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<p> It is possible that the context is not valid (see <a href="#isValid">isValid</a>()), for
example, if the underlying hardware does not support the format
attributes that were requested.

<h3 class=fn><a href="qimage.html">QImage</a> <a name="convertToGLFormat"></a>QGLWidget::convertToGLFormat ( const&nbsp;<a href="qimage.html">QImage</a>&nbsp;&amp;&nbsp;img )<tt> [static]</tt>
</h3> Converts the image <em>img</em> into the unnamed format expected by OpenGL
functions such as glTexImage2D(). The returned image is not usable
as a <a href="qimage.html">QImage</a>, but <a href="qimage.html#width">QImage::width</a>(), <a href="qimage.html#height">QImage::height</a>() and
<a href="qimage.html#bits">QImage::bits</a>() may be used with OpenGL. The following few lines are
from the texture example. Most of the code is irrelevant, so we just
quote the few lines we want:
<p> 

<pre>        <a href="qimage.html">QImage</a> tex1, tex2, buf;
        if ( !buf.load( "gllogo.bmp" ) ) {  // Load first image from file
</pre>
<p> We create <em>tex1</em> (and another variable) for OpenGL, and load a real
image into <em>buf</em>.
<p> <pre>    <a name="x2089"></a>    tex1 = QGLWidget::<a href="#convertToGLFormat">convertToGLFormat</a>( buf );  // flipped 32bit RGBA
</pre>
<p> A few lines later, we convert <em>buf</em> into OpenGL format and store it
in <em>tex1</em>.
<p> <pre>    <a name="x2092"></a><a name="x2091"></a>    glTexImage2D( GL_TEXTURE_2D, 0, 3, tex1.<a href="qimage.html#width">width</a>(), tex1.<a href="qimage.html#height">height</a>(), 0,
    <a name="x2090"></a>                  GL_RGBA, GL_UNSIGNED_BYTE, tex1.<a href="qimage.html#bits">bits</a>() );
</pre>
<p> Another function in the same example uses <em>tex1</em> with OpenGL.

<p>Example: <a href="qglwidget.html#x2089">opengl/texture/gltexobj.cpp</a>.
<h3 class=fn>bool <a name="doubleBuffer"></a>QGLWidget::doubleBuffer () const
</h3>

Returns TRUE if the contained GL rendering context has double
buffering; otherwise returns FALSE.
<p>See also <a href="qglformat.html#doubleBuffer">QGLFormat::doubleBuffer</a>().

<h3 class=fn><a href="qglformat.html">QGLFormat</a> <a name="format"></a>QGLWidget::format () const
</h3>

Returns the format of the contained GL rendering context.

<h3 class=fn>void <a name="glDraw"></a>QGLWidget::glDraw ()<tt> [virtual protected]</tt>
</h3>
Executes the virtual function <a href="#paintGL">paintGL</a>().
<p> The widget's rendering context will become the current context and
<a href="#initializeGL">initializeGL</a>() will be called if it hasn't already been called.

<h3 class=fn>void <a name="glInit"></a>QGLWidget::glInit ()<tt> [virtual protected]</tt>
</h3>
Initializes OpenGL for this widget's context. Calls the virtual
function <a href="#initializeGL">initializeGL</a>().

<h3 class=fn><a href="qimage.html">QImage</a> <a name="grabFrameBuffer"></a>QGLWidget::grabFrameBuffer ( bool&nbsp;withAlpha = FALSE )<tt> [virtual]</tt>
</h3>
Returns an image of the frame buffer. If <em>withAlpha</em> is TRUE the
alpha channel is included.

<h3 class=fn>void <a name="initializeGL"></a>QGLWidget::initializeGL ()<tt> [virtual protected]</tt>
</h3>
This virtual function is called once before the first call to
<a href="#paintGL">paintGL</a>() or <a href="#resizeGL">resizeGL</a>(), and then once whenever the widget has
been assigned a new <a href="qglcontext.html">QGLContext</a>.  Reimplement it in a subclass.
<p> This function should set up any required OpenGL context rendering
flags, defining display lists, etc.
<p> There is no need to call <a href="#makeCurrent">makeCurrent</a>() because this has already been
done when this function is called.

<h3 class=fn>void <a name="initializeOverlayGL"></a>QGLWidget::initializeOverlayGL ()<tt> [virtual protected]</tt>
</h3>
This virtual function is used in the same manner as <a href="#initializeGL">initializeGL</a>()
except that it operates on the widget's overlay context instead of the
widget's main context. This means that <a href="#initializeOverlayGL">initializeOverlayGL</a>() is called
once before the first call to <a href="#paintOverlayGL">paintOverlayGL</a>() or <a href="#resizeOverlayGL">resizeOverlayGL</a>().
Reimplement it in a subclass.
<p> This function should set up any required OpenGL context rendering
flags, defining display lists, etc. for the overlay context.
<p> There is no need to call <a href="#makeOverlayCurrent">makeOverlayCurrent</a>() because this has already
been done when this function is called.

<h3 class=fn>bool <a name="isSharing"></a>QGLWidget::isSharing () const
</h3>

<p> Returns TRUE if display list sharing with another QGLWidget was
requested in the constructor, and the GL system was able to provide
it; otherwise returns FALSE. The GL system may fail to provide display
list sharing if the two QGLWidgets use different formats.
<p> <p>See also <a href="#format">format</a>().

<h3 class=fn>bool <a name="isValid"></a>QGLWidget::isValid () const
</h3>

<p> Returns TRUE if the widget has a valid GL rendering context; otherwise
returns FALSE. A widget will be invalid if the system has no <a href="qglformat.html#hasOpenGL">OpenGL support</a>.
<p> 
<h3 class=fn>void <a name="makeCurrent"></a>QGLWidget::makeCurrent ()<tt> [virtual]</tt>
</h3>

<p> Makes this widget the current widget for OpenGL
operations, i.e. makes the widget's rendering context the current
OpenGL rendering context.

<h3 class=fn>void <a name="makeOverlayCurrent"></a>QGLWidget::makeOverlayCurrent ()<tt> [virtual]</tt>
</h3>

Makes the overlay context of this widget current. Use this if you
need to issue OpenGL commands to the overlay context outside of
<a href="#initializeOverlayGL">initializeOverlayGL</a>(), <a href="#resizeOverlayGL">resizeOverlayGL</a>(), and <a href="#paintOverlayGL">paintOverlayGL</a>().
<p> Does nothing if this widget has no overlay.
<p> <p>See also <a href="#makeCurrent">makeCurrent</a>().

<h3 class=fn>const&nbsp;<a href="qglcontext.html">QGLContext</a>&nbsp;* <a name="overlayContext"></a>QGLWidget::overlayContext () const
</h3>

Returns the overlay context of this widget, or 0 if this widget has
no overlay.
<p> <p>See also <a href="#context">context</a>().

<h3 class=fn>void <a name="paintEvent"></a>QGLWidget::paintEvent ( <a href="qpaintevent.html">QPaintEvent</a>&nbsp;* )<tt> [virtual protected]</tt>
</h3>
Handles paint events. Will cause the virtual <a href="#paintGL">paintGL</a>() function to
be called.
<p> The widget's rendering context will become the current context and
<a href="#initializeGL">initializeGL</a>() will be called if it hasn't already been called.

<p>Reimplemented from <a href="qwidget.html#paintEvent">QWidget</a>.
<h3 class=fn>void <a name="paintGL"></a>QGLWidget::paintGL ()<tt> [virtual protected]</tt>
</h3>
This virtual function is called whenever the widget needs to be painted.
Reimplement it in a subclass.
<p> There is no need to call <a href="#makeCurrent">makeCurrent</a>() because this has already been
done when this function is called.

<h3 class=fn>void <a name="paintOverlayGL"></a>QGLWidget::paintOverlayGL ()<tt> [virtual protected]</tt>
</h3>
This virtual function is used in the same manner as <a href="#paintGL">paintGL</a>() except
that it operates on the widget's overlay context instead of the
widget's main context. This means that <a href="#paintOverlayGL">paintOverlayGL</a>() is called
whenever the widget's overlay needs to be painted.
Reimplement it in a subclass.
<p> There is no need to call <a href="#makeOverlayCurrent">makeOverlayCurrent</a>() because this
has already been done when this function is called.

<h3 class=fn>void <a name="qglClearColor"></a>QGLWidget::qglClearColor ( const&nbsp;<a href="qcolor.html">QColor</a>&nbsp;&amp;&nbsp;c ) const
</h3>
Convenience function for specifying the clearing color to
OpenGL. Calls glClearColor (in RGBA mode) or glClearIndex (in
color-index mode) with the color <em>c</em>. Applies to the current GL
context.
<p> <p>See also <a href="#qglColor">qglColor</a>(), <a href="qglcontext.html#currentContext">QGLContext::currentContext</a>() and <a href="qcolor.html">QColor</a>.

<h3 class=fn>void <a name="qglColor"></a>QGLWidget::qglColor ( const&nbsp;<a href="qcolor.html">QColor</a>&nbsp;&amp;&nbsp;c ) const
</h3>
Convenience function for specifying a drawing color to OpenGL. Calls
glColor3 (in RGBA mode) or glIndex (in color-index mode) with the
color <em>c</em>. Applies to the current GL context.
<p> <p>See also <a href="#qglClearColor">qglClearColor</a>(), <a href="qglcontext.html#currentContext">QGLContext::currentContext</a>() and <a href="qcolor.html">QColor</a>.

<h3 class=fn><a href="qpixmap.html">QPixmap</a> <a name="renderPixmap"></a>QGLWidget::renderPixmap ( int&nbsp;w = 0, int&nbsp;h = 0, bool&nbsp;useContext = FALSE )<tt> [virtual]</tt>
</h3>
Renders the current scene on a pixmap and returns the pixmap.
<p> You may use this method on both visible and invisible QGLWidgets.
<p> This method will create a pixmap and a temporary <a href="qglcontext.html">QGLContext</a> to render
on the pixmap. It will then call <a href="#initializeGL">initializeGL</a>(), <a href="#resizeGL">resizeGL</a>(), and
<a href="#paintGL">paintGL</a>() on this context. Finally, the widget's original GL context
is restored.
<p> The size of the pixmap will be <em>w</em> pixels wide and <em>h</em> pixels high
unless one of these parameters is 0 (the default), in which case the
pixmap will have the same size as the widget.
<p> If <em>useContext</em> is TRUE, this method will try to be more efficient
by using the existing GL context to render the pixmap. The default
is FALSE. Only use TRUE if you understand the risks.
<p> Overlays are not rendered onto the pixmap.
<p> If the GL rendering context and the desktop have different
bit depths, the result will most likely look surprising.
<p> Note that the creation of display lists, modifications of the view
frustum etc. should be done from within initializeGL(). If this is
not done, the temporary QGLContext will not be initialized properly,
and the rendered pixmap may be incomplete/corrupted.

<h3 class=fn>void <a name="resizeEvent"></a>QGLWidget::resizeEvent ( <a href="qresizeevent.html">QResizeEvent</a>&nbsp;* )<tt> [virtual protected]</tt>
</h3>

Handles resize events. Calls the virtual function <a href="#resizeGL">resizeGL</a>().

<p>Reimplemented from <a href="qwidget.html#resizeEvent">QWidget</a>.
<h3 class=fn>void <a name="resizeGL"></a>QGLWidget::resizeGL ( int&nbsp;width, int&nbsp;height )<tt> [virtual protected]</tt>
</h3>

This virtual function is called whenever the widget has been resized.
The new size is passed in <em>width</em> and <em>height</em>.
Reimplement it in a subclass.
<p> There is no need to call <a href="#makeCurrent">makeCurrent</a>() because this has already been
done when this function is called.

<h3 class=fn>void <a name="resizeOverlayGL"></a>QGLWidget::resizeOverlayGL ( int&nbsp;width, int&nbsp;height )<tt> [virtual protected]</tt>
</h3>

This virtual function is used in the same manner as <a href="#paintGL">paintGL</a>() except
that it operates on the widget's overlay context instead of the
widget's main context. This means that <a href="#resizeOverlayGL">resizeOverlayGL</a>() is called
whenever the widget has been resized.
The new size is passed in <em>width</em> and <em>height</em>.
Reimplement it in a subclass.
<p> There is no need to call <a href="#makeOverlayCurrent">makeOverlayCurrent</a>() because
this has already been done when this function is called.

<h3 class=fn>void <a name="setAutoBufferSwap"></a>QGLWidget::setAutoBufferSwap ( bool&nbsp;on )<tt> [protected]</tt>
</h3>

<p> If <em>on</em> is TRUE automatic GL buffer swapping is switched on;
otherwise it is switched off.
<p> If <em>on</em> is TRUE and the widget is using a double-buffered format, the
background and foreground GL buffers will automatically be swapped
after each time the <a href="#paintGL">paintGL</a>() function has been called.
<p> The buffer auto-swapping is on by default.
<p> <p>See also <a href="#autoBufferSwap">autoBufferSwap</a>(), <a href="#doubleBuffer">doubleBuffer</a>() and <a href="#swapBuffers">swapBuffers</a>().

<h3 class=fn>void <a name="setColormap"></a>QGLWidget::setColormap ( const&nbsp;<a href="qglcolormap.html">QGLColormap</a>&nbsp;&amp;&nbsp;cmap )
</h3>

<p> Set the colormap for this widget to <em>cmap</em>.
Usually it is only top-level widgets that can have colormaps installed.
<p> <p>See also <a href="#colormap">colormap</a>().

<h3 class=fn>void <a name="swapBuffers"></a>QGLWidget::swapBuffers ()<tt> [virtual]</tt>
</h3>

Swaps the screen contents with an off-screen buffer. This only works
if the widget's format specifies double buffer mode.
<p> Normally, there is no need to explicitly call this function because
it is done automatically after each widget repaint, i.e. each
time after <a href="#paintGL">paintGL</a>() has been executed.
<p> <p>See also <a href="#doubleBuffer">doubleBuffer</a>(), <a href="#setAutoBufferSwap">setAutoBufferSwap</a>() and <a href="qglformat.html#setDoubleBuffer">QGLFormat::setDoubleBuffer</a>().

<h3 class=fn>void <a name="updateGL"></a>QGLWidget::updateGL ()<tt> [virtual slot]</tt>
</h3>

Updates the widget by calling <a href="#glDraw">glDraw</a>().

<h3 class=fn>void <a name="updateOverlayGL"></a>QGLWidget::updateOverlayGL ()<tt> [virtual slot]</tt>
</h3>

Updates the widget's overlay (if any). Will cause the virtual
function <a href="#paintOverlayGL">paintOverlayGL</a>() to be executed.
<p> The widget's rendering context will become the current context and
<a href="#initializeGL">initializeGL</a>() will be called if it hasn't already been called.

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