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RedHat 9 (Linux i386) - man page for qglwidget (redhat section 3qt)

QGLWidget(3qt)									   QGLWidget(3qt)

NAME
       QGLWidget - Widget for rendering OpenGL graphics

SYNOPSIS
       #include <qgl.h>

       Inherits QWidget and QGL.

   Public Members
       QGLWidget ( QWidget * parent = 0, const char * name = 0, const QGLWidget * shareWidget =
	   0, WFlags f = 0 )
       QGLWidget ( const QGLFormat & format, QWidget * parent = 0, const char * name = 0, const
	   QGLWidget * shareWidget = 0, WFlags f = 0 )
       ~QGLWidget ()
       void qglColor ( const QColor & c ) const
       void qglClearColor ( const QColor & c ) const
       bool isValid () const
       bool isSharing () const
       virtual void makeCurrent ()
       bool doubleBuffer () const
       virtual void swapBuffers ()
       QGLFormat format () const
       const QGLContext * context () const
       virtual QPixmap renderPixmap ( int w = 0, int h = 0, bool useContext = FALSE )
       virtual QImage grabFrameBuffer ( bool withAlpha = FALSE )
       virtual void makeOverlayCurrent ()
       const QGLContext * overlayContext () const
       const QGLColormap & colormap () const
       void setColormap ( const QGLColormap & cmap )
       void renderText ( int x, int y, const QString & str, const QFont & fnt = QFont ( ), int
	   listBase = 2000 )
       void renderText ( double x, double y, double z, const QString & str, const QFont & fnt =
	   QFont ( ), int listBase = 2000 )

   Public Slots
       virtual void updateGL ()
       virtual void updateOverlayGL ()

   Static Public Members
       QImage convertToGLFormat ( const QImage & img )

   Protected Members
       virtual void initializeGL ()
       virtual void resizeGL ( int width, int height )
       virtual void paintGL ()
       virtual void initializeOverlayGL ()
       virtual void resizeOverlayGL ( int width, int height )
       virtual void paintOverlayGL ()
       void setAutoBufferSwap ( bool on )
       bool autoBufferSwap () const
       virtual void paintEvent ( QPaintEvent * )
       virtual void resizeEvent ( QResizeEvent * )
       virtual void glInit ()
       virtual void glDraw ()

DESCRIPTION
       The QGLWidget class is a widget for rendering OpenGL graphics.

       QGLWidget provides functionality for displaying OpenGL<sup>*</sup> graphics integrated
       into a Qt application. It is very simple to use. You inherit from it and use the subclass
       like any other QWidget, except that instead of drawing the widget's contents using
       QPainter etc. you use the standard OpenGL rendering commands.

       QGLWidget provides three convenient virtual functions that you can reimplement in your
       subclass to perform the typical OpenGL tasks:

       paintGL() - Renders the OpenGL scene. Gets called whenever the widget needs to be updated.

       resizeGL() - Sets up the OpenGL viewport, projection, etc. Gets called whenever the the
       widget has been resized (and also when it is shown for the first time because all newly
       created widgets get a resize event automatically).

       initializeGL() - Sets up the OpenGL rendering context, defines display lists, etc. Gets
       called once before the first time resizeGL() or paintGL() is called.

       Here is a rough outline of how a QGLWidget subclass might look:

	   class MyGLDrawer : public QGLWidget
	   {
	       Q_OBJECT        // must include this if you use Qt signals/slots
	   public:
	       MyGLDrawer( QWidget *parent, const char *name )
		   : QGLWidget(parent, name) {}
	   protected:
	       void initializeGL()
	       {
		   // Set up the rendering context, define display lists etc.:
		   ...
		   glClearColor( 0.0, 0.0, 0.0, 0.0 );
		   glEnable(GL_DEPTH_TEST);
		   ...
	       }
	       void resizeGL( int w, int h )
	       {
		   // setup viewport, projection etc.:
		   glViewport( 0, 0, (GLint)w, (GLint)h );
		   ...
		   glFrustum( ... );
		   ...
	       }
	       void paintGL()
	       {
		   // draw the scene:
		   ...
		   glRotatef( ... );
		   glMaterialfv( ... );
		   glBegin( GL_QUADS );
		   glVertex3f( ... );
		   glVertex3f( ... );
		   ...
		   glEnd();
		   ...
	       }
	   };

       If you need to trigger a repaint from places other than paintGL() (a typical example is
       when using timers to animate scenes), you should call the widget's updateGL() function.

       Your widget's OpenGL rendering context is made current when paintGL(), resizeGL(), or
       initializeGL() is called. If you need to call the standard OpenGL API functions from other
       places (e.g. in your widget's constructor or in your own paint functions), you must call
       makeCurrent() first.

       QGLWidget provides advanced functions for requesting a new display format and you can even
       set a new rendering context.

       You can also share OpenGL display lists between QGLWidgets (see the documentation of the
       QGLWidget constructors for details).

Overlays
       The QGLWidget creates a GL overlay context in addition to the normal context if overlays
       are supported by the underlying system.

       If you want to use overlays, you specify it in the format. (Note: Overlay must be
       requested in the format passed to the QGLWidget constructor.) Your GL widget should also
       implement some or all of these virtual methods:

       paintOverlayGL()

       resizeOverlayGL()

       initializeOverlayGL()

       These methods work in the same way as the normal paintGL() etc. functions, except that
       they will be called when the overlay context is made current. You can explicitly make the
       overlay context current by using makeOverlayCurrent(), and you can access the overlay
       context directly (e.g. to ask for its transparent color) by calling overlayContext().

       On X servers in which the default visual is in an overlay plane, non-GL Qt windows can
       also be used for overlays. See the examples/opengl/overlay_x11 example program for
       details.

       <sup>*</sup> OpenGL is a trademark of Silicon Graphics, Inc. in the United States and
       other countries.

       See also Graphics Classes and Image Processing Classes.

MEMBER FUNCTION DOCUMENTATION
QGLWidget::QGLWidget ( QWidget * parent = 0, const char * name = 0, const QGLWidget * shareWidget
       = 0, WFlags f = 0 )
       Constructs an OpenGL widget with a parent widget and a name.

       The default format is used. The widget will be invalid if the system has no OpenGL
       support.

       The parent, name and widget flag, f, arguments are passed to the QWidget constructor.

       If the shareWidget parameter points to a valid QGLWidget, this widget will share OpenGL
       display lists with shareWidget. If this widget and shareWidget have different formats,
       display list sharing may fail. You can check whether display list sharing succeeded by
       calling isSharing().

       The initialization of OpenGL rendering state, etc. should be done by overriding the
       initializeGL() function, rather than in the constructor of your QGLWidget subclass.

       See also QGLFormat::defaultFormat().

QGLWidget::QGLWidget ( const QGLFormat & format, QWidget * parent = 0, const char * name = 0,
       const QGLWidget * shareWidget = 0, WFlags f = 0 )
       Constructs an OpenGL widget with parent parent, called name.

       The format argument specifies the desired rendering options. If the underlying
       OpenGL/Window system cannot satisfy all the features requested in format, the nearest
       subset of features will be used. After creation, the format() method will return the
       actual format obtained.

       The widget will be invalid if the system has no OpenGL support.

       The parent, name and widget flag, f, arguments are passed to the QWidget constructor.

       If the shareWidget parameter points to a valid QGLWidget, this widget will share OpenGL
       display lists with shareWidget. If this widget and shareWidget have different formats,
       display list sharing may fail. You can check whether display list sharing succeeded by
       calling isSharing().

       The initialization of OpenGL rendering state, etc. should be done by overriding the
       initializeGL() function, rather than in the constructor of your QGLWidget subclass.

       See also QGLFormat::defaultFormat() and isValid().

QGLWidget::~QGLWidget ()
       Destroys the widget.

bool QGLWidget::autoBufferSwap () const [protected]
       Returns TRUE if the widget is doing automatic GL buffer swapping; otherwise returns FALSE.

       See also setAutoBufferSwap().

const QGLColormap &; QGLWidget::colormap () const
       Returns the colormap for this widget.

       Usually it is only top-level widgets that can have different colormaps installed. Asking
       for the colormap of a child widget will return the colormap for the child's top-level
       widget.

       If no colormap has been set for this widget, the QColormap returned will be empty.

       See also setColormap().

const QGLContext * QGLWidget::context () const
       Returns the context of this widget.

       It is possible that the context is not valid (see isValid()), for example, if the
       underlying hardware does not support the format attributes that were requested.

QImage QGLWidget::convertToGLFormat ( const QImage & img ) [static]
       Converts the image img into the unnamed format expected by OpenGL functions such as
       glTexImage2D(). The returned image is not usable as a QImage, but QImage::width(),
       QImage::height() and QImage::bits() 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 relevant
       bits:

	       QImage tex1, tex2, buf;
	       if ( !buf.load( "gllogo.bmp" ) ) {  // Load first image from file

       We create tex1 (and another variable) for OpenGL, and load a real image into buf.

	       tex1 = QGLWidget::convertToGLFormat( buf );  // flipped 32bit RGBA

       A few lines later, we convert buf into OpenGL format and store it in tex1.

	       glTexImage2D( GL_TEXTURE_2D, 0, 3, tex1.width(), tex1.height(), 0,
			     GL_RGBA, GL_UNSIGNED_BYTE, tex1.bits() );

       Another function in the same example uses tex1 with OpenGL.

       Example: opengl/texture/gltexobj.cpp.

bool QGLWidget::doubleBuffer () const
       Returns TRUE if the contained GL rendering context has double buffering; otherwise returns
       FALSE.

       See also QGLFormat::doubleBuffer().

QGLFormat QGLWidget::format () const
       Returns the format of the contained GL rendering context.

void QGLWidget::glDraw () [virtual protected]
       Executes the virtual function paintGL().

       The widget's rendering context will become the current context and initializeGL() will be
       called if it hasn't already been called.

void QGLWidget::glInit () [virtual protected]
       Initializes OpenGL for this widget's context. Calls the virtual function initializeGL().

QImage QGLWidget::grabFrameBuffer ( bool withAlpha = FALSE ) [virtual]
       Returns an image of the frame buffer. If withAlpha is TRUE the alpha channel is included.

       Depending on your hardware, you can explicitly select which color buffer to grab with a
       glReadBuffer() call before calling this function.

void QGLWidget::initializeGL () [virtual protected]
       This virtual function is called once before the first call to paintGL() or resizeGL(), and
       then once whenever the widget has been assigned a new QGLContext. Reimplement it in a
       subclass.

       This function should set up any required OpenGL context rendering flags, defining display
       lists, etc.

       There is no need to call makeCurrent() because this has already been done when this
       function is called.

void QGLWidget::initializeOverlayGL () [virtual protected]
       This virtual function is used in the same manner as initializeGL() except that it operates
       on the widget's overlay context instead of the widget's main context. This means that
       initializeOverlayGL() is called once before the first call to paintOverlayGL() or
       resizeOverlayGL(). Reimplement it in a subclass.

       This function should set up any required OpenGL context rendering flags, defining display
       lists, etc. for the overlay context.

       There is no need to call makeOverlayCurrent() because this has already been done when this
       function is called.

bool QGLWidget::isSharing () const
       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.

       See also format().

bool QGLWidget::isValid () const
       Returns TRUE if the widget has a valid GL rendering context; otherwise returns FALSE. A
       widget will be invalid if the system has no OpenGL support.

void QGLWidget::makeCurrent () [virtual]
       Makes this widget the current widget for OpenGL operations, i.e. makes the widget's
       rendering context the current OpenGL rendering context.

void QGLWidget::makeOverlayCurrent () [virtual]
       Makes the overlay context of this widget current. Use this if you need to issue OpenGL
       commands to the overlay context outside of initializeOverlayGL(), resizeOverlayGL(), and
       paintOverlayGL().

       Does nothing if this widget has no overlay.

       See also makeCurrent().

const QGLContext * QGLWidget::overlayContext () const
       Returns the overlay context of this widget, or 0 if this widget has no overlay.

       See also context().

void QGLWidget::paintEvent ( QPaintEvent * ) [virtual protected]
       Handles paint events. Will cause the virtual paintGL() function to be called.

       The widget's rendering context will become the current context and initializeGL() will be
       called if it hasn't already been called.

       Reimplemented from QWidget.

void QGLWidget::paintGL () [virtual protected]
       This virtual function is called whenever the widget needs to be painted. Reimplement it in
       a subclass.

       There is no need to call makeCurrent() because this has already been done when this
       function is called.

void QGLWidget::paintOverlayGL () [virtual protected]
       This virtual function is used in the same manner as paintGL() except that it operates on
       the widget's overlay context instead of the widget's main context. This means that
       paintOverlayGL() is called whenever the widget's overlay needs to be painted. Reimplement
       it in a subclass.

       There is no need to call makeOverlayCurrent() because this has already been done when this
       function is called.

void QGLWidget::qglClearColor ( const QColor & c ) const
       Convenience function for specifying the clearing color to OpenGL. Calls glClearColor (in
       RGBA mode) or glClearIndex (in color-index mode) with the color c. Applies to the current
       GL context.

       See also qglColor(), QGLContext::currentContext(), and QColor.

void QGLWidget::qglColor ( const QColor & c ) const
       Convenience function for specifying a drawing color to OpenGL. Calls glColor3 (in RGBA
       mode) or glIndex (in color-index mode) with the color c. Applies to the current GL
       context.

       See also qglClearColor(), QGLContext::currentContext(), and QColor.

QPixmap QGLWidget::renderPixmap ( int w = 0, int h = 0, bool useContext = FALSE ) [virtual]
       Renders the current scene on a pixmap and returns the pixmap.

       You can use this method on both visible and invisible QGLWidgets.

       This method will create a pixmap and a temporary QGLContext to render on the pixmap. It
       will then call initializeGL(), resizeGL(), and paintGL() on this context. Finally, the
       widget's original GL context is restored.

       The size of the pixmap will be w pixels wide and h pixels high unless one of these
       parameters is 0 (the default), in which case the pixmap will have the same size as the
       widget.

       If useContext 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.

       Overlays are not rendered onto the pixmap.

       If the GL rendering context and the desktop have different bit depths, the result will
       most likely look surprising.

       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.

void QGLWidget::renderText ( int x, int y, const QString & str, const QFont & fnt = QFont ( ),
       int listBase = 2000 )
       Renders the string str into the GL context of this widget.

       x and y are specified in window coordinates, with the origin in the upper left-hand corner
       of the window. If fnt is not specified, the currently set application font will be used to
       render the string. To change the color of the rendered text you can use the glColor() call
       (or the qglColor() convenience function), just before the renderText() call. Note that if
       you have GL_LIGHTING enabled, the string will not appear in the color you want. You should
       therefore switch lighting off before using renderText().

       listBase specifies the index of the first display list that is generated by this function.
       The default value is 2000. 256 display lists will be generated, one for each of the first
       256 characters in the font that is used to render the string. If several fonts are used in
       the same widget, the display lists for these fonts will follow the last generated list.
       You would normally not have to change this value unless you are using lists in the same
       range. The lists are deleted when the widget is destroyed.

void QGLWidget::renderText ( double x, double y, double z, const QString & str, const QFont & fnt
       = QFont ( ), int listBase = 2000 )
       This is an overloaded member function, provided for convenience. It behaves essentially
       like the above function.

       x, y and z are specified in scene or object coordinates relative to the currently set
       projection and model matrices. This can be useful if you want to annotate models with text
       labels and have the labels move with the model as it is rotated etc.

void QGLWidget::resizeEvent ( QResizeEvent * ) [virtual protected]
       Handles resize events. Calls the virtual function resizeGL().

       Reimplemented from QWidget.

void QGLWidget::resizeGL ( int width, int height ) [virtual protected]
       This virtual function is called whenever the widget has been resized. The new size is
       passed in width and height. Reimplement it in a subclass.

       There is no need to call makeCurrent() because this has already been done when this
       function is called.

void QGLWidget::resizeOverlayGL ( int width, int height ) [virtual protected]
       This virtual function is used in the same manner as paintGL() except that it operates on
       the widget's overlay context instead of the widget's main context. This means that
       resizeOverlayGL() is called whenever the widget has been resized. The new size is passed
       in width and height. Reimplement it in a subclass.

       There is no need to call makeOverlayCurrent() because this has already been done when this
       function is called.

void QGLWidget::setAutoBufferSwap ( bool on ) [protected]
       If on is TRUE automatic GL buffer swapping is switched on; otherwise it is switched off.

       If on is TRUE and the widget is using a double-buffered format, the background and
       foreground GL buffers will automatically be swapped after each paintGL() call.

       The buffer auto-swapping is on by default.

       See also autoBufferSwap(), doubleBuffer(), and swapBuffers().

void QGLWidget::setColormap ( const QGLColormap & cmap )
       Set the colormap for this widget to cmap. Usually it is only top-level widgets that can
       have colormaps installed.

       See also colormap().

void QGLWidget::swapBuffers () [virtual]
       Swaps the screen contents with an off-screen buffer. This only works if the widget's
       format specifies double buffer mode.

       Normally, there is no need to explicitly call this function because it is done
       automatically after each widget repaint, i.e. each time after paintGL() has been executed.

       See also doubleBuffer(), setAutoBufferSwap(), and QGLFormat::setDoubleBuffer().

void QGLWidget::updateGL () [virtual slot]
       Updates the widget by calling glDraw().

void QGLWidget::updateOverlayGL () [virtual slot]
       Updates the widget's overlay (if any). Will cause the virtual function paintOverlayGL() to
       be executed.

       The widget's rendering context will become the current context and initializeGL() will be
       called if it hasn't already been called.

SEE ALSO
       http://doc.trolltech.com/qglwidget.html http://www.trolltech.com/faq/tech.html

COPYRIGHT
       Copyright 1992-2001 Trolltech AS, http://www.trolltech.com.  See the license file included
       in the distribution for a complete license statement.

AUTHOR
       Generated automatically from the source code.

BUGS
       If you find a bug in Qt, please report it as described in
       http://doc.trolltech.com/bughowto.html.	Good bug reports help us to help you. Thank you.

       The definitive Qt documentation is provided in HTML format; it is located at
       $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is
       provided as a convenience for those users who prefer man pages, although this format is
       not officially supported by Trolltech.

       If you find errors in this manual page, please report them to qt-bugs@trolltech.com.
       Please include the name of the manual page (qglwidget.3qt) and the Qt version (3.1.1).

Trolltech AS				 9 December 2002			   QGLWidget(3qt)


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