QGLContext Class Reference


The QGLContext class encapsulates an OpenGL rendering context. More...

#include <qgl.h>

List of all member functions.

Public Members

Protected Members


Detailed Description

The QGLContext class encapsulates an OpenGL rendering context.

An OpenGL rendering context is a complete set of OpenGL state variables.


Member Function Documentation

QGLContext::QGLContext ( const QGLFormat & format, QPaintDevice * device )

Constructs an OpenGL context for the paint device device, which must be a widget or a pixmap. The format specify several display options for this context.

The context will be invalid if the format settings cannot be satified by the underlying OpenGL/Window system.

See also: isValid().

QGLContext::~QGLContext () [virtual]

Destroys the OpenGL context.

bool QGLContext::chooseContext () [protected]

This semi-internal function is called by create(). It creates a system-dependent OpenGL handle that matches the specified format.

Windows: Calls choosePixelFormat() which finds a matching pixel format identifier.

X11: Calls chooseVisual() which finds an appropriate X visual.

choosePixelFormat() and chooseVisual() can be reimplemented in a subclass if you need to choose a very custom context.

bool QGLContext::create ()

Creates the GL context. Returns TRUE if it was successful in creating a context that satisfies the requested format, otherwise FALSE is returned (the context is invalid).

Implementation note: 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 chooseContext() (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.

See also: chooseContext() and isValid().

QPaintDevice* QGLContext::device () const

Returns the paint device set for this context.

See also: QGLContext::QGLContext().

void QGLContext::doneCurrent () [protected]

Resets the current OpenGL rendering context. Normally, you do not need to call this function, because makeCurrent() takes care of that.

const QGLFormatQGLContext::format () const

Returns the format.

See also: setFormat().

bool QGLContext::isValid () const

Returns TRUE if the characteristics specified in the display format could be fulfilled by the OpenGL driver/window system.

void QGLContext::makeCurrent ()

Makes this context the current OpenGL rendering context. All gl functions you call operate on this context until another context is made current.

void QGLContext::reset ()

Resets the context and makes it invalid.

See also: create() and isValid().

void QGLContext::setFormat ( const QGLFormat & format )

Sets a new OpenGL context specification format. The context is reset. Call create() to create a new context that matches this format.

    QGLContext *cx;
      ...
    QGLFormat f;
    f.setAlpha( TRUE );
    f.setStereo( TRUE );
    cx->setFormat( f );
    if ( !cx->create() )
        ; // could not create context

See also: format(), reset() and create().

void QGLContext::swapBuffers ()

Swaps the screen contents with an off-screen buffer. Works only if the context is in double buffer mode.

See also: QGLFormat::setDoubleBuffer().


This file is part of the OpenGL support for the Qt toolkit, copyright © 1992-97 Troll Tech, all rights reserved. You may use the OpenGL support classes on the same terms that you may use Qt.

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