CopperSpice API  1.9.1
QGLFormat Class Reference

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:

fmt.setAlpha(true);
fmt.setStereo(true);

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

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:

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

Member Enumeration Documentation

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.

ConstantValueDescription
QGLFormat::NoProfile0 OpenGL version is lower than 3.2.
QGLFormat::CoreProfile1 Functionality deprecated in OpenGL version 3.0 is not available.
QGLFormat::CompatibilityProfile2 Functionality from earlier OpenGL versions is available.

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.

ConstantValueDescription
QGLFormat::OpenGL_Version_None0x00000000 If no OpenGL is present or if no OpenGL context is current.
QGLFormat::OpenGL_Version_1_10x00000001 OpenGL version 1.1 or higher is present.
QGLFormat::OpenGL_Version_1_20x00000002 OpenGL version 1.2 or higher is present.
QGLFormat::OpenGL_Version_1_30x00000004 OpenGL version 1.3 or higher is present.
QGLFormat::OpenGL_Version_1_40x00000008 OpenGL version 1.4 or higher is present.
QGLFormat::OpenGL_Version_1_50x00000010 OpenGL version 1.5 or higher is present.
QGLFormat::OpenGL_Version_2_00x00000020 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_10x00000040 OpenGL version 2.1 or higher is present.
QGLFormat::OpenGL_Version_3_00x00001000 OpenGL version 3.0 or higher is present.
QGLFormat::OpenGL_Version_3_10x00002000 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_20x00004000 OpenGL version 3.2 or higher is present.
QGLFormat::OpenGL_Version_3_30x00008000 OpenGL version 3.3 or higher is present.
QGLFormat::OpenGL_Version_4_00x00010000 OpenGL version 4.0 or higher is present.
QGLFormat::OpenGL_ES_CommonLite_Version_1_00x00000100 OpenGL ES version 1.0 Common Lite or higher is present.
QGLFormat::OpenGL_ES_Common_Version_1_00x00000080 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_10x00000400 OpenGL ES version 1.1 Common Lite or higher is present.
QGLFormat::OpenGL_ES_Common_Version_1_10x00000200 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_00x00000800 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);
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:

format.setDoubleBuffer(true);
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.