QGLContext¶

PyQt5.QtOpenGL.QGLContext

Description¶

The QGLContext class encapsulates an OpenGL rendering context.

An OpenGL rendering context is a complete set of OpenGL state variables. The rendering context’s FormatOption 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.

Classes¶

BindOptions

Enums¶

BindOption

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

Member	Value	Description
DefaultBindOption	LinearFilteringBindOption \| InvertedYBindOption \| MipmapBindOption	In Qt 4.5 and earlier, bindTexture() would mirror the image and automatically generate mipmaps. This option helps preserve this default behavior.
InvertedYBindOption	0x0001	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.
LinearFilteringBindOption	0x0008	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.
MipmapBindOption	0x0002	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.
NoBindOption	0x0000	Don’t do anything, pass the texture straight through.
PremultipliedAlphaBindOption	0x0004	Specifies that the image should be uploaded with premultiplied alpha and does a conversion accordingly.

Methods¶

__init__(QGLFormat)

Constructs an OpenGL context with the given format which specifies several display options for the context.

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.

Note that after a QGLContext object has been constructed, create() must be called explicitly to create the actual OpenGL context. The context will be isValid() if it was not possible to obtain a GL context at all.

See also

format(), isValid().

@staticmethod areSharing(QGLContext, QGLContext) → bool: Returns true if context1 and context2 are sharing their GL resources such as textures, shader programs, etc; otherwise returns false.

bindTexture(str) → int

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().

bindTexture(QImage, target: int = GL_TEXTURE_2D, format: int = GL_RGBA) → int

Generates and binds a 2D GL texture to the current context, based on image. The generated texture id is returned and can be used in later glBindTexture() calls.

This is an overloaded function.

bindTexture(QPixmap, target: int = GL_TEXTURE_2D, format: int = GL_RGBA) → int

This is an overloaded function.

Generates and binds a 2D GL texture based on pixmap.

bindTexture(QImage, int, int, Union[BindOptions, BindOption]) → int

Generates and binds a 2D GL texture to the current context, based on image. The generated texture id is returned and can be used in later glBindTexture() calls.

The target parameter specifies the texture target. The default target is GL_TEXTURE_2D.

The format parameter sets the internal format for the texture. The default format is GL_RGBA.

The binding options are a set of options used to decide how to bind the texture to the context.

The texture that is generated is cached, so multiple calls to with the same QImage will return the same texture id.

Note that we assume default values for the glPixelStore() and glPixelTransfer() parameters.

See also

deleteTexture().

bindTexture(QPixmap, int, int, Union[BindOptions, BindOption]) → int

This is an overloaded function.

Generates and binds a 2D GL texture to the current context, based on pixmap.

chooseContext(shareContext: QGLContext = None) → bool: TODO

create(shareContext: QGLContext = None) → 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 format(). 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().

@staticmethod currentContext() → QGLContext: TODO

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

See also

bindTexture().

device() → QPaintDevice: TODO

deviceIsPixmap() → bool: TODO

doneCurrent(): TODO

drawTexture(QRectF, int, textureTarget: int = GL_TEXTURE_2D)

This function supports the following use cases:

On OpenGL and OpenGL ES 1.x it draws the given texture, textureId, to the given target rectangle, target, in OpenGL model space. The textureTarget should be a 2D texture target.
On OpenGL and OpenGL ES 2.x, if a painter is active, not inside a beginNativePainting / endNativePainting block, and uses the engine with type OpenGL2, the function will draw the given texture, textureId, to the given target rectangle, target, respecting the current painter state. This will let you draw a texture with the clip, transform, render hints, and composition mode set by the painter. Note that the texture target needs to be GL_TEXTURE_2D for this use case, and that this is the only supported use case under OpenGL ES 2.x.

drawTexture(Union[QPointF, QPoint], int, textureTarget: int = GL_TEXTURE_2D)

This function supports the following use cases:

By default it draws the given texture, textureId, at the given point in OpenGL model space. The textureTarget should be a 2D texture target.
If a painter is active, not inside a beginNativePainting / endNativePainting block, and uses the engine with type OpenGL2, the function will draw the given texture, textureId, at the given point, respecting the current painter state. This will let you draw a texture with the clip, transform, render hints, and composition mode set by the painter. Note that the texture target needs to be GL_TEXTURE_2D for this use case.

Note: This function is not supported under any version of OpenGL ES.

format() → QGLFormat: See also

setFormat().

getProcAddress(str) → sip.voidptr: TODO

initialized() → bool: See also

setInitialized().

isSharing() → bool: TODO

isValid() → bool: TODO

makeCurrent(): TODO

moveToThread(QThread): TODO

overlayTransparentColor() → QColor: TODO

requestedFormat() → QGLFormat: TODO

reset(): TODO

setFormat(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.

# QGLContext *cx;
# //  ...
# QGLFormat f;
# 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().

setInitialized(bool): See also

initialized().

@staticmethod setTextureCacheLimit(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().

setWindowCreated(bool): See also

windowCreated().

swapBuffers(): TODO

@staticmethod textureCacheLimit() → int: Returns the current texture cache limit in kilobytes.

See also

setTextureCacheLimit().

windowCreated() → bool: See also

setWindowCreated().