bionic (3) XkbKeyActionsPtr.3.gz

NAME

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

SYNOPSIS

       XkbKeyActionPtr XkbKeyActionsPtr (XkbDescPtr xkb, KeyCode keycode);

ARGUMENTS

       - xkb  Xkb description of interest

       - keycode
              keycode of interest

DESCRIPTION

       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 associated 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  consumption  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 concatenates 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 something greater than zero.

STRUCTURES

       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;

SEE ALSO

       XkbKeyNumActions(3)