The QGLFormat class specifies the display format of an OpenGL rendering context. More...

Public Typedefs
using	OpenGLVersionFlags = QFlags< OpenGLVersionFlag >

Public Types
enum	OpenGLContextProfile

enum	OpenGLVersionFlag

Public Methods
	QGLFormat ()

	QGLFormat (const QGLFormat &other)

	QGLFormat (QGL::FormatOptions options, int plane=0)

	~QGLFormat ()

bool	accum () const

int	accumBufferSize () const

bool	alpha () const

int	alphaBufferSize () const

int	blueBufferSize () const

bool	depth () const

int	depthBufferSize () const

bool	directRendering () const

bool	doubleBuffer () const

int	greenBufferSize () const

bool	hasOverlay () const

int	majorVersion () const

int	minorVersion () const

QGLFormat &	operator= (const QGLFormat &other)

int	plane () const

OpenGLContextProfile	profile () const

int	redBufferSize () const

bool	rgba () const

bool	sampleBuffers () const

int	samples () const

void	setAccum (bool enable)

void	setAccumBufferSize (int size)

void	setAlpha (bool enable)

void	setAlphaBufferSize (int size)

void	setBlueBufferSize (int size)

void	setDepth (bool enable)

void	setDepthBufferSize (int size)

void	setDirectRendering (bool enable)

void	setDoubleBuffer (bool enable)

void	setGreenBufferSize (int size)

void	setOption (QGL::FormatOptions options)

void	setOverlay (bool enable)

void	setPlane (int plane)

void	setProfile (OpenGLContextProfile profile)

void	setRedBufferSize (int size)

void	setRgba (bool enable)

void	setSampleBuffers (bool enable)

void	setSamples (int numSamples)

void	setStencil (bool enable)

void	setStencilBufferSize (int size)

void	setStereo (bool enable)

void	setSwapInterval (int interval)

void	setVersion (int major, int minor)

bool	stencil () const

int	stencilBufferSize () const

bool	stereo () const

int	swapInterval () const

bool	testOption (QGL::FormatOptions options) const

Static Public Methods
static QGLFormat	defaultFormat ()

static QGLFormat	defaultOverlayFormat ()

static bool	hasOpenGL ()

static bool	hasOpenGLOverlays ()

static OpenGLVersionFlags	openGLVersionFlags ()

static void	setDefaultFormat (const QGLFormat &format)

static void	setDefaultOverlayFormat (const QGLFormat &format)

Friends
bool	operator!= (const QGLFormat &value_1, const QGLFormat &value_2)

bool	operator== (const QGLFormat &value_1, const QGLFormat &value_2)

Detailed Description

The QGLFormat class specifies the display format of an OpenGL rendering context. A display format contains various characteristics.

Double or single buffering
Depth buffer
RGBA or color index mode
Alpha channel
Accumulation buffer
Stencil buffer
Stereo buffers
Direct rendering
Presence of an overlay
Plane of an overlay
Multisample buffers

You can also specify preferred bit depths for the color buffer, depth buffer, alpha buffer, accumulation buffer and the stencil buffer with the functions: setRedBufferSize(), setGreenBufferSize(), setBlueBufferSize(), setDepthBufferSize(), setAlphaBufferSize(), setAccumBufferSize() and setStencilBufferSize().

Note that even if you specify that you prefer a 32 bit depth buffer (e.g. with setDepthBufferSize(32)), the format that is chosen may not have a 32 bit depth buffer, even if there is a format available with a 32 bit depth buffer. The main reason for this is how the system dependent picking algorithms work on the different platforms, and some format options may have higher precedence than others.

You create and tell a QGLFormat object what rendering options you want from an OpenGL rendering context.

OpenGL drivers or accelerated hardware may or may not support advanced features such as alpha channel or stereographic viewing. If you request some features that the driver/hardware does not provide when you create a QGLWidget, you will get a rendering context with the nearest subset of features.

There are different ways to define the display characteristics of a rendering context. One is to create a QGLFormat and make it the default for the entire application:

QGLFormat fmt;
fmt.setAlpha(true);
fmt.setStereo(true);
 
QGLFormat::setDefaultFormat(fmt);

Or you can specify the desired format when creating an object of your QGLWidget subclass:

QGLFormat fmt;
fmt.setDoubleBuffer(false);                 // single buffer
fmt.setDirectRendering(false);              // software rendering
MyGLWidget* myWidget = new MyGLWidget(fmt, ...);

After the widget has been created, you can find out which of the requested features the system was able to provide:

QGLFormat fmt;
fmt.setOverlay(true);
fmt.setStereo(true);
 
MyGLWidget *myWidget = new MyGLWidget(fmt, ...);
 
if (! myWidget->format().stereo()) {
    // ok, goggles off
    if (! myWidget->format().hasOverlay()) {
        qFatal("Cool hardware required");
    }
}

OpenGL is a trademark of Silicon Graphics, Inc. in the United States and other countries.

See also: QGLContext, QGLWidget

Member Typedef Documentation

QGLFormat::OpenGLVersionFlags

Typedef for QFlags<OpenGLVersionFlag> which contains an OR combination of OpenGLVersionFlag values.

Refer to QGLFormat::OpenGLVersionFlag for the enum documentation.

Member Enumeration Documentation

enum QGLFormat::OpenGLContextProfile

This enum describes the OpenGL context profiles that can be specified for contexts implementing OpenGL version 3.2 or higher. These profiles are different from OpenGL ES profiles.

Constant	Value	Description
`QGLFormat::NoProfile`	`0`	OpenGL version is lower than 3.2.
`QGLFormat::CoreProfile`	`1`	Functionality deprecated in OpenGL version 3.0 is not available.
`QGLFormat::CompatibilityProfile`	`2`	Functionality from earlier OpenGL versions is available.

enum QGLFormat::OpenGLVersionFlag

This enum describes the various OpenGL versions which are recognized by CopperSpice. Use the QGLFormat::openGLVersionFlags() function to identify which versions that are supported at runtime.

Refer to http://www.opengl.org for more information about the different revisions of OpenGL.

Constant	Value	Description
`QGLFormat::OpenGL_Version_None`	`0x00000000`	If no OpenGL is present or if no OpenGL context is current.
`QGLFormat::OpenGL_Version_1_1`	`0x00000001`	OpenGL version 1.1 or higher is present.
`QGLFormat::OpenGL_Version_1_2`	`0x00000002`	OpenGL version 1.2 or higher is present.
`QGLFormat::OpenGL_Version_1_3`	`0x00000004`	OpenGL version 1.3 or higher is present.
`QGLFormat::OpenGL_Version_1_4`	`0x00000008`	OpenGL version 1.4 or higher is present.
`QGLFormat::OpenGL_Version_1_5`	`0x00000010`	OpenGL version 1.5 or higher is present.
`QGLFormat::OpenGL_Version_2_0`	`0x00000020`	OpenGL version 2.0 or higher is present. Note that version 2.0 supports all the functionality of version 1.5.
`QGLFormat::OpenGL_Version_2_1`	`0x00000040`	OpenGL version 2.1 or higher is present.
`QGLFormat::OpenGL_Version_3_0`	`0x00001000`	OpenGL version 3.0 or higher is present.
`QGLFormat::OpenGL_Version_3_1`	`0x00002000`	OpenGL version 3.1 or higher is present. Note that OpenGL version 3.1 or higher does not necessarily support all the features of version 3.0 and lower.
`QGLFormat::OpenGL_Version_3_2`	`0x00004000`	OpenGL version 3.2 or higher is present.
`QGLFormat::OpenGL_Version_3_3`	`0x00008000`	OpenGL version 3.3 or higher is present.
`QGLFormat::OpenGL_Version_4_0`	`0x00010000`	OpenGL version 4.0 or higher is present.
`QGLFormat::OpenGL_ES_CommonLite_Version_1_0`	`0x00000100`	OpenGL ES version 1.0 Common Lite or higher is present.
`QGLFormat::OpenGL_ES_Common_Version_1_0`	`0x00000080`	OpenGL ES version 1.0 Common or higher is present. The Common profile supports all the features of Common Lite.
`QGLFormat::OpenGL_ES_CommonLite_Version_1_1`	`0x00000400`	OpenGL ES version 1.1 Common Lite or higher is present.
`QGLFormat::OpenGL_ES_Common_Version_1_1`	`0x00000200`	OpenGL ES version 1.1 Common or higher is present. The Common profile supports all the features of Common Lite.
`QGLFormat::OpenGL_ES_Version_2_0`	`0x00000800`	OpenGL ES version 2.0 or higher is present. Note that OpenGL ES version 2.0 does not support all the features of OpenGL ES 1.x. So if OpenGL_ES_Version_2_0 is returned, none of the ES 1.x flags are returned.

See also: openGLVersionFlags()

Constructor & Destructor Documentation

QGLFormat::QGLFormat ( )

Constructs a QGLFormat object with the following default settings:

Double buffer: Enabled
Depth buffer: Enabled
RGBA: Enabled (i.e., color index disabled)
Alpha channel: Disabled
Accumulator buffer: Disabled./li>
Stencil buffer: Enabled
Stereo: Disabled
Direct rendering: Enabled
Overlay: Disabled
Plane: 0 (i.e., normal plane)
Multisample buffers: Disabled

QGLFormat::QGLFormat	(	QGL::FormatOptions	options,
		int	plane = `0`
	)

Creates a QGLFormat object that is a copy of the current defaultFormat().

If options is not 0 then the default format is modified by the specified format options. The options parameter should be QGL::FormatOption values OR'ed together.

This constructor makes it easy to specify a certain desired format in classes derived from QGLWidget.

// The rendering in MyGLWidget depends on using
// stencil buffer and alpha channel
 
MyGLWidget::MyGLWidget(QWidget* parent) : QGLWidget(QGLFormat(QGL::StencilBuffer | QGL::AlphaChannel), parent)
{
   if (! format().stencil()) {
      qWarning("Unable to retrieve the stencil buffer; results will be suboptimal");
   }
 
   if (! format().alpha()) {
      qWarning("Unable to retrieve the alpha channel; results will be suboptimal");
   }
 
 }

Note that there are QGL::FormatOption values to turn format settings both on and off, e.g. QGL::DepthBuffer> and QGL::NoDepthBuffer, QGL::DirectRendering and QGL::IndirectRendering, etc.

The plane parameter defaults to 0 and is the plane which this format should be associated with. Not all OpenGL implementations supports overlay/underlay rendering planes.

See also: defaultFormat(), setOption(), setPlane()

QGLFormat::QGLFormat ( const QGLFormat & other )

Constructs a copy of other.

QGLFormat::~QGLFormat ( )

Destroys the QGLFormat.

Method Documentation

bool QGLFormat::accum ( ) const

inline

Returns true if the accumulation buffer is enabled, otherwise returns false. The accumulation buffer is disabled by default.

See also: setAccum(), setAccumBufferSize()

int QGLFormat::accumBufferSize ( ) const

Returns the accumulation buffer size.

See also: setAccumBufferSize(), accum(), setAccum()

bool QGLFormat::alpha ( ) const

inline

Returns true if the alpha buffer in the framebuffer is enabled, otherwise returns false. The alpha buffer is disabled by default.

See also: setAlpha(), setAlphaBufferSize()

int QGLFormat::alphaBufferSize ( ) const

Returns the alpha buffer size.

See also: alpha(), setAlpha(), setAlphaBufferSize()

int QGLFormat::blueBufferSize ( ) const

Returns the blue buffer size.

See also: setBlueBufferSize()

QGLFormat QGLFormat::defaultFormat ( )

static

Returns the default QGLFormat for the application. All QGLWidget objects that are created use this format unless another format is specified, e.g. when they are constructed. If no special default format has been set using setDefaultFormat(), the default format is the same as that created with QGLFormat().

See also: setDefaultFormat()

QGLFormat QGLFormat::defaultOverlayFormat ( )

static

Returns the default QGLFormat for overlay contexts. The default overlay format contains the following settings.

Double buffer: Disabled.
Depth buffer: Disabled.
RGBA: Disabled (i.e., color index enabled).
Alpha channel: Disabled.
Accumulator buffer: Disabled.
Stencil buffer: Disabled.
Stereo: Disabled.
Direct rendering: Enabled.
Overlay: Disabled.
Multisample buffers: Disabled.
Plane: 1 (i.e., first overlay plane).

See also: setDefaultOverlayFormat(), setDefaultFormat()

bool QGLFormat::depth ( ) const

inline

Returns true if the depth buffer is enabled, otherwise returns false. The depth buffer is enabled by default.

See also: setDepth(), setDepthBufferSize()

int QGLFormat::depthBufferSize ( ) const

Returns the depth buffer size.

See also: depth(), setDepth(), setDepthBufferSize()

bool QGLFormat::directRendering ( ) const

inline

Returns true if direct rendering is enabled, otherwise returns false.

Direct rendering is enabled by default.

See also: setDirectRendering()

bool QGLFormat::doubleBuffer ( ) const

inline

Returns true if double buffering is enabled, otherwise returns false. Double buffering is enabled by default.

See also: setDoubleBuffer()

int QGLFormat::greenBufferSize ( ) const

Returns the green buffer size.

See also: setGreenBufferSize()

bool QGLFormat::hasOpenGL ( )

static

Returns true if the window system has any OpenGL support, otherwise returns false.

Warning: This function must not be called until the QApplication object has been created.

bool QGLFormat::hasOpenGLOverlays ( )

static

Returns true if the window system supports OpenGL overlays, otherwise returns false.

Warning: This function must not be called until the QApplication object has been created.

bool QGLFormat::hasOverlay ( ) const

inline

Returns true if overlay plane is enabled, otherwise returns false.

Overlay is disabled by default.

See also: setOverlay()

int QGLFormat::majorVersion ( ) const

Returns the OpenGL major version.

See also: setVersion(), minorVersion()

int QGLFormat::minorVersion ( ) const

Returns the OpenGL minor version.

See also: setVersion(), majorVersion()

OpenGLVersionFlags QGLFormat::openGLVersionFlags ( )

static

Identifies, at runtime, which OpenGL versions that are supported by the current platform.

Note that if OpenGL version 1.5 is supported, its predecessors (i.e., version 1.4 and lower) are also supported. To identify the support of a particular feature, like multi texturing, test for the version in which the feature was first introduced (i.e., version 1.3 in the case of multi texturing) to adapt to the largest possible group of runtime platforms.

This function needs a valid current OpenGL context to work, otherwise it will return OpenGL_Version_None.

See also: hasOpenGL(), hasOpenGLOverlays()

QGLFormat & QGLFormat::operator= ( const QGLFormat & other )

Copy assigns from other and returns a reference to this object.

int QGLFormat::plane ( ) const

Returns the plane of this format. The default for normal formats is 0, which means the normal plane. The default for overlay formats is 1, which is the first overlay plane.

See also: setPlane(), defaultOverlayFormat()

OpenGLContextProfile QGLFormat::profile ( ) const

Returns the OpenGL context profile.

See also: setProfile()

int QGLFormat::redBufferSize ( ) const

Returns the red buffer size.

See also: setRedBufferSize()

bool QGLFormat::rgba ( ) const

inline

Returns true if RGBA color mode is set. Returns false if color index mode is set. The default color mode is RGBA.

See also: setRgba()

bool QGLFormat::sampleBuffers ( ) const

inline

Returns true if multisample buffer support is enabled, otherwise returns false.

The multisample buffer is disabled by default.

See also: setSampleBuffers()

int QGLFormat::samples ( ) const

Returns the number of samples per pixel when multisampling is enabled. By default, the highest number of samples that is available is used.

See also: setSampleBuffers(), sampleBuffers(), setSamples()

void QGLFormat::setAccum ( bool enable )

If enable is true enables the accumulation buffer, otherwise disables the accumulation buffer. The accumulation buffer is disabled by default. The accumulation buffer is used to create blur effects and multiple exposures.

See also: accum(), setAccumBufferSize()

void QGLFormat::setAccumBufferSize ( int size )

Set the preferred accumulation buffer size, where size is the bit depth for each RGBA component.

See also: accum(), setAccum(), accumBufferSize()

void QGLFormat::setAlpha ( bool enable )

If enable is true enables the alpha buffer, otherwise disables the alpha buffer. The alpha buffer is disabled by default. The alpha buffer is typically used for implementing transparency or translucency. The A in RGBA specifies the transparency of a pixel.

See also: alpha(), setAlphaBufferSize()

void QGLFormat::setAlphaBufferSize ( int size )

Set the preferred alpha buffer size to size. This function implicitly enables the alpha channel.

See also: setRedBufferSize(), setGreenBufferSize(), alphaBufferSize()

void QGLFormat::setBlueBufferSize ( int size )

Set the preferred blue buffer size to size.

See also: blueBufferSize(), setRedBufferSize(), setGreenBufferSize(), setAlphaBufferSize()

void QGLFormat::setDefaultFormat ( const QGLFormat & format )

static

Sets a new default QGLFormat for the application to format. To set single buffering as the default instead of double buffering, your main() might contain code similar to the following.

QGLFormat format;
format.setDoubleBuffer(false);
 
QGLFormat::setDefaultFormat(format);

See also: defaultFormat()

void QGLFormat::setDefaultOverlayFormat ( const QGLFormat & format )

static

Sets a new default QGLFormat for overlay contexts to format. This format is used whenever a QGLWidget is created with a format that hasOverlay() enabled.

For example, to set up a double buffered overlay context use code similar to the following. You can query after widget creation, whether the underlying OpenGL system was able to provide the requested specification:

QGLFormat format = QGLFormat::defaultOverlayFormat();
format.setDoubleBuffer(true);
 
QGLFormat::setDefaultOverlayFormat(format);
 
MyGLWidget* myWidget = new MyGLWidget(QGLFormat(QGL::HasOverlay));
 
if (myWidget->format().hasOverlay()) {
   // check the format of the overlay
 
   QGLContext* olContext = myWidget->overlayContext();
 
   if (olContext->format().doubleBuffer()) {
      // yes, we got a double buffered overlay
 
   } else {
      // no, only single buffered overlays are available
 
   }
}

See also: defaultOverlayFormat()

void QGLFormat::setDepth ( bool enable )

If enable is true enables the depth buffer, otherwise disables the depth buffer. The depth buffer is enabled by default.

The purpose of a depth buffer (or Z-buffering) is to remove hidden surfaces. Pixels are assigned Z values based on the distance to the viewer. A pixel with a high Z value is closer to the viewer than a pixel with a low Z value. This information is used to decide whether to draw a pixel or not.

See also: depth(), setDepthBufferSize()

void QGLFormat::setDepthBufferSize ( int size )

Set the minimum depth buffer size to size.

See also: depthBufferSize(), setDepth(), depth()

void QGLFormat::setDirectRendering ( bool enable )

If enable is true enables direct rendering, otherwise disables direct rendering. Direct rendering is enabled by default.

Enabling this option will make OpenGL bypass the underlying window system and render directly from hardware to the screen, if this is supported by the system.

See also: directRendering()

void QGLFormat::setDoubleBuffer ( bool enable )

If enable is true sets double buffering, otherwise sets single buffering. Double buffering is enabled by default.

Double buffering is a technique where graphics are rendered on an off-screen buffer and not directly to the screen. When the drawing has been completed, the program calls a swapBuffers() function to exchange the screen contents with the buffer. The result is flicker-free drawing and often better performance. Single buffered contexts are currently not supported with EGL.

See also: doubleBuffer(), QGLContext::swapBuffers(), QGLWidget::swapBuffers()

void QGLFormat::setGreenBufferSize ( int size )

Set the preferred green buffer size to size.

See also: greenBufferSize(), setRedBufferSize(), setBlueBufferSize(), setAlphaBufferSize()

void QGLFormat::setOption ( QGL::FormatOptions options )

Sets the format option to options.

See also: testOption()

void QGLFormat::setOverlay ( bool enable )

If enable is true enables an overlay plane, otherwise disables the overlay plane. Enabling the overlay plane will cause QGLWidget to create an additional context in an overlay plane. See the QGLWidget documentation for further information.

See also: hasOverlay()

void QGLFormat::setPlane ( int plane )

Sets the current plane where 0 is the normal plane, 1 is the first overlay plane, 2 is the second overlay plane. Negatvie values are the underlay planes.

In contrast to other format specifications the plane specifications will be matched exactly. This means that if you specify a plane that the underlying OpenGL system can not provide, an invalid QGLWidget will be created.

See also: plane()

void QGLFormat::setProfile ( OpenGLContextProfile profile )

Set the OpenGL context profile to profile. The profile is ignored if the requested OpenGL version is less than 3.2.

See also: profile()

void QGLFormat::setRedBufferSize ( int size )

Set the preferred red buffer size to size.

See also: redBufferSize(), setGreenBufferSize(), setBlueBufferSize(), setAlphaBufferSize()

void QGLFormat::setRgba ( bool enable )

If enable is true sets RGBA mode. If enable is false the method sets the color index mode.

The default color mode is RGBA. RGBA is the preferred mode for most OpenGL applications. In RGBA color mode you specify colors as red + green + blue + alpha quadruplets. In color index mode you specify an index into a color lookup table.

See also: rgba()

void QGLFormat::setSampleBuffers ( bool enable )

If enable is true, a GL context with multisample buffer support is picked, otherwise ignored.

See also: sampleBuffers(), setSamples(), samples()

void QGLFormat::setSamples ( int numSamples )

Set the preferred number of samples per pixel when multisampling is enabled to numSamples. By default, the highest number of samples available is used.

See also: setSampleBuffers(), sampleBuffers(), samples()

void QGLFormat::setStencil ( bool enable )

If enable is true enables the stencil buffer, otherwise disables the stencil buffer. The stencil buffer is enabled by default. The stencil buffer masks certain parts of the drawing area so that masked parts are not drawn on.

See also: stencil(), setStencilBufferSize()

void QGLFormat::setStencilBufferSize ( int size )

Set the preferred stencil buffer size to size.

See also: stencilBufferSize(), setStencil(), stencil()

void QGLFormat::setStereo ( bool enable )

If enable is true enables stereo buffering, otherwise disables stereo buffering. Stereo buffering is disabled by default. Stereo buffering provides extra color buffers to generate left-eye and right-eye images.

See also: stereo()

void QGLFormat::setSwapInterval ( int interval )

Set the preferred swap interval. This can be used to sync the GL drawing into a system window to the vertical refresh of the screen. Setting an interval value of 0 will turn the vertical refresh syncing off, any value higher than 0 will turn the vertical syncing on.

On Windows and X11, where the WGL_EXT_swap_control and GLX_SGI_video_sync extensions are used, the interval parameter can be used to set the minimum number of video frames that are displayed before a buffer swap will occur. In effect, setting the interval to 10, means there will be 10 vertical retraces between every buffer swap.

On Windows the WGL_EXT_swap_control extension has to be present, and under X11 the GLX_SGI_video_sync extension has to be present.

See also: swapInterval()

void QGLFormat::setVersion	(	int	major,
		int	minor
	)

Set the OpenGL version to the major and minor numbers. If a context compatible with the requested OpenGL version can not be created, a context compatible with version 1.x is created instead.

See also: majorVersion(), minorVersion()

bool QGLFormat::stencil ( ) const

inline

Returns true if the stencil buffer is enabled, otherwise returns false. The stencil buffer is enabled by default.

See also: setStencil(), setStencilBufferSize()

int QGLFormat::stencilBufferSize ( ) const

Returns the stencil buffer size.

See also: stencil(), setStencil(), setStencilBufferSize()

bool QGLFormat::stereo ( ) const

inline

Returns true if stereo buffering is enabled, otherwise returns false. Stereo buffering is disabled by default.

See also: setStereo()

int QGLFormat::swapInterval ( ) const

Returns the currently set swap interval. -1 is returned if setting the swap interval is not supported in the system GL implementation.

See also: setSwapInterval()

bool QGLFormat::testOption ( QGL::FormatOptions options ) const

Returns true if format options is set, otherwise returns false.

See also: setOption()

Friends And Related Function Documentation

bool operator!=	(	const QGLFormat &	value_1,
		const QGLFormat &	value_2
	)

friend

Returns false if all the options of the two QGLFormat objects value_1 and value_2 are equal, otherwise returns true.

bool operator==	(	const QGLFormat &	value_1,
		const QGLFormat &	value_2
	)

friend

Returns true if all the options of the two QGLFormat objects value_1 and value_2 are equal, otherwise returns false.

Public Typedefs

Public Types

Public Methods

Static Public Methods

Friends

Detailed Description

Member Typedef Documentation

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation

Friends And Related Function Documentation