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CentOS 7.0 - man page for xkbkeyactionsptr (centos section 3)

XkbKeyActionsPtr(3)			  XKB FUNCTIONS 		      XkbKeyActionsPtr(3)

       XkbKeyActionsPtr  -  Returns a pointer to the two-dimensional array of key actions associ-
       ated with the key corresponding to keycode

       XkbKeyActionPtr XkbKeyActionsPtr (XkbDescPtr xkb, KeyCode keycode);

       - xkb  Xkb description of interest

       - keycode
	      keycode of interest

       A key action defines the effect key presses and releases have on the internal state of the
       server.	For example, the expected key action associated with pressing the Shift key is to
       set the Shift modifier. There is zero or one key action associated with each keysym  bound
       to each key.

       Just  as the entire list of key symbols for the keyboard mapping is held in the syms field
       of the client map, the entire list of key actions for the keyboard mapping is held in  the
       acts  array  of	the server map. The total size of acts is specified by size_acts, and the
       number of entries is specified by num_acts.

       The key_acts array, indexed by keycode, describes the actions associated with a	key.  The
       key_acts array has min_key_code unused entries at the start to allow direct indexing using
       a keycode. If a key_acts entry is zero, it means the key does not have any actions associ-
       ated  with  it. If an entry is not zero, the entry represents an index into the acts field
       of the server map, much as the offset field of a KeySymMapRec structure is an  index  into
       the syms field of the client map.

       The  reason the acts field is a linear list of XkbActions is to reduce the memory consump-
       tion associated with a keymap.  Because Xkb allows individual keys to have multiple  shift
       levels and a different number of groups per key, a single two-dimensional array of KeySyms
       would potentially be very large and sparse. Instead, Xkb provides a small  two-dimensional
       array  of  XkbActions  for each key. To store all of these individual arrays, Xkb concate-
       nates each array together in the acts field of the server map.

       The key action structures consist only of fields of type char or unsigned char.	 This  is
       done  to  optimize  data transfer when the server sends bytes over the wire. If the fields
       are anything but bytes, the server has to sift through all of the  actions  and	swap  any
       nonbyte fields. Because they consist of nothing but bytes, it can just copy them out.

       XkbKeyActionsPtr  returns a pointer to the two-dimensional array of key actions associated
       with the key corresponding to keycode.  Use XkbKeyActionsPtr only if the key actually  has
       some  actions  associated  with it, that is, XkbKeyNumActions (xkb, keycode) returns some-
       thing greater than zero.

       The KeySymMapRec structure is defined as follows:

	   #define XkbNumKbdGroups	       4
	   #define XkbMaxKbdGroup	       (XkbNumKbdGroups-1)

	   typedef struct {		       /* map to keysyms for a single keycode
	       unsigned char	   kt_index[XkbNumKbdGroups];  /* key type index for
       each group */
	       unsigned char	   group_info; /* # of groups and out of range group
       handling */
	       unsigned char	   width;      /* max # of shift levels for key */
	       unsigned short	   offset;     /* index to keysym table in syms array
       } XkbSymMapRec, *XkbSymMapPtr;


X Version 11				   libX11 1.6.0 		      XkbKeyActionsPtr(3)

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