GLXContext glXImportContextEXT( Display *dpy, GLXContextID contextID)
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
If contextID refers to a direct rendering context then no error is generated but glXImportContextEXT returns NULL.
glXImportContextEXT is part of the EXT_import_context extension, not part of the core GLX command set. If GLX_EXT_import_context is included in the string returned by glXQueryExtensionsString, when called with argument GLX_EXTENSIONS, extension EXT_import_context is supported.