<h2>Static Public Members</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#cacheLimit">cacheLimit</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#clear">clear</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#find">find</a></b> ( const QString & <i>key</i>, QPixmap * <i>pixmap</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#find-3">find</a></b> ( const Key & <i>key</i>, QPixmap * <i>pixmap</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#insert">insert</a></b> ( const QString & <i>key</i>, const QPixmap & <i>pixmap</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> Key </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#insert-2">insert</a></b> ( const QPixmap & <i>pixmap</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#remove">remove</a></b> ( const QString & <i>key</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#remove-2">remove</a></b> ( const Key & <i>key</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#replace">replace</a></b> ( const Key & <i>key</i>, const QPixmap & <i>pixmap</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qpixmapcache.html#setCacheLimit">setCacheLimit</a></b> ( int <i>n</i> )</td></tr>
</table>
<a name="details"></a>
<!-- $$$QPixmapCache-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QPixmapCache class provides an application-wide cache for pixmaps.</p>
<p>This class is a tool for optimized drawing with <a href="qpixmap.html">QPixmap</a>. You can use it to store temporary pixmaps that are expensive to generate without using more storage space than <a href="qpixmapcache.html#cacheLimit">cacheLimit</a>(). Use <a href="qpixmapcache.html#insert">insert</a>() to insert pixmaps, <a href="qpixmapcache.html#find">find</a>() to find them, and <a href="qpixmapcache.html#clear">clear</a>() to empty the cache.</p>
<p>QPixmapCache contains no member data, only static functions to access the global pixmap cache. It creates an internal <a href="qcache.html">QCache</a> object for caching the pixmaps.</p>
<p>The cache associates a pixmap with a user-provided string as a key, or with a <a href="qpixmapcache-key.html">QPixmapCache::Key</a> that the cache generates. Using <a href="qpixmapcache-key.html">QPixmapCache::Key</a> for keys is faster than using strings. The string API is very convenient for complex keys but the <a href="qpixmapcache-key.html">QPixmapCache::Key</a> API will be very efficient and convenient for a one-to-one object-to-pixmap mapping — in this case, you can store the keys as members of an object.</p>
<p>If two pixmaps are inserted into the cache using equal keys then the last pixmap will replace the first pixmap in the cache. This follows the behavior of the <a href="qhash.html">QHash</a> and <a href="qcache.html">QCache</a> classes.</p>
<p>The cache becomes full when the total size of all pixmaps in the cache exceeds <a href="qpixmapcache.html#cacheLimit">cacheLimit</a>(). The initial cache limit is 2048 KB (2 MB) on embedded platforms, 10240 KB (10 MB) on desktop platforms; you can change this by calling <a href="qpixmapcache.html#setCacheLimit">setCacheLimit</a>() with the required value. A pixmap takes roughly (<i>width</i> * <i>height</i> * <i>depth</i>)/8 bytes of memory.</p>
<p>The <i>Qt Quarterly</i> article <a href="http://doc.qt.digia.com/qq/qq12-qpixmapcache.html">Optimizing with QPixmapCache</a> explains how to use QPixmapCache to speed up applications by caching the results of painting.</p>
</div>
<p><b>See also </b><a href="qcache.html">QCache</a> and <a href="qpixmap.html">QPixmap</a>.</p>
<!-- @@@QPixmapCache -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$cacheLimit[overload1]$$$cacheLimit -->
<h3 class="fn"><a name="cacheLimit"></a><span class="type">int</span> QPixmapCache::<span class="name">cacheLimit</span> ()<tt> [static]</tt></h3>
<p>Returns the cache limit (in kilobytes).</p>
<p>The default cache limit is 2048 KB on embedded platforms, 10240 KB on desktop platforms.</p>
<p><b>See also </b><a href="qpixmapcache.html#setCacheLimit">setCacheLimit</a>().</p>
<!-- @@@cacheLimit -->
<!-- $$$clear[overload1]$$$clear -->
<h3 class="fn"><a name="clear"></a><span class="type">void</span> QPixmapCache::<span class="name">clear</span> ()<tt> [static]</tt></h3>
<p>Removes all pixmaps from the cache.</p>
<!-- @@@clear -->
<!-- $$$find[overload1]$$$findconstQString&QPixmap* -->
<h3 class="fn"><a name="find"></a><span class="type">bool</span> QPixmapCache::<span class="name">find</span> ( const <span class="type"><a href="qstring.html">QString</a></span> & <i>key</i>, <span class="type"><a href="qpixmap.html">QPixmap</a></span> * <i>pixmap</i> )<tt> [static]</tt></h3>
<p>Looks for a cached pixmap associated with the given <i>key</i> in the cache. If the pixmap is found, the function sets <i>pixmap</i> to that pixmap and returns true; otherwise it leaves <i>pixmap</i> alone and returns false.</p>
<p>Example:</p>
<pre class="cpp"> <span class="type"><a href="qpixmap.html">QPixmap</a></span> pm;
<span class="keyword">if</span> (<span class="operator">!</span><span class="type"><a href="qpixmapcache.html">QPixmapCache</a></span><span class="operator">::</span>find(<span class="string">"my_big_image"</span><span class="operator">,</span> <span class="operator">&</span>pm)) {
pm<span class="operator">.</span>load(<span class="string">"bigimage.png"</span>);
<span class="type"><a href="qpixmapcache.html">QPixmapCache</a></span><span class="operator">::</span>insert(<span class="string">"my_big_image"</span><span class="operator">,</span> pm);
}
painter<span class="operator">-</span><span class="operator">></span>drawPixmap(<span class="number">0</span><span class="operator">,</span> <span class="number">0</span><span class="operator">,</span> pm);</pre>
<p>This function was introduced in Qt 4.6.</p>
<!-- @@@find -->
<!-- $$$find$$$findconstKey&QPixmap* -->
<h3 class="fn"><a name="find-3"></a><span class="type">bool</span> QPixmapCache::<span class="name">find</span> ( const <span class="type"><a href="qpixmapcache-key.html">Key</a></span> & <i>key</i>, <span class="type"><a href="qpixmap.html">QPixmap</a></span> * <i>pixmap</i> )<tt> [static]</tt></h3>
<p>Looks for a cached pixmap associated with the given <i>key</i> in the cache. If the pixmap is found, the function sets <i>pixmap</i> to that pixmap and returns true; otherwise it leaves <i>pixmap</i> alone and returns false. If the pixmap is not found, it means that the <i>key</i> is no longer valid, so it will be released for the next insertion.</p>
<p>This function was introduced in Qt 4.6.</p>
<!-- @@@find -->
<!-- $$$insert[overload1]$$$insertconstQString&constQPixmap& -->
<h3 class="fn"><a name="insert"></a><span class="type">bool</span> QPixmapCache::<span class="name">insert</span> ( const <span class="type"><a href="qstring.html">QString</a></span> & <i>key</i>, const <span class="type"><a href="qpixmap.html">QPixmap</a></span> & <i>pixmap</i> )<tt> [static]</tt></h3>
<p>Inserts a copy of the pixmap <i>pixmap</i> associated with the <i>key</i> into the cache.</p>
<p>All pixmaps inserted by the Qt library have a key starting with "$qt", so your own pixmap keys should never begin "$qt".</p>
<p>When a pixmap is inserted and the cache is about to exceed its limit, it removes pixmaps until there is enough room for the pixmap to be inserted.</p>
<p>The oldest pixmaps (least recently accessed in the cache) are deleted when more space is needed.</p>
<p>The function returns true if the object was inserted into the cache; otherwise it returns false.</p>
<p><b>See also </b><a href="qpixmapcache.html#setCacheLimit">setCacheLimit</a>().</p>
<!-- @@@insert -->
<!-- $$$insert$$$insertconstQPixmap& -->
<h3 class="fn"><a name="insert-2"></a><span class="type"><a href="qpixmapcache-key.html">Key</a></span> QPixmapCache::<span class="name">insert</span> ( const <span class="type"><a href="qpixmap.html">QPixmap</a></span> & <i>pixmap</i> )<tt> [static]</tt></h3>
<p>Inserts a copy of the given <i>pixmap</i> into the cache and returns a key that can be used to retrieve it.</p>
<p>When a pixmap is inserted and the cache is about to exceed its limit, it removes pixmaps until there is enough room for the pixmap to be inserted.</p>
<p>The oldest pixmaps (least recently accessed in the cache) are deleted when more space is needed.</p>
<p>This function was introduced in Qt 4.6.</p>
<p><b>See also </b><a href="qpixmapcache.html#setCacheLimit">setCacheLimit</a>() and <a href="qpixmapcache.html#replace">replace</a>().</p>
<!-- @@@insert -->
<!-- $$$remove[overload1]$$$removeconstQString& -->
<h3 class="fn"><a name="remove"></a><span class="type">void</span> QPixmapCache::<span class="name">remove</span> ( const <span class="type"><a href="qstring.html">QString</a></span> & <i>key</i> )<tt> [static]</tt></h3>
<p>Removes the pixmap associated with <i>key</i> from the cache.</p>
<!-- @@@remove -->
<!-- $$$remove$$$removeconstKey& -->
<h3 class="fn"><a name="remove-2"></a><span class="type">void</span> QPixmapCache::<span class="name">remove</span> ( const <span class="type"><a href="qpixmapcache-key.html">Key</a></span> & <i>key</i> )<tt> [static]</tt></h3>
<p>Removes the pixmap associated with <i>key</i> from the cache and releases the key for a future insertion.</p>
<p>This function was introduced in Qt 4.6.</p>
<!-- @@@remove -->
<!-- $$$replace[overload1]$$$replaceconstKey&constQPixmap& -->
<h3 class="fn"><a name="replace"></a><span class="type">bool</span> QPixmapCache::<span class="name">replace</span> ( const <span class="type"><a href="qpixmapcache-key.html">Key</a></span> & <i>key</i>, const <span class="type"><a href="qpixmap.html">QPixmap</a></span> & <i>pixmap</i> )<tt> [static]</tt></h3>
<p>Replaces the pixmap associated with the given <i>key</i> with the <i>pixmap</i> specified. Returns true if the <i>pixmap</i> has been correctly inserted into the cache; otherwise returns false.</p>
<p>This function was introduced in Qt 4.6.</p>
<p><b>See also </b><a href="qpixmapcache.html#setCacheLimit">setCacheLimit</a>() and <a href="qpixmapcache.html#insert">insert</a>().</p>
<!-- @@@replace -->
<!-- $$$setCacheLimit[overload1]$$$setCacheLimitint -->
<h3 class="fn"><a name="setCacheLimit"></a><span class="type">void</span> QPixmapCache::<span class="name">setCacheLimit</span> ( <span class="type">int</span> <i>n</i> )<tt> [static]</tt></h3>
<p>Sets the cache limit to <i>n</i> kilobytes.</p>
<p>The default setting is 2048 KB on embedded platforms, 10240 KB on desktop platforms.</p>
<p><b>See also </b><a href="qpixmapcache.html#cacheLimit">cacheLimit</a>().</p>
<!-- @@@setCacheLimit -->
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