1XkbKeyAction(3)                  XKB FUNCTIONS                 XkbKeyAction(3)
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NAME

6       XkbKeyAction -  Returns the key action
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SYNOPSIS

9       XkbAction XkbKeyAction (XkbDescPtr xkb, KeyCode keycode, int idx);
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ARGUMENTS

12       - xkb  Xkb description of interest
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14       - keycode
15              keycode of interest
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17       - idx  index for group and shift level
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DESCRIPTION

20       A  key  action  defines the effect key presses and releases have on the
21       internal state of the server. For example, the expected key action  as‐
22       sociated  with  pressing  the  Shift  key is to set the Shift modifier.
23       There is zero or one key action associated with each  keysym  bound  to
24       each key.
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26       Just as the entire list of key symbols for the keyboard mapping is held
27       in the syms field of the client map, the entire list of key actions for
28       the  keyboard  mapping is held in the acts array of the server map. The
29       total size of acts is specified by size_acts, and the number of entries
30       is specified by num_acts.
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32       The  key_acts  array, indexed by keycode, describes the actions associ‐
33       ated with a key. The key_acts array has min_key_code unused entries  at
34       the start to allow direct indexing using a keycode. If a key_acts entry
35       is zero, it means the key does not have any actions associated with it.
36       If  an  entry  is not zero, the entry represents an index into the acts
37       field of the server map, much as the offset  field  of  a  KeySymMapRec
38       structure is an index into the syms field of the client map.
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40       The  reason  the acts field is a linear list of XkbActions is to reduce
41       the memory consumption associated with a keymap.   Because  Xkb  allows
42       individual keys to have multiple shift levels and a different number of
43       groups per key, a single two-dimensional array of KeySyms would  poten‐
44       tially  be very large and sparse. Instead, Xkb provides a small two-di‐
45       mensional array of XkbActions for each key. To store all of these indi‐
46       vidual  arrays,  Xkb concatenates each array together in the acts field
47       of the server map.
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49       The key action structures consist only of fields of type  char  or  un‐
50       signed  char.   This  is done to optimize data transfer when the server
51       sends bytes over the wire. If the fields are anything  but  bytes,  the
52       server  has  to  sift  through  all of the actions and swap any nonbyte
53       fields.  Because they consist of nothing but bytes, it  can  just  copy
54       them out.
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56       XkbKeyAction  returns  the  key action indexed by idx in the two-dimen‐
57       sional array of key actions associated with the  key  corresponding  to
58       keycode.idx  may be computed from the group and shift level of interest
59       as follows:
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61           idx = group_index * key_width + shift_level
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STRUCTURES

64       The KeySymMapRec structure is defined as follows:
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66           #define XkbNumKbdGroups             4
67           #define XkbMaxKbdGroup              (XkbNumKbdGroups-1)
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69           typedef struct {                    /* map to keysyms for a single keycode
70       */
71               unsigned char       kt_index[XkbNumKbdGroups];  /* key type index for
72       each group */
73               unsigned char       group_info; /* # of groups and out of range group
74       handling */
75               unsigned char       width;      /* max # of shift levels for key */
76               unsigned short      offset;     /* index to keysym table in syms array
77       */
78       } XkbSymMapRec, *XkbSymMapPtr;
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83X Version 11                    libX11 1.7.3.1                 XkbKeyAction(3)
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