1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
|
<?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>QPixmapCache Class Reference</title><style>h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm }
a:link { color: #004faf; text-decoration: none }
a:visited { color: #672967; text-decoration: none }
td.postheader { font-family: sans-serif }
tr.address { font-family: sans-serif }
body { background: #ffffff; color: black; }
</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">QPixmapCache Class Reference<br /><sup><sup>[<a href="qtgui.html">QtGui</a> module]</sup></sup></h1><p>The QPixmapCache class provides an application-wide cache for
pixmaps. <a href="#details">More...</a></p>
<h3>Types</h3><ul><li><div class="fn" />class <b><a href="qpixmapcache-key.html">Key</a></b></li></ul><h3>Methods</h3><ul><li><div class="fn" /><b><a href="qpixmapcache.html#QPixmapCache">__init__</a></b> (<i>self</i>)</li><li><div class="fn" /><b><a href="qpixmapcache.html#QPixmapCache-2">__init__</a></b> (<i>self</i>, QPixmapCache)</li></ul><h3>Static Methods</h3><ul><li><div class="fn" />int <b><a href="qpixmapcache.html#cacheLimit">cacheLimit</a></b> ()</li><li><div class="fn" /><b><a href="qpixmapcache.html#clear">clear</a></b> ()</li><li><div class="fn" />QPixmap <b><a href="qpixmapcache.html#find">find</a></b> (QString <i>key</i>)</li><li><div class="fn" />bool <b><a href="qpixmapcache.html#find-2">find</a></b> (QString <i>key</i>, QPixmap <i>pixmap</i>)</li><li><div class="fn" />bool <b><a href="qpixmapcache.html#find-3">find</a></b> (Key <i>key</i>, QPixmap <i>pixmap</i>)</li><li><div class="fn" />bool <b><a href="qpixmapcache.html#insert">insert</a></b> (QString <i>key</i>, QPixmap)</li><li><div class="fn" />Key <b><a href="qpixmapcache.html#insert-2">insert</a></b> (QPixmap <i>pixmap</i>)</li><li><div class="fn" /><b><a href="qpixmapcache.html#remove">remove</a></b> (QString <i>key</i>)</li><li><div class="fn" /><b><a href="qpixmapcache.html#remove-2">remove</a></b> (Key <i>key</i>)</li><li><div class="fn" />bool <b><a href="qpixmapcache.html#replace">replace</a></b> (Key <i>key</i>, QPixmap <i>pixmap</i>)</li><li><div class="fn" /><b><a href="qpixmapcache.html#setCacheLimit">setCacheLimit</a></b> (int)</li></ul><a name="details" /><hr /><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 &#8212; 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>
<hr /><h2>Method Documentation</h2><h3 class="fn"><a name="QPixmapCache" />QPixmapCache.__init__ (<i>self</i>)</h3><h3 class="fn"><a name="QPixmapCache-2" />QPixmapCache.__init__ (<i>self</i>, <a href="qpixmapcache.html">QPixmapCache</a>)</h3><h3 class="fn"><a name="cacheLimit" />int QPixmapCache.cacheLimit ()</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>
<h3 class="fn"><a name="clear" />QPixmapCache.clear ()</h3><p>Removes all pixmaps from the cache.</p>
<h3 class="fn"><a name="find" /><a href="qpixmap.html">QPixmap</a> QPixmapCache.find (QString <i>key</i>)</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>
<h3 class="fn"><a name="find-2" />bool QPixmapCache.find (QString <i>key</i>, <a href="qpixmap.html">QPixmap</a> <i>pixmap</i>)</h3><h3 class="fn"><a name="find-3" />bool QPixmapCache.find (<a href="qpixmapcache-key.html">Key</a> <i>key</i>, <a href="qpixmap.html">QPixmap</a> <i>pixmap</i>)</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>
<h3 class="fn"><a name="insert" />bool QPixmapCache.insert (QString <i>key</i>, <a href="qpixmap.html">QPixmap</a>)</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>
<h3 class="fn"><a name="insert-2" /><a href="qpixmapcache-key.html">Key</a> QPixmapCache.insert (<a href="qpixmap.html">QPixmap</a> <i>pixmap</i>)</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>
<h3 class="fn"><a name="remove" />QPixmapCache.remove (QString <i>key</i>)</h3><p>Removes the pixmap associated with <i>key</i> from the
cache.</p>
<h3 class="fn"><a name="remove-2" />QPixmapCache.remove (<a href="qpixmapcache-key.html">Key</a> <i>key</i>)</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>
<h3 class="fn"><a name="replace" />bool QPixmapCache.replace (<a href="qpixmapcache-key.html">Key</a> <i>key</i>, <a href="qpixmap.html">QPixmap</a> <i>pixmap</i>)</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>
<h3 class="fn"><a name="setCacheLimit" />QPixmapCache.setCacheLimit (int)</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>
<address><hr /><div align="center"><table border="0" cellspacing="0" width="100%"><tr class="address"><td align="left" width="25%">PyQt 4.11.4 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>
|
