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Name Strings
Version 3, May 20, 2015
This extension affects the definition of SGIX_FBConfig.
This extension allows multiple X clients to share an indirect
rendering context.
Additional convenience procedures to get the current Display*
bound to a context as well as other context information are
also added.
Does glXImportGLXContext also need to take an XVisualInfo*?
No. This information will be retrieved from the server.
New Procedures and Functions
Display *glXGetCurrentDisplayEXT();
int glXQueryContextInfoEXT(Display *dpy, GLXContext context,
int attribute,int *value);
GLXContextID glXGetContextIDEXT(const GLXContext context);
GLXContext glXImportContextEXT(Display *dpy, GLXContextID contextID);
void glXFreeContextEXT(Display *dpy, GLXContext context);
New Tokens
Accepted by the <attribute> parameter of glXQueryContextInfoEXT:
Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)
Additions to Chapter 3 of the 1.0 Specification (Rasterization)
Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations
and the Frame Buffer)
Additions to Chapter 5 of the 1.0 Specification (Special Functions)
Additions to Chapter 6 of the 1.0 Specification (State and State Requests)
Additions to the GLX Specification
[Add the following to Section 3.2.4 of the GLX Specification
(Rendering Contexts)]
To get the display associated with the current context, use
Display *glXGetCurrentDisplayEXT();
If there is no current context, NULL is returned. No round trip
is forced to the server; unlike most X calls that return a value,
glXGetCurrentDisplayEXT does not flush any pending events.
To obtain the value of a context's attribute, use
int glXQueryContextInfoEXT(Display *dpy, GLXContext context,
int attribute, int *value);
glxQueryContextInfoEXT returns through <value> the value of
<attribute> for <context>. It may cause a round trip to the
The values and types corresponding to each GLX context attribute
are listed in the table below.
GLX context attribute type context information
--------------------- ---- -------------------
GLX_SHARE_CONTEXT_EXT XID xid of the share list context
GLX_SCREEN_EXT int screen number
glxQueryContextInfoEXT returns GLX_BAD_ATTRIBUTE if <attribute>
is not a valid GLX context attribute or GLX_BAD_CONTEXT if <context>
is invalid, otherwise it returns Success.
To obtain the XID of a GLXContext, use
GLXContextID glXGetContextIDEXT(const GLXContext context);
No round trip is forced to the server; unlike most X calls that
return a value, glXGetContextIDEXT does not flush any pending
events. If <context> is NULL, None is returned. If <context> is not
NULL and is not a valid GLXContext name, behavior is undefined.
To create a GLXContext given the XID of an existing GLXContext, use
GLXContext glXImportContextEXT(Display *dpy,
GLXContextID contextID);
glXImportContextEXT may be used in place of glXCreateContext to
share another process's indirect rendering context.
Only the server-side context information can be shared between
X clients; client-side state, such as pixel storage modes,
cannot be shared. Thus, glXImportContextEXT, must allocate
memory to store client-side information. This memory is freed
by calling glXFreeContextEXT.
This call does not create a new XID. It merely makes an
existing object available to the importing client (Display *).
Like any XID, it goes away when the creating client drops its
connection or the ID is explicitly deleted. Note that this is
when the XID goes away. The object goes away when the XID
goes away AND the context is not current to any thread.
If <contextID> does not refer to a valid context, then
a BadContext error is generated; if <contextID> refers to
direct rendering context then no error is generated but
glXImportContextEXT returns NULL.
To free the client-side part of a GLXContext that was created
with glXImportContext, use
void glXFreeContextEXT(Display *dpy, GLXContext context);
glXFreeContext does not free the server-side context information
or the XID associated with the server-side context.
[Add the following clarification to glXMakeCurrent]
If <context> is current to some other thread, then glXMakeCurrent
will generate a BadAccess error.
If <context> is current to some other thread or process, then
glXMakeCurrent will generate a BadAccess error.
GLX Protocol
One new GLX protocol command is added.
1 CARD8 opcode (X assigned)
1 17 GLX opcode (glXVendorPrivateWithReply)
2 4 request length
4 1024 vendor specific opcode
4 unused corresponds to context tag in header
4 GLX_CONTEXT context id
1 1 Reply
1 unused
2 CARD16 sequence number
4 2*n reply length
4 CARD32 n
20 unused
8*n LISTofCARD32 attribute, value pairs
New State
New Implementation Dependent State
Revision History
Version 3, 2015/05/20 - Specify behavior of glXGetContextIDEXT when an
invalid <context> is passed (Bug 8344).
Version 2, 2006/08/24 - Fixed opcode for QueryContextInfo per Ian
Romanick (opcode is 1024 per glx.spec, which is used to generate
glxproto.h - not 15 as has been in the extension spec since 1995).
Version 1.14, 1995/10/14 - Last update from SGI.