2003-2014
The Khronos Group Inc.
eglQueryContext
3G
eglQueryContext
return EGL rendering context information
C Specification
EGLBoolean eglQueryContext
EGLDisplay display
EGLContext context
EGLint attribute
EGLint * value
Parameters
display
Specifies the EGL display connection.
context
Specifies the EGL rendering context to query.
attribute
Specifies the EGL rendering context attribute to be returned.
value
Returns the requested value.
Description
eglQueryContext returns in
value the value of
attribute for context.
attribute can be one of the following:
EGL_CONFIG_ID
Returns the ID of the EGL frame buffer configuration
with respect to which the context was created.
EGL_CONTEXT_CLIENT_TYPE
Returns the type of client API which the context
supports (one of
EGL_OPENGL_API,
EGL_OPENGL_ES_API, or
EGL_OPENVG_API).
EGL_CONTEXT_CLIENT_VERSION
Returns the version of the client API which the
context supports, as specified at context creation
time. The resulting value is only meaningful for an
OpenGL ES context.
EGL_RENDER_BUFFER
Returns the buffer which client API rendering
via the context will use. The value returned
depends on properties of both the context, and
the surface to which the context is bound:
If the context is bound to a pixmap surface,
then EGL_SINGLE_BUFFER will
be returned.
If the context is bound to a pbuffer surface,
then EGL_BACK_BUFFER will
be returned.
If the context is bound to a window surface,
then either EGL_BACK_BUFFER
or EGL_SINGLE_BUFFER may be
returned. The value returned depends on both the
buffer requested by the setting of the
EGL_RENDER_BUFFER property
of the surface (which may be queried by calling
eglQuerySurface), and on
the client API (not all client APIs support
single-buffer rendering to window surfaces).
If the context is not bound to a surface, such
as an OpenGL ES context bound to a framebuffer
object, then EGL_NONE will
be returned.
Notes
Attributes EGL_CONTEXT_CLIENT_TYPE and
EGL_RENDER_BUFFER are supported only if
the EGL version is 1.2 or greater.
Attribute EGL_CONTEXT_CLIENT_VERSION is
supported only if the EGL version is 1.3 or greater.
Errors
EGL_FALSE is returned on failure,
EGL_TRUE otherwise.
value is not modified when
EGL_FALSE is returned.
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_CONTEXT is generated if
context is not an EGL rendering context.
EGL_BAD_ATTRIBUTE is generated if
attribute is not a valid context attribute.
See Also
eglCreateContext