The core protocol does not provide any information to clients other than that actually used to interpret events. This makes it difficult to write an application that presents the keyboard to a user in an easy-to-understand way. Such applications have to examine the vendor string and keycodes to determine the type of keyboard connected to the server and then examine keysyms and modifier mappings to determine the effects of most modifiers (the Shift , Lock and Control modifiers are defined by the core protocol but no semantics are implied for any other modifiers). To make it easier for applications to present a keyboard to the user, Xkb supports symbolic names for most components of the keyboard extension. Most of these symbolic names are grouped into the names component of the keyboard description. The names component of the keyboard description is defined as follows: #define XkbKeyNameLength 4 #define XkbKeyNumVirtualMods 16 #define XkbKeyNumIndicators 32 #define XkbKeyNumKbdGroups 4 #define XkbMaxRadioGroups 32 typedef struct { char name[XkbKeyNameLength]; /* symbolic key names */ } XkbKeyNameRec,*XkbKeyNamePtr; typedef struct { char real[XkbKeyNameLength]; /* this key name must be in the keys array */ char alias[XkbKeyNameLength]; /* symbolic key name as alias for the key */ } XkbKeyAliasRec,*XkbKeyAliasPtr; typedef struct _XkbNamesRec { Atom keycodes; /* identifies range and meaning of keycodes */ Atom geometry; /* identifies physical location, size, and shape of keys */ Atom symbols; /* identifies the symbols logically bound to the keys */ Atom types; /* identifies the set of key types */ Atom compat; /* identifies actions for keys using core protocol */ Atom vmods[XkbNumVirtualMods]; /* symbolic names for virtual modifiers */ Atom indicators[XkbNumIndicators]; /* symbolic names for indicators */ Atom groups[XkbNumKbdGroups]; /* symbolic names for keyboard groups */ XkbKeyNamePtr keys; /* symbolic key name array */ XkbKeyAliasPtr key_aliases; /* real/alias symbolic name pairs array */ Atom * radio_groups; /* radio group name array */ Atom phys_symbols; /* identifies the symbols engraved on the keyboard */ unsigned char num_keys; /* number of keys in the keys array */ unsigned char num_key_aliases; /* number of keys in the key_aliases array */ unsigned short num_rg; /* number of radio groups */ } XkbNamesRec,*XkbNamesPtr; /* The keycodes name identifies the range and meaning of the keycodes returned by the keyboard in question. The geometry name, on the other hand, identifies the physical location, size and shape of the various keys on the keyboard. As an example to distinguish between these two names, consider function keys on PC-compatible keyboards. Function keys are sometimes above the main keyboard and sometimes to the left of the main keyboard, but the same keycode is used for the key that is logically F1 regardless of physical position. Thus, all PC-compatible keyboards share a similar keycodes name but may have different geometry names. The keycodes name is intended to be a very general description of the keycodes returned by a keyboard; a single keycodes name might cover keyboards with differing numbers of keys provided all keys have the same semantics when present. For example, 101 and 102 key PC keyboards might use the same name. In these cases, applications can use the keyboard geometry name to determine which subset of the named keycodes is in use. The symbols name identifies the symbols logically bound to the keys. The symbols name is a human or application-readable description of the intended locale or usage of the keyboard with these symbols. The phys_symbols name, on the other hand, identifies the symbols actually engraved on the keyboard. Given this, the symbols name and phys_symbols names might be different. For example, the description for a keyboard that has English US engravings, but that is using Swiss German symbols might have a phys_symbols name of "en_US" and a symbols name of "de_CH." The types name provides some information about the set of key types (see section 15.2) that can be associated with the keyboard. In addition, each key type can have a name, and each shift level of a type can have a name. Although these names are stored in the map description with each of the types, they are accessed using the same methods as the other symbolic names. The compat name provides some information about the rules used to bind actions to keys that are changed using core protocol requests. Xkb provides symbolic names for each of the 4 keyboard groups, 16 virtual modifiers, 32 keyboard indicators, and 4 keyboard groups. These names are held in the vmods , indicators , and groups fixed-length arrays. Each key has a four-byte symbolic name. All of the symbolic key names are held in the keys array, and num_keys reports the number of entries that are in the keys array. For each key, the key name links keys with similar functions or in similar positions on keyboards that report different keycodes. For example, the F1 key may emit keycode 23 on one keyboard and keycode 86 on another. By naming this key "FK01" on both keyboards, the keyboard layout designer can reuse parts of keyboard descriptions for different keyboards. Key aliases allow the keyboard layout designer to assign multiple key names to a single key. This allows the keyboard layout designer to refer to keys using either their position or their "function." For example, a keyboard layout designer may wish to refer to the left arrow key on a PC keyboard using the ISO9995-5 positional specification of A31 or using the functional specification of LEFT. The key_aliases field holds a variable-length array of real and alias key name pairs, and the total number of entries in the key_aliases array is held in num_key_aliases . For each real and alias key name pair, the real field refers to the a name in the keys array, and the alias field refers to the alias for that key. Using the previous example, the keyboard designer may use the name A31 in the keys array, but also define the name LEFT as an alias for A31 in the key_aliases array. Key aliases defined in the geometry component of a keyboard mapping (see Chapter 13) override those defined in the keycodes component of the server database, which are stored in the XkbNamesRec ( xkb->names ). Therefore, consider the key aliases defined by the geometry before considering key aliases supplied by the XkbNamesRec . A radio group is a set of keys whose behavior simulates a set of radio buttons. Once a key in a radio group is pressed, it stays logically depressed until another key in the group is pressed, at which point the previously depressed key is logically released. Consequently, at most one key in a radio group can be logically depressed at one time. Each radio group in the keyboard description can have a name. These names are held in the variable-length array radio_groups , and num_rg tells how many elements are in the radio_groups array. Xkb provides several functions that work with symbolic names. Each of these functions uses a mask to specify individual fields of the structures described above. These masks and their relationships to the fields in a keyboard description are shown in Table 18.1. Mask Bit Value Keyboard Component Field XkbKeycodesNameMask (1<<0) Xkb->names keycodes XkbGeometryNameMask (1<<1) Xkb->names geometry XkbSymbolsNameMask (1<<2) Xkb->names symbols XkbPhysSymbolsNameMask (1<<3) Xkb->names phys_symbols XkbTypesNameMask (1<<4) Xkb->names type XkbCompatNameMask (1<<5) Xkb->names compat XkbKeyTypeNamesMask (1<<6) Xkb->map type[*].name XkbKTLevelNamesMask (1<<7) Xkb->map type[*].lvl_names[*] XkbIndicatorNamesMask (1<<8) Xkb->names indicators[*] XkbKeyNamesMask (1<<9) Xkb->names keys[*], num_keys XkbKeyAliasesMask (1<<10) Xkb->names key_aliases[*], num_key_aliases XkbVirtualModNamesMask (1<<11) Xkb->names vmods[*] XkbGroupNamesMask (1<<12) Xkb->names groups[*] XkbRGNamesMask (1<<13) Xkb->names radio_groups[*], num_rg XkbComponentNamesMask (0x3f) Xkb->names keycodes, geometry, symbols, physical symbols, types, and compatibility map XkbAllNamesMask (0x3fff) Xkb->names all name components To obtain symbolic names from the server, use XkbGetNames . Status XkbGetNames ( dpy, which, Xkb ) Display * dpy ; /* connection to the X server */ unsigned int which ; /* mask of names or map components to be updated */ XkbDescPtr xkb /* keyboard description to be updated */ XkbGetNames retrieves symbolic names for the components of the keyboard extension from the X server. The which parameter specifies the name components to be updated in the xkb parameter, and is the bitwise inclusive OR of the valid names mask bits defined in Table 18.1. If the names field of the keyboard description xkb is NULL , XkbGetNames allocates and initializes the names component of the keyboard description before obtaining the values specified by which . If the names field of xkb is not NULL , XkbGetNames obtains the values specified by which and copies them into the keyboard description Xkb . If the map component of the xkb parameter is NULL , XkbGetNames does not retrieve type or shift level names, even if XkbKeyTypeNamesMask or XkbKTLevelNamesMask are set in which . XkbGetNames can return Success , or BadAlloc , BadLength , BadMatch , and BadImplementation errors. To free symbolic names, use XkbFreeNames (see section 18.6) To change the symbolic names in the server, first modify a local copy of the keyboard description and then use either XkbSetNames, or, to save network traffic, use a XkbNameChangesRec structure and call XkbChangeNames to download the changes to the server. XkbSetNames and XkbChangeNames can generate BadAlloc , BadAtom , BadLength , BadMatch, and BadImplementation errors. Bool XkbSetNames ( dpy, which, first_type, num_types, xkb ) Display * dpy ; /* connection to the X server */ unsigned int which ; /* mask of names or map components to be changed */ unsigned int first_type ; /* first type whose name is to be changed */ unsigned int num_types ; /* number of types for which names are to be changed */ XkbDescPtr xkb ; /* keyboard description from which names are to be taken */ Use XkbSetNames to change many names at the same time. For each bit set in which , XkbSetNames takes the corresponding value (or values in the case of arrays) from the keyboard description xkb and sends it to the server. The first_type and num_types arguments are used only if XkbKeyTypeNamesMask or XkbKTLevelNamesMask is set in which and specify a subset of the types for which the corresponding names are to be changed. If either or both of these mask bits are set but the specified types are illegal, XkbSetNames returns False and does not update any of the names specified in which . The specified types are illegal if xkb does not include a map component or if first_type and num_types specify types that are not defined in the keyboard description. The XkbNameChangesRec allows applications to identify small modifications to the symbolic names and effectively reduces the amount of traffic sent to the server: typedef struct _XkbNameChanges { unsigned int changed; /* name components that have changed */ unsigned char first_type; /* first key type with a new name */ unsigned char num_types; /* number of types with new names */ unsigned char first_lvl; /* first key type with new level names */ unsigned char num_lvls; /* number of key types with new level names */ unsigned char num_aliases; /* if key aliases changed, total number of key aliases */ unsigned char num_rg; /* if radio groups changed, total number of radio groups */ unsigned char first_key; /* first key with a new name */ unsigned char num_keys; /* number of keys with new names */ unsigned short changed_vmods; /* mask of virtual modifiers for which names have changed */ unsigned long changed_indicators; /* mask of indicators for which names were changed */ unsigned char changed_groups; /* mask of groups for which names were changed */ } XkbNameChangesRec, *XkbNameChangesPtr The changed field specifies the name components that have changed and is the bitwise inclusive OR of the valid names mask bits defined in Table 18.1. The rest of the fields in the structure specify the ranges that have changed for the various kinds of symbolic names, as shown in Table 18.2. Mask Fields Component Field XkbKeyTypeNamesMask first_type, num_types Xkb->map type[*].name XkbKTLevelNamesMask first_lvl, num_lvls Xkb->map type[*].lvl_names[*] XkbKeyAliasesMask num_aliases Xkb->names key_aliases[*] XkbRGNamesMask num_rg Xkb->names radio_groups[*] XkbKeyNamesMask first_key, num_keys Xkb->names keys[*] XkbVirtualModNamesMask changed_vmods Xkb->names vmods[*] XkbIndicatorNamesMask changed_indicators Xkb->names indicators[*] XkbGroupNamesMask changed_groups Xkb->names groups[*] XkbChangeNames provides a more flexible method for changing symbolic names than XkbSetNames and requires the use of an XkbNameChangesRec structure. Bool XkbChangeNames ( dpy, xkb, changes ) Display * dpy ; /* connection to the X server */ XkbDescPtr xkb ; /* keyboard description from which names are to be taken */ XkbNameChangesPtr changes ; /* names map components to be updated on the server */ XkbChangeNames copies any names specified by changes from the keyboard description, xkb , to the X server specified by dpy . XkbChangeNames aborts and returns False if any illegal type names or type shift level names are specified by changes . Whenever a symbolic name changes in the server’s keyboard description, the server sends a XkbNamesNotify event to all interested clients. To receive name notify events, use XkbSelectEvents (see section 4.3) with XkbNamesNotifyMask in both the bits_to_change and values_for_bits parameters. To receive events for only specific names, use XkbSelectEventDetails . Set the event_type parameter to XkbNamesNotify , and set both the bits_to_change and values_for_bits detail parameter to a mask composed of a bitwise OR of masks in Table 18.1. The structure for the XkbNamesNotify event is defined as follows: typedef struct { int type; /* Xkb extension base event code */ unsigned long serial; /* X server serial number for event */ Bool send_event; /* True => synthetically generated */ Display * display; /* server connection where event generated */ Time time; /* server time when event generated */ int xkb_type; /* XkbNamesNotify */ int device; /* Xkb device ID, will not be XkbUseCoreKbd */ unsigned int changed; /* mask of name components that have changed */ int first_type; /* first key type with a new name */ int num_types; /* number of types with new names */ int first_lvl; /* first key type with new level names */ int num_lvls; /* number of key types with new level names */ int num_aliases; /* if key aliases changed, total number of key aliases */ int num_radio_groups; /* if radio groups changed, total number of radio groups */ unsigned int changed_vmods; /* mask of virtual modifiers for which names have changed */ unsigned int changed_groups; /* mask of groups for which names were changed */ unsigned int changed_indicators; /* mask of indicators for which names were changed */ int first_key; /* first key with a new name */ int num_keys; /* number of keys with new names */ } XkbNamesNotifyEvent; The changed field specifies the name components that have changed and is the bitwise inclusive OR of the valid names mask bits defined in Table 18.1. The other fields in this event are interpreted as the like-named fields in an XkbNameChangesRec , as previously defined. When your application receives a X kbNamesNotify event, you can note the changed names in a changes structure using XkbNoteNameChanges . void XkbNoteNameChanges ( old , new , wanted ) XkbNameChangesPtr old ; /* XkbNameChanges structure to be updated */ XkbNamesNotifyEvent * new ; /* event from which changes are to be copied */ unsigned int wanted ; /* types of names for which changes are to be noted */ The wanted parameter is the bitwise inclusive OR of the valid names mask bits shown in Table 18.1. XkbNoteNameChanges copies any changes that are reported in new and specified in wanted into the changes record specified by old . To update the local copy of the keyboard description with the actual values, pass to XkbGetNameChanges the results of one or more calls to XkbNoteNameChanges . Status XkbGetNameChanges ( dpy , xkb , changes ) Display * dpy ; /* connection to the X server */ XkbDescPtr xkb ; /* keyboard description to which names are copied */ XkbNameChangesPtr changes ; /* names components to be obtained from the server */ XkbGetNameChanges examines the changes parameter, retrieves the necessary information from the server, and places the results into the xkb keyboard description. XkbGetNamesChanges can generate BadAlloc , BadImplementation, and BadMatch errors. Most applications do not need to directly allocate symbolic names structures. Do not allocate a names structure directly using malloc or Xmalloc if your application changes the number of key aliases or radio groups or constructs a symbolic names structure without loading the necessary components from the X server. Instead use XkbAllocNames . Status XkbAllocNames ( xkb, which, num_rg, num_key_aliases) XkbDescPtr xkb; /* keyboard description for which names are to be allocated */ unsigned int which; /* mask of names to be allocated */ int num_rg; /* total number of radio group names needed */ int num_key_aliases; /* total number of key aliases needed */ XkbAllocNames can return BadAlloc , BadMatch, and BadValue errors. The which parameter is the bitwise inclusive OR of the valid names mask bits defined in Table 18.1. Do not free symbolic names structures directly using free or XFree . Use XkbFreeNames instead. void XkbFreeNames ( xkb, which, free_map) XkbDescPtr xkb ; /* keyboard description for which names are to be freed */ unsigned int which ; /* mask of names components to be freed */ Bool free_map ; /* True => XkbNamesRec structure itself should be freed */ The which parameter is the bitwise inclusive OR of the valid names mask bits defined in Table 18.1.