# eglCreateContext

create a new EGL rendering context

## C Specification

`EGLContext eglCreateContext(` | EGLDisplay display,
| EGLConfig config,
| EGLContext share_context,
| EGLint const * attrib_list`)`

## Parameters

`display`

  Specifies the EGL display connection.

`config`

  Specifies the EGL frame buffer configuration that defines the frame buffer resource available to the rendering context.

`share_context`

  Specifies another EGL rendering context with which to share data, as defined by the client API corresponding to the contexts. Data is also shared with all other contexts with which `share_context` shares data. `EGL_NO_CONTEXT` indicates that no sharing is to take place.

`attrib_list`

  Specifies attributes and attribute values for the context being created. Only the attribute `EGL_CONTEXT_CLIENT_VERSION` may be specified.

## Description

`eglCreateContext` creates an EGL rendering context for the current rendering API (as set with `eglBindAPI`) and returns a handle to the context. The context can then be used to render into an EGL drawing surface. If `eglCreateContext` fails to create a rendering context, `EGL_NO_CONTEXT` is returned.

If `share_context` is not `EGL_NO_CONTEXT`, then all shareable data in the context (as defined by the client API specification for the current rendering API) are shared by context `share_context`, all other contexts `share_context` already shares with, and the newly created context. An arbitrary number of rendering contexts can share data. However, all rendering contexts that share data must themselves exist in the same address space. Two rendering contexts share an address space if both are owned by a single process.

`attrib_list` specifies a list of attributes for the context. The list has the same structure as described for `eglChooseConfig`. The attributes and attribute values which may be specified are as follows:

`EGL_CONTEXT_CLIENT_VERSION`

  Must be followed by an integer that determines which version of an OpenGL ES context to create. A value of 1 specifies creation of an OpenGL ES 1.x context. An attribute value of 2 specifies creation of an OpenGL ES 2.x context. The default value is 1. This attribute can only be specified when creating a OpenGL ES context (e.g. when the current rendering API is `EGL_OPENGL_ES_API`).

## Notes

The current rendering API is only respected if the EGL version is 1.2 or greater. Otherwise, an OpenGL ES context will always be created.

The `EGL_CONTEXT_CLIENT_VERSION` attribute is only supported if the EGL version is 1.3 or greater.

A process is a single execution environment, implemented in a single address space, consisting of one or more threads.

A thread is one of a set of subprocesses that share a single address space, but maintain separate program counters, stack spaces, and other related global data. A thread is the only member of its subprocess group is equivalent to a process.

## Errors

`EGL_NO_CONTEXT` is returned if creation of the context fails.

`EGL_BAD_MATCH` is generated if the current rendering API is `EGL_NONE` (this can only arise in an EGL implementation which does not support OpenGL ES, prior to the first call to `eglBindAPI`).

`EGL_BAD_MATCH` is generated if the server context state for `share_context` exists in an address space which cannot be shared with the newly created context, if `share_context` was created on a different display than the one referenced by `config`, or if the contexts are otherwise incompatible.

`EGL_BAD_DISPLAY` is generated if `display` is not an EGL display connection.

`EGL_NOT_INITIALIZED` is generated if `display` has not been initialized.

`EGL_BAD_CONFIG` is generated if `config` is not an EGL frame buffer configuration, or does not support the current rendering API. This includes requesting creation of an OpenGL ES 1.x context when the `EGL_RENDERABLE_TYPE` attribute of `config` does not contain `EGL_OPENGL_ES_BIT`, or creation of an OpenGL ES 2.x context when the attribute does not contain `EGL_OPENGL_ES2_BIT`.

`EGL_BAD_CONTEXT` is generated if `share_context` is not an EGL rendering context of the same client API type as the newly created context and is not `EGL_NO_CONTEXT`.

`EGL_BAD_ATTRIBUTE` is generated if `attrib_list` contains an invalid context attribute or if an attribute is not recognized or out of range. Note that attribute `EGL_CONTEXT_CLIENT_VERSION` is only valid when the current rendering API is `EGL_OPENGL_ES_API`.

`EGL_BAD_ALLOC` is generated if there are not enough resources to allocate the new context.

## See Also

eglDestroyContext, eglChooseConfig, eglGetConfigs, eglMakeCurrent

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