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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
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<title>Castle Game Engine: CastleVideos: Class TVideosCache</title>
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<h2>Castle Game Engine</h2><p><a href="introduction.html" class="navigation">Introduction</a></p><p><a href="AllUnits.html" class="navigation">Units</a></p><p><a href="ClassHierarchy.html" class="navigation">Class Hierarchy</a></p><p><a href="AllClasses.html" class="navigation">Classes, Interfaces, Objects and Records</a></p><p><a href="AllTypes.html" class="navigation">Types</a></p><p><a href="AllVariables.html" class="navigation">Variables</a></p><p><a href="AllConstants.html" class="navigation">Constants</a></p><p><a href="AllFunctions.html" class="navigation">Functions and Procedures</a></p><p><a href="AllIdentifiers.html" class="navigation">Identifiers</a></p></td><td class="content">
<a name="TVideosCache"></a><h1 class="cio">Class TVideosCache</h1>
<table class="sections wide_list">
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<td><a class="section" href="#PasDoc-Description">Description</a></td><td><a class="section" href="#PasDoc-Hierarchy">Hierarchy</a></td><td>Fields</td><td><a class="section" href="#PasDoc-Methods">Methods</a></td><td><a class="section" href="#PasDoc-Properties">Properties</a></td></tr></table>
<a name="PasDoc-Description"></a><h2 class="unit">Unit</h2>
<p class="unitlink">
<a href="CastleVideos.html">CastleVideos</a></p>
<h2 class="declaration">Declaration</h2>
<p class="declaration">
<code>type TVideosCache = class(TObject)</code></p>
<h2 class="description">Description</h2>
<p>
A cache of loaded videos.
<p>The idea is that instead of creating <a class="normal" href="CastleVideos.TVideo.html">TVideo</a> instance and calling <a class="normal" href="CastleVideos.TVideo.html#LoadFromFile">TVideo.LoadFromFile</a>, you instead call <code>Video := Cache.Video_IncReference(...)</code>. Later, instead of freeing this video, call <code><a class="normal" href="CastleVideos.TVideosCache.html#Video_DecReference">Video_DecReference</a>(Video)</code>. From your point of view, things will work the same. But if you expect to load many videos from the same URL, then you will get a great speed and memory saving, because video will only be actually loaded once. This may happen e.g. if you have a VRML / X3D file with lots of MovieTexture nodes with the same urls.
<p>Notes:
<p></p>
<ul class="paragraph_spacing">
<li><p>All passed here URLs must be absolute.</p></li>
<li><p>Note that in case of problems with loading, <a class="normal" href="CastleVideos.TVideosCache.html#Video_IncReference">Video_IncReference</a> may raise an exception, just like normal <a class="normal" href="CastleVideos.TVideo.html#LoadFromFile">TVideo.LoadFromFile</a>. In this case it's guaranteed that no reference will be incremented, of course. If <a class="normal" href="CastleVideos.TVideosCache.html#Video_IncReference">Video_IncReference</a> returns in a normal way, then it will return something non-<code>Nil</code> for sure.</p></li>
<li><p><a class="normal" href="CastleVideos.TVideosCache.html#Video_DecReference">Video_DecReference</a> alwas sets Video to <code>Nil</code>, like FreeAndNil.</p></li>
<li><p>All videos handled here are always loaded. So <a class="normal" href="CastleVideos.TVideosCache.html#Video_IncReference">Video_IncReference</a> always returns <a class="normal" href="CastleVideos.TVideo.html">TVideo</a> with <a class="normal" href="CastleVideos.TVideo.html#Loaded">TVideo.Loaded</a> = <code>True</code>. And you are forbidden from closing this video by <a class="normal" href="CastleVideos.TVideo.html#Close">TVideo.Close</a> yourself.</p></li>
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<p>
<p>Note that before destroying this object you must free all videos, i.e. call <a class="normal" href="CastleVideos.TVideosCache.html#Video_DecReference">Video_DecReference</a> for all videos allocated by <a class="normal" href="CastleVideos.TVideosCache.html#Video_IncReference">Video_IncReference</a>. <i>This class is not a lousy way of avoiding memory leaks</i> — it would be a bad idea, because it would cause sloppy programming, where memory is unnecessarily allocated for a long time. In fact, this class asserts in destructor that no videos are in cache anymore, so if you compiled with assertions enabled, this class does the job of memory-leak detector.</p>
<a name="PasDoc-Hierarchy"></a><h2 class="hierarchy">Hierarchy</h2>
<ul class="hierarchy"><li class="ancestor">TObject</li>
<li class="thisitem">TVideosCache</li></ul><h2 class="overview">Overview</h2>
<a name="PasDoc-Methods"></a><h3 class="summary">Methods</h3>
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<td class="visibility"><a href="legend.html"><img src="protected.gif" alt="Protected" title="Protected"></a></td>
<td class="itemcode"><code>procedure <b><a href="CastleVideos.TVideosCache.html#CheckEmpty">CheckEmpty</a></b>;</code></td>
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<td class="itemcode"><code>constructor <b><a href="CastleVideos.TVideosCache.html#Create">Create</a></b>;</code></td>
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<td class="itemcode"><code>destructor <b><a href="CastleVideos.TVideosCache.html#Destroy">Destroy</a></b>; override;</code></td>
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<td class="itemcode"><code>function <b><a href="CastleVideos.TVideosCache.html#Video_IncReference">Video_IncReference</a></b>(const URL: string; out AlphaChannel: <a href="CastleImages.html#TAlphaChannel">TAlphaChannel</a>): <a href="CastleVideos.TVideo.html">TVideo</a>;</code></td>
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<td class="itemcode"><code>procedure <b><a href="CastleVideos.TVideosCache.html#Video_DecReference">Video_DecReference</a></b>(var Video: <a href="CastleVideos.TVideo.html">TVideo</a>);</code></td>
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<td class="itemcode"><code>function <b><a href="CastleVideos.TVideosCache.html#Empty">Empty</a></b>: boolean; virtual;</code></td>
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<a name="PasDoc-Properties"></a><h3 class="summary">Properties</h3>
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<td class="itemcode"><code>property <b><a href="CastleVideos.TVideosCache.html#OnEmpty">OnEmpty</a></b>: TProcedure read FOnEmpty write FOnEmpty;</code></td>
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<h2 class="description">Description</h2>
<h3 class="detail">Methods</h3>
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<td class="itemcode"><a name="CheckEmpty"></a><code>procedure <b>CheckEmpty</b>;</code></td>
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<p>
If cache is empty, calls <a class="normal" href="CastleVideos.TVideosCache.html#OnEmpty">OnEmpty</a>. Note that <a class="normal" href="CastleVideos.TVideosCache.html#OnEmpty">OnEmpty</a> may destroy current instance, so call <code>CheckEmpty</code> only when you finished processing — Self may be invalid afterwards.</p>
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<td class="itemcode"><a name="Create"></a><code>constructor <b>Create</b>;</code></td>
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<td class="itemcode"><a name="Destroy"></a><code>destructor <b>Destroy</b>; override;</code></td>
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<td class="itemcode"><a name="Video_IncReference"></a><code>function <b>Video_IncReference</b>(const URL: string; out AlphaChannel: <a href="CastleImages.html#TAlphaChannel">TAlphaChannel</a>): <a href="CastleVideos.TVideo.html">TVideo</a>;</code></td>
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<td class="itemcode"><a name="Video_DecReference"></a><code>procedure <b>Video_DecReference</b>(var Video: <a href="CastleVideos.TVideo.html">TVideo</a>);</code></td>
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<td class="itemcode"><a name="Empty"></a><code>function <b>Empty</b>: boolean; virtual;</code></td>
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<h3 class="detail">Properties</h3>
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<td class="itemcode"><a name="OnEmpty"></a><code>property <b>OnEmpty</b>: TProcedure read FOnEmpty write FOnEmpty;</code></td>
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<p>
Called when cache becomes empty. This is only for internal usage by <a class="normal" href="X3DNodes.html">X3DNodes</a> unit for now.</p>
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