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<?xml version="1.0" encoding="UTF-8"?>
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<title>Qt 4.8: QGLContext Class Reference</title>
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<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<h3><a name="toc">Contents</a></h3>
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<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="#protected-functions">Protected Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
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<h1 class="title">QGLContext Class Reference</h1>
<!-- $$$QGLContext-brief -->
<p>The QGLContext class encapsulates an OpenGL rendering context. <a href="#details">More...</a></p>
<!-- @@@QGLContext -->
<pre class="cpp"> <span class="preprocessor">#include <QGLContext></span></pre><ul>
<li><a href="qglcontext-members.html">List of all members, including inherited members</a></li>
<li><a href="qglcontext-obsolete.html">Obsolete members</a></li>
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<a name="public-types"></a>
<h2>Public Types</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> enum </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#BindOption-enum">BindOption</a></b> { NoBindOption, InvertedYBindOption, MipmapBindOption, PremultipliedAlphaBindOption, LinearFilteringBindOption, DefaultBindOption }</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> flags </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#BindOption-enum">BindOptions</a></b></td></tr>
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<a name="public-functions"></a>
<h2>Public Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#QGLContext">QGLContext</a></b> ( const QGLFormat & <i>format</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#dtor.QGLContext">~QGLContext</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> GLuint </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#bindTexture">bindTexture</a></b> ( const QImage & <i>image</i>, GLenum <i>target</i>, GLint <i>format</i>, BindOptions <i>options</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> GLuint </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#bindTexture-2">bindTexture</a></b> ( const QString & <i>fileName</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> GLuint </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#bindTexture-3">bindTexture</a></b> ( const QImage & <i>image</i>, GLenum <i>target</i> = GL_TEXTURE_2D, GLint <i>format</i> = GL_RGBA )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> GLuint </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#bindTexture-4">bindTexture</a></b> ( const QPixmap & <i>pixmap</i>, GLenum <i>target</i> = GL_TEXTURE_2D, GLint <i>format</i> = GL_RGBA )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> GLuint </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#bindTexture-5">bindTexture</a></b> ( const QPixmap & <i>pixmap</i>, GLenum <i>target</i>, GLint <i>format</i>, BindOptions <i>options</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual bool </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#create">create</a></b> ( const QGLContext * <i>shareContext</i> = 0 )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#deleteTexture">deleteTexture</a></b> ( GLuint <i>id</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QPaintDevice * </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#device">device</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#doneCurrent">doneCurrent</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#drawTexture">drawTexture</a></b> ( const QRectF & <i>target</i>, GLuint <i>textureId</i>, GLenum <i>textureTarget</i> = GL_TEXTURE_2D )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#drawTexture-2">drawTexture</a></b> ( const QPointF & <i>point</i>, GLuint <i>textureId</i>, GLenum <i>textureTarget</i> = GL_TEXTURE_2D )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QGLFormat </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#format">format</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void * </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#getProcAddress">getProcAddress</a></b> ( const QString & <i>proc</i> ) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#isSharing">isSharing</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#isValid">isValid</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#makeCurrent">makeCurrent</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QColor </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#overlayTransparentColor">overlayTransparentColor</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QGLFormat </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#requestedFormat">requestedFormat</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#reset">reset</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#setFormat">setFormat</a></b> ( const QGLFormat & <i>format</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#swapBuffers">swapBuffers</a></b> () const</td></tr>
</table>
<a name="static-public-members"></a>
<h2>Static Public Members</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#areSharing">areSharing</a></b> ( const QGLContext * <i>context1</i>, const QGLContext * <i>context2</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const QGLContext * </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#currentContext">currentContext</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QGLContext * </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#fromPlatformGLContext">fromPlatformGLContext</a></b> ( QPlatformGLContext * <i>platformContext</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#setTextureCacheLimit">setTextureCacheLimit</a></b> ( int <i>size</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#textureCacheLimit">textureCacheLimit</a></b> ()</td></tr>
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<a name="protected-functions"></a>
<h2>Protected Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> virtual bool </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#chooseContext">chooseContext</a></b> ( const QGLContext * <i>shareContext</i> = 0 )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void * </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#chooseMacVisual">chooseMacVisual</a></b> ( GDHandle <i>handle</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual int </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#choosePixelFormat">choosePixelFormat</a></b> ( void * <i>dummyPfd</i>, HDC <i>pdc</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual void * </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#chooseVisual">chooseVisual</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#deviceIsPixmap">deviceIsPixmap</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#initialized">initialized</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#setInitialized">setInitialized</a></b> ( bool <i>on</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#setWindowCreated">setWindowCreated</a></b> ( bool <i>on</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qglcontext.html#windowCreated">windowCreated</a></b> () const</td></tr>
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<a name="details"></a>
<!-- $$$QGLContext-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QGLContext class encapsulates an OpenGL rendering context.</p>
<p>An OpenGL rendering context is a complete set of OpenGL state variables. The rendering context's <a href="qgl.html#FormatOption-enum">format</a> is set in the constructor, but it can also be set later with <a href="qglcontext.html#setFormat">setFormat</a>(). The format options that are actually set are returned by <a href="qglcontext.html#format">format</a>(); the options you asked for are returned by <a href="qglcontext.html#requestedFormat">requestedFormat</a>(). Note that after a QGLContext object has been constructed, the actual OpenGL context must be created by explicitly calling the <a href="qglcontext.html#create">create()</a> function. The <a href="qglcontext.html#makeCurrent">makeCurrent</a>() function makes this context the current rendering context. You can make <i>no</i> context current using <a href="qglcontext.html#doneCurrent">doneCurrent</a>(). The <a href="qglcontext.html#reset">reset</a>() function will reset the context and make it invalid.</p>
<p>You can examine properties of the context with, e.g. <a href="qglcontext.html#isValid">isValid</a>(), <a href="qglcontext.html#isSharing">isSharing</a>(), <a href="qglcontext.html#initialized">initialized</a>(), <a href="qglcontext.html#windowCreated">windowCreated</a>() and <a href="qglcontext.html#overlayTransparentColor">overlayTransparentColor</a>().</p>
<p>If you're using double buffering you can swap the screen contents with the off-screen buffer using <a href="qglcontext.html#swapBuffers">swapBuffers</a>().</p>
<p>Please note that QGLContext is not <a href="threads-reentrancy.html#thread-safe">thread-safe</a>.</p>
</div>
<!-- @@@QGLContext -->
<div class="types">
<h2>Member Type Documentation</h2>
<!-- $$$BindOption$$$NoBindOption$$$InvertedYBindOption$$$MipmapBindOption$$$PremultipliedAlphaBindOption$$$LinearFilteringBindOption$$$MemoryManagedBindOption$$$CanFlipNativePixmapBindOption$$$DefaultBindOption$$$InternalBindOption -->
<h3 class="flags"><a name="BindOption-enum"></a>enum QGLContext::<span class="name">BindOption</span><br/>flags QGLContext::<span class="name">BindOptions</span></h3>
<p>A set of options to decide how to bind a texture using <a href="qglcontext.html#bindTexture">bindTexture</a>().</p>
<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"><tt>QGLContext::NoBindOption</tt></td><td class="topAlign"><tt>0x0000</tt></td><td class="topAlign">Don't do anything, pass the texture straight through.</td></tr>
<tr><td class="topAlign"><tt>QGLContext::InvertedYBindOption</tt></td><td class="topAlign"><tt>0x0001</tt></td><td class="topAlign">Specifies that the texture should be flipped over the X axis so that the texture coordinate 0,0 corresponds to the top left corner. Inverting the texture implies a deep copy prior to upload.</td></tr>
<tr><td class="topAlign"><tt>QGLContext::MipmapBindOption</tt></td><td class="topAlign"><tt>0x0002</tt></td><td class="topAlign">Specifies that <a href="qglcontext.html#bindTexture">bindTexture</a>() should try to generate mipmaps. If the GL implementation supports the <tt>GL_SGIS_generate_mipmap</tt> extension, mipmaps will be automatically generated for the texture. Mipmap generation is only supported for the <tt>GL_TEXTURE_2D</tt> target.</td></tr>
<tr><td class="topAlign"><tt>QGLContext::PremultipliedAlphaBindOption</tt></td><td class="topAlign"><tt>0x0004</tt></td><td class="topAlign">Specifies that the image should be uploaded with premultiplied alpha and does a conversion accordingly.</td></tr>
<tr><td class="topAlign"><tt>QGLContext::LinearFilteringBindOption</tt></td><td class="topAlign"><tt>0x0008</tt></td><td class="topAlign">Specifies that the texture filtering should be set to GL_LINEAR. Default is GL_NEAREST. If mipmap is also enabled, filtering will be set to GL_LINEAR_MIPMAP_LINEAR.</td></tr>
<tr><td class="topAlign"><tt>QGLContext::DefaultBindOption</tt></td><td class="topAlign"><tt>LinearFilteringBindOption | InvertedYBindOption | MipmapBindOption</tt></td><td class="topAlign">In Qt 4.5 and earlier, <a href="qglcontext.html#bindTexture">bindTexture</a>() would mirror the image and automatically generate mipmaps. This option helps preserve this default behavior.</td></tr>
</table>
<p>Used by x11 from pixmap to choose whether or not it can bind the pixmap upside down or not.</p>
<p>Used by paint engines to indicate that the pixmap should be memory managed along side with the pixmap/image that it stems from, e.g. installing destruction hooks in them.</p>
<p>This enum was introduced or modified in Qt 4.6.</p>
<p>The BindOptions type is a typedef for <a href="qflags.html">QFlags</a><BindOption>. It stores an OR combination of BindOption values.</p>
<!-- @@@BindOption -->
</div>
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QGLContext[overload1]$$$QGLContextconstQGLFormat& -->
<h3 class="fn"><a name="QGLContext"></a>QGLContext::<span class="name">QGLContext</span> ( const <span class="type"><a href="qglformat.html">QGLFormat</a></span> & <i>format</i> )</h3>
<p>Constructs an OpenGL context with the given <i>format</i> which specifies several display options for the context.</p>
<p>If the underlying OpenGL/Window system cannot satisfy all the features requested in <i>format</i>, the nearest subset of features will be used. After creation, the <a href="qglcontext.html#format">format</a>() method will return the actual format obtained.</p>
<p>Note that after a <a href="qglcontext.html">QGLContext</a> object has been constructed, <a href="qglcontext.html#create">create</a>() must be called explicitly to create the actual OpenGL context. The context will be <a href="qglcontext.html#isValid">invalid</a> if it was not possible to obtain a GL context at all.</p>
<p><b>See also </b><a href="qglcontext.html#format">format</a>() and <a href="qglcontext.html#isValid">isValid</a>().</p>
<!-- @@@QGLContext -->
<!-- $$$~QGLContext[overload1]$$$~QGLContext -->
<h3 class="fn"><a name="dtor.QGLContext"></a>QGLContext::<span class="name">~QGLContext</span> ()<tt> [virtual]</tt></h3>
<p>Destroys the OpenGL context and frees its resources.</p>
<!-- @@@~QGLContext -->
<!-- $$$areSharing[overload1]$$$areSharingconstQGLContext*constQGLContext* -->
<h3 class="fn"><a name="areSharing"></a><span class="type">bool</span> QGLContext::<span class="name">areSharing</span> ( const <span class="type">QGLContext</span> * <i>context1</i>, const <span class="type">QGLContext</span> * <i>context2</i> )<tt> [static]</tt></h3>
<p>Returns true if <i>context1</i> and <i>context2</i> are sharing their GL resources such as textures, shader programs, etc; otherwise returns false.</p>
<p>This function was introduced in Qt 4.6.</p>
<!-- @@@areSharing -->
<!-- $$$bindTexture[overload1]$$$bindTextureconstQImage&GLenumGLintBindOptions -->
<h3 class="fn"><a name="bindTexture"></a><span class="type">GLuint</span> QGLContext::<span class="name">bindTexture</span> ( const <span class="type"><a href="qimage.html">QImage</a></span> & <i>image</i>, <span class="type">GLenum</span> <i>target</i>, <span class="type">GLint</span> <i>format</i>, <span class="type"><a href="qglcontext.html#BindOption-enum">BindOptions</a></span> <i>options</i> )</h3>
<p>Generates and binds a 2D GL texture to the current context, based on <i>image</i>. The generated texture id is returned and can be used in later <tt>glBindTexture()</tt> calls.</p>
<p>The <i>target</i> parameter specifies the texture target. The default target is <tt>GL_TEXTURE_2D</tt>.</p>
<p>The <i>format</i> parameter sets the internal format for the texture. The default format is <tt>GL_RGBA</tt>.</p>
<p>The binding <i>options</i> are a set of options used to decide how to bind the texture to the context.</p>
<p>The texture that is generated is cached, so multiple calls to bindTexture() with the same <a href="qimage.html">QImage</a> will return the same texture id.</p>
<p>Note that we assume default values for the glPixelStore() and glPixelTransfer() parameters.</p>
<p>This function was introduced in Qt 4.6.</p>
<p><b>See also </b><a href="qglcontext.html#deleteTexture">deleteTexture</a>().</p>
<!-- @@@bindTexture -->
<!-- $$$bindTexture$$$bindTextureconstQString& -->
<h3 class="fn"><a name="bindTexture-2"></a><span class="type">GLuint</span> QGLContext::<span class="name">bindTexture</span> ( const <span class="type"><a href="qstring.html">QString</a></span> & <i>fileName</i> )</h3>
<p>This is an overloaded function.</p>
<p>Reads the compressed texture file <i>fileName</i> and generates a 2D GL texture from it.</p>
<p>This function can load DirectDrawSurface (DDS) textures in the DXT1, DXT3 and DXT5 DDS formats if the <tt>GL_ARB_texture_compression</tt> and <tt>GL_EXT_texture_compression_s3tc</tt> extensions are supported.</p>
<p>Since 4.6.1, textures in the ETC1 format can be loaded if the <tt>GL_OES_compressed_ETC1_RGB8_texture</tt> extension is supported and the ETC1 texture has been encapsulated in the PVR container format. Also, textures in the PVRTC2 and PVRTC4 formats can be loaded if the <tt>GL_IMG_texture_compression_pvrtc</tt> extension is supported.</p>
<p><b>See also </b><a href="qglcontext.html#deleteTexture">deleteTexture</a>().</p>
<!-- @@@bindTexture -->
<!-- $$$bindTexture$$$bindTextureconstQImage&GLenumGLint -->
<h3 class="fn"><a name="bindTexture-3"></a><span class="type">GLuint</span> QGLContext::<span class="name">bindTexture</span> ( const <span class="type"><a href="qimage.html">QImage</a></span> & <i>image</i>, <span class="type">GLenum</span> <i>target</i> = GL_TEXTURE_2D, <span class="type">GLint</span> <i>format</i> = GL_RGBA )</h3>
<p>Generates and binds a 2D GL texture to the current context, based on <i>image</i>. The generated texture id is returned and can be used in later <tt>glBindTexture()</tt> calls.</p>
<p>This is an overloaded function.</p>
<!-- @@@bindTexture -->
<!-- $$$bindTexture$$$bindTextureconstQPixmap&GLenumGLint -->
<h3 class="fn"><a name="bindTexture-4"></a><span class="type">GLuint</span> QGLContext::<span class="name">bindTexture</span> ( const <span class="type"><a href="qpixmap.html">QPixmap</a></span> & <i>pixmap</i>, <span class="type">GLenum</span> <i>target</i> = GL_TEXTURE_2D, <span class="type">GLint</span> <i>format</i> = GL_RGBA )</h3>
<p>This is an overloaded function.</p>
<p>Generates and binds a 2D GL texture based on <i>pixmap</i>.</p>
<!-- @@@bindTexture -->
<!-- $$$bindTexture$$$bindTextureconstQPixmap&GLenumGLintBindOptions -->
<h3 class="fn"><a name="bindTexture-5"></a><span class="type">GLuint</span> QGLContext::<span class="name">bindTexture</span> ( const <span class="type"><a href="qpixmap.html">QPixmap</a></span> & <i>pixmap</i>, <span class="type">GLenum</span> <i>target</i>, <span class="type">GLint</span> <i>format</i>, <span class="type"><a href="qglcontext.html#BindOption-enum">BindOptions</a></span> <i>options</i> )</h3>
<p>This is an overloaded function.</p>
<p>Generates and binds a 2D GL texture to the current context, based on <i>pixmap</i>.</p>
<p>This function was introduced in Qt 4.6.</p>
<!-- @@@bindTexture -->
<!-- $$$chooseContext[overload1]$$$chooseContextconstQGLContext* -->
<h3 class="fn"><a name="chooseContext"></a><span class="type">bool</span> QGLContext::<span class="name">chooseContext</span> ( const <span class="type">QGLContext</span> * <i>shareContext</i> = 0 )<tt> [virtual protected]</tt></h3>
<p>This semi-internal function is called by <a href="qglcontext.html#create">create</a>(). It creates a system-dependent OpenGL handle that matches the <a href="qglcontext.html#format">format</a>() of <i>shareContext</i> as closely as possible, returning true if successful or false if a suitable handle could not be found.</p>
<p>On Windows, it calls the virtual function <a href="qglcontext.html#choosePixelFormat">choosePixelFormat</a>(), which finds a matching pixel format identifier. On X11, it calls the virtual function <a href="qglcontext.html#chooseVisual">chooseVisual</a>() which finds an appropriate X visual. On other platforms it may work differently.</p>
<!-- @@@chooseContext -->
<!-- $$$chooseMacVisual[overload1]$$$chooseMacVisualGDHandle -->
<h3 class="fn"><a name="chooseMacVisual"></a><span class="type">void</span> * QGLContext::<span class="name">chooseMacVisual</span> ( <span class="type">GDHandle</span> <i>handle</i> )<tt> [virtual protected]</tt></h3>
<p><b>Mac OS X only:</b> This virtual function tries to find a visual that matches the format, reducing the demands if the original request cannot be met.</p>
<p>The algorithm for reducing the demands of the format is quite simple-minded, so override this method in your subclass if your application has spcific requirements on visual selection.</p>
<p>The <i>handle</i> argument is always zero and is not used</p>
<p><b>See also </b><a href="qglcontext.html#chooseContext">chooseContext</a>().</p>
<!-- @@@chooseMacVisual -->
<!-- $$$choosePixelFormat[overload1]$$$choosePixelFormatvoid*HDC -->
<h3 class="fn"><a name="choosePixelFormat"></a><span class="type">int</span> QGLContext::<span class="name">choosePixelFormat</span> ( <span class="type">void</span> * <i>dummyPfd</i>, <span class="type">HDC</span> <i>pdc</i> )<tt> [virtual protected]</tt></h3>
<p><b>Win32 only:</b> This virtual function chooses a pixel format that matches the OpenGL <a href="qglcontext.html#setFormat">format</a>. Reimplement this function in a subclass if you need a custom context.</p>
<p><b>Warning:</b> The <i>dummyPfd</i> pointer and <i>pdc</i> are used as a <tt>PIXELFORMATDESCRIPTOR*</tt>. We use <tt>void</tt> to avoid using Windows-specific types in our header files.</p>
<p><b>See also </b><a href="qglcontext.html#chooseContext">chooseContext</a>().</p>
<!-- @@@choosePixelFormat -->
<!-- $$$chooseVisual[overload1]$$$chooseVisual -->
<h3 class="fn"><a name="chooseVisual"></a><span class="type">void</span> * QGLContext::<span class="name">chooseVisual</span> ()<tt> [virtual protected]</tt></h3>
<p><b>X11 only:</b> This virtual function tries to find a visual that matches the format, reducing the demands if the original request cannot be met.</p>
<p>The algorithm for reducing the demands of the format is quite simple-minded, so override this method in your subclass if your application has spcific requirements on visual selection.</p>
<p><b>See also </b><a href="qglcontext.html#chooseContext">chooseContext</a>().</p>
<!-- @@@chooseVisual -->
<!-- $$$create[overload1]$$$createconstQGLContext* -->
<h3 class="fn"><a name="create"></a><span class="type">bool</span> QGLContext::<span class="name">create</span> ( const <span class="type">QGLContext</span> * <i>shareContext</i> = 0 )<tt> [virtual]</tt></h3>
<p>Creates the GL context. Returns true if it was successful in creating a valid GL rendering context on the paint device specified in the constructor; otherwise returns false (i.e. the context is invalid).</p>
<p>After successful creation, <a href="qglcontext.html#format">format</a>() returns the set of features of the created GL rendering context.</p>
<p>If <i>shareContext</i> points to a valid <a href="qglcontext.html">QGLContext</a>, this method will try to establish OpenGL display list and texture object sharing between this context and the <i>shareContext</i>. Note that this may fail if the two contexts have different <a href="qglcontext.html#format">formats</a>. Use <a href="qglcontext.html#isSharing">isSharing</a>() to see if sharing is in effect.</p>
<p><b>Warning:</b> Implementation note: initialization of C++ class members usually takes place in the class constructor. <a href="qglcontext.html">QGLContext</a> is an exception because it must be simple to customize. The virtual functions <a href="qglcontext.html#chooseContext">chooseContext</a>() (and <a href="qglcontext.html#chooseVisual">chooseVisual</a>() for X11) can be reimplemented in a subclass to select a particular context. The problem is that virtual functions are not properly called during construction (even though this is correct C++) because C++ constructs class hierarchies from the bottom up. For this reason we need a create() function.</p>
<p><b>See also </b><a href="qglcontext.html#chooseContext">chooseContext</a>(), <a href="qglcontext.html#format">format</a>(), and <a href="qglcontext.html#isValid">isValid</a>().</p>
<!-- @@@create -->
<!-- $$$currentContext[overload1]$$$currentContext -->
<h3 class="fn"><a name="currentContext"></a>const <span class="type">QGLContext</span> * QGLContext::<span class="name">currentContext</span> ()<tt> [static]</tt></h3>
<p>Returns the current context, i.e. the context to which any OpenGL commands will currently be directed. Returns 0 if no context is current.</p>
<p><b>See also </b><a href="qglcontext.html#makeCurrent">makeCurrent</a>().</p>
<!-- @@@currentContext -->
<!-- $$$deleteTexture[overload1]$$$deleteTextureGLuint -->
<h3 class="fn"><a name="deleteTexture"></a><span class="type">void</span> QGLContext::<span class="name">deleteTexture</span> ( <span class="type">GLuint</span> <i>id</i> )</h3>
<p>Removes the texture identified by <i>id</i> from the texture cache, and calls glDeleteTextures() to delete the texture from the context.</p>
<p><b>See also </b><a href="qglcontext.html#bindTexture">bindTexture</a>().</p>
<!-- @@@deleteTexture -->
<!-- $$$device[overload1]$$$device -->
<h3 class="fn"><a name="device"></a><span class="type"><a href="qpaintdevice.html">QPaintDevice</a></span> * QGLContext::<span class="name">device</span> () const</h3>
<p>Returns the paint device set for this context.</p>
<p><b>See also </b><a href="qglcontext.html#QGLContext">QGLContext::QGLContext</a>().</p>
<!-- @@@device -->
<!-- $$$deviceIsPixmap[overload1]$$$deviceIsPixmap -->
<h3 class="fn"><a name="deviceIsPixmap"></a><span class="type">bool</span> QGLContext::<span class="name">deviceIsPixmap</span> () const<tt> [protected]</tt></h3>
<p>Returns true if the paint device of this context is a pixmap; otherwise returns false.</p>
<!-- @@@deviceIsPixmap -->
<!-- $$$doneCurrent[overload1]$$$doneCurrent -->
<h3 class="fn"><a name="doneCurrent"></a><span class="type">void</span> QGLContext::<span class="name">doneCurrent</span> ()<tt> [virtual]</tt></h3>
<p>Makes no GL context the current context. Normally, you do not need to call this function; <a href="qglcontext.html">QGLContext</a> calls it as necessary.</p>
<!-- @@@doneCurrent -->
<!-- $$$drawTexture[overload1]$$$drawTextureconstQRectF&GLuintGLenum -->
<h3 class="fn"><a name="drawTexture"></a><span class="type">void</span> QGLContext::<span class="name">drawTexture</span> ( const <span class="type"><a href="qrectf.html">QRectF</a></span> & <i>target</i>, <span class="type">GLuint</span> <i>textureId</i>, <span class="type">GLenum</span> <i>textureTarget</i> = GL_TEXTURE_2D )</h3>
<p>This function supports the following use cases:</p>
<ul>
<li>On OpenGL and OpenGL ES 1.x it draws the given texture, <i>textureId</i>, to the given target rectangle, <i>target</i>, in OpenGL model space. The <i>textureTarget</i> should be a 2D texture target.</li>
<li>On OpenGL and OpenGL ES 2.x, if a painter is active, not inside a beginNativePainting / endNativePainting block, and uses the engine with type <a href="qpaintengine.html#Type-enum">QPaintEngine::OpenGL2</a>, the function will draw the given texture, <i>textureId</i>, to the given target rectangle, <i>target</i>, respecting the current painter state. This will let you draw a texture with the clip, transform, render hints, and composition mode set by the painter. Note that the texture target needs to be GL_TEXTURE_2D for this use case, and that this is the only supported use case under OpenGL ES 2.x.</li>
</ul>
<p>This function was introduced in Qt 4.4.</p>
<!-- @@@drawTexture -->
<!-- $$$drawTexture$$$drawTextureconstQPointF&GLuintGLenum -->
<h3 class="fn"><a name="drawTexture-2"></a><span class="type">void</span> QGLContext::<span class="name">drawTexture</span> ( const <span class="type"><a href="qpointf.html">QPointF</a></span> & <i>point</i>, <span class="type">GLuint</span> <i>textureId</i>, <span class="type">GLenum</span> <i>textureTarget</i> = GL_TEXTURE_2D )</h3>
<p>This function supports the following use cases:</p>
<ul>
<li>By default it draws the given texture, <i>textureId</i>, at the given <i>point</i> in OpenGL model space. The <i>textureTarget</i> should be a 2D texture target.</li>
<li>If a painter is active, not inside a beginNativePainting / endNativePainting block, and uses the engine with type <a href="qpaintengine.html#Type-enum">QPaintEngine::OpenGL2</a>, the function will draw the given texture, <i>textureId</i>, at the given <i>point</i>, respecting the current painter state. This will let you draw a texture with the clip, transform, render hints, and composition mode set by the painter. Note that the texture target needs to be GL_TEXTURE_2D for this use case.</li>
</ul>
<p><b>Note:</b> This function is not supported under any version of OpenGL ES.</p>
<p>This function was introduced in Qt 4.4.</p>
<!-- @@@drawTexture -->
<!-- $$$format[overload1]$$$format -->
<h3 class="fn"><a name="format"></a><span class="type"><a href="qglformat.html">QGLFormat</a></span> QGLContext::<span class="name">format</span> () const</h3>
<p>Returns the frame buffer format that was obtained (this may be a subset of what was requested).</p>
<p><b>See also </b><a href="qglcontext.html#setFormat">setFormat</a>() and <a href="qglcontext.html#requestedFormat">requestedFormat</a>().</p>
<!-- @@@format -->
<!-- $$$fromPlatformGLContext[overload1]$$$fromPlatformGLContextQPlatformGLContext* -->
<h3 class="fn"><a name="fromPlatformGLContext"></a><span class="type">QGLContext</span> * QGLContext::<span class="name">fromPlatformGLContext</span> ( <span class="type">QPlatformGLContext</span> * <i>platformContext</i> )<tt> [static]</tt></h3>
<p>Returns a OpenGL context for the platform-specific OpenGL context given by <i>platformContext</i>.</p>
<p>This function was introduced in Qt 4.8.</p>
<!-- @@@fromPlatformGLContext -->
<!-- $$$getProcAddress[overload1]$$$getProcAddressconstQString& -->
<h3 class="fn"><a name="getProcAddress"></a><span class="type">void</span> * QGLContext::<span class="name">getProcAddress</span> ( const <span class="type"><a href="qstring.html">QString</a></span> & <i>proc</i> ) const</h3>
<p>Returns a function pointer to the GL extension function passed in <i>proc</i>. 0 is returned if a pointer to the function could not be obtained.</p>
<!-- @@@getProcAddress -->
<!-- $$$initialized[overload1]$$$initialized -->
<h3 class="fn"><a name="initialized"></a><span class="type">bool</span> QGLContext::<span class="name">initialized</span> () const<tt> [protected]</tt></h3>
<p>Returns true if this context has been initialized, i.e. if <a href="qglwidget.html#initializeGL">QGLWidget::initializeGL</a>() has been performed on it; otherwise returns false.</p>
<p><b>See also </b><a href="qglcontext.html#setInitialized">setInitialized</a>().</p>
<!-- @@@initialized -->
<!-- $$$isSharing[overload1]$$$isSharing -->
<h3 class="fn"><a name="isSharing"></a><span class="type">bool</span> QGLContext::<span class="name">isSharing</span> () const</h3>
<p>Returns true if this context is sharing its GL context with another <a href="qglcontext.html">QGLContext</a>, otherwise false is returned. Note that context sharing might not be supported between contexts with different formats.</p>
<!-- @@@isSharing -->
<!-- $$$isValid[overload1]$$$isValid -->
<h3 class="fn"><a name="isValid"></a><span class="type">bool</span> QGLContext::<span class="name">isValid</span> () const</h3>
<p>Returns true if a GL rendering context has been successfully created; otherwise returns false.</p>
<!-- @@@isValid -->
<!-- $$$makeCurrent[overload1]$$$makeCurrent -->
<h3 class="fn"><a name="makeCurrent"></a><span class="type">void</span> QGLContext::<span class="name">makeCurrent</span> ()<tt> [virtual]</tt></h3>
<p>Makes this context the current OpenGL rendering context. All GL functions you call operate on this context until another context is made current.</p>
<p>In some very rare cases the underlying call may fail. If this occurs an error message is output to stderr.</p>
<!-- @@@makeCurrent -->
<!-- $$$overlayTransparentColor[overload1]$$$overlayTransparentColor -->
<h3 class="fn"><a name="overlayTransparentColor"></a><span class="type"><a href="qcolor.html">QColor</a></span> QGLContext::<span class="name">overlayTransparentColor</span> () const</h3>
<p>If this context is a valid context in an overlay plane, returns the plane's transparent color. Otherwise returns an {<a href="qcolor.html#isValid">QColor::isValid</a>()}{invalid} color.</p>
<p>The returned <a href="qcolor.html">QColor</a> object will generally work as expected only when passed as the argument to <a href="qglwidget.html#qglColor">QGLWidget::qglColor</a>() or <a href="qglwidget.html#qglClearColor">QGLWidget::qglClearColor</a>(). Under certain circumstances it can also be used to draw transparent graphics with a <a href="qpainter.html">QPainter</a>.</p>
<!-- @@@overlayTransparentColor -->
<!-- $$$requestedFormat[overload1]$$$requestedFormat -->
<h3 class="fn"><a name="requestedFormat"></a><span class="type"><a href="qglformat.html">QGLFormat</a></span> QGLContext::<span class="name">requestedFormat</span> () const</h3>
<p>Returns the frame buffer format that was originally requested in the constructor or <a href="qglcontext.html#setFormat">setFormat</a>().</p>
<p><b>See also </b><a href="qglcontext.html#format">format</a>().</p>
<!-- @@@requestedFormat -->
<!-- $$$reset[overload1]$$$reset -->
<h3 class="fn"><a name="reset"></a><span class="type">void</span> QGLContext::<span class="name">reset</span> ()</h3>
<p>Resets the context and makes it invalid.</p>
<p><b>See also </b><a href="qglcontext.html#create">create</a>() and <a href="qglcontext.html#isValid">isValid</a>().</p>
<!-- @@@reset -->
<!-- $$$setFormat[overload1]$$$setFormatconstQGLFormat& -->
<h3 class="fn"><a name="setFormat"></a><span class="type">void</span> QGLContext::<span class="name">setFormat</span> ( const <span class="type"><a href="qglformat.html">QGLFormat</a></span> & <i>format</i> )</h3>
<p>Sets a <i>format</i> for this context. The context is <a href="qglcontext.html#reset">reset</a>.</p>
<p>Call <a href="qglcontext.html#create">create</a>() to create a new GL context that tries to match the new format.</p>
<pre class="cpp"> <span class="type"><a href="qglcontext.html">QGLContext</a></span> <span class="operator">*</span>cx;
<span class="comment">// ...</span>
<span class="type"><a href="qglformat.html">QGLFormat</a></span> f;
f<span class="operator">.</span>setStereo(<span class="keyword">true</span>);
cx<span class="operator">-</span><span class="operator">></span>setFormat(f);
<span class="keyword">if</span> (<span class="operator">!</span>cx<span class="operator">-</span><span class="operator">></span>create())
exit(); <span class="comment">// no OpenGL support, or cannot render on the specified paintdevice</span>
<span class="keyword">if</span> (<span class="operator">!</span>cx<span class="operator">-</span><span class="operator">></span>format()<span class="operator">.</span>stereo())
exit(); <span class="comment">// could not create stereo context</span></pre>
<p><b>See also </b><a href="qglcontext.html#format">format</a>(), <a href="qglcontext.html#reset">reset</a>(), and <a href="qglcontext.html#create">create</a>().</p>
<!-- @@@setFormat -->
<!-- $$$setInitialized[overload1]$$$setInitializedbool -->
<h3 class="fn"><a name="setInitialized"></a><span class="type">void</span> QGLContext::<span class="name">setInitialized</span> ( <span class="type">bool</span> <i>on</i> )<tt> [protected]</tt></h3>
<p>If <i>on</i> is true the context has been initialized, i.e. QGLContext::setInitialized() has been called on it. If <i>on</i> is false the context has not been initialized.</p>
<p><b>See also </b><a href="qglcontext.html#initialized">initialized</a>().</p>
<!-- @@@setInitialized -->
<!-- $$$setTextureCacheLimit[overload1]$$$setTextureCacheLimitint -->
<h3 class="fn"><a name="setTextureCacheLimit"></a><span class="type">void</span> QGLContext::<span class="name">setTextureCacheLimit</span> ( <span class="type">int</span> <i>size</i> )<tt> [static]</tt></h3>
<p>This function sets the limit for the texture cache to <i>size</i>, expressed in kilobytes.</p>
<p>By default, the cache limit is approximately 64 MB.</p>
<p><b>See also </b><a href="qglcontext.html#textureCacheLimit">textureCacheLimit</a>().</p>
<!-- @@@setTextureCacheLimit -->
<!-- $$$setWindowCreated[overload1]$$$setWindowCreatedbool -->
<h3 class="fn"><a name="setWindowCreated"></a><span class="type">void</span> QGLContext::<span class="name">setWindowCreated</span> ( <span class="type">bool</span> <i>on</i> )<tt> [protected]</tt></h3>
<p>If <i>on</i> is true the context has had a window created for it. If <i>on</i> is false no window has been created for the context.</p>
<p><b>See also </b><a href="qglcontext.html#windowCreated">windowCreated</a>().</p>
<!-- @@@setWindowCreated -->
<!-- $$$swapBuffers[overload1]$$$swapBuffers -->
<h3 class="fn"><a name="swapBuffers"></a><span class="type">void</span> QGLContext::<span class="name">swapBuffers</span> () const<tt> [virtual]</tt></h3>
<p>Swaps the screen contents with an off-screen buffer. Only works if the context is in double buffer mode.</p>
<p><b>See also </b><a href="qglformat.html#setDoubleBuffer">QGLFormat::setDoubleBuffer</a>().</p>
<!-- @@@swapBuffers -->
<!-- $$$textureCacheLimit[overload1]$$$textureCacheLimit -->
<h3 class="fn"><a name="textureCacheLimit"></a><span class="type">int</span> QGLContext::<span class="name">textureCacheLimit</span> ()<tt> [static]</tt></h3>
<p>Returns the current texture cache limit in kilobytes.</p>
<p><b>See also </b><a href="qglcontext.html#setTextureCacheLimit">setTextureCacheLimit</a>().</p>
<!-- @@@textureCacheLimit -->
<!-- $$$windowCreated[overload1]$$$windowCreated -->
<h3 class="fn"><a name="windowCreated"></a><span class="type">bool</span> QGLContext::<span class="name">windowCreated</span> () const<tt> [protected]</tt></h3>
<p>Returns true if a window has been created for this context; otherwise returns false.</p>
<p><b>See also </b><a href="qglcontext.html#setWindowCreated">setWindowCreated</a>().</p>
<!-- @@@windowCreated -->
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