QGLWidget(3qt)QGLWidget(3qt)NAMEQGLWidget - 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 ( QGLContext * context, QWidget * parent, 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 ()
void doneCurrent ()
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 functions for requesting a new display format and
you can also create widgets with customized rendering contexts.
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 DOCUMENTATIONQGLWidget::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 ( QGLContext * context, QWidget * parent, const char *
name = 0, const QGLWidget * shareWidget = 0, WFlags f = 0 )
Constructs an OpenGL widget with parent parent, called name.
The context argument is a pointer to the QGLContext that you wish to be
bound to this widget. This allows you to pass in your own QGLContext
sub-classes.
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 ( 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() );
Note the dimension restrictions for texture images as described in the
glTexImage2D() documentation. The width must be 2^m + 2*border and the
height 2^n + 2*border where m and n are integers and border is either 0
or 1.
Another function in the same example uses tex1 with OpenGL.
Example: opengl/texture/gltexobj.cpp.
void QGLWidget::doneCurrent ()
Makes no GL context the current context. Normally, you do not need to
call this function; QGLContext calls it as necessary. However, it may
be useful in multithreaded environments.
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.
Note: This function only works reliably with ASCII strings.
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 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
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Trolltech AS 2 February 2007 QGLWidget(3qt)