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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Qt Toolkit - QGLContext Class</title><style type="text/css"><!--
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<h1 align=center>QGLContext Class Reference<br><small>[ <a href="opengl.html">OpenGL module</a> ]</small></h1><br clear="all">
<p>
The QGLContext class encapsulates an OpenGL rendering context.
<a href="#details">More...</a>
<p>
<code>#include &lt;<a href="qgl-h.html">qgl.h</a>&gt;</code>
<p>
Inherits <a href="qgl.html">QGL</a>.
<p><a href="qglcontext-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li><div class="fn"><a href="#cd1859"><b>QGLContext</b></a>(constQGLFormat&amp;format, QPaintDevice*device)</div>
<li><div class="fn">virtual<a href="#ad3237"><b>~QGLContext</b></a>()</div>
<li><div class="fn">virtualbool<a href="#ebdd54"><b>create</b></a>(constQGLContext*shareContext=0)</div>
<li><div class="fn">bool<a href="#8a42ec"><b>isValid</b></a>()const</div>
<li><div class="fn">bool<a href="#bf8d5f"><b>isSharing</b></a>()const</div>
<li><div class="fn">virtualvoid<a href="#0283b5"><b>reset</b></a>()</div>
<li><div class="fn">QGLFormat<a href="#df01e6"><b>format</b></a>()const</div>
<li><div class="fn">virtualvoid<a href="#87cf0f"><b>setFormat</b></a>(constQGLFormat&amp;format)</div>
<li><div class="fn">virtualvoid<a href="#fba7ee"><b>makeCurrent</b></a>()</div>
<li><div class="fn">virtualvoid<a href="#35dbed"><b>swapBuffers</b></a>()const</div>
<li><div class="fn">QPaintDevice*<a href="#4cbbbd"><b>device</b></a>()const</div>
<li><div class="fn">QColor<a href="#d4abe1"><b>overlayTransparentColor</b></a>()const</div>
</ul>
<h2>Static Public Members</h2>
<ul>
<li><div class="fn">constQGLContext*<a href="#8859cd"><b>currentContext</b></a>()</div>
</ul>
<h2>Protected Members</h2>
<ul>
<li><div class="fn">virtualbool<a href="#664a3c"><b>chooseContext</b></a>(constQGLContext*shareContext=0)</div>
<li><div class="fn">virtualvoid<a href="#7bc880"><b>doneCurrent</b></a>()</div>
<li><div class="fn">bool<a href="#1c27f5"><b>deviceIsPixmap</b></a>()const</div>
<li><div class="fn">bool<a href="#2bad53"><b>windowCreated</b></a>()const</div>
<li><div class="fn">void<a href="#26ab67"><b>setWindowCreated</b></a>(boolon)</div>
<li><div class="fn">bool<a href="#f7fb11"><b>initialized</b></a>()const</div>
<li><div class="fn">void<a href="#b0b908"><b>setInitialized</b></a>(boolon)</div>
<li><div class="fn">uint<b>colorIndex</b>(constQColor&amp;c)const(internal)</div>
</ul>
<hr><h2><a name="details"></a>Detailed Description</h2>
The QGLContext class encapsulates an OpenGL rendering context.
<p>
An OpenGL rendering context is a complete set of OpenGL state
variables.

<hr><h2>Member Function Documentation</h2>
<h3 class="fn"><a name="cd1859"></a>QGLContext::QGLContext(const<a href="qglformat.html">QGLFormat</a>&amp;format, <a href="qpaintdevice.html">QPaintDevice</a>*device)</h3>
<p>Constructs an OpenGL context for the paint device <em>device,</em> which
can be a widget or a pixmap. The <em>format</em> specifies several display
options for this context.
<p>If the underlying OpenGL/Window system cannot satisfy all the
features requested in <em>format,</em> the nearest subset of features will
be used. After creation, the <a href="#df01e6">format</a>() method will return the actual
format obtained.
<p>The context will be <a href="#8a42ec">invalid</a> if it was not
possible to obtain a GL context at all.
<p>See also  <a href="#df01e6">format</a>() and <a href="#8a42ec">isValid</a>().
<h3 class="fn"><a name="ad3237"></a>QGLContext::~QGLContext() <code>[virtual]</code></h3>
<p>Destroys the OpenGL context.
<h3 class="fn">bool<a name="664a3c"></a>QGLContext::chooseContext(constQGLContext*shareContext=0=0) <code>[virtualprotected]</code></h3>
<p>This semi-internal function is called by <a href="#ebdd54">create</a>(). It creates a
system-dependent OpenGL handle that matches the specified <a href="#df01e6">format</a> as closely as possible.
<p><strong>Windows</strong>: Calls choosePixelFormat() which finds a
matching pixel format identifier.
<p><strong>X11</strong>: Calls chooseVisual() which finds an appropriate
X visual.
<p>choosePixelFormat() and chooseVisual() can be reimplemented in a
subclass if you need to choose a very custom context.
<h3 class="fn">bool<a name="ebdd54"></a>QGLContext::create(constQGLContext*shareContext=0) <code>[virtual]</code></h3>
<p>Creates the GL context. Returns TRUE if it was successful in
creating a GL rendering context on the paint device specified in the
constructor, otherwise FALSE is returned (the context is invalid).
<p>After successful creation, <a href="#df01e6">format</a>() returns the set of features of
the created GL rendering context.
<p>If <em>shareContext</em> points to a valid QGLContext, this method will
try to establish OpenGL display list sharing between this context
and <em>shareContext.</em> Note that this may fail if the two contexts
have different formats. Use <a href="#bf8d5f">isSharing</a>() to test.
<p><strong>Implementation note:</strong> Initialization of C++ class members
usually takes place in the class constructor. QGLContext is an exception
because it must be simple to customize. The virtual functions
<a href="#664a3c">chooseContext</a>() (and chooseVisual() for X11) can be reimplemented in a
subclass to select a particular context. The trouble is that virtual
functions are not properly called during construction (which is indeed
correct C++), hence we need a create() function.
<p>See also  <a href="#664a3c">chooseContext</a>(), <a href="#df01e6">format</a>() and <a href="#8a42ec">isValid</a>().
<h3 class="fn">constQGLContext*<a name="8859cd"></a>QGLContext::currentContext() <code>[static]</code></h3>
<p>Returns the current context, i.e. the context to which any OpenGL
commands will currently be directed to. Returns 0 if no context is
current.
<p>See also  <a href="#fba7ee">makeCurrent</a>().
<h3 class="fn"><a href="qpaintdevice.html">QPaintDevice</a>*<a name="4cbbbd"></a>QGLContext::device()const</h3>
<p>Returns the paint device set for this context.
<p>See also  <a href="#cd1859">QGLContext::QGLContext</a>().
<h3 class="fn">bool<a name="1c27f5"></a>QGLContext::deviceIsPixmap()const <code>[protected]</code></h3>
<p>Returns TRUE if the paint device of this context is a pixmap,
otherwise FALSE.
<h3 class="fn">void<a name="7bc880"></a>QGLContext::doneCurrent() <code>[virtualprotected]</code></h3>
<p>Makes no GL context the current context. Normally, you do not need
to call this function, QGLContext calls it as necessary.
<h3 class="fn"><a href="qglformat.html">QGLFormat</a><a name="df01e6"></a>QGLContext::format()const</h3>
<p>Returns the format.
<h3 class="fn">bool<a name="f7fb11"></a>QGLContext::initialized()const <code>[protected]</code></h3>
<p>Returns TRUE if this context has been initialized, i.e. if
<a href="qglwidget.html#97a643">QGLWidget::initializeGL</a>() has been performed on it.
<p>See also  <a href="#b0b908">setInitialized</a>().
<h3 class="fn">bool<a name="bf8d5f"></a>QGLContext::isSharing()const</h3>
<p>Returns TRUE if display list sharing with another context was
requested in the <a href="#ebdd54">create</a>() call, and the GL system was able to
fulfill this request. Note that display list sharing may possibly
not be supported between contexts with different formats.
<h3 class="fn">bool<a name="8a42ec"></a>QGLContext::isValid()const</h3>
<p>Returns TRUE if a GL rendering context has been successfully created.
<h3 class="fn">void<a name="fba7ee"></a>QGLContext::makeCurrent() <code>[virtual]</code></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.
<h3 class="fn"><a href="qcolor.html">QColor</a><a name="d4abe1"></a>QGLContext::overlayTransparentColor()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#5cd295">invalid</a> color.
<p>The returned color's <a href="qcolor.html#4cec2b">pixel</a> value is
the index of the transparent color in the colormap of the overlay
plane. The color's RGB values are meaningless, of course.
<p>The returned <a href="qcolor.html">QColor</a> object will generally only work as expected when
passed as the argument to <a href="qglwidget.html#f60400">QGLWidget::qglColor</a>() or
<a href="qglwidget.html#83fed2">QGLWidget::qglClearColor</a>(). Under certain circumstances it can also
be used to draw transparent graphics with a <a href="qpainter.html">QPainter</a>; see the
"overlay_x11" example for details.
<h3 class="fn">void<a name="0283b5"></a>QGLContext::reset() <code>[virtual]</code></h3>
<p>Resets the context and makes it invalid.
<p>See also  <a href="#ebdd54">create</a>() and <a href="#8a42ec">isValid</a>().
<h3 class="fn">void<a name="87cf0f"></a>QGLContext::setFormat(const<a href="qglformat.html">QGLFormat</a>&amp;format) <code>[virtual]</code></h3>
<p>Sets a <em>format</em> for this context. The context is <a href="#0283b5">reset</a>.
<p>Call <a href="#ebdd54">create</a>() to create a new GL context that tries to match the new
format.
<p><pre>    <a href="qglcontext.html">QGLContext</a> *cx;
      ...
    <a href="qglformat.html">QGLFormat</a> f;
    f.<a href="qglformat.html#82dd03">setStereo</a>( TRUE );
    cx-&gt;<a href="#87cf0f">setFormat</a>( f );
    if ( !cx-&gt;<a href="#ebdd54">create</a>() )
        exit(); // no OpenGL support, or cannot render on specified paintdevice
    if ( !cx-&gt;<a href="#df01e6">format</a>().stereo() )
        exit(); // could not create stereo context
</pre>
<p>See also  <a href="#df01e6">format</a>(), <a href="#0283b5">reset</a>() and <a href="#ebdd54">create</a>().
<h3 class="fn">void<a name="b0b908"></a>QGLContext::setInitialized(boolon) <code>[protected]</code></h3>
<p>Tells the context whether it has been initialized, i.e. whether
<a href="qglwidget.html#97a643">QGLWidget::initializeGL</a>() has been performed on it.
<p>See also  <a href="#f7fb11">initialized</a>().
<h3 class="fn">void<a name="26ab67"></a>QGLContext::setWindowCreated(boolon) <code>[protected]</code></h3>
<p>Tells the context whether a window has already been created for it.
<p>See also  <a href="#2bad53">windowCreated</a>().
<h3 class="fn">void<a name="35dbed"></a>QGLContext::swapBuffers()const <code>[virtual]</code></h3>
<p>Swaps the screen contents with an off-screen buffer. Works only if
the context is in double buffer mode.
<p>See also  <a href="qglformat.html#38644f">QGLFormat::setDoubleBuffer</a>().
<h3 class="fn">bool<a name="2bad53"></a>QGLContext::windowCreated()const <code>[protected]</code></h3>
<p>Returns TRUE if a window has been created for this context,
otherwise FALSE.
<p>See also  <a href="#26ab67">setWindowCreated</a>().
<h3 class="fn">uint<a name="8a428b"></a>QGLContext::colorIndex(const<a href="qcolor.html">QColor</a>&amp;c)const <code>[protected]</code></h3>
<p>For internal use only.
<hr><p>
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