Provided by: libx11-doc_1.6.2-1ubuntu2.1_all 
NAME
XkbApplyCompatMapToKey - Apply the new compatibility mapping to an individual key to get
its semantics updated
SYNOPSIS
Bool XkbApplyCompatMapToKey (XkbDescPtr xkb, KeyCode key, XkbChangesPtr changes);
ARGUMENTS
- xkb keyboard description to be updated
- key key to be updated
- changes
notes changes to the Xkb keyboard description
DESCRIPTION
XkbApplyCompatMapToKey essentially performs the operation described in Core Keyboard
Mapping to Xkb Keyboard Mapping Transformation to a specific key. This updates the
behavior, actions, repeat status, and virtual modifier bindings of the key.
Core Keyboard Mapping to Xkb Keyboard Mapping Transformation
When a core protocol keyboard mapping request is received by the server, the server's core
keyboard map is updated, and then the Xkb map maintained by the server is updated. Because
a client may have explicitly configured some of the Xkb keyboard mapping in the server,
this automatic regeneration of the Xkb keyboard mapping from the core protocol keyboard
mapping should not modify any components of the Xkb keyboard mapping that were explicitly
set by a client. The client must set explicit override controls to prevent this from
happening (see Explicit Components-Avoiding Automatic Remapping by the Server). The core-
to-Xkb mapping is done as follows:
Explicit Components-Avoiding Automatic Remapping by the Server
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.
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.
The explicit components masks are held in the explicit 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 1.
Table 1 Explicit Component Masks
───────────────────────────────────────────────────────────────
Bit in Explicit Mask Value Protects Against
───────────────────────────────────────────────────────────────
ExplicitKeyType1 (1<<0) Automatic determination of the
key type associated with
Group1.
ExplicitKeyType2 (1<<1) Automatic determination of the
key type associated with
Group2.
ExplicitKeyType3 (1<<2) Automatic determination of the
key type associated with
Group3.
ExplicitKeyType4 (1<<3) Automatic determination of the
key type associated with
Group4.
ExplicitInterpret (1<<4) Application of any of the
fields of a symbol
interpretation to the key in
question.
ExplicitAutoRepeat (1<<5) Automatic determination of
auto-repeat status for the
key, as specified in a symbol
interpretation.
ExplicitBehavior (1<<6) Automatic assignment of the
XkbKB_Lock behavior to the
key, if the XkbSI_LockingKey
flag is set in a symbol
interpretation.
ExplicitVModMap (1<<7) 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.
1. Map the symbols from the keys in the core keyboard map to groups and symbols on keys
in the Xkb keyboard map. The core keyboard mapping is of fixed width, so each key in
the core mapping has the same number of symbols associated with it. The Xkb mapping
allows a different number of symbols to be associated with each key; those symbols may
be divided into a different number of groups (1-4) for each key. For each key, this
process therefore involves partitioning the fixed number of symbols from the core
mapping into a set of variable-length groups with a variable number of symbols in each
group. For example, if the core protocol map is of width five, the partition for one
key might result in one group with two symbols and another with three symbols. A
different key might result in two groups with two symbols plus a third group with one
symbol. The core protocol map requires at least two symbols in each of the first two
groups.
1a. For each changed key, determine the number of groups represented in the new core
keyboard map. This results in a tentative group count for each key in the Xkb map.
1b. For each changed key, determine the number of symbols in each of the groups found in
step 1a. There is one explicit override control associated with each of the four
possible groups for each Xkb key, ExplicitKeyType1 through ExplicitKeyType4. If no
explicit override control is set for a group, the number of symbols used for that
group from the core map is two. If the explicit override control is set for a group
on the key, the number of symbols used for that Xkb group from the core map is the
width of the Xkb group with one exception: because of the core protocol requirement
for at least two symbols in each of groups one and two, the number of symbols used for
groups one and two is the maximum of 2 or the width of the Xkb group.
1c. For each changed key, assign the symbols in the core map to the appropriate group on
the key. If the total number of symbols required by the Xkb map for a particular key
needs more symbols than the core protocol map contains, the additional symbols are
taken to be NoSymbol keysyms appended to the end of the core set. If the core map
contains more symbols than are needed by the Xkb map, trailing symbols in the core map
are discarded. In the absence of an explicit override for group one or two, symbols
are assigned in order by group; the first symbols in the core map are assigned to
group one, in order, followed by group two, and so on. For example, if the core map
contained eight symbols per key, and a particular Xkb map contained 2 symbols for G1
and G2 and three for G3, the symbols would be assigned as (G is group, L is shift
level):
G1L1 G1L2 G2L1 G2L2 G3L1 G3L2 G3L3
If an explicit override control is set for group one or two, the symbols are taken
from the core set in a somewhat different order. The first four symbols from the core
set are assigned to G1L1, G1L2, G2L1, G2L2, respectively. If group one requires more
symbols, they are taken next, and then any additional symbols needed by group two.
Group three and four symbols are taken in complete sequence after group two. For
example, a key with four groups and three symbols in each group would take symbols
from the core set in the following order:
G1L1 G1L2 G2L1 G2L2 G1L3 G2L3 G3L1 G3L2 G3L3 G4L1 G4L2 G4L3
As previously noted, the core protocol map requires at lease two symbols in groups one
and two. Because of this, if an explicit override control for an Xkb key is set and
group one and / or group two is of width one, it is not possible to generate the
symbols taken from the core protocol set and assigned to position G1L2 and / or G2L2.
1d. For each group on each changed key, assign a key type appropriate for the symbols in
the group.
1e. For each changed key, remove any empty or redundant groups.
At this point, the groups and their associated symbols have been assigned to the
corresponding key definitions in the Xkb map.
2. Apply symbol interpretations to modify key operation. This phase is completely skipped
if the ExplicitInterpret override control bit is set in the explicit controls mask
for the Xkb key (see Explicit Components-Avoiding Automatic Remapping by the Server).
2a. For each symbol on each changed key, attempt to match the symbol and modifiers from
the Xkb map to a symbol interpretation describing how to generate the symbol.
2b. When a match is found in step 2a, apply the symbol interpretation to change the
semantics associated with the symbol in the Xkb key map. If no match is found, apply a
default interpretation.
The symbol interpretations used in step 2 are configurable and may be specified using
XkbSymInterpretRec structures referenced by the sym_interpret field of an XkbCompatMapRec.
Symbol Interpretations - the XkbSymInterpretRec Structure
Symbol interpretations are used to guide the X server when it modifies the Xkb keymap in
step 2. An initial set of symbol interpretations is loaded by the server when it starts. A
client may add new ones using XkbSetCompatMap.
Symbol interpretations result in key semantics being set. When a symbol interpretation is
applied, the following components of server key event processing may be modified for the
particular key involved:
Virtual modifier map
Auto repeat
Key behavior (may be set to XkbKB_Lock)
Key action
The XkbSymInterpretRec structure specifies a symbol interpretation:
typedef struct {
KeySym sym; /∗ keysym of interest or NULL */
unsigned char flags; /∗ XkbSI_AutoRepeat, XkbSI_LockingKey */
unsigned char match; /∗ specifies how mods is interpreted */
unsigned char mods; /∗ modifier bits, correspond to eight real modifiers */
unsigned char virtual_mod; /∗ 1 modifier to add to key virtual mod map */
XkbAnyAction act; /∗ action to bind to symbol position on key */
} XkbSymInterpretRec,*XkbSymInterpretPtr;
If sym is not NULL, it limits the symbol interpretation to keys on which that particular
keysym is selected by the modifiers matching the criteria specified by mods and match. If
sym is NULL, the interpretation may be applied to any symbol selected on a key when the
modifiers match the criteria specified by mods and match.
match must be one of the values shown in Table 2 and specifies how the real modifiers
specified in mods are to be interpreted.
Table 2 Symbol Interpretation Match Criteria
───────────────────────────────────────────────────────────
Match Criteria Value Effect
───────────────────────────────────────────────────────────
XkbSI_NoneOf (0) None of the bits that are on
in mods can be set, but other
bits can be.
XkbSI_AnyOfOrNone (1) Zero or more of the bits that
are on in mods can be set, as
well as others.
XkbSI_AnyOf (2) One or more of the bits that
are on in mods can be set, as
well as any others.
XkbSI_AllOf (3) All of the bits that are on in
mods must be set, but others
may be set as well.
XkbSI_Exactly (4) All of the bits that are on in
mods must be set, and no other
bits may be set.
In addition to the above bits, match may contain the XkbSI_LevelOneOnly bit, in which case
the modifier match criteria specified by mods and match applies only if sym is in level
one of its group; otherwise, mods and match are ignored and the symbol matches a condition
where no modifiers are set.
#define XkbSI_LevelOneOnly (0x80) /∗ use mods + match only if sym is level 1 */
If no matching symbol interpretation is found, the server uses a default interpretation
where:
sym = 0
flags = XkbSI_AutoRepeat
match = XkbSI_AnyOfOrNone
mods = 0
virtual_mod = XkbNoModifier
act = SA_NoAction
When a matching symbol interpretation is found in step 2a, the interpretation is applied
to modify the Xkb map as follows.
The act field specifies a single action to be bound to the symbol position; any key event
that selects the symbol causes the action to be taken. Valid actions are defined in Key
Actions.
If the Xkb keyboard map for the key does not have its ExplicitVModMap control set, the
XkbSI_LevelOneOnly bit and symbol position are examined. If the XkbSI_LevelOneOnly bit is
not set in match or the symbol is in position G1L1, the virtual_mod field is examined. If
virtual_mod is not XkbNoModifier, virtual_mod specifies a single virtual modifier to be
added to the virtual modifier map for the key. virtual_mod is specified as an index in
the range [0..15].
If the matching symbol is in position G1L1 of the key, two bits in the flags field
potentially specify additional behavior modifications:
#define XkbSI_AutoRepeat (1<<0) /∗ key repeats if sym is in position G1L1 */
#define XkbSI_LockingKey (1<<1) /∗ set KB_Lock behavior if sym is in psn G1L1 */
If the Xkb keyboard map for the key does not have its ExplicitAutoRepeat control set, its
auto repeat behavior is set based on the value of the XkbSI_AutoRepeat bit. If the
XkbSI_AutoRepeat bit is set, the auto-repeat behavior of the key is turned on; otherwise,
it is turned off.
If the Xkb keyboard map for the key does not have its ExplicitBehavior control set, its
locking behavior is set based on the value of the XkbSI_LockingKey bit. If
XkbSI_LockingKey is set, the key behavior is set to KB_Lock; otherwise, it is turned off.
SEE ALSO
XkbKeyAction(3), XkbKeyActionEntry(3), XkbKeyActionsPtr(3), XkbKeyHasActions(3),
XkbKeyNumActions(3)