Man page 3 : XkbQueryExtension

XkbQueryExtension - Determines the compatibility of a library at runtime.

Bool XkbQueryExtension (Display * dpy , int * opcode_rtrn , int * event_rtrn , int * error_rtrn , int * major_in_out , int * minor_in_out );

• dpy
      connection to the X server
• opcode_rtrn
      backfilled with the major extension opcode
• event_rtrn
      backfilled with the extension base event code
• error_rtrn
      backfilled with the extension base error code
• major_in_out
      compile time lib major version in, server major version out
• minor_in_out
      compile time lib min version in, server minor version out

Call XkbQueryExtensionto check for the presence and compatibility of the extension in the server and to initialize the extension. Because of potential version mismatches, you cannot use the generic extension mechanism functions ( XQueryExtensionand XInitExtension) for checking for the presence of, and initializing the Xkb extension. You must call XkbQueryExtensionor XkbOpenDisplaybefore using any other Xkb library interfaces, unless such usage is explicitly allowed in the interface description in this document. The exceptions are: XkbIgnoreExtension, XkbLibraryVersion,and a handful of audible-bell functions. You should not use any other Xkb functions if the extension is not present or is uninitialized. In general, calls to Xkb library functions made prior to initializing the Xkb extension cause BadAccess protocol errors. XkbQueryExtensionboth determines whether a compatible Xkb extension is present in the X server and initializes the extension when it is present. The XkbQueryExtensionfunction determines whether a compatible version of the X Keyboard Extension is present in the server. If a compatible extension is present, XkbQueryExtensionreturns True; otherwise, it returns False. If a compatible version of Xkb is present, XkbQueryExtensioninitializes the extension. It backfills the major opcode for the keyboard extension in opcode_rtrn,the base event code in event_rtrn,the base error code in error_rtrn,and the major and minor version numbers of the extension in major_in_outand minor_in_out.The major opcode is reported in the req_majorfields of some Xkb events. For a discussion of the base event code.

• True
                 The XkbQueryExtensionfunction returns True if it determines a compatible version of the X Keyboard Extension is present in the server.
• False
                 The XkbQueryExtensionfunction returns False if it determines a compatible version of the X Keyboard Extension is not present in the server.

R XkbIgnoreExtension (3),

R XkbLibraryVersion (3),

R XkbOpenDisplay (3)