XkbChangeMap(3) Update only partial components of a keyboard description, modify


Bool XkbChangeMap (Display *dpy, XkbDescPtr xkb, XkbMapChangesPtr changes);


- dpy
connection to X server
- xkb
description from which new values are taken
- changes
identifies component parts to update


To update only partial components of a keyboard description, modify the appropriate fields in the server and map components of a local copy of the keyboard description, then call XkbChangeMap with an XkbMapChangesRec structure indicating which components have changed.

XkbChangeMap copies any components specified by the changes structure from the keyboard description, xkb, to the X server specified by dpy.

If any components specified by changes are not present in the xkb parameter, XkbChangeMap returns False. Otherwise, it sends a request to the server and returns True.

XkbChangeMap can generate BadAlloc, BadLength, and BadValue protocol errors.


The XkbChangeMap function returns True if the components specified by changes are present in the xkb parameter.
The XkbChangeMap function returns False if the components specified by changes are not present in the xkb parameter.


Use the XkbMapChangesRec structure to identify and track partial modifications to the mapping components and to reduce the amount of traffic between the server and clients.

typedef struct _XkbMapChanges {
    unsigned short   changed;            /* identifies valid components in 
structure */
    KeyCode          min_key_code;       /* lowest numbered keycode for device 
    KeyCode          max_key_code;       /* highest numbered keycode for device 
    unsigned char    first_type;         /* index of first key type modified */
    unsigned char    num_types;          /* # types modified */
    KeyCode          first_key_sym;      /* first key whose key_sym_map changed 
    unsigned char    num_key_syms;       /* # key_sym_map entries changed */
    KeyCode          first_key_act;      /* first key whose key_acts entry 
changed */
    unsigned char    num_key_acts;       /* # key_acts entries changed */
    KeyCode          first_key_behavior; /* first key whose behaviors changed */
    unsigned char    num_key_behaviors;  /* # behaviors entries changed */
    KeyCode          first_key_explicit; /* first key whose explicit entry 
changed */
    unsigned char    num_key_explicit;   /* # explicit entries changed */
    KeyCode          first_modmap_key;   /* first key whose modmap entry changed 
    unsigned char    num_modmap_keys;    /* # modmap entries changed */
    KeyCode          first_vmodmap_key;  /* first key whose vmodmap changed */
    unsigned char    num_vmodmap_keys;   /* # vmodmap entries changed */
    unsigned char    pad1;               /* reserved */
    unsigned short   vmods;              /* mask indicating which vmods changed 
} XkbMapChangesRec,*XkbMapChangesPtr;


Unable to allocate storage
The length of a request is shorter or longer than that required to minimally contain the arguments
An argument is out of range