xref: /xsrc/external/mit/libX11/dist/specs/XKB/ch16.xml

<chapter id='xkb_server_keyboard_mapping'>
<title>Xkb Server Keyboard Mapping</title>

<para>
The <emphasis>
server</emphasis>
 field of the complete Xkb keyboard description (see section 6.1) is a pointer
to the Xkb server map.
</para>


<para>
Figure 16.1 shows the relationships between elements in the server map:
</para>

<mediaobject>
 <imageobject> <imagedata format="SVG" fileref="XKBlib-16.svg"/>
 </imageobject>
<caption>Server Map Relationships</caption>
 </mediaobject>


<!--
<H5 CLASS="Figure">
Server Map Relationships</H5>
-->

<para>
The Xkb server map contains the information the server needs to interpret key
events and is of type <emphasis>
XkbServerMapRec</emphasis>
:
</para>

<para><programlisting>
#define XkbNumVirtualMods            16
</programlisting></para>

<para><programlisting>
typedef struct {                         /* Server Map */
      unsigned short     num_acts;       /* # of occupied entries in <emphasis> acts</emphasis> */
      unsigned short     size_acts;      /* # of entries in <emphasis> acts</emphasis> */
      XkbAction *        acts;           /* linear 2d tables of key actions, 1 per keycode */
      XkbBehavior *      behaviors;      /* key behaviors,1 per keycode */
      unsigned short *   key_acts;       /* index into <emphasis> acts</emphasis> , 1 per keycode */
      unsigned char *    explicit;       /* explicit overrides of core remapping, 1 per key */
      unsigned char      vmods[XkbNumVirtualMods];  /* real mods bound to virtual mods */
      unsigned short *   vmodmap;        /* virtual mods bound to key, 1 per keycode*/
} <emphasis>XkbServerMapRec</emphasis>, *XkbServerMapPtr;
</programlisting></para>

<para>
The <emphasis>
num_acts</emphasis>
, <emphasis>
size_acts</emphasis>
, <emphasis>
acts</emphasis>
, and <emphasis>
key_acts</emphasis>
 fields specify the key actions, defined in section 16.1. The <emphasis>
behaviors</emphasis>
 field describes the behavior for each key and is defined in section 16.2. The
<emphasis>
explicit</emphasis>
 field describes the explicit components for a key and is defined in section
16.3. The <emphasis>
vmods</emphasis>
 and the <emphasis>
vmodmap</emphasis>
 fields describe the virtual modifiers and the per-key virtual modifier mapping
and are defined in section 16.4.
</para>

<sect1 id='key_actions'>
<title>Key Actions</title>

<para>
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 <emphasis>
Shift</emphasis>
 key is to set the <emphasis>
Shift</emphasis>
 modifier. There is zero or one key action associated with each keysym bound to
each key.
</para>


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


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

<para>
The reason the <emphasis>
acts</emphasis>
 field is a linear list of <emphasis>
XkbAction</emphasis>
s 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 <emphasis>
KeySyms</emphasis>
 would potentially be very large and sparse. Instead, Xkb provides a small
two-dimensional array of <emphasis>
XkbAction</emphasis>
s for each key. To store all of these individual arrays, Xkb concatenates each
array together in the <emphasis>
acts</emphasis>
 field of the server map.
</para>


<para>
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.
</para>


<para>
Xkb provides the following macros, to simplify accessing information pertaining
to key actions:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
Bool <emphasis>
XkbKeyHasActions</emphasis>
(<emphasis>
xkb, keycode</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr            <emphasis>
xkb</emphasis>
;                  /* Xkb description of interest */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
KeyCode            <emphasis>
keycode</emphasis>
;                  /* keycode of interest */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbKeyHasActions</emphasis>
 returns <emphasis>
True</emphasis>
 if the key corresponding to <emphasis>
keycode</emphasis>
 has any actions associated with it; otherwise, it returns <emphasis>
False</emphasis>
.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
int <emphasis>
XkbKeyNumActions</emphasis>
(<emphasis>
xkb, keycode</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr            <emphasis>
xkb</emphasis>
;                  /* Xkb description of interest */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
KeyCode            <emphasis>
keycode</emphasis>
;                  /* keycode of interest */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbKeyNumActions</emphasis>
 computes the number of actions associated with the key corresponding to
<emphasis>
keycode</emphasis>
. This should be the same value as the result of <emphasis>
XkbKeyNumSyms</emphasis>
 (see section 15.3.3).
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
XkbKeyActionPtr <emphasis>
XkbKeyActionsPtr</emphasis>
(<emphasis>
xkb, keycode</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr            <emphasis>
xkb</emphasis>
;                  /* Xkb description of interest */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
KeyCode            <emphasis>
keycode</emphasis>
;                  /* keycode of interest */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

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


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
XkbAction <emphasis>
XkbKeyAction</emphasis>
(<emphasis>
xkb, keycode, idx</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr            <emphasis>
xkb</emphasis>
;                  /* Xkb description of interest */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
KeyCode            <emphasis>
keycode</emphasis>
;                  /* keycode of interest */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int            <emphasis>
idx</emphasis>
;                  /* index for group and shift level */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbKeyAction</emphasis>
 returns the key action indexed by <emphasis>
idx</emphasis>
 in the two-dimensional array of key actions associated with the key
corresponding to <emphasis>
keycode</emphasis>
. <emphasis>
idx</emphasis>
 may be computed from the group and shift level of interest as follows:
</para>

<literallayout>
     idx = group_index * key_width + shift_level
</literallayout>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
XkbAction <emphasis>
XkbKeyActionEntry</emphasis>
(<emphasis>
xkb, keycode, shift, grp</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr            <emphasis>
xkb</emphasis>
;                  /* Xkb description of interest */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
KeyCode            <emphasis>
keycode</emphasis>
;                  /* keycode of interest */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int            <emphasis>
shift</emphasis>
;                  /* shift level within group */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int            <emphasis>
grp</emphasis>
;                  /* group index for group of interest */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbKeyActionEntry</emphasis>
 returns the key action corresponding to group <emphasis>
grp</emphasis>
 and shift level <emphasis>
lvl</emphasis>
 from the two-dimensional table of key actions associated with the key
corresponding to <emphasis>
keycode</emphasis>
.
</para>


<sect2 id='the_xkbaction_structure'>
<title>The XkbAction Structure</title>

<para>
The description for an action is held in an <emphasis>
XkbAction</emphasis>
 structure, which is a union of all possible Xkb action types:
</para>

<para><programlisting>
typedef union _XkbAction {
      XkbAnyAction              any;
      XkbModAction              mods;
      XkbGroupAction            group;
      XkbISOAction              iso;
      XkbPtrAction              ptr;
      XkbPtrBtnAction           btn;
      XkbPtrDfltAction          dflt;
      XkbSwitchScreenAction     screen;
      XkbCtrlsAction            ctrls;
      XkbMessageAction          msg;
      XkbRedirectKeyAction      redirect;
      XkbDeviceBtnAction        devbtn;
      XkbDeviceValuatorAction   devval;
      unsigned char             type;
} <emphasis>XkbAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field is provided for convenience and is the same as the type field in the
individual structures. The following sections describe the individual
structures for each action in detail.
</para>


</sect2>
<sect2 id='the_xkbanyaction_structure'>
<title>The XkbAnyAction Structure</title>

<para>
The <emphasis>
XkbAnyAction</emphasis>
 structure is a convenience structure that refers to any of the actions:
</para>

<para><programlisting>
#define      XkbAnyActionDataSize       7
</programlisting></para>

<para><programlisting>
typedef struct _XkbAnyAction {
   unsigned char    type;            /* type of action; determines interpretation for data */
   unsigned char    data[XkbAnyActionDataSize];
} <emphasis>XkbAnyAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
data</emphasis>
 field represents a structure for an action, and its interpretation depends on
the <emphasis>
type</emphasis>
 field. The valid values for the <emphasis>
type</emphasis>
 field, and the data structures associated with them are shown in Table 16.1:
</para>

<table frame='none'>
<title>Action Types</title>
<tgroup cols='4'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Type</entry>
  <entry>Structure for Data</entry>
  <entry>XkbAction Union Member</entry>
  <entry>Section</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_NoAction</emphasis></entry>
    <entry>
<emphasis>XkbSA_NoAction</emphasis>
 means the server does not perform an action for the key; this action does not
have an associated data structure.
    </entry>
    <entry>any</entry>
    <entry></entry>
  </row>
  <row rowsep='0'>
    <entry>
<para><emphasis>XkbSA_SetMods</emphasis></para>
<para><emphasis>XkbSA_LatchMods</emphasis></para>
<para><emphasis>XkbSA_LockMods</emphasis></para>
    </entry>
    <entry><para><emphasis>XkbModAction</emphasis></para></entry>
    <entry>mods</entry>
    <entry>16.1.3</entry>
  </row>
  <row rowsep='0'>
    <entry>
<para><emphasis>XkbSA_SetGroup</emphasis></para>
<para><emphasis>XkbSA_LatchGroup</emphasis></para>
<para><emphasis>XkbSA_LockGroup</emphasis></para>
    </entry>
    <entry><emphasis>XkbGroupAction</emphasis></entry>
    <entry>group</entry>
    <entry>16.1.4</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_MovePtr</emphasis></entry>
    <entry><emphasis>XkbPtrAction</emphasis></entry>
    <entry>ptr</entry>
    <entry>16.1.5</entry>
  </row>
  <row rowsep='0'>
    <entry>
<para><emphasis>XKbSA_PtrBtn</emphasis></para>
<para><emphasis>XkbSA_LockPtrBtn</emphasis></para>
    </entry>
    <entry><emphasis>XkbPtrBtnAction</emphasis></entry><entry>btn</entry>
    <entry>16.1.6</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetPtrDflt</emphasis></entry>
    <entry><emphasis>XkbPtrDfltAction</emphasis></entry>
    <entry>dflt</entry>
    <entry>16.1.7</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISOLock</emphasis></entry>
    <entry><emphasis>XkbISOAction</emphasis></entry>
    <entry>iso</entry>
    <entry>16.1.8</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SwitchScreen</emphasis></entry>
    <entry><emphasis>XkbSwitchScreenAction</emphasis></entry>
    <entry>screen</entry>
    <entry>16.1.9</entry>
  </row>
  <row rowsep='0'>
    <entry>
<para><emphasis>XkbSA_SetControls</emphasis></para>
<para><emphasis>XkbSA_LockControls</emphasis></para>
    </entry>
    <entry><emphasis>XkbCtrlsAction</emphasis></entry>
    <entry>ctrls</entry>
    <entry>16.1.10</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ActionMessage</emphasis></entry>
    <entry><emphasis>XkbMessgeAction</emphasis></entry>
    <entry>msg</entry>
    <entry>16.1.11</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_RedirectKey</emphasis></entry>
    <entry><emphasis>XkbRedirectKeyAction</emphasis></entry>
    <entry>redirect</entry>
    <entry>16.1.12</entry>
  </row>
  <row rowsep='0'>
    <entry>
<para><emphasis>XkbSA_DeviceBtn</emphasis></para>
<para><emphasis>XKbSA_LockDeviceBtn</emphasis></para>
    </entry>
    <entry><emphasis>XkbDeviceBtnAction</emphasis></entry>
    <entry>devbtn</entry>
    <entry>16.1.13</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_DeviceValuator</emphasis></entry>
    <entry><emphasis>XkbDeviceValuatorAction</emphasis></entry>
    <entry>devval</entry>
    <entry>16.1.14</entry>
  </row>
</tbody>
</tgroup>
</table>

</sect2>
<sect2 id='actions_for_changing_modifiers_state'>
<title>Actions for Changing Modifiers’ State</title>

<para>
Actions associated with the <emphasis>
XkbModAction</emphasis>
 structure change the state of the modifiers when keys are pressed and released
(see Chapter 7 for a discussion of modifiers):
</para>

<para><programlisting>
typedef struct _XkbModAction {
      unsigned char     type;         /* <emphasis> XkbSA_{Set|Latch|Lock}Mods</emphasis> */
      unsigned char     flags;        /* with <emphasis> type</emphasis> , controls the effect on modifiers */
      unsigned char     mask;         /* same as <emphasis> mask</emphasis> field of a modifier description */
      unsigned char     real_mods;    /* same as <emphasis> real_mods</emphasis> field of a modifier description */
      unsigned char     vmods1;       /* derived from <emphasis> vmods</emphasis> field of a modifier description */
      unsigned char     vmods2;       /* derived from <emphasis> vmods</emphasis> field of a modifier description */
} <emphasis>XkbModAction</emphasis>;
</programlisting></para>

<para>
In the following description, the term <emphasis>
action modifiers</emphasis>
 means the real modifier bits associated with this action. Depending on the
value of <emphasis>
flags</emphasis>
 (see Table 16.3), these are designated either in the <emphasis>
mask</emphasis>
 field of the <emphasis>
XkbModAction</emphasis>
 structure itself or the real modifiers bound to the key for which the action
is being used. In the latter case, this is the client <emphasis>
map</emphasis>
-&gt;<emphasis>
modmap</emphasis>
[<emphasis>
keycode</emphasis>
] field.
</para>


<para>
The <emphasis>
type</emphasis>
 field can have any of the values shown in Table 16.2.
</para>

<table frame='none'>
<title>Modifier Action Types</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Type</entry>
  <entry>Effect</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetMods</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
A key press adds any action modifiers to the keyboard’s base modifiers.
    </para>
  </listitem>
  <listitem>
    <para>
A key release clears any action modifiers in the keyboard’s base modifiers,
provided no other key affecting the same modifiers is logically down.
    </para>
  </listitem>
  <listitem>
    <para>
If no other keys are physically depressed when this key is released, and
<emphasis>
XkbSA_ClearLocks</emphasis>
 is set in the <emphasis>
flags</emphasis>
 field, the key release unlocks any action modifiers.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LatchMods</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
Key press and key release events have the same effect as for <emphasis>
XkbSA_SetMods</emphasis>
; if no keys are physically depressed when this key is released, key release
events have the following additional effects:
    </para>
  </listitem>
  <listitem>
    <para>
Modifiers unlocked due to <emphasis>
XkbSA_ClearLocks</emphasis>
 have no further effect.
    </para>
  </listitem>
  <listitem>
    <para>
If <emphasis>
XkbSA_LatchToLock</emphasis>
 is set in the <emphasis>
flags</emphasis>
 field, a key release locks and then unlatches any remaining action modifiers
that are already latched.
    </para>
  </listitem>
  <listitem>
    <para>
A key release latches any action modifiers not used by the <emphasis>
XkbSA_ClearLocks</emphasis>
 and <emphasis>
XkbSA_LatchToLock</emphasis>
 flags.
    </para>
  </listitem>
  </itemizedlist>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockMods</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
A key press sets the base state of any action modifiers. If <emphasis>
XkbSA_LockNoLock</emphasis>
 is set in the <emphasis>
flags</emphasis>
 field, a key press also sets the locked state of any action modifiers.
    </para>
  </listitem>
  <listitem>
    <para>
A key release clears any action modifiers in the keyboard’s base modifiers,
provided no other key that affects the same modifiers is down. If <emphasis>
XkbSA_LockNoUnlock</emphasis>
 is not set in the <emphasis>
flags</emphasis>
 field, and any of the action modifiers were locked before the corresponding
key press occurred, a key release unlocks them.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
flags</emphasis>
 field is composed of the bitwise inclusive OR of the masks shown in Table
16.3. A general meaning is given in the table, but the exact meaning depends on
the action <emphasis>type</emphasis>.
</para>

<table frame='none'>
<title>Modifier Action Flags</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_UseModMapMods</emphasis></entry>
    <entry>
If set, the action modifiers are determined by the modifiers bound by the
modifier mapping of the key. Otherwise, the action modifiers are set to the
modifiers specified by the <emphasis>
mask</emphasis>
, <emphasis>
real_mods</emphasis>
, <emphasis>
vmod1</emphasis>
, and <emphasis>
vmod2</emphasis>
 fields.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ClearLocks</emphasis></entry>
    <entry>
If set and no keys are physically depressed when this key transition
occurs, the server unlocks any action modifiers.
   </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LatchToLock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
XkbSA_LatchMods</emphasis>
, the server locks the action modifiers if they are already latched.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoLock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
XkbSA_LockMods</emphasis>
, the server only unlocks the action modifiers.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoUnlock</emphasis></entry>
    <entry>
If set, and the action is <emphasis>
XkbSA_LockMods</emphasis>
, the server only locks the action modifiers.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
If <emphasis>
XkbSA_UseModMapMods</emphasis>
 is not set in the <emphasis>
flags</emphasis>
 field, the <emphasis>
mask</emphasis>
, <emphasis>
real_mods</emphasis>
, <emphasis>
vmods1</emphasis>
, and <emphasis>
vmods2 </emphasis>
fields are used to determine the action modifiers. Otherwise they are ignored
and the modifiers bound to the key (client <emphasis>
map</emphasis>
-&gt;<emphasis>
modmap</emphasis>
[<emphasis>
keycode</emphasis>
]) are used instead.
</para>


<para>
The <emphasis>
mask</emphasis>
, <emphasis>
real_mods</emphasis>
, <emphasis>
vmods1</emphasis>
, and <emphasis>
vmods2</emphasis>
 fields represent the components of an Xkb modifier description (see section
7.2). While the <emphasis>
mask</emphasis>
 and <emphasis>
real_mods</emphasis>
 fields correspond directly to the <emphasis>
mask</emphasis>
 and <emphasis>
real_mods</emphasis>
 fields of an Xkb modifier description, the <emphasis>
vmods1</emphasis>
 and <emphasis>
vmods2</emphasis>
 fields are combined to correspond to the <emphasis>
vmods</emphasis>
 field of an Xkb modifier description. Xkb provides the following macros, to
convert between the two formats:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
unsigned short <emphasis>
XkbModActionVMods</emphasis>
(<emphasis>
act</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbAction            <emphasis>
act</emphasis>
;                  /* action from which to extract virtual mods */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbModActionVMods</emphasis>
 returns the <emphasis>
vmods1</emphasis>
 and <emphasis>
vmods2</emphasis>
 fields of <emphasis>
act</emphasis>
 converted to the <emphasis>
vmods</emphasis>
 format of an Xkb modifier description.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSetModActionVMods</emphasis>
(<emphasis>
act, vmods</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbAction            <emphasis>
act</emphasis>
;                  /* action in which to set vmods */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned short            <emphasis>
vmods</emphasis>
;                  /* virtual mods to set */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSetModActionVMods</emphasis>
 sets the <emphasis>
vmods1</emphasis>
 and <emphasis>
vmods2</emphasis>
 fields of <emphasis>
act</emphasis>
 using the <emphasis>
vmods</emphasis>
 format of an Xkb modifier description.
</para>

<note><para>Despite the fact that the first parameter of these two macros is of
type XkbAction, these macros may be used only with Actions of type <emphasis>
XkbModAction</emphasis>
 and <emphasis>
XkbISOAction</emphasis>
.</para></note>


</sect2>
<sect2 id='actions_for_changing_group_state'>
<title>Actions for Changing Group State</title>

<para>
Actions associated with the <emphasis>
XkbGroupAction</emphasis>
 structure change the current group state when keys are pressed and released
(see Chapter 5 for a description of groups and keyboard state):
</para>

<para><programlisting>
typedef struct _XkbGroupAction {
      unsigned char   type;       /* <emphasis> XkbSA_{Set|Latch|Lock}Group</emphasis> */
      unsigned char   flags;      /* with <emphasis> type</emphasis> , controls the effect on groups */
      char            group_XXX;  /* represents a group index or delta */
} <emphasis>XkbGroupAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field can have any of the following values:
</para>

<table frame='none'>
<title>Group Action Types</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Type</entry>
  <entry>Effect</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetGroup</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
If the <emphasis>
XkbSA_GroupAbsolute</emphasis>
 bit is set in the <emphasis>
flags</emphasis>
 field, key press events change the base keyboard group to the group specified
by the <emphasis>
group_XXX</emphasis>
 field. Otherwise, key press events change the base keyboard group by adding
the <emphasis>
group_XXX</emphasis>
 field to the base keyboard group. In either case, the resulting effective
keyboard group is brought back into range depending on the value of the
<emphasis>
groups_wrap</emphasis>
 field of the controls structure (see section 10.7.1).
    </para>
  </listitem>
  <listitem>
    <para>
If a key with an <emphasis>
XkbSA_ISOLock</emphasis>
 action (see section 16.1.8) is pressed while this key is down, the key release
of this key has no effect. Otherwise, the key release cancels the effects of
the key press.
    </para>
  </listitem>
  <listitem>
    <para>
If the <emphasis>
XkbSA_ClearLocks</emphasis>
 bit is set in the flags field, and no keys are physically depressed when this
key is released, the key release also sets the locked keyboard group to
<emphasis>
Group1</emphasis>
.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LatchGroup</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
Key press and key release events have the same effect as for <emphasis>
XkbSA_SetGroup</emphasis>
; if no keys are physically depressed when this key is released, key release
events have the following additional effects.
    </para>
  </listitem>
  <listitem>
    <para>
If the <emphasis>
XkbSA_LatchToLock</emphasis>
 bit is set in the <emphasis>
flags</emphasis>
 field and the latched keyboard group index is nonzero, the key release adds
the delta applied by the corresponding key press to the locked keyboard group
and subtracts it from the latched keyboard group. The locked and effective
keyboard group are brought back into range according to the value of the
<emphasis>
groups_wrap</emphasis>
 field of the controls structure.
    </para>
  </listitem>
  <listitem>
    <para>
Otherwise, the key press adds the key press delta to the latched keyboard group.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockGroup</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
If the <emphasis>
XkbSA_GroupAbsolute</emphasis>
 is set in the <emphasis>
flags</emphasis>
 field, key press events set the locked keyboard group to the group specified
by the <emphasis>
group_XXX</emphasis>
 field. Otherwise, key press events add the group specified by the <emphasis>
group_XXX</emphasis>
 field to the locked keyboard group. In either case, the resulting locked and
effective keyboard groups are brought back into range depending on the value of
the <emphasis>
groups_wrap</emphasis>
 field of the controls structure.
    </para>
  </listitem>
  <listitem>
    <para>
A key release has no effect.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
flags</emphasis>
 field is composed of the bitwise inclusive OR of the masks shown in Table
16.5. A general meaning is given in the table, but the exact meaning depends on
the action <emphasis>
type</emphasis>
.
</para>

<table frame='none'>
<title>Group Action Flags</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ClearLocks</emphasis></entry>
    <entry>
If set and no keys are physically depressed when this key transition occurs,
the server sets the locked keyboard group to <emphasis>
Group1</emphasis>
 on a key release.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LatchToLock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
SA_LatchGroup</emphasis>
, the server locks the action group if it is already latched.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_GroupAbsolute</emphasis></entry>
    <entry>
If set, the <emphasis>
group_XXX</emphasis>
 field represents an absolute group number. Otherwise, it represents a group
delta to be added to the current group to determine the new group number.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
group_XXX</emphasis>
 field represents a signed character. Xkb provides the following macros to
convert between a signed integer value and a signed character:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
int <emphasis>
XkbSAGroup</emphasis>
(<emphasis>
act</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbAction            <emphasis>
act</emphasis>
;                  /* action from which to extract group */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSAGroup</emphasis>
 returns the <emphasis>
group_XXX</emphasis>
 field of <emphasis>
act</emphasis>
 converted to a signed int.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSASetGroup</emphasis>
(<emphasis>
act, grp</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbAction            <emphasis>
act</emphasis>
;                  /* action from which to set group */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int            <emphasis>
grp</emphasis>
;                  /* group index to set in <emphasis>
group_XXX</emphasis>
 */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSASetGroup</emphasis>
 sets the <emphasis>
group_XXX</emphasis>
 field of <emphasis>
act</emphasis>
 from the group index <emphasis>
grp</emphasis>
.
</para>

<note><para>Despite the fact that the first parameter of these two macros is of
type XkbAction, these macros may only be used with Actions of type <emphasis>
XkbGroupAction</emphasis>
 and <emphasis>
XkbISOAction</emphasis>
.</para></note>


</sect2>
<sect2 id='actions_for_moving_the_pointer'>
<title>Actions for Moving the Pointer</title>

<para>
Actions associated with the <emphasis>
XkbPtrAction</emphasis>
 structure move the pointer when keys are pressed and released:
</para>

<para><programlisting>
typedef struct _XkbPtrAction {
      unsigned char      type;      /* <emphasis> XkbSA_MovePtr</emphasis> */
      unsigned char      flags;     /* determines type of pointer motion */
      unsigned char      high_XXX;  /* x coordinate, high bits*/
      unsigned char      low_XXX;   /* y coordinate, low bits */
      unsigned char      high_YYY;  /* x coordinate, high bits */
      unsigned char      low_YYY;   /* y coordinate, low bits */
} <emphasis>XkbPtrAction</emphasis>;
</programlisting></para>

<para>
If the <emphasis>
MouseKeys</emphasis>
 control is not enabled (see section 10.5.1), <emphasis>
KeyPress</emphasis>
 and <emphasis>
KeyRelease</emphasis>
 events are treated as though the action is <emphasis>
XkbSA_NoAction</emphasis>.
</para>

<para>
If the <emphasis>
MouseKeys</emphasis>
 control is enabled, a server action of type <emphasis>
XkbSA_MovePtr</emphasis>
 instructs the server to generate core pointer <emphasis>
MotionNotify</emphasis>
 events rather than the usual <emphasis>
KeyPress</emphasis>
 event, and the corresponding <emphasis>
KeyRelease</emphasis>
 event disables any mouse keys timers that were created as a result of handling
the <emphasis>
XkbSA_MovePtr</emphasis>
 action.
</para>


<para>
The <emphasis>
type</emphasis>
 field of the <emphasis>
XkbPtrAction</emphasis>
 structure is always <emphasis>
XkbSA_MovePtr</emphasis>
.
</para>


<para>
The <emphasis>
flags</emphasis>
 field is a bitwise inclusive OR of the masks shown in Table 16.6.
</para>

<table frame='none'>
<title>Pointer Action Types</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Action Type</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_NoAcceleration</emphasis></entry>
    <entry>
If not set, and the <emphasis>
MouseKeysAccel</emphasis>
 control is enabled (see section 10.5.2), the <emphasis>
KeyPress</emphasis>
 initiates a mouse keys timer for this key; every time the timer expires, the
cursor moves.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_MoveAbsoluteX</emphasis></entry>
    <entry>If set, the X portion of the structure specifies the new pointer X
coordinate. Otherwise, the X portion is added to the current pointer X
coordinate to determine the new pointer X coordinate.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_MoveAbsoluteY</emphasis></entry>
    <entry>
If set, the Y portion of the structure specifies the new
pointer Y coordinate. Otherwise, the Y portion is added
to the current pointer Y coordinate to determine the new pointer Y coordinate.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
Each of the X and Y coordinantes of the <emphasis>
XkbPtrAction</emphasis>
 structure is composed of two signed 16-bit values, that is, the X coordinate
is composed of <emphasis>
high_XXX</emphasis>
 and <emphasis>
low_XXX</emphasis>
, and similarly for the Y coordinate. Xkb provides the following macros, to
convert between a signed integer and two signed 16-bit values in <emphasis>
XkbPtrAction</emphasis>
 structures:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
int <emphasis>
XkbPtrActionX</emphasis>
(<emphasis>
act</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbPtrAction            <emphasis>
act</emphasis>
;                  /* action from which to extract X */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbPtrActionX</emphasis>
 returns the <emphasis>
high_XXX</emphasis>
 and <emphasis>
low_XXX</emphasis>
 fields of <emphasis>
act</emphasis>
 converted to a signed int.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
int <emphasis>
XkbPtrActionY</emphasis>
(<emphasis>
act</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbPtrAction            <emphasis>
act</emphasis>
;                  /* action from which to extract Y */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbPtrActionY</emphasis>
 returns the <emphasis>
high_YYY</emphasis>
 and <emphasis>
low_YYY</emphasis>
 fields of <emphasis>
act</emphasis>
 converted to a signed int.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSetPtrActionX</emphasis>
(<emphasis>
act</emphasis>
, <emphasis>
x</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbPtrAction            <emphasis>
act</emphasis>
;                  /* action in which to set X */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int            <emphasis>
x;      </emphasis>
            /* new value to set */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSetPtrActionX</emphasis>
 sets the <emphasis>
high_XXX</emphasis>
 and <emphasis>
low_XXX</emphasis>
 fields of <emphasis>
act</emphasis>
 from the signed integer value <emphasis>
x</emphasis>
.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSetPtrActionY</emphasis>
(<emphasis>
act, y</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbPtrAction            <emphasis>
act</emphasis>
;                  /* action in which to set Y */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int            <emphasis>
y</emphasis>
;                  /* new value to set */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSetPtrActionX</emphasis>
 sets the <emphasis>
high_YYY</emphasis>
 and <emphasis>
low_YYY</emphasis>
 fields of <emphasis>
act</emphasis>
 from the signed integer value <emphasis>
y</emphasis>
.
</para>


</sect2>
<sect2 id='actions_for_simulating_pointer_button_press_and_release'>
<title>Actions for Simulating Pointer Button Press and Release</title>

<para>
Actions associated with the <emphasis>
XkbPtrBtnAction</emphasis>
 structure simulate the press and release of pointer buttons when keys are
pressed and released:
</para>

<para><programlisting>
typedef struct _XkbPtrBtnAction {
      unsigned char   type;     /*<emphasis> XkbSA_PtrBtn, XkbSA_LockPtrBtn</emphasis> */
      unsigned char   flags;    /* with <emphasis> type</emphasis> , controls the effect on pointer buttons*/
      unsigned char   count;    /* controls number of ButtonPress and ButtonRelease events */
      unsigned char   button;   /* pointer button to simulate */
} <emphasis>XkbPtrBtnAction</emphasis>;
</programlisting></para>

<para>
If the <emphasis>
MouseKeys</emphasis>
 (see section 10.5.1) control is not enabled, <emphasis>
KeyPress</emphasis>
 and <emphasis>
KeyRelease</emphasis>
 events are treated as though the action is <emphasis>
XkbSA_NoAction</emphasis>
.
</para>


<para>
The <emphasis>
type</emphasis>
 field can have any one of the values shown in Table 16.7.
</para>

<table frame='none'>
<title>Pointer Button Action Types</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Type</entry>
  <entry>Effect</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_PtrBtn</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
If<emphasis>
 XkbSA_UseDfltButton</emphasis>
 is set in the <emphasis>
flags</emphasis>
 field, the event is generated for the pointer button specified by the
<emphasis>
mk_dflt_btn</emphasis>
 attribute of the <emphasis>
MouseKeys</emphasis>
 control (see section 10.5.1). Otherwise, the event is generated for the button
specified by the <emphasis>
button</emphasis>
 field.
    </para>
  </listitem>
  <listitem>
    <para>
If the mouse button specified for this action is logically down, the key press
and corresponding key release are ignored and have no effect. Otherwise, a key
press causes one or more core pointer button events instead of the usual
<emphasis>
KeyPress</emphasis>
 event. If <emphasis>
count</emphasis>
 is <emphasis>
zero</emphasis>
, a key press generates a single <emphasis>
ButtonPress</emphasis>
 event; if <emphasis>
count</emphasis>
 is greater than <emphasis>
zero</emphasis>
, a key press generates <emphasis>
count</emphasis>
 pairs of <emphasis>
ButtonPress</emphasis>
 and <emphasis>
ButtonRelease</emphasis>
 events.
    </para>
  </listitem>
  <listitem>
    <para>
If <emphasis>
count</emphasis>
 is <emphasis>
zero</emphasis>
, a key release generates a core pointer <emphasis>
ButtonRelease</emphasis>
 that matches the event generated by the corresponding <emphasis>
KeyPress</emphasis>
; if <emphasis>
count</emphasis>
 is nonzero, a key release does not cause a <emphasis>
ButtonRelease</emphasis>
 event. A key release never generates a key <emphasis>
KeyRelease</emphasis>
 event.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockPtrBtn</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
If the button specified by the <emphasis>
MouseKeys</emphasis>
 default button<emphasis>
 </emphasis>
or <emphasis>
button</emphasis>
 is not locked, a key press causes a <emphasis>
ButtonPress</emphasis>
 event instead of a <emphasis>
KeyPress</emphasis>
 event and locks the button. If the button is already locked or if <emphasis>
XkbSA_LockNoUnlock</emphasis>
 is set in the <emphasis>
flags</emphasis>
 field, a key press is ignored and has no effect.
    </para>
  </listitem>
  <listitem>
    <para>
If the corresponding key press was ignored, and if <emphasis>
XkbSA_LockNoLock</emphasis>
 is not set in the <emphasis>
flags</emphasis>
 field, a key release generates a <emphasis>
ButtonRelease</emphasis>
 event instead of a <emphasis>
KeyRelease</emphasis>
 event and unlocks the specified button. If the corresponding key press locked
a button, the key release is ignored and has no effect.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
flags</emphasis>
 field is composed of the bitwise inclusive OR of the masks shown in Table
16.8. A general meaning is given in the table, but the exact meaning depends on
the action <emphasis>
type.</emphasis>
:
</para>

<table frame='none'>
<title>Pointer Button Action Flags</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_UseDfltButton</emphasis></entry>
    <entry>
If set, the action uses the pointer button specified by the <emphasis>
mk_dflt_btn</emphasis>
 attribute of the <emphasis>
MouseKeys</emphasis>
 control (see section 10.5.1). Otherwise, the action uses the pointer button
specified by the<emphasis>
 button </emphasis>
field.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoLock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
XkbSA_LockPtrBtn</emphasis>
, the server only unlocks the pointer button.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoUnlock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
XkbSA_LockPtrBtn</emphasis>
, the server only locks the pointer button.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

</sect2>
<sect2 id='actions_for_changing_the_pointer_button_simulated'>
<title>Actions for Changing the Pointer Button Simulated</title>

<para>
Actions associated with the <emphasis>
XkbPtrDfltAction</emphasis>
 structure change the <emphasis>
mk_dflt_btn</emphasis>
 attribute of the <emphasis>
MouseKeys</emphasis>
 control (see section 10.5.1):
</para>

<para><programlisting>
typedef struct _XkbPtrDfltAction {
      unsigned char   type;      /* <emphasis> XkbSA_SetPtrDflt</emphasis> */
      unsigned char   flags;     /* controls the pointer button number */
      unsigned char   affect;    /* <emphasis> XkbSA_AffectDfltBtn</emphasis> */
      char            valueXXX;  /* new default button member */
} <emphasis>XkbPtrDfltAction</emphasis>;
</programlisting></para>

<para>
If the <emphasis>
MouseKeys</emphasis>
 control is not enabled, <emphasis>
KeyPress</emphasis>
 and <emphasis>
KeyRelease</emphasis>
 events are treated as though the action is <emphasis>
XkbSA_NoAction</emphasis>
. Otherwise, this action changes the <emphasis>
mk_dflt_btn</emphasis>
 attribute of the <emphasis>
MouseKeys</emphasis>
 control.
</para>


<para>
The <emphasis>
type</emphasis>
 field of the <emphasis>
XkbPtrDfltAction</emphasis>
 structure should always be <emphasis>
XkbSA_SetPtrDflt</emphasis>
.
</para>


<para>
The <emphasis>
flags</emphasis>
 field is composed of the bitwise inclusive OR of the values shown in Table
16.9 (currently there is only one value defined).
</para>

<table frame='none'>
<title>Pointer Default Flags</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_DfltBtnAbsolute</emphasis></entry>
    <entry>
If set, the <emphasis>
value</emphasis>
 field represents an absolute pointer button. Otherwise, the <emphasis>
value</emphasis>
 field represents the amount to be added to the current default button.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
affect</emphasis>
 field specifies what changes as a result of this action. The only valid value
for the <emphasis>
affect</emphasis>
 field is <emphasis>XkbSA_AffectDfltBtn</emphasis>.
</para>

<para>
The <emphasis>
valueXXX</emphasis>
 field is a signed character that represents the new button value for the
<emphasis>
mk_dflt_btn</emphasis>
 attribute of the <emphasis>
MouseKeys</emphasis>
 control (see section 10.5.1). If <emphasis>
XkbSA_DfltBtnAbsolute</emphasis>
 is set in <emphasis>
flags</emphasis>
, <emphasis>
valueXXX</emphasis>
 specifies the button to be used; otherwise, <emphasis>
valueXXX</emphasis>
 specifies the amount to be added to the current default button. In either
case, illegal button choices are wrapped back around into range. Xkb provides
the following macros, to convert between the integer and signed character
values in <emphasis>
XkbPtrDfltAction</emphasis>
 structures:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
int <emphasis>
XkbSAPtrDfltValue</emphasis>
(<emphasis>
act</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbAction            <emphasis>
act</emphasis>
;                  /* action from which to extract group */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSAPtrDfltValue</emphasis>
 returns the <emphasis>
valueXXX</emphasis>
 field of <emphasis>
act</emphasis>
 converted to a signed int.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSASetPtrDfltValue</emphasis>
(<emphasis>
act, val</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbPtrDfltAction            <emphasis>
act</emphasis>
;                  /* action in which to set <emphasis>
valueXXX</emphasis>
 */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int            <emphasis>
val</emphasis>
;                  /* value to set in <emphasis>
valueXXX</emphasis>
 */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSASetPtrDfltValue</emphasis>
 sets the <emphasis>
valueXXX</emphasis>
 field of <emphasis>
act</emphasis>
 from <emphasis>
val</emphasis>
.
</para>


</sect2>
<sect2 id='actions_for_locking_modifiers_and_group'>
<title>Actions for Locking Modifiers and Group</title>

<para>
Actions associated with the <emphasis>
XkbISOAction</emphasis>
 structure lock modifiers and the group according to the ISO9995 specification.
</para>


<para>
Operated by itself, the <emphasis>
XkbISOAction</emphasis>
 is just a caps lock. Operated simultaneously with another modifier key, it
transforms the other key into a locking key. For example, press <emphasis>
ISO_Lock</emphasis>
, press and release <emphasis>
Control_L</emphasis>
, release <emphasis>
ISO_Lock</emphasis>
 ends up locking the <emphasis>
Control</emphasis>
 modifier.
</para>


<para>
The default behavior is to convert:
</para>

<literallayout>
     {Set,Latch}Mods to: LockMods
     {Set,Latch}Group to: LockGroup
     SetPtrBtn to: LockPtrBtn
     SetControls to: LockControls
</literallayout>

<para>
The <emphasis>
affects</emphasis>
 field allows you to turn those effects on or off individually. Set <emphasis>
XkbSA_ISONoAffectMods</emphasis>
 to disable the first, <emphasis>
XkbSA_ISONoAffectGroup</emphasis>
 to disable the second, and so forth.
</para>

<para><programlisting>
typedef struct _XkbISOAction {
      unsigned char   type;        /* <emphasis>XkbSA_ISOLock</emphasis> */
      unsigned char   flags;       /* controls changes to group or modifier state */
      unsigned char   mask;        /* same as <emphasis>mask</emphasis> field of a modifier description */
      unsigned char   real_mods;   /* same as <emphasis>real_mods</emphasis> field of a modifier description */
      char            group_XXX;   /* group index or delta group */
      unsigned char   affect;      /* specifies whether to affect mods, group, ptrbtn, or controls*/
      unsigned char   vmods1;      /* derived from <emphasis>vmods</emphasis> field of a modifier description */
      unsigned char   vmods2;      /* derived from <emphasis>vmods</emphasis> field of a modifier description */
} <emphasis>XkbISOAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field of the <emphasis>
XkbISOAction</emphasis>
 structure should always be <emphasis>
XkbSA_ISOLock</emphasis>
.
</para>


<para>
The interpretation of the <emphasis>
flags</emphasis>
 field depends on whether the <emphasis>
XkbSA_ISODfltIsGroup</emphasis>
 is set in the <emphasis>
flags</emphasis>
 field or not.
</para>


<para>
If the <emphasis>
XkbSA_ISODfltIsGroup</emphasis>
 is set in the <emphasis>
flags</emphasis>
 field, the action is used to change the group state. The remaining valid bits
of the <emphasis>
flags</emphasis>
 field are composed of a bitwise inclusive OR using the masks shown in Table
16.10.
</para>

<table frame='none'>
<title>ISO Action Flags when XkbSA_ISODfltIsGroup is Set</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISODfltIsGroup</emphasis></entry>
    <entry>
      <para>
If set, the action is used to change the base group state. Must be set for the
remaining bits in this table to carry their interpretations.
      </para>
      <para>
A key press sets the base group as specified by the <emphasis>
group_XXX</emphasis>
 field and the <emphasis>
XkbSA_GroupAbsolute</emphasis>
 bit of the <emphasis>
flags</emphasis>
 field (see section Note). If no other actions are transformed by the <emphasis>
XkbISO_Lock</emphasis>
 action, a key release locks the group. Otherwise, a key release clears group
set by the key press.
      </para>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_GroupAbsolute</emphasis></entry>
    <entry>
If set, the <emphasis>
group_XXX</emphasis>
 field represents an absolute group number. Otherwise, it represents a group
delta to be added to the current group to determine the new group number.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectMods</emphasis></entry>
    <entry>
If not set, any <emphasis>
XkbSA_SetMods</emphasis>
 or <emphasis>
XkbSA_LatchMods</emphasis>
 actions that occur simultaneously with the <emphasis>
XkbSA_ISOLock</emphasis>
 action are treated as <emphasis>
XkbSA_LockMod</emphasis>
 actions instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectGroup</emphasis></entry>
    <entry>
If not set, any <emphasis>
XkbSA_SetGroup</emphasis>
 or <emphasis>
XkbSA_LatchGroup</emphasis>
 actions that occur simultaneously with the <emphasis>
XkbSA_ISOLock</emphasis>
 action are treated as <emphasis>
XkbSA_LockGroup</emphasis>
 actions instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectPtr</emphasis></entry>
    <entry>
If not set, any <emphasis>
XkbSA_PtrBtn</emphasis>
 actions that occur simultaneously with the <emphasis>
XkbSA_ISOLock</emphasis>
 action are treated as <emphasis>
XkbSA_LockPtrBtn</emphasis>
 actions instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectCtrls</emphasis></entry>
    <entry>
If not set, any <emphasis>
XkbSA_SetControls</emphasis>
 actions that occur simultaneously with the <emphasis>
XkbSA_ISOLock</emphasis>
 action are treated as <emphasis>
XkbSA_LockControls</emphasis>
 actions instead.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
If the <emphasis>
XkbSA_ISODfltIsGroup</emphasis>
 is not set in the <emphasis>
flags</emphasis>
 field, the action is used to change the modifier state and the remaining valid
bits of the <emphasis>
flags</emphasis>
 field are composed of a bitwise inclusive OR using the masks shown in Table
16.11.
</para>

<table frame='none'>
<title>ISO Action Flags when XkbSA_ISODfltIsGroup is Not Set</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISODfltIsGroup</emphasis> </entry>
    <entry>
      <para>
If not set, action is used to change the base modifier state. Must not be set
for the remaining bits in this table to carry their interpretations.
      </para>
      <para>
A key press sets the action modifiers in the keyboard’s base modifiers using
the <emphasis>
mask</emphasis>
, <emphasis>
real_mods</emphasis>
, <emphasis>
vmods1</emphasis>
, and <emphasis>
vmods2 </emphasis>
fields (see section 16.1.3). If no other actions are transformed by the
<emphasis>
XkbISO_Lock</emphasis>
 action, a key release locks the action modifiers. Otherwise, a key release
clears the base modifiers set by the key press.
      </para>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_UseModMapMods</emphasis></entry>
    <entry>
If set, the action modifiers are determined by the modifiers bound by the
modifier mapping of the key. Otherwise, the action modifiers are set to the
modifiers specified by the <emphasis>
mask</emphasis>
, <emphasis>
real_mods</emphasis>
, <emphasis>
vmod1</emphasis>
, and <emphasis>
vmod2</emphasis>
 fields.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoLock</emphasis></entry>
    <entry>If set, the server only unlocks the action modifiers.</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoUnlock</emphasis></entry>
    <entry>If set, the server only locks the action modifiers. </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectMods</emphasis></entry>
    <entry>
If not set, any <emphasis>
XkbSA_SetMods</emphasis>
 or <emphasis>
XkbSA_LatchMods</emphasis>
 actions that occur simultaneously with the <emphasis>
XkbSA_ISOLock</emphasis>
 action are treated as <emphasis>
XkbSA_LockMod</emphasis>
 actions instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectGroup</emphasis></entry>
    <entry>
If not set, any <emphasis>
XkbSA_SetGroup</emphasis>
 or <emphasis>
XkbSA_LatchGroup</emphasis>
 actions that occur simultaneously with the <emphasis>
XkbSA_ISOLock</emphasis>
 action are treated as <emphasis>
XkbSA_LockGroup</emphasis>
 actions instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectPtr</emphasis></entry>
    <entry>
If not set, any <emphasis>
XkbSA_PtrBtn</emphasis>
 actions that occur simultaneously with the <emphasis>
XkbSA_ISOLock</emphasis>
 action are treated as <emphasis>
XkbSA_LockPtrBtn</emphasis>
 actions instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectCtrls</emphasis></entry>
    <entry>
If not set, any <emphasis>
XkbSA_SetControls</emphasis>
 actions that occur simultaneously with the <emphasis>
XkbSA_ISOLock</emphasis>
 action are treated as <emphasis>
XkbSA_LockControls</emphasis>
 actions instead.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
group_XXX</emphasis>
 field represents a signed character. Xkb provides macros to convert between a
signed integer value and a signed character as shown in section Note.
</para>


<para>
The <emphasis>
mask</emphasis>
, <emphasis>
real_mods</emphasis>
, <emphasis>
vmods1</emphasis>
, and <emphasis>
vmods2</emphasis>
 fields represent the components of an Xkb modifier description (see section
7.2). While the <emphasis>
mask</emphasis>
 and <emphasis>
real_mods</emphasis>
 fields correspond directly to the <emphasis>
mask</emphasis>
 and <emphasis>
real_mods</emphasis>
 fields of an Xkb modifier description, the <emphasis>
vmods1</emphasis>
 and <emphasis>
vmods2</emphasis>
 fields are combined to correspond to the <emphasis>
vmods</emphasis>
 field of an Xkb modifier description. Xkb provides macros to convert between
the two formats as shown in section 16.1.3.
</para>


<para>
The <emphasis>
affect</emphasis>
 field is composed of a bitwise inclusive OR using the masks shown in Table
16.11.
</para>

<table frame='none'>
<title>ISO Action Affect Field Values</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Affect</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISODNoAffectMods</emphasis></entry>
    <entry>
If <emphasis>
XkbSA_ISONoAffectMods</emphasis>
 is not set, any <emphasis>
SA_SetMods</emphasis>
 or <emphasis>
SA_LatchMods</emphasis>
 actions occurring simultaneously with the <emphasis>
XkbISOAction</emphasis>
 are treated as <emphasis>
SA_LockMods</emphasis>
 instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectGroup</emphasis></entry>
    <entry>
If <emphasis>
XkbSA_ISONoAffectGroup</emphasis>
 is not set, any <emphasis>
SA_SetGroup</emphasis>
 or <emphasis>
SA_LatchGroup</emphasis>
 actions occurring simultaneously with the <emphasis>
XkbISOAction</emphasis>
 are treated as <emphasis>
SA_LockGroup</emphasis>
 instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectPtr</emphasis></entry>
    <entry>
If <emphasis>
XkbSA_ISONoAffectPtr</emphasis>
 is not set, any <emphasis>
SA_PtrBtn</emphasis>
 actions occurring simultaneously with the <emphasis>
XkbISOAction</emphasis>
 are treated as <emphasis>
SA_LockPtrBtn</emphasis>
 instead.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_ISONoAffectCtrls</emphasis></entry>
    <entry>
If <emphasis>
XkbSA_ISONoAffectCtrls</emphasis>
 is not set, any <emphasis>
SA_SetControls</emphasis>
 actions occurring simultaneously with the <emphasis>
XkbISOAction</emphasis>
 are treated as <emphasis>
SA_LockControls</emphasis>
 instead.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

</sect2>
<sect2 id='actions_for_changing_the_active_screen'>
<title>Actions for Changing the Active Screen</title>

<para>
Actions associated with the <emphasis>
XkbSwitchScreen</emphasis>
 action structure change the active screen on a multiscreen display:
</para>

<note><para>This action is optional. Servers are free to ignore the action or
any of its flags if they do not support the requested behavior. If the action
is ignored, it behaves like <emphasis>
XkbSA_NoAction</emphasis>
. Otherwise, key press and key release events do not generate an event.
</para></note>

<para><programlisting>
typedef struct _XkbSwitchScreenAction {
      unsigned char   type;        /* <emphasis> XkbSA_SwitchScreen</emphasis> */
      unsigned char   flags;       /* controls screen switching */
      char            screenXXX;   /* screen number or delta */
} <emphasis>XkbSwitchScreenAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field of the <emphasis>
XkbSwitchScreenAction</emphasis>
 structure should always be <emphasis>
XkbSA_SwitchScreen</emphasis>.
</para>


<para>
The <emphasis>
flags</emphasis>
 field is composed of the bitwise inclusive OR of the masks shown in Table
16.13.
</para>

<table frame='none'>
<title>Switch Screen Action Flags</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SwitchAbsolute</emphasis></entry>
    <entry>
If set, the <emphasis>
screenXXX</emphasis>
 field represents the index of the new screen. Otherwise, it represents an
offset from the current screen to the new screen.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SwitchApplication</emphasis></entry>
    <entry>
If not set, the action should switch to another screen on the same
server. Otherwise, it should switch to another X server or application that
shares the same physical display.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
screenXXX</emphasis>
 field is a signed character value that represents either the relative or
absolute screen index, depending on the state of the <emphasis>
XkbSA_SwitchAbsolute</emphasis>
 bit in the <emphasis>
flags</emphasis>
 field. Xkb provides the following macros to convert between the integer and
signed character value for screen numbers in <emphasis>
XkbSwitchScreenAction</emphasis>
 structures:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
int <emphasis>
XkbSAScreen</emphasis>
(<emphasis>
act</emphasis>
)                        /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbSwitchScreenAction                  <emphasis>
act</emphasis>
;      /* action from which to extract screen */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSAScreen</emphasis>
 returns the <emphasis>
screenXXX</emphasis>
 field of <emphasis>
act</emphasis>
 converted to a signed int.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSASetScreen</emphasis>
(<emphasis>
act, s</emphasis>
)                        /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbSwitchScreenAction                  <emphasis>
act</emphasis>
;      /* action in which to set <emphasis>
screenXXX</emphasis>
 */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int                  <emphasis>
s</emphasis>
;      /* value to set in <emphasis>
screenXXX</emphasis>
 */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSASetScreen</emphasis>
 sets the <emphasis>
screenXXX</emphasis>
 field of <emphasis>
act</emphasis>
 from <emphasis>
s</emphasis>
.
</para>


</sect2>
<sect2 id='actions_for_changing_boolean_controls_state'>
<title>Actions for Changing Boolean Controls State</title>

<para>
Actions associated with the <emphasis>
XkbCtrlsAction</emphasis>
 structure change the state of the boolean controls (see section 10.1):
</para>

<para><programlisting>
typedef struct _XkbCtrlsAction {
      unsigned char     type;        /* <emphasis> XkbSA_SetControls,
                                        XkbSA_LockControls</emphasis> */
      unsigned char     flags;       /* with <emphasis> type</emphasis>,
                                        controls enabling and disabling of controls */
      unsigned char     ctrls3;      /* <emphasis>ctrls0</emphasis> through
                                        <emphasis> ctrls3</emphasis> represent the boolean controls */
      unsigned char     ctrls2;      /* <emphasis>ctrls0</emphasis> through
                                        <emphasis> ctrls3</emphasis> represent the boolean controls */
      unsigned char     ctrls1;      /* <emphasis>ctrls0</emphasis> through
                                        <emphasis> ctrls3</emphasis> represent the boolean controls */
      unsigned char     ctrls0;      /* <emphasis>ctrls0</emphasis> through
                                        <emphasis> ctrls3</emphasis> represent the boolean controls */
} <emphasis>XkbCtrlsAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field can have any one of the values shown in Table 16.14.
</para>

<table frame='none'>
<title>Controls Action Types</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Type</entry>
  <entry>Effect</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetControls</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
A key press enables any boolean controls specified in the <emphasis>
ctrls</emphasis>
 fields that were not already enabled at the time of the key press.
    </para>
  </listitem>
  <listitem>
    <para>
A key release disables any controls enabled by the key press.
    </para>
  </listitem>
  <listitem>
    <para>
This action can cause <emphasis>
XkbControlsNotify</emphasis>
 events (see section 10.1).
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockControls</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
If the <emphasis>
XkbSA_LockNoLock</emphasis>
 bit is not set in the <emphasis>
flags</emphasis>
 field, a key press enables any controls specified in the <emphasis>
ctrls</emphasis>
 fields that were not already enabled at the time of the key press.
    </para>
  </listitem>
  <listitem>
    <para>
If the <emphasis>
XkbSA_LockNoUnlock</emphasis>
 bit is not set in the <emphasis>
flags</emphasis>
 field, a key release disables any controls specified in the <emphasis>
ctrls</emphasis>
 fields that were not already disabled at the time of the key press.
    </para>
  </listitem>
  <listitem>
    <para>
This action can cause <emphasis>
XkbControlsNotify</emphasis>
 events (see section 10.1).
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
flags</emphasis>
 field is composed of the bitwise inclusive OR of the masks shown in Table
16.15.
</para>

<table frame='none'>
<title>Control Action Flags</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoLock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
XkbSA_LockControls</emphasis>
, the server only disables controls.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoUnlock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
XkbSA_LockControls</emphasis>
, the server only enables controls.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
XkbSA_SetControls</emphasis>
 action implements a key that enables a boolean control when pressed and
disables it when released. The <emphasis>
XkbSA_LockControls</emphasis>
 action is used to implement a key that toggles the state of a boolean control
each time it is pressed and released. The <emphasis>
XkbSA_LockNoLock</emphasis>
 and <emphasis>
XkbSA_LockNoUnlock</emphasis>
 flags allow modifying the toggling behavior to only unlock or only lock the
boolean control.
</para>


<para>
The <emphasis>
ctrls0</emphasis>
, <emphasis>
ctrls1</emphasis>
, <emphasis>
ctrls2</emphasis>
, and <emphasis>
ctrls3</emphasis>
 fields represent the boolean controls in the <emphasis>
enabled_ctrls</emphasis>
 field of the controls structure (see section 10.1). Xkb provides the following
macros, to convert between the two formats:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
unsigned int <emphasis>
XkbActionCtrls</emphasis>
(<emphasis>
act</emphasis>
)                        /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbCtrlsAction            <emphasis>
act</emphasis>
;            /* action from which to extract controls */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbActionCtrls</emphasis>
 returns the <emphasis>
ctrls</emphasis>
 fields of <emphasis>
act</emphasis>
 converted to an unsigned int.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSAActionSetCtrls</emphasis>
(<emphasis>
act, ctrls</emphasis>
)                        /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbCtrlsAction                  <emphasis>
act</emphasis>
;      /* action in which to set ctrls0-ctrls3 */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int                  <emphasis>
ctrls</emphasis>
;      /* value to set in ctrls0-ctrls3 */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSAActionSetCtrls</emphasis>
 sets the <emphasis>
ctrls0</emphasis>
 through <emphasis>
ctrls3</emphasis>
 fields of <emphasis>
act</emphasis>
 from <emphasis>
ctrls</emphasis>
.
</para>


</sect2>
<sect2 id='actions_for_generating_messages'>
<title>Actions for Generating Messages</title>

<para>
Actions associated with the <emphasis>
XkbMessageAction</emphasis>
 structure generate <emphasis>
XkbActionMessage</emphasis>
 events:
</para>

<para><programlisting>
#define            XkbActionMessageLength                  6
</programlisting></para>
<para><programlisting>
typedef struct _XkbMessageAction {
      unsigned char   type;             /* <emphasis> XkbSA_ActionMessage</emphasis> */
      unsigned char   flags;            /* controls event generation via key presses and releases */
      unsigned char   message[XkbActionMessageLength];    /* message */
} <emphasis>XkbMessageAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field of the <emphasis>
XkbMessageAction</emphasis>
 structure should always be <emphasis>
XkbSA_ActionMessage</emphasis>
.
</para>


<para>
The <emphasis>
flags</emphasis>
 field is composed of the bitwise inclusive OR of the masks shown in Table
16.16.
</para>

<table frame='none'>
<title>Message Action Flags</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_MessageOnPress</emphasis></entry>
    <entry>
If set, key press events generate an <emphasis>
XkbActionMessage</emphasis>
 event that reports the keycode, event type, and contents of the <emphasis>
message</emphasis>
 field.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_MessageOnRelease</emphasis></entry>
    <entry>
If set, key release events generate an <emphasis>
XkbActionMessage</emphasis>
 event that reports the keycode, event type, and contents of the <emphasis>
message</emphasis>
 field.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_MessageGenKeyEvent</emphasis></entry>
    <entry>
If set, key press and key release events generate <emphasis>
KeyPress</emphasis>
 and <emphasis>
KeyRelease</emphasis>
 events, regardless of whether they generate <emphasis>
XkbActionMessage</emphasis>
 events.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
message</emphasis>
 field is an array of <emphasis>
XkbActionMessageLength</emphasis>
 unsigned characters and may be set to anything the keymap designer wishes.
</para>

<sect3 id='detecting_key_action_messages'>
<title>Detecting Key Action Messages</title>

<para>
To receive <emphasis>
XkbActionMessage</emphasis>
 events by calling either <emphasis>
XkbSelectEvents</emphasis>
 or <emphasis>
XkbSelectEventDetails</emphasis>
 (see section 4.3).
</para>


<para>
To receive <emphasis>
XkbActionMessage</emphasis>
 events under all possible conditions, use <emphasis>
XkbSelectEvents</emphasis>
 and pass <emphasis>
XkbActionMessageMask</emphasis>
 in both <emphasis>
bits_to_change</emphasis>
 and <emphasis>
values_for_bits</emphasis>
.
</para>


<para>
The <emphasis>
XkbActionMessage</emphasis>
 event has no event details. However, you can call <emphasis>
XkbSelectEventDetails</emphasis>
 using <emphasis>
XkbActionMessage</emphasis>
 as the <emphasis>
event_type</emphasis>
 and specifying <emphasis>
XkbAllActionMessageMask</emphasis>
 in <emphasis>
bits_to_change</emphasis>
 and <emphasis>
values_for_bits.</emphasis>
 This has the same effect as a call to <emphasis>
XkbSelectEvents</emphasis>.
</para>


<para>
The structure for the <emphasis>
XkbActionMessage</emphasis>
 event is defined as follows:
</para>

<para><programlisting>
typedef struct _XkbActionMessage {
      int            type;            /* Xkb extension base event code */
      unsigned long  serial;          /* X server serial number for event */
      Bool           send_event;      /* <emphasis>True</emphasis> =&gt; synthetically generated */
      Display *      display;         /* server connection where event generated */
      Time           time;            /* server time when event generated */
      int            xkb_type;        /* <emphasis>XkbActionMessage</emphasis> */
      int            device;          /* Xkb device ID, will not be <emphasis> XkbUseCoreKbd</emphasis> */
      KeyCode        keycode;         /* keycode of key triggering event */
      Bool           press;           /* <emphasis>True</emphasis> =&gt; key press,
                                         <emphasis>False</emphasis> =&gt; release */
      Bool           key_event_follows; /* <emphasis>True</emphasis> =&gt; KeyPress/KeyRelease follows */
      char           message[XkbActionMessageLength+1];                       /* message text */
} <emphasis>XkbActionMessageEvent</emphasis>;
</programlisting></para>

<para>
The <emphasis>
keycode</emphasis>
 is the keycode of the key that was pressed or released. The <emphasis>
press</emphasis>
 field specifies whether the event was the result of a key press or key
release.
</para>


<para>
The <emphasis>
key_event_follows</emphasis>
 specifies whether a <emphasis>
KeyPress</emphasis>
 (if <emphasis>
press</emphasis>
 is <emphasis>
True</emphasis>
) or <emphasis>
KeyRelease</emphasis>
 (if <emphasis>
press</emphasis>
 is <emphasis>
False</emphasis>
) event is also sent to the client. As with all other Xkb events, <emphasis>
XkbActionMessageEvent</emphasis>
s are delivered to all clients requesting them, regardless of the current
keyboard focus. However, the <emphasis>
KeyPress</emphasis>
 or <emphasis>
KeyRelease</emphasis>
 event that conditionally follows an <emphasis>
XkbActionMessageEvent</emphasis>
 is sent only to the client selected by the current keyboard focus. <emphasis>
key_event_follows</emphasis>
 is <emphasis>
True</emphasis>
 only for the client that is actually sent the following <emphasis>
KeyPress</emphasis>
 or <emphasis>
KeyRelease</emphasis>
 event.
</para>


<para>
The <emphasis>
message</emphasis>
 field is set to the message specified in the action and is guaranteed to be
<emphasis>
NULL</emphasis>
-terminated; the Xkb extension forces a <emphasis>
NULL</emphasis>
 into <emphasis>
message</emphasis>
[<emphasis>
XkbActionMessageLength</emphasis>
].
</para>


</sect3>
</sect2>
<sect2 id='actions_for_generating_a_different_keycode'>
<title>Actions for Generating a Different Keycode</title>

<para>
Actions associated with the <emphasis>
XkbRedirectKeyAction</emphasis>
 structure generate <emphasis>
KeyPress</emphasis>
 and <emphasis>
KeyRelease</emphasis>
 events containing a keycode different from the key that was pressed or
released:
</para>

<para><programlisting>
typedef struct      _XkbRedirectKeyAction {
      unsigned char      type;          /* <emphasis> XkbSA_RedirectKey</emphasis> */
      unsigned char      new_key;       /* keycode to be put in event */
      unsigned char      mods_mask;     /* mask of real mods to be reset */
      unsigned char      mods;          /* mask of real mods to take values from */
      unsigned char      vmods_mask0;   /* first half of mask of virtual mods to be reset */
      unsigned char      vmods_mask1;   /* other half of mask of virtual mods to be reset */
      unsigned char      vmods0;        /* first half of mask of virtual mods to take values from */
      unsigned char      vmods1;        /* other half of mask of virtual mods to take values from */
} <emphasis>XkbRedirectKeyAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field for the <emphasis>
XkbRedirectKeyAction</emphasis>
 structure should always be <emphasis>
XkbSA_RedirectKey</emphasis>
.
</para>


<para>
Key presses cause a <emphasis>
KeyPress</emphasis>
 event for the key specified by the <emphasis>
new_key</emphasis>
 field instead of the actual key. The state reported in this event reports the
current effective modifiers changed as follows: any real modifiers selected by
the <emphasis>
mods_mask</emphasis>
 field are set to corresponding values from the <emphasis>
mods</emphasis>
 field. Any real modifiers bound to the virtual modifiers specified by the
<emphasis>
vmods_mask0</emphasis>
 and <emphasis>
vmods_mask1</emphasis>
 fields are either set or cleared, depending on the corresponding values in the
<emphasis>
vmods0</emphasis>
 and <emphasis>
vmods1</emphasis>
 fields. If the real and virtual modifier definitions specify conflicting
values for a single modifier, the real modifier definition has priority.
</para>


<para>
Key releases cause a <emphasis>
KeyRelease</emphasis>
 event for the key specified by the <emphasis>
new_key</emphasis>
 field instead of the actual key. The state for this event consists of the
effective keyboard modifiers at the time of the release, changed as described
previously.
</para>


<para>
The <emphasis>
XkbSA_RedirectKey</emphasis>
 action normally redirects to another key on the same device as the key that
caused the event, unless that device does not belong to the input extension
<emphasis>
KeyClass</emphasis>
, in which case this action causes an event on the core keyboard device. (The
input extension categorizes devices by breaking them into classes. Keyboards,
and other input devices with keys, are classified as KeyClass devices by the
input extension.)
</para>


<para>
The <emphasis>
vmods_mask0</emphasis>
 and <emphasis>
vmods_mask1</emphasis>
 fields actually represent one <emphasis>
vmods_mask</emphasis>
 value, as described in Chapter 7. Xkb provides the following macros, to
convert between the two formats:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
unsigned int <emphasis>
XkbSARedirectVModsMask</emphasis>
(<emphasis>
act</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbRedirectKeyAction                  <emphasis>
act</emphasis>
;            /* action from which to extract vmods */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSARedirectVModsMask</emphasis>
 returns the <emphasis>
vmods_mask0</emphasis>
 and <emphasis>
vmods_mask1</emphasis>
 fields of <emphasis>
act</emphasis>
 converted to an unsigned int.
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSARedirectSetVModsMask</emphasis>
(<emphasis>
act, vm</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbRedirectKeyAction                  <emphasis>
act</emphasis>
;            /* action in which to set vmods */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int                  <emphasis>
vm</emphasis>
;            /* new value for virtual modifier mask */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbSARedirectSetVModsMask</emphasis>
 sets the <emphasis>
vmods_mask0</emphasis>
 and <emphasis>
vmods_mask1</emphasis>
 fields of <emphasis>
act</emphasis>
 from <emphasis>
vm</emphasis>
.
</para>


<para>
Similarly, the <emphasis>
vmods0</emphasis>
 and <emphasis>
vmods1</emphasis>
 fields actually represent one <emphasis>
vmods </emphasis>
value, as described in Chapter 7. To convert between the two formats, Xkb
provides the following convenience macros:
</para>


<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
unsigned int <emphasis>
XkbSARedirectVMods</emphasis>
(<emphasis>
act</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbRedirectKeyAction                  <emphasis>
act</emphasis>
;            /* action from which to extract vmods */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<literallayout>
     <emphasis>XkbSARedirectVModsMask</emphasis> returns the <emphasis>vmods0</emphasis>
     and <emphasis>vmods1</emphasis> fields of <emphasis>act</emphasis>
     converted to an unsigned int.
</literallayout>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
void <emphasis>
XkbSARedirectSetVMods</emphasis>
(<emphasis>
act, vm</emphasis>
)                              /* macro */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbRedirectKeyAction                  <emphasis>
act</emphasis>
;            /* action in which to set vmods */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int                  <emphasis>
v</emphasis>
;            /* new value for virtual modifiers */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>
<literallayout>
     <emphasis> XkbSARedirectSetVModsMask</emphasis> sets the <emphasis>vmods0</emphasis>
     and <emphasis>vmods1</emphasis> of <emphasis>act</emphasis> from <emphasis>v</emphasis>.
</literallayout>

</sect2>
<sect2 id='actions_for_generating_devicebuttonpress_and_devicebuttonrelease'>
<title>Actions for Generating DeviceButtonPress and DeviceButtonRelease</title>

<para>
Actions associated with <emphasis>
XkbDeviceBtnAction</emphasis>
 structures generate <emphasis>
DeviceButtonPress</emphasis>
 and <emphasis>
DeviceButtonRelease</emphasis>
 events instead of normal <emphasis>
KeyPress</emphasis>
 and <emphasis>
KeyRelease</emphasis>
 events:
</para>

<para><programlisting>
typedef struct _XkbDeviceBtnAction {
      unsigned char    type;      /* <emphasis> XkbSA_DeviceBtn, XkbSA_LockDeviceBtn</emphasis> */
      unsigned char    flags;     /* with <emphasis> type</emphasis> , specifies locking or unlocking */
      unsigned char    count;     /* controls number of DeviceButtonPress and Release events */
      unsigned char    button;    /* index of button on <emphasis> device</emphasis> */
      unsigned char    device;    /* device ID of an X input extension device */
} <emphasis>XkbDeviceBtnAction</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field can have any one of the values shown in Table 16.17.
</para>

<table frame='none'>
<title>Device Button Action Types</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Type</entry>
  <entry>Effect</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_DeviceBtn</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
If the button specified by this action is logically down, the key press and
corresponding release are ignored and have no effect. If the device or button
specified by this action are illegal, this action behaves like <emphasis>
XkbSA_NoAction</emphasis>.
    </para>
  </listitem>
  <listitem>
    <para>
Otherwise, key presses cause one or more input extension device events instead
of the usual key press event. If the <emphasis>
count</emphasis>
 field is zero, a key press generates a single <emphasis>
DeviceButtonPress</emphasis>
 event. If count is greater than zero, a key press event generates <emphasis>
count</emphasis>
 pairs of <emphasis>
DeviceButtonPress</emphasis>
 and <emphasis>
DeviceButtonRelease</emphasis>
 events.
    </para>
  </listitem>
  <listitem>
    <para>
If <emphasis>
count</emphasis>
 is zero, a key release generates an input extension <emphasis>
DeviceButtonRelease</emphasis>
 event that matches the event generated by the corresponding key press. If
<emphasis>
count</emphasis>
 is nonzero, a key release does not cause a <emphasis>
DeviceButtonRelease</emphasis>
 event. Key releases never cause <emphasis>
KeyRelease</emphasis>
 events.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockDeviceBtn</emphasis></entry>
    <entry>
<itemizedlist>
  <listitem>
    <para>
If the device or button specified by this action are illegal, this action
behaves like <emphasis>XkbSA_NoAction</emphasis>.
    </para>
  </listitem>
  <listitem>
    <para>
Otherwise, if the specified button is not locked and the <emphasis>
XkbSA_LockNoLock</emphasis>
 bit is not set in the <emphasis>
flags</emphasis>
 field, a key press generates an input extension <emphasis>
DeviceButtonPress</emphasis>
 event instead of a <emphasis>
KeyPress</emphasis>
 event and locks the button. If the button is already locked or if <emphasis>
XkbSA_LockNoLock</emphasis>
 bit is set in the <emphasis>
flags</emphasis>
 field, the key press is ignored and has no effect.
    </para>
  </listitem>
  <listitem>
    <para>
If the corresponding key press was ignored, and if the <emphasis>
XkbSA_LockNoUnlock</emphasis>
 bit is not set in the <emphasis>
flags</emphasis>
 field, a key release generates an input extension <emphasis>
DeviceButtonRelease</emphasis>
 event instead of a <emphasis>
KeyRelease</emphasis>
 event and unlocks the button. If the corresponding key press locked a button,
the key release is ignored and has no effect.
    </para>
  </listitem>
</itemizedlist>
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
The <emphasis>
flags</emphasis>
 field is composed of the bitwise inclusive OR of the masks shown in Table
16.18.
</para>

<table frame='none'>
<title>Device Button Action Flags</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Flag</entry>
  <entry>Meaning</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoLock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
XkbSA_LockDeviceBtn</emphasis>
, the server only unlocks the button.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_LockNoUnlock</emphasis></entry>
    <entry>
If set, and the action type is <emphasis>
XkbSA_LockDeviceBtn</emphasis>
, the server only locks the button.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

</sect2>
<sect2 id='actions_for_simulating_events_from_device_valuators'>
<title>Actions for Simulating Events from Device Valuators</title>

<para>
A <emphasis>
valuator</emphasis>
 manipulates a range of values for some entity, like a mouse axis, a slider or
a dial. Actions associated with <emphasis>
XkbDeviceValuatorAction</emphasis>
 structures are used to simulate events from one or two input extension device
valuators.
</para>

<para><programlisting>
typedef struct _XkbDeviceValuatorAction {
      unsigned char    type;        /*<emphasis> XkbSA_DeviceValuator</emphasis> */
      unsigned char    device;      /* device ID */
      unsigned char    v1_what;     /* determines how valuator is to behave for valuator 1 */
      unsigned char    v1_ndx;      /* specifies a real valuator */
      unsigned char    v1_value;    /* the value for valuator 1 */
      unsigned char    v2_what;     /* determines how valuator is to behave for valuator 2 */
      unsigned char    v2_ndx;      /* specifies a real valuator */
      unsigned char    v2_value;    /* the value for valuator 1 */
} <emphasis>XkbDeviceValuatorAction</emphasis>;
</programlisting></para>

<para>
If <emphasis>
device</emphasis>
 is illegal or if neither <emphasis>
v1_ndx</emphasis>
 nor <emphasis>
v2_ndx</emphasis>
 specifies a legal valuator, this action behaves like <emphasis>
XkbSA_NoAction</emphasis>.
</para>


<para>
The low four bits of <emphasis>
v1_what</emphasis>
 and <emphasis>
v2_what</emphasis>
 specify the corresponding scale value (denoted <emphasis>
val&lt;n&gt;Scale</emphasis>
 in Table 16.17), if needed. The high four bits of <emphasis>
v1_what</emphasis>
 and <emphasis>
v2_what</emphasis>
 specify the operation to perform to set the values. The high four bits of
<emphasis>
v1_what</emphasis>
 and <emphasis>
v2_what</emphasis>
 can have the values shown in Table 16.17; the use of <emphasis>
val&lt;n&gt;Scale</emphasis>
 is shown in that table also.
</para>

<table frame='none'>
<title>Device Valuator v&lt;n&gt;_what High Bits Values</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Value of high bits</entry>
  <entry>Effect</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_IgnoreVal</emphasis></entry>
    <entry>No action</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetValMin</emphasis></entry>
    <entry>
<emphasis>v&lt;n&gt;_value</emphasis> is set to its minimum legal value.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetValCenter</emphasis></entry>
    <entry>
<emphasis>v&lt;n&gt;_value</emphasis>is centered (to (max-min)/2).
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetValMax</emphasis></entry>
    <entry>
<emphasis>v&lt;n&gt;_value</emphasis> is set to its maximum legal value.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetValRelative</emphasis></entry>
    <entry>
<emphasis>v&lt;n&gt;_value</emphasis> * (2
<emphasis>val&lt;n&gt;Scale</emphasis>) is added to
<emphasis>v&lt;n&gt;_value</emphasis>.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbSA_SetValAbsolute</emphasis></entry>
    <entry>
<emphasis>v&lt;n&gt;_value</emphasis>
 is set to (2 <emphasis>val&lt;n&gt;Scale</emphasis>).
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
Illegal values for <emphasis>
XkbSA_SetValRelative</emphasis>
 or <emphasis>
XkbSA_SetValAbsolute</emphasis>
 are clamped into range. Note that all of these possibilities are legal for
absolute valuators. For relative valuators, only <emphasis>
XkbSA_SetValRelative</emphasis>
 is permitted. Part of the input extension description of a device is the range
of legal values for all absolute valuators, whence the maximum and minimum
legal values shown in Table 16.17.
</para>


<para>
The following two masks are provided as a convenience to select either portion
of <emphasis>
v1_what</emphasis>
 or <emphasis>
v2_what</emphasis>
:
</para>

<literallayout>
      #define XkbSA_ValOpMask      (0x70)
      #define XkbSA_ValScaleMask      (0x07)
</literallayout>

<para>
<emphasis>
v1_ndx</emphasis>
 and <emphasis>
v2_ndx</emphasis>
 specify valuators that actually exists. For example, most mice have two
valuators (x and y axes) so the only legal values for a mouse would be 0 and 1.
For a dial box with eight dials, any value in the range 0..7 would be correct.
</para>


</sect2>
<sect2 id='obtaining_key_actions_for_keys_from_the_server'>
<title>Obtaining Key Actions for Keys from the Server</title>

<para>
To update the actions (the <emphasis>
key_acts</emphasis>
 array) for a subset of the keys in a keyboard description, use <emphasis>
XkbGetKeyActions</emphasis>
.
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
Status <emphasis>
XkbGetKeyActions</emphasis>
(<emphasis>
dpy</emphasis>
,<emphasis>
 first</emphasis>
, <emphasis>
num</emphasis>
,<emphasis>
 xkb</emphasis>
)
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
Display *<emphasis>
            dpy</emphasis>
;            /* connection to X server */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
first</emphasis>
;            /* keycode of first key of interest */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
num</emphasis>
;            /* number of keys desired */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr             <emphasis>
xkb</emphasis>
;            /* pointer to keyboard description where result is stored */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbGetKeyActions</emphasis>
 sends a request to the server to obtain the actions for <emphasis>
num</emphasis>
 keys on the keyboard starting with key <emphasis>
first</emphasis>
. It waits for a reply and returns the actions in the <emphasis>
server</emphasis>
-&gt;<emphasis>
key_acts</emphasis>
 field of <emphasis>
xkb</emphasis>
. If successful, <emphasis>
XkbGetKeyActions</emphasis>
 returns <emphasis>
Success</emphasis>
. The <emphasis>
xkb</emphasis>
 parameter must be a pointer to a valid Xkb keyboard description.
</para>


<para>
If the <emphasis>
server</emphasis>
 map in the <emphasis>
xkb</emphasis>
 parameter has not been allocated, <emphasis>
XkbGetKeyActions</emphasis>
 allocates and initializes it before obtaining the actions.
</para>


<para>
If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, <emphasis>
XkbGetKeyActions</emphasis>
 returns <emphasis>
BadAccess</emphasis>
. If <emphasis>
num</emphasis>
 is less than 1 or greater than <emphasis>
XkbMaxKeyCount</emphasis>
, <emphasis>
XkbGetKeyActions</emphasis>
 returns <emphasis>
BadValue</emphasis>
. If any allocation errors occur, <emphasis>
XkbGetKeyActions</emphasis>
 returns <emphasis>
BadAlloc</emphasis>
.
</para>


</sect2>
<sect2 id='changing_the_number_of_actions_bound_to_a_key'>
<title>Changing the Number of Actions Bound to a Key</title>

<para>
To change the number of actions bound to a key, use <emphasis>
XkbResizeKeyAction</emphasis>
.
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
XkbAction *<emphasis>
XkbResizeKeyActions</emphasis>
(<emphasis>
xkb</emphasis>
,<emphasis>
 key</emphasis>
,<emphasis>
 needed</emphasis>
)
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescRec *<emphasis>
            xkb</emphasis>
;            /* keyboard description to change */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int <emphasis>
            key</emphasis>
;            /* keycode of key to change */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
int <emphasis>
            needed</emphasis>
;            /* new number of actions required */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
The <emphasis>
xkb</emphasis>
 parameter points to the keyboard description containing the <emphasis>
key</emphasis>
 whose number of actions is to be changed. The <emphasis>
key</emphasis>
 parameter is the keycode of the key to change, and <emphasis>
needed</emphasis>
 specifies the new number of actions required for the key.
</para>


<para>
<emphasis>
XkbResizeKeyActions</emphasis>
 reserves the space needed for the actions and returns a pointer to the
beginning of the new array that holds the actions. It can change the <emphasis>
acts</emphasis>
, <emphasis>
num_acts</emphasis>
, and <emphasis>
size_acts</emphasis>
 fields of <emphasis>
xkb</emphasis>
-&gt;<emphasis>
server</emphasis>
 if it is necessary to reallocate the <emphasis>
acts </emphasis>
array.
</para>


<para>
If <emphasis>
needed</emphasis>
 is greater than the current number of keysyms for the key, <emphasis>
XkbResizeKeyActions</emphasis>
 initializes all new actions in the array to <emphasis>
NoAction</emphasis>
.
</para>


<para>
Because the number of actions needed by a key is normally computed as width *
number of groups, and <emphasis>
XkbResizeKeyActions</emphasis>
 does not modify either the width or number of groups for the key, a
discrepancy exists on return from <emphasis>
XkbResizeKeyActions</emphasis>
 between the space allocated for the actions and the number required. The
unused entries in the list of actions returned by <emphasis>
XkbResizeKeyActions</emphasis>
 are not preserved across future calls to any of the map editing functions, so
you must update the key actions (which updates the width and number of groups
for the key) before calling another allocator function. A call to <emphasis>
XkbChangeTypesOfKey</emphasis>
 updates these.
</para>


<para>
If any allocation errors occur while resizing the number of actions bound to
the key, <emphasis>
XkbResizeKeyActions</emphasis>
 returns <emphasis>
NULL</emphasis>
.
</para>

<note><para>A change to the number of actions bound to a key should be
accompanied by a change in the number of symbols bound to a key. Refer to
section 15.3.7 for more information on changing the number of symbols bound to
a key.</para></note>


</sect2>
</sect1>
<sect1 id='key_behavior'>
<title>Key Behavior</title>

<para>
Key behavior refers to the demeanor of a key. For example, the expected
behavior of the <emphasis>
CapsLock</emphasis>
 key is that it logically locks when pressed, and then logically unlocks when
pressed again.
</para>


<sect2 id='radio_groups2'>
<title>Radio Groups</title>

<para>
Keys that belong to the same radio group have the <emphasis>
XkbKB_RadioGroup</emphasis>
 type in the <emphasis>
type</emphasis>
 field and the radio group index specified in the <emphasis>
data</emphasis>
 field in the <emphasis>
XkbBehavior</emphasis>
 structure. If the radio group has a name in the <emphasis>
XkbNamesRec</emphasis>
 structure, the radio group index is the index into the <emphasis>
radio_group</emphasis>
 array in the <emphasis>
XkbNamesRec</emphasis>
 structure. A radio group key when pressed stays logically down until another
key in the radio group is pressed, when the first key becomes logically up and
the new key becomes logically down. Setting the <emphasis>
XkbKB_RGAllowNone</emphasis>
 bit in the behavior for all of the keys of the radio group means that pressing
the logically down member of the radio group causes it to logically release, in
which case none of the keys of the radio group would be logically down. If
<emphasis>
XkbKB_RGAllowNone</emphasis>
 is not set, there is no way to release the logically down member of the group.
</para>


<para>
The low five bits of the <emphasis>
data</emphasis>
 field of the <emphasis>
XkbBehavior</emphasis>
 structure are the group number, the high three bits are flags. The only flag
currently defined is:
</para>

<para><programlisting>
#define      XkbRG_AllowNone      0x80
</programlisting></para>

</sect2>
<sect2 id='the_xkbbehavior_structure'>
<title>The XkbBehavior Structure</title>

<para>
The <emphasis>
behaviors</emphasis>
 field of the server map is an array of <emphasis>
XkbBehavior</emphasis>
 structures, indexed by keycode, and contains the behavior for each key. The
<emphasis>
XkbBehavior</emphasis>
 structure is defined as follows:
</para>

<para><programlisting>
typedef struct _XkbBehavior {
      unsigned char  type;                  /* behavior type + optional
                                               <emphasis> XkbKB_Permanent</emphasis> bit */
      unsigned char  data;
} <emphasis>XkbBehavior</emphasis>;
</programlisting></para>

<para>
The <emphasis>
type</emphasis>
 field specifies the Xkb behavior, and the value of the <emphasis>
data</emphasis>
 field depends on the <emphasis>
type</emphasis>
. Xkb supports the key behaviors shown in Table 16.20.
</para>

<table frame='none'>
<title>Key Behaviors</title>
<tgroup cols='2'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Type</entry>
  <entry>Effect</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>XkbKB_Default</emphasis></entry>
    <entry>
Press and release events are processed normally. The <emphasis>
data</emphasis>
 field is unused.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbKB_Lock</emphasis></entry>
    <entry>
If a key is logically up (that is, the corresponding bit of the core key map is
cleared) when it is pressed, the key press is processed normally and the
corresponding release is ignored. If the key is logically down when pressed,
the key press is ignored but the corresponding release is processed normally.
The <emphasis>
data</emphasis>
 field is unused.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbKB_RadioGroup</emphasis></entry>
    <entry>
      <para>
If another member of the radio group is logically down (all members of the
radio group have the same index, specified in <emphasis>
data</emphasis>
) when a key is pressed, the server synthesizes a key release for the member
that is logically down and then processes the new key press event normally.
      </para>
      <para>
If the key itself is logically down when pressed, the key press event is
ignored, but the processing of the corresponding key release depends on the
value of the <emphasis>
Xkb_RGAllowNone</emphasis>
 bit in <emphasis>
flags</emphasis>
. If it is set, the key release is processed normally; otherwise, the key
release is also ignored.
      </para>
      <para>
All other key release events are ignored.
      </para>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbKB_Overlay1</emphasis></entry>
    <entry>
If the <emphasis>
Overlay1</emphasis>
 control is enabled (see section 10.4), <emphasis>
data</emphasis>
 is interpreted as a keycode, and events from this key are reported as if they
came from <emphasis>
data</emphasis>
’s keycode. Otherwise, press and release events are processed normally.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>XkbKB_Overlay2</emphasis></entry>
    <entry>
If the <emphasis>
Overlay2</emphasis>
 control is enabled (see section 10.4), <emphasis>
data</emphasis>
 is interpreted as a keycode, and events from this key are reported as if they
came from <emphasis>
data</emphasis>
’s keycode. Otherwise, press and release events are processed normally.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<para>
Xkb also provides the mask, <emphasis>
XkbKB_Permanent</emphasis>
 to specify whether the key behavior type should be simulated by Xkb or whether
the key behavior describes an unalterable physical, electrical, or software
aspect of the keyboard. If the <emphasis>
XkbKB_Permanent</emphasis>
 bit is not set in the <emphasis>
type</emphasis>
 field, Xkb simulates the behavior in software. Otherwise, Xkb relies upon the
keyboard to implement the behavior.
</para>


</sect2>
<sect2 id='obtaining_key_behaviors_for_keys_from_the_server'>
<title>Obtaining Key Behaviors for Keys from the Server</title>

<para>
To obtain the behaviors (the <emphasis>
behaviors</emphasis>
 array) for a subset of the keys in a keyboard description from the server, use
<emphasis>
XkbGetKeyBehaviors</emphasis>
:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
Status <emphasis>
XkbGetKeyBehaviors</emphasis>
(<emphasis>
dpy</emphasis>
,<emphasis>
 first</emphasis>
,<emphasis>
 num</emphasis>
,<emphasis>
 xkb</emphasis>
)
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
Display *<emphasis>
            dpy</emphasis>
;            /* connection to server */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
first</emphasis>
;            /* keycode of first key to get */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
num</emphasis>
;            /* number of keys for which behaviors are desired */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr             <emphasis>
xkb</emphasis>
;            /* Xkb description to contain the result */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbGetKeyBehaviors</emphasis>
 sends a request to the server to obtain the behaviors for <emphasis>
num</emphasis>
 keys on the keyboard starting with the key whose keycode is <emphasis>
first</emphasis>
. It waits for a reply and returns the behaviors in the <emphasis>
server</emphasis>
-&gt;<emphasis>
behaviors</emphasis>
 field of <emphasis>
xkb</emphasis>
. If successful, <emphasis>
XkbGetKeyBehaviors</emphasis>
 returns <emphasis>
Success</emphasis>
.
</para>


<para>
If the <emphasis>
server</emphasis>
 map in the <emphasis>
xkb</emphasis>
 parameter has not been allocated, <emphasis>
XkbGetKeyBehaviors</emphasis>
 allocates and initializes it before obtaining the actions.
</para>


<para>
If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, <emphasis>
XkbGetKeyBehaviors</emphasis>
 returns <emphasis>
BadAccess</emphasis>
. If <emphasis>
num</emphasis>
 is less than 1 or greater than <emphasis>
XkbMaxKeyCount</emphasis>
, <emphasis>
XkbGetKeyBehaviors</emphasis>
 returns <emphasis>
BadValue</emphasis>
. If any allocation errors occur, <emphasis>
XkbGetKeyBehaviors</emphasis>
 returns <emphasis>
BadAlloc</emphasis>
.
</para>


</sect2>
</sect1>
<sect1 id='explicit_components_avoiding_automatic_remapping_by_the_server'>
<title>Explicit Components—Avoiding Automatic Remapping by the Server</title>

<para>
Whenever a client remaps the keyboard using core protocol requests, Xkb
examines the map to determine likely default values for the components that
cannot be specified using the core protocol (see section 17.1.2 for more
information on how Xkb chooses the default values).
</para>


<para>
This automatic remapping might replace definitions explicitly requested by an
application, so the Xkb keyboard description defines an explicit components
mask for each key. Any aspects of the automatic remapping listed in the
explicit components mask for a key are not changed by the automatic keyboard
mapping.
</para>


<para>
The explicit components masks are held in the <emphasis>
explicit</emphasis>
 field of the server map, which is an array indexed by keycode. Each entry in
this array is a mask that is a bitwise inclusive OR of the values shown in
Table 16.21.
</para>

<table frame='none'>
<title>Explicit Component Masks</title>
<tgroup cols='3'>
<colspec colsep='0'/>
<colspec colsep='0'/>
<colspec colsep='0'/>
<thead>
<row rowsep='0'>
  <entry>Bit in Explicit Mask</entry>
  <entry>Value</entry>
  <entry>Protects Against</entry>
</row>
</thead>
<tbody>
  <row rowsep='0'>
    <entry><emphasis>ExplicitKeyType1</emphasis></entry>
    <entry>(1&lt;&lt;0)</entry>
    <entry>
Automatic determination of the key type associated with <emphasis>
Group1.</emphasis>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>ExplicitKeyType2</emphasis></entry>
    <entry>(1&lt;&lt;1)</entry>
    <entry>
Automatic determination of the key type associated with <emphasis>
Group2.</emphasis>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>ExplicitKeyType3</emphasis></entry>
    <entry>(1&lt;&lt;2)</entry>
    <entry>
Automatic determination of the key type associated with <emphasis>
Group3.</emphasis>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>ExplicitKeyType4</emphasis></entry>
    <entry>(1&lt;&lt;3)</entry>
    <entry>
Automatic determination of the key type associated with <emphasis>
Group4.</emphasis>
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>ExplicitInterpret</emphasis></entry>
    <entry>(1&lt;&lt;4)</entry>
    <entry>
Application of any of the fields of a symbol interpretation to the
key in question.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>ExplicitAutoRepeat</emphasis></entry>
    <entry>(1&lt;&lt;5)</entry>
    <entry>Automatic determination of auto-repeat status for the key, as
specified in a symbol interpretation.</entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>ExplicitBehavior</emphasis></entry>
    <entry>(1&lt;&lt;6)</entry>
    <entry>
Automatic assignment of the <emphasis>
XkbKB_Lock</emphasis>
 behavior to the key, if the <emphasis>
XkbSI_LockingKey</emphasis>
 flag is set in a symbol interpretation.
    </entry>
  </row>
  <row rowsep='0'>
    <entry><emphasis>ExplicitVModMap</emphasis></entry>
    <entry>(1&lt;&lt;7)</entry>
    <entry>
Automatic determination of the virtual modifier map for the key
based on the actions assigned to the key and the symbol interpretations that
match the key.
    </entry>
  </row>
</tbody>
</tgroup>
</table>

<sect2 id='obtaining_explicit_components_for_keys_from_the_server'>
<title>Obtaining Explicit Components for Keys from the Server</title>

<para>
To obtain the explicit components (the <emphasis>
explicit</emphasis>
 array) for a subset of the keys in a keyboard description, use <emphasis>
XkbGetKeyExplicitComponents</emphasis>.
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
Status <emphasis>
XkbGetKeyExplicitComponents</emphasis>
(<emphasis>
dpy</emphasis>
,<emphasis>
 first</emphasis>
,<emphasis>
 num</emphasis>
,<emphasis>
 xkb</emphasis>
)
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
Display *<emphasis>
            dpy</emphasis>
;            /* connection to server */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
first</emphasis>
;            /* keycode of first key to fetch */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
num</emphasis>
;            /* number of keys for which to get explicit info */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr             <emphasis>
xkb</emphasis>
;            /* Xkb description in which to put results */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbGetKeyExplicitComponents</emphasis>
 sends a request to the server to obtain the explicit components for <emphasis>
num</emphasis>
 keys on the keyboard starting with key <emphasis>
first</emphasis>
. It waits for a reply and returns the explicit components in the <emphasis>
server</emphasis>
-&gt;<emphasis>
explicit</emphasis>
 array of <emphasis>
xkb</emphasis>
. If successful, <emphasis>
XkbGetKeyExplicitComponents</emphasis>
 returns <emphasis>
Success</emphasis>
. The <emphasis>
xkb</emphasis>
 parameter must be a pointer to a valid Xkb keyboard description.
</para>


<para>
If the <emphasis>
server</emphasis>
 map in the <emphasis>
xkb</emphasis>
 parameter has not been allocated, <emphasis>
XkbGetKeyExplicitComponents</emphasis>
 allocates and initializes it before obtaining the actions.
</para>


<para>
If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, <emphasis>
XkbGetKeyExplicitComponents</emphasis>
 returns <emphasis>
BadMatch</emphasis>
. If <emphasis>
num</emphasis>
 is less than 1 or greater than <emphasis>
XkbMaxKeyCount</emphasis>
, <emphasis>
XkbGetKeyExplicitComponents</emphasis>
 returns <emphasis>
BadValue</emphasis>
. If any allocation errors occur, <emphasis>
XkbGetKeyExplicitComponents</emphasis>
 returns <emphasis>
BadAlloc</emphasis>
.
</para>


</sect2>
</sect1>
<sect1 id='virtual_modifier_mapping'>
<title>Virtual Modifier Mapping</title>

<para>
The <emphasis>
vmods</emphasis>
 member of the server map is a fixed-length array containing <emphasis>
XkbNumVirtualMods</emphasis>
 entries. Each entry corresponds to a virtual modifier and provides the binding
of the virtual modifier to the real modifier bits. Each entry in the <emphasis>
vmods</emphasis>
 array is a bitwise inclusive OR of the legal modifier masks:
</para>

<literallayout>
     <emphasis>ShiftMask</emphasis>
     <emphasis>LockMask</emphasis>
     <emphasis>ControlMask</emphasis>
     <emphasis>Mod1Mask</emphasis>
     <emphasis>Mod2Mask</emphasis>
     <emphasis>Mod3Mask</emphasis>
     <emphasis>Mod4Mask</emphasis>
     <emphasis>Mod5Mask</emphasis>
</literallayout>

<para>
The <emphasis>
vmodmap</emphasis>
 member of the server map is similar to the <emphasis>
modmap</emphasis>
 array of the client map (see section 15.4), but is used to define the virtual
modifier mapping for each key. Like the <emphasis>
modmap</emphasis>
 member, it is indexed by keycode, and each entry is a mask representing the
virtual modifiers bound to the corresponding key:
</para>

<itemizedlist>
  <listitem>
    <para>
Each of the bits in a <emphasis>
vmodmap</emphasis>
 entry represents an index into the <emphasis>
vmods</emphasis>
 member. That is, bit 0 of a <emphasis>
vmodmap</emphasis>
 entry refers to index 0 of the <emphasis>
vmods</emphasis>
 array, bit 1 refers to index 1, and so on.
    </para>
  </listitem>
  <listitem>
    <para>
If a bit is set in the <emphasis>
vmodmap</emphasis>
 entry for a key, that key is bound to the corresponding virtual modifier in
the <emphasis>
vmods</emphasis>
 array.
    </para>
  </listitem>
</itemizedlist>

<para>
The <emphasis>
vmodmap</emphasis>
 and <emphasis>
vmods</emphasis>
 members of the server map are the "master" virtual modifier definitions. Xkb
automatically propagates any changes to these fields to all other fields that
use virtual modifier mappings.
</para>


<para>
The overall relationship of fields dealing with virtual modifiers in an Xkb
keyboard description are shown in Figure 16.2.
</para>

<mediaobject>
 <imageobject> <imagedata format="SVG" fileref="XKBlib-17.svg"/>
 </imageobject>
<caption>Virtual Modifier Relationships</caption>
</mediaobject>



<!--
<H5 CLASS="Figure">
Virtual Modifier Relationships</H5>
-->

<sect2 id='obtaining_virtual_modifier_bindings_from_the_server'>
<title>Obtaining Virtual Modifier Bindings from the Server</title>

<para>
To obtain a subset of the virtual modifier bindings (the <emphasis>
vmods</emphasis>
 array) in a keyboard description, use <emphasis>
XkbGetVirtualMods</emphasis>
:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
Status <emphasis>
XkbGetVirtualMods</emphasis>
(<emphasis>
dpy</emphasis>
,<emphasis>
 which</emphasis>
,<emphasis>
 xkb</emphasis>
)
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
Display *<emphasis>
            dpy</emphasis>
;            /* connection to server */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
which</emphasis>
;            /* mask indicating virtual modifier bindings to get */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr            <emphasis>
xkb</emphasis>
;            /* Xkb description where results will be placed */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbGetVirtualMods</emphasis>
 sends a request to the server to obtain the <emphasis>
vmods</emphasis>
 entries for the virtual modifiers specified in the mask, <emphasis>
which</emphasis>
, and waits for a reply. See section 7.1 for a description of how to determine
the virtual modifier mask. For each bit set in <emphasis>
which</emphasis>
, <emphasis>
XkbGetVirtualMods</emphasis>
 updates the corresponding virtual modifier definition in the <emphasis>
server-&gt;vmods</emphasis>
 array of <emphasis>
xkb</emphasis>
. The <emphasis>
xkb</emphasis>
 parameter must be a pointer to a valid Xkb keyboard description. If
successful, <emphasis>
XkbGetVirtualMods</emphasis>
 returns <emphasis>
Success</emphasis>
.
</para>


<para>
If the <emphasis>
server</emphasis>
 map has not been allocated in the <emphasis>
xkb</emphasis>
 parameter, <emphasis>
XkbGetVirtualMods</emphasis>
 allocates and initializes it before obtaining the virtual modifier bindings.
</para>


<para>
If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, <emphasis>
XkbGetVirtualMods</emphasis>
 returns <emphasis>
BadMatch</emphasis>
. Any errors in allocation cause <emphasis>
XkbGetVirtualMods </emphasis>
to return <emphasis>
BadAlloc</emphasis>.
</para>


</sect2>
<sect2 id='obtaining_per_key_virtual_modifier_mappings_from_the_server'>
<title>Obtaining Per-Key Virtual Modifier Mappings from the Server</title>

<para>
To obtain the virtual modifier map (the <emphasis>
vmodmap</emphasis>
 array) for a subset of the keys in a keyboard description, use <emphasis>
XkbGetKeyVirtualModMap</emphasis>
:
</para>

<informaltable frame='none'>
<tgroup cols='1'>
<colspec colsep='0'/>
<tbody>
  <row rowsep='0'>
    <entry role='functiondecl'>
Status <emphasis>
XkbGetKeyVirtualModMap</emphasis>
(<emphasis>
dpy</emphasis>
,<emphasis>
 first</emphasis>
,<emphasis>
 num</emphasis>
,<emphasis>
 xkb</emphasis>
)
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
Display *<emphasis>
            dpy</emphasis>
;            /* connection to server */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
first</emphasis>
;            /* keycode of first key to fetch */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
unsigned int            <emphasis>
num</emphasis>
;            /* # keys for which virtual mod maps are desired */
    </entry>
  </row>
  <row rowsep='0'>
    <entry role='functionargdecl'>
XkbDescPtr             <emphasis>
xkb</emphasis>
;            /* Xkb description where results will be placed */
    </entry>
</row>
</tbody>
</tgroup>
</informaltable>

<para>
<emphasis>
XkbGetKeyVirutalModmap </emphasis>
sends a request to the server to obtain the virtual modifier mappings for
<emphasis>
num</emphasis>
 keys on the keyboard starting with key <emphasis>
first</emphasis>
. It waits for a reply and returns the virtual modifier mappings in the
<emphasis>
server</emphasis>
-&gt;<emphasis>
vmodmap</emphasis>
 array of <emphasis>
xkb</emphasis>
. If successful, <emphasis>
XkbGetKeyVirtualModMap</emphasis>
 returns <emphasis>
Success</emphasis>
. The <emphasis>
xkb</emphasis>
 parameter must be a pointer to a valid Xkb keyboard description
</para>


<para>
If the <emphasis>
server</emphasis>
 map in the <emphasis>
xkb</emphasis>
 parameter has not been allocated, <emphasis>
XkbGetKeyVirtualModMap</emphasis>
 allocates and initializes it before obtaining the virtual modifier mappings.
</para>


<para>
If the server does not have a compatible version of Xkb, or the Xkb extension
has not been properly initialized, <emphasis>
XkbGetKeyVirtualModMap</emphasis>
 returns <emphasis>
BadMatch</emphasis>
. If <emphasis>
num</emphasis>
 is less than 1 or greater than <emphasis>
XkbMaxKeyCount</emphasis>
, <emphasis>
XkbGetKeyVirtualModMap</emphasis>
 returns <emphasis>
BadValue</emphasis>
. If any allocation errors occur, <emphasis>
XkbGetKeyVirtualModMap</emphasis>
 returns <emphasis>
BadAlloc</emphasis>
.
</para>

</sect2>
</sect1>
</chapter>