XkbSetBounceKeysDelay (3) - Linux Manuals

XkbSetBounceKeysDelay: Sets the BounceKeys delay for a keyboard device


XkbSetBounceKeysDelay - Sets the BounceKeys delay for a keyboard device


Bool XkbSetBounceKeysDelay (Display *display, unsigned int device_spec, unsigned int *delay);


- display
connection to X server
- device_spec
device ID, or XkbUseCoreKbd
- delay
backfilled with bounce keys delay, ms


The server can generate XkbAccessXNotify events for some of the global keyboard controls. The detail field describes what AccessX event just occurred and can be any of the values in Table 1.

Table 1 AccessXNotify Events


XkbAXN_SKPress A key was pressed when SlowKeys was enabled.
XkbAXN_SKAccept A key was accepted (held longer than the SlowKeys delay).
XkbAXN_SKRelease An accepted SlowKeys key was released.
XkbAXN_SKReject A key was rejected (released before the SlowKeys delay expired).
XkbAXN_BKAccept A key was accepted by BounceKeys.
XkbAXN_BKReject A key was rejected (pressed before the BounceKeys delay expired).
XkbAXN_AXKWarning AccessXKeys is about to turn on/off StickyKeys or BounceKeys.

The keycode field reports the keycode of the key for which the event occurred. If the action is related to SlowKeys, the slowKeysDelay field contains the current SlowKeys acceptance delay. If the action is related to BounceKeys, the debounceDelay field contains the current BounceKeys debounce delay.

Selecting for AccessX Events

To receive XkbAccessXNotify events under all possible conditions, use XkbSelectEvents and pass XkbAccesXNotifyMask in both bits_to_change and values_for_bits.

To receive XkbStateNotify events only under certain conditions, use XkbSelectEventDetails using XkbAccessXNotify as the event_type and specifying the desired state changes in bits_to_change and values_for_bits using mask bits from Table 2.

Table 2 AccessXNotify Event Details

XkbAccessXNotify Event DetailsValueCircumstances

XkbAXN_SKPressMask(1<<0) Slow key press notification wanted
XkbAXN_SKAcceptMask(1<<1) Slow key accept notification wanted
XkbAXN_SKRejectMask(1<<2) Slow key reject notification wanted
XkbAXN_SKReleaseMask(1<<3) Slow key release notification wanted
XkbAXN_BKAcceptMask(1<<4) Bounce key accept notification wanted
XkbAXN_BKRejectMask(1<<5) Bounce key reject notification wanted
XkbAXN_AXKWarningMask(1<<6) AccessX warning notification wanted
XkbAllAccessXEventsMask(0x7f) All AccessX features notifications wanted

Some users may accidentally "bounce" on a key when they release it. They press it once, then accidentally press it again after they release it. The BounceKeys control temporarily disables a key after it has been pressed, effectively "debouncing" the keyboard. The period of time the key is disabled after it is released is known as the BounceKeys delay. BounceKeys is a boolean control.

When the BounceKeys control is active, the server reports acceptance or rejection of any key to interested clients by sending an appropriate AccessXNotify event.

XkbSetBounceKeysDelay sends a request to configure the BounceKeys control to the server. It does not wait for a reply and normally returns True. Specifying a value of zero for the delay parameter causes XkbSetBounceKeysDelay to generate a BadValue protocol error. If a compatible version of the Xkb extension is not available in the server, XkbSetBounceKeysDelay returns False.


The XkbSetBounceKeysDelay function returns True when it sends a request to configure the BounceKeys control to the server.
The XkbSetBounceKeysDelay function returns False if a compatible version of the Xkb extension is not available in the server.


The structure for the XkbAccessXNotify event type is 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;       /* XkbAccessXNotify */
    int            device;         /* Xkb device ID, will not be XkbUseCoreKbd 
    int            detail;         /* XkbAXN_* */
    KeyCode        keycode;        /* key of event */
    int            slowKeysDelay;  /* current SlowKeys delay */
    int            debounceDelay;  /* current debounce delay */
} XkbAccessXNotifyEvent;


An argument is out of range