QGLContext

The QGLContext class encapsulates an OpenGL rendering context. More…

Inheritance diagram of PySide2.QtOpenGL.QGLContext

Synopsis

Functions

Virtual functions

Static functions

Detailed Description

An OpenGL rendering context is a complete set of OpenGL state variables. The rendering context’s format is set in the constructor, but it can also be set later with setFormat() . The format options that are actually set are returned by format() ; the options you asked for are returned by requestedFormat() . Note that after a QGLContext object has been constructed, the actual OpenGL context must be created by explicitly calling the create() function. The makeCurrent() function makes this context the current rendering context. You can make no context current using doneCurrent() . The reset() function will reset the context and make it invalid.

You can examine properties of the context with, e.g. isValid() , isSharing() , initialized() , windowCreated() and overlayTransparentColor() .

If you’re using double buffering you can swap the screen contents with the off-screen buffer using swapBuffers() .

Please note that QGLContext is not thread safe.

class PySide2.QtOpenGL.QGLContext(format)
Parameters:

format – PySide2.QtOpenGL.QGLFormat

PySide2.QtOpenGL.QGLContext.BindOption

A set of options to decide how to bind a texture using bindTexture() .

Constant

Description

QGLContext.NoBindOption

Don’t do anything, pass the texture straight through.

QGLContext.InvertedYBindOption

Specifies that the texture should be flipped over the X axis so that the texture coordinate 0,0 corresponds to the top left corner. Inverting the texture implies a deep copy prior to upload.

QGLContext.MipmapBindOption

Specifies that bindTexture() should try to generate mipmaps. If the GL implementation supports the GL_SGIS_generate_mipmap extension, mipmaps will be automatically generated for the texture. Mipmap generation is only supported for the GL_TEXTURE_2D target.

QGLContext.PremultipliedAlphaBindOption

Specifies that the image should be uploaded with premultiplied alpha and does a conversion accordingly.

QGLContext.LinearFilteringBindOption

Specifies that the texture filtering should be set to GL_LINEAR. Default is GL_NEAREST. If mipmap is also enabled, filtering will be set to GL_LINEAR_MIPMAP_LINEAR.

QGLContext.DefaultBindOption

In Qt 4.5 and earlier, bindTexture() would mirror the image and automatically generate mipmaps. This option helps preserve this default behavior.

New in version 4.6.

static PySide2.QtOpenGL.QGLContext.areSharing(context1, context2)
Parameters:
Return type:

bool

Returns true if context1 and context2 are sharing their GL resources such as textures, shader programs, etc; otherwise returns false .

PySide2.QtOpenGL.QGLContext.bindTexture(image[, target=GL_TEXTURE_2D[, format=GL_RGBA]])
Parameters:
Return type:

GLuint

PySide2.QtOpenGL.QGLContext.bindTexture(image, target, format, options)
Parameters:
Return type:

GLuint

PySide2.QtOpenGL.QGLContext.bindTexture(pixmap[, target=GL_TEXTURE_2D[, format=GL_RGBA]])
Parameters:
Return type:

GLuint

PySide2.QtOpenGL.QGLContext.bindTexture(pixmap, target, format, options)
Parameters:
Return type:

GLuint

PySide2.QtOpenGL.QGLContext.bindTexture(fileName)
Parameters:

fileName – str

Return type:

GLuint

This is an overloaded function.

Reads the compressed texture file fileName and generates a 2D GL texture from it.

This function can load DirectDrawSurface (DDS) textures in the DXT1, DXT3 and DXT5 DDS formats if the GL_ARB_texture_compression and GL_EXT_texture_compression_s3tc extensions are supported.

Since 4.6.1, textures in the ETC1 format can be loaded if the GL_OES_compressed_ETC1_RGB8_texture extension is supported and the ETC1 texture has been encapsulated in the PVR container format. Also, textures in the PVRTC2 and PVRTC4 formats can be loaded if the GL_IMG_texture_compression_pvrtc extension is supported.

See also

deleteTexture()

PySide2.QtOpenGL.QGLContext.chooseContext([shareContext=None])
Parameters:

shareContext – PySide2.QtOpenGL.QGLContext

Return type:

bool

This semi-internal function is called by create() . It creates a system-dependent OpenGL handle that matches the format() of shareContext as closely as possible, returning true if successful or false if a suitable handle could not be found.

On Windows, it calls the virtual function choosePixelFormat(), which finds a matching pixel format identifier. On X11, it calls the virtual function chooseVisual() which finds an appropriate X visual. On other platforms it may work differently.

PySide2.QtOpenGL.QGLContext.colorIndex(c)
Parameters:

c – PySide2.QtGui.QColor

Return type:

uint

PySide2.QtOpenGL.QGLContext.contextHandle()
Return type:

PySide2.QtGui.QOpenGLContext

Returns the OpenGL context handle.

PySide2.QtOpenGL.QGLContext.create([shareContext=None])
Parameters:

shareContext – PySide2.QtOpenGL.QGLContext

Return type:

bool

Creates the GL context. Returns true if it was successful in creating a valid GL rendering context on the paint device specified in the constructor; otherwise returns false (i.e. the context is invalid).

If the OpenGL implementation on your system does not support the requested version of OpenGL context, then QGLContext will try to create the closest matching version. The actual created context properties can be queried using the QGLFormat returned by the format() function. For example, if you request a context that supports OpenGL 4.3 Core profile but the driver and/or hardware only supports version 3.2 Core profile contexts then you will get a 3.2 Core profile context.

After successful creation, format() returns the set of features of the created GL rendering context.

If shareContext points to a valid QGLContext , this method will try to establish OpenGL display list and texture object sharing between this context and the shareContext . Note that this may fail if the two contexts have different formats . Use isSharing() to see if sharing is in effect.

Warning

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 problem is that virtual functions are not properly called during construction (even though this is correct C++) because C++ constructs class hierarchies from the bottom up. For this reason we need a function.

See also

chooseContext() format() isValid()

static PySide2.QtOpenGL.QGLContext.currentContext()
Return type:

PySide2.QtOpenGL.QGLContext

Returns the current context, i.e. the context to which any OpenGL commands will currently be directed. Returns 0 if no context is current.

See also

makeCurrent()

PySide2.QtOpenGL.QGLContext.deleteTexture(tx_id)
Parameters:

tx_id – GLuint

Removes the texture identified by id from the texture cache, and calls glDeleteTextures() to delete the texture from the context.

See also

bindTexture()

PySide2.QtOpenGL.QGLContext.device()
Return type:

PySide2.QtGui.QPaintDevice

Returns the paint device set for this context.

See also

QGLContext()

PySide2.QtOpenGL.QGLContext.deviceIsPixmap()
Return type:

bool

Returns true if the paint device of this context is a pixmap; otherwise returns false .

Since Qt 5 the paint device is never actually a pixmap. renderPixmap() is however still simulated using framebuffer objects and readbacks, and this function will return true in this case.

PySide2.QtOpenGL.QGLContext.doneCurrent()

Makes no GL context the current context. Normally, you do not need to call this function; QGLContext calls it as necessary.

PySide2.QtOpenGL.QGLContext.drawTexture(point, textureId[, textureTarget=GL_TEXTURE_2D])
Parameters:
PySide2.QtOpenGL.QGLContext.drawTexture(target, textureId[, textureTarget=GL_TEXTURE_2D])
Parameters:
PySide2.QtOpenGL.QGLContext.format()
Return type:

PySide2.QtOpenGL.QGLFormat

Returns the frame buffer format that was obtained (this may be a subset of what was requested).

See also

setFormat() requestedFormat()

static PySide2.QtOpenGL.QGLContext.fromOpenGLContext(platformContext)
Parameters:

platformContext – PySide2.QtGui.QOpenGLContext

Return type:

PySide2.QtOpenGL.QGLContext

Returns an OpenGL context for the window context specified by the context parameter.

PySide2.QtOpenGL.QGLContext.initialized()
Return type:

bool

Returns true if this context has been initialized, i.e. if initializeGL() has been performed on it; otherwise returns false .

See also

setInitialized()

PySide2.QtOpenGL.QGLContext.isSharing()
Return type:

bool

Returns true if this context is sharing its GL context with another QGLContext , otherwise false is returned. Note that context sharing might not be supported between contexts with different formats.

PySide2.QtOpenGL.QGLContext.isValid()
Return type:

bool

Returns true if a GL rendering context has been successfully created; otherwise returns false .

PySide2.QtOpenGL.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.

In some very rare cases the underlying call may fail. If this occurs an error message is output to stderr.

If you call this from a thread other than the main UI thread, make sure you’ve first pushed the context to the relevant thread from the UI thread using moveToThread() .

PySide2.QtOpenGL.QGLContext.moveToThread(thread)
Parameters:

thread – PySide2.QtCore.QThread

Moves the QGLContext to the given thread .

Enables calling swapBuffers() and makeCurrent() on the context in the given thread.

PySide2.QtOpenGL.QGLContext.overlayTransparentColor()
Return type:

PySide2.QtGui.QColor

If this context is a valid context in an overlay plane, returns the plane’s transparent color. Otherwise returns an invalid color.

The returned color’s pixel value is the index of the transparent color in the colormap of the overlay plane. (Naturally, the color’s RGB values are meaningless.)

The returned QColor object will generally work as expected only when passed as the argument to qglColor() or qglClearColor() . Under certain circumstances it can also be used to draw transparent graphics with a QPainter .

PySide2.QtOpenGL.QGLContext.requestedFormat()
Return type:

PySide2.QtOpenGL.QGLFormat

Returns the frame buffer format that was originally requested in the constructor or setFormat() .

See also

format()

PySide2.QtOpenGL.QGLContext.reset()

Resets the context and makes it invalid.

See also

create() isValid()

PySide2.QtOpenGL.QGLContext.setDevice(pDev)
Parameters:

pDev – PySide2.QtGui.QPaintDevice

See also

device()

PySide2.QtOpenGL.QGLContext.setFormat(format)
Parameters:

format – PySide2.QtOpenGL.QGLFormat

Sets a format for this context. The context is reset .

Call create() to create a new GL context that tries to match the new format.

cx = QGLContext()
#  ...
f = QGLFormat()
f.setStereo(True)
cx.setFormat(f)
if !cx.create():
    exit() # no OpenGL support, or cannot render on the specified paintdevice
if !cx.format().stereo():
    exit() # could not create stereo context

See also

format() reset() create()

PySide2.QtOpenGL.QGLContext.setInitialized(on)
Parameters:

on – bool

If on is true the context has been initialized, i.e. has been called on it. If on is false the context has not been initialized.

See also

initialized()

static PySide2.QtOpenGL.QGLContext.setTextureCacheLimit(size)
Parameters:

size – int

This function sets the limit for the texture cache to size , expressed in kilobytes.

By default, the cache limit is approximately 64 MB.

See also

textureCacheLimit()

PySide2.QtOpenGL.QGLContext.setValid(valid)
Parameters:

valid – bool

See also

isValid()

PySide2.QtOpenGL.QGLContext.setWindowCreated(on)
Parameters:

on – bool

If on is true the context has had a window created for it. If on is false no window has been created for the context.

See also

windowCreated()

PySide2.QtOpenGL.QGLContext.swapBuffers()

Call this to finish a frame of OpenGL rendering, and make sure to call makeCurrent() again before issuing any further OpenGL commands, for example as part of a new frame.

static PySide2.QtOpenGL.QGLContext.textureCacheLimit()
Return type:

int

Returns the current texture cache limit in kilobytes.

See also

setTextureCacheLimit()

PySide2.QtOpenGL.QGLContext.windowCreated()
Return type:

bool

Returns true if a window has been created for this context; otherwise returns false .

See also

setWindowCreated()