(list-extensions display)
See XListExtensions. Returns a vector of strings.
(query-extension display name)
See XQueryExtension.
name is a string or a symbol.
Returns a list of three elements: the major opcode (an integer) or #f
if the extension has no major opcode, the base event type code (an
integer) of #f if the extension has no additional event types, and
the base error code (an integer) of #f if the extension has no
additional error codes.
query-extension returns #f if the specified extension is not present.