GLContext

class GLContext(**properties: Any)

Superclasses: DrawContext, Object

GdkGLContext is an object representing a platform-specific OpenGL draw context.

GdkGLContext’s are created for a surface using create_gl_context, and the context will match the characteristics of the surface.

A GdkGLContext is not tied to any particular normal framebuffer. For instance, it cannot draw to the surface back buffer. The GDK repaint system is in full control of the painting to that. Instead, you can create render buffers or textures and use cairo_draw_from_gl in the draw function of your widget to draw them. Then GDK will handle the integration of your rendering with that of other widgets.

Support for GdkGLContext is platform-specific and context creation can fail, returning None context.

A GdkGLContext has to be made “current” in order to start using it, otherwise any OpenGL call will be ignored.

Creating a new OpenGL context

In order to create a new GdkGLContext instance you need a GdkSurface, which you typically get during the realize call of a widget.

A GdkGLContext is not realized until either make_current or realize is called. It is possible to specify details of the GL context like the OpenGL version to be used, or whether the GL context should have extra state validation enabled after calling create_gl_context by calling realize. If the realization fails you have the option to change the settings of the GdkGLContext and try again.

Using a GdkGLContext

You will need to make the GdkGLContext the current context before issuing OpenGL calls; the system sends OpenGL commands to whichever context is current. It is possible to have multiple contexts, so you always need to ensure that the one which you want to draw with is the current one before issuing commands:

gdk_gl_context_make_current (context);

You can now perform your drawing using OpenGL commands.

You can check which GdkGLContext is the current one by using get_current; you can also unset any GdkGLContext that is currently set by calling clear_current.

Methods

class GLContext

clear_current() → None

Clears the current GdkGLContext.

Any OpenGL call after this function returns will be ignored until make_current is called.

get_allowed_apis() → GLAPI

Gets the allowed APIs set via set_allowed_apis().

Added in version 4.6.

get_api() → GLAPI

Gets the API currently in use.

If the renderer has not been realized yet, 0 is returned.

Added in version 4.6.

get_current() → GLContext | None

Retrieves the current GdkGLContext.

get_debug_enabled() → bool

Retrieves whether the context is doing extra validations and runtime checking.

See set_debug_enabled.

get_display() → Display | None

Retrieves the display the context is created for

get_forward_compatible() → bool

Retrieves whether the context is forward-compatible.

See set_forward_compatible.

get_required_version() → tuple[int, int]

Retrieves required OpenGL version set as a requirement for the context realization. It will not change even if a greater OpenGL version is supported and used after the context is realized. See get_version for the real version in use.

See set_required_version.

get_shared_context() → GLContext | None

Used to retrieves the GdkGLContext that this context share data with.

As many contexts can share data now and no single shared context exists anymore, this function has been deprecated and now always returns None.

Deprecated since version 4.4: Use is_shared to check if contexts can be shared.

get_surface() → Surface | None

Retrieves the surface used by the context.

get_use_es() → bool

Checks whether the context is using an OpenGL or OpenGL ES profile.

get_version() → tuple[int, int]

Retrieves the OpenGL version of the context.

The context must be realized prior to calling this function.

is_legacy() → bool

Whether the GdkGLContext is in legacy mode or not.

The GdkGLContext must be realized before calling this function.

When realizing a GL context, GDK will try to use the OpenGL 3.2 core profile; this profile removes all the OpenGL API that was deprecated prior to the 3.2 version of the specification. If the realization is successful, this function will return False.

If the underlying OpenGL implementation does not support core profiles, GDK will fall back to a pre-3.2 compatibility profile, and this function will return True.

You can use the value returned by this function to decide which kind of OpenGL API to use, or whether to do extension discovery, or what kind of shader programs to load.

is_shared(other: GLContext) → bool

Checks if the two GL contexts can share resources.

When they can, the texture IDs from other can be used in self. This is particularly useful when passing GdkGLTexture objects between different contexts.

Contexts created for the same display with the same properties will always be compatible, even if they are created for different surfaces. For other contexts it depends on the GL backend.

Both contexts must be realized for this check to succeed. If either one is not, this function will return False.

Added in version 4.4.

Parameters:

other – the GdkGLContext that should be compatible with self

make_current() → None

Makes the context the current one.

realize() → bool

Realizes the given GdkGLContext.

It is safe to call this function on a realized GdkGLContext.

set_allowed_apis(apis: GLAPI) → None

Sets the allowed APIs. When realize() is called, only the allowed APIs will be tried. If you set this to 0, realizing will always fail.

If you set it on a realized context, the property will not have any effect. It is only relevant during realize().

By default, all APIs are allowed.

Added in version 4.6.

Parameters:

apis – the allowed APIs

set_debug_enabled(enabled: bool) → None

Sets whether the GdkGLContext should perform extra validations and runtime checking.

This is useful during development, but has additional overhead.

The GdkGLContext must not be realized or made current prior to calling this function.

Parameters:

enabled – whether to enable debugging in the context

set_forward_compatible(compatible: bool) → None

Sets whether the GdkGLContext should be forward-compatible.

Forward-compatible contexts must not support OpenGL functionality that has been marked as deprecated in the requested version; non-forward compatible contexts, on the other hand, must support both deprecated and non deprecated functionality.

The GdkGLContext must not be realized or made current prior to calling this function.

Parameters:

compatible – whether the context should be forward-compatible

set_required_version(major: int, minor: int) → None

Sets the major and minor version of OpenGL to request.

Setting major and minor to zero will use the default values.

Setting major and minor lower than the minimum versions required by GTK will result in the context choosing the minimum version.

The context must not be realized or made current prior to calling this function.

Parameters:

• major – the major version to request

• minor – the minor version to request

set_use_es(use_es: int) → None

Requests that GDK create an OpenGL ES context instead of an OpenGL one.

Not all platforms support OpenGL ES.

The context must not have been realized.

By default, GDK will attempt to automatically detect whether the underlying GL implementation is OpenGL or OpenGL ES once the context is realized.

You should check the return value of get_use_es after calling realize to decide whether to use the OpenGL or OpenGL ES API, extensions, or shaders.

Parameters:

use_es – whether the context should use OpenGL ES instead of OpenGL, or -1 to allow auto-detection

Properties

class GLContext

props.allowed_apis: GLAPI

The allowed APIs.

Added in version 4.6.

props.api: GLAPI

The API currently in use.

Added in version 4.6.

props.shared_context: GLContext

Always None

As many contexts can share data now and no single shared context exists anymore, this function has been deprecated and now always returns None.

Deprecated since version 4.4: Use is_shared to check if contexts can be shared.