The XGetExtensionVersion request queries the
version of the input extension, and returns an XExtensionVersion structure.
This structure contains a major_version and minor_version number which
can be compared with constants defined in XI.h. Support for additional protocol
requests added to the input extension after its initial release is indicated
by a version number corresponding to the added requests. Each version contains
all the protocol requests contained by previous versions.
You should use
XFree to free the XExtensionVersion structure.