# Bells

The core X protocol allows only applications to explicitly sound the system bell with a given duration, pitch, and volume. Xkb extends this capability by allowing clients to attach symbolic names to bells, disable audible bells, and receive an event whenever the keyboard bell is rung. For the purposes of this document, the audible bell is defined to be the system bell, or the default keyboard bell, as opposed to any other audible sound generated elsewhere in the system.

audible bell
bell audible

You can ask to receive XkbBellNotify events (see section 9.4) when any client rings any one of the following:

- The default bell

- Any bell on an input device that can be specified by a bell_class and bell_id pair

- Any bell specified only by an arbitrary name. (This is, from the server’s point of view, merely a name, and not connected with any physical sound-generating device. Some client application must generate the sound, or visual feedback, if any, that is associated with the name.)

You can also ask to receive XkbBellNotify events when the server rings the default bell or if any client has requested events only (without the bell sounding) for any of the bell types previously listed.

You can disable audible bells on a global basis (to set the AudibleBell control, see ). For example, a client that replaces the keyboard bell with some other audible cue might want to turn off the AudibleBell control to prevent the server from also generating a sound and avoid cacophony. If you disable audible bells and request to receive XkbBellNotify events, you can generate feedback different from the default bell.

You can, however, override the AudibleBell control by calling one of the functions that force the ringing of a bell in spite of the setting of the AudibleBell control — `XkbForceDeviceBell` or `XkbForceBell` (see section 9.3.3). In this case the server does not generate a bell event.

Just as some keyboards can produce keyclicks to indicate when a key is pressed or repeating, Xkb can provide feedback for the controls by using special beep codes. The AccessXFeedback control is used to configure the specific types of operations that generate feedback. See section 10.6.3 for a discussion on AccessXFeedback control.

This chapter describes bell names, the functions used to generate named bells, and the events the server generates for bells.

## Bell Names

You can associate a name to an act of ringing a bell by converting the name to an Atom and then using this name when you call the functions listed in this chapter. If an event is generated as a result, the name is then passed to all other clients interested in receiving XkbBellNotify events. Note that these are arbitrary names and that there is no binding to any sounds. Any sounds or other effects (such as visual bells on the screen) must be generated by a client application upon receipt of the bell event containing the name. There is no default name for the default keyboard bell. The server does generate some predefined bells for the AccessX controls (see section 10.6.3). These named bells are shown in Table 9.1; the name is included in any bell event sent to clients that have requested to receive XkbBellNotify events.

Predefined Bells

Action | Named Bell
--- | ---
Indicator turned on | AX_IndicatorOn
Indicator turned off | AX_IndicatorOff
More than one indicator changed state | AX_IndicatorChange
Control turned on | AX_FeatureOn
Control turned off | AX_FeatureOff
More than one control changed state | AX_FeatureChange
SlowKeys and BounceKeys about to be turned on or off | AX_SlowKeysWarning
SlowKeys key pressed | AX_SlowKeyPress
SlowKeys key accepted | AX_SlowKeyAccept
SlowKeys key rejected | AX_SlowKeyReject
Accepted SlowKeys key released | AX_SlowKeyRelease
BounceKeys key rejected | AX_BounceKeyReject
StickyKeys key latched | AX_StickyLatch
StickyKeys key locked | AX_StickyLock
StickyKeys key unlocked | AX_StickyUnlock

## Audible Bells

Using Xkb you can generate bell events that do not necessarily ring the system bell. This is useful if you need to use an audio server instead of the system beep. For example, when an audio client starts, it could disable the audible bell (the system bell) and then listen for XkbBellNotify events (see section 9.4). When it receives a XkbBellNotify event, the audio client could then send a request to an audio server to play a sound.

You can control the audible bells feature by passing the XkbAudibleBellMask to `XkbChangeEnabledControls` (see section 10.1.1). If you set XkbAudibleBellMask on, the server rings the system bell when a bell event occurs. This is the default. If you set XkbAudibleBellMask off and a bell event occurs, the server does not ring the system bell unless you call `XkbForceDeviceBell` or `XkbForceBell` (see section 9.3.3).

Audible bells are also part of the per-client auto-reset controls. For more information on auto-reset controls, see section 10.1.2.

## Bell Functions

Use the functions described in this section to ring bells and to generate bell events.

The input extension has two types of feedbacks that can generate bells — bell feedback and keyboard feedback. Some of the functions in this section have bell_class and bell_id parameters; set them as follows: Set bell_class to BellFeedbackClass or KbdFeedbackClass. A device can have more than one feedback of each type; set bell_id to the particular bell feedback of bell_class type.

Table 9.2 shows the conditions that cause a bell to sound or an XkbBellNotifyEvent to be generated when a bell function is called.

Bell Sounding and Bell Event Generating

Function called | AudibleBell | Server sounds a bell | Server sends an XkbBellNotifyEvent
--- | --- | --- | ---
XkbDeviceBell | On | Yes | Yes
XkbDeviceBell | Off | No | Yes
XkbBell | On | Yes | Yes
XkbBell | Off | No | Yes
XkbDeviceBellEvent | On or Off | No | Yes
XkbBellEvent | On or Off | No | Yes
XkbDeviceForceBell | On or Off | Yes | No
XkbForceBell | On or Off | Yes | No

### Generating Named Bells

To ring the bell on an X input extension device or the default keyboard, use `XkbDeviceBell`.

Bool `XkbDeviceBell` Display *display Window window unsigned int device_spec unsigned int bell_class unsigned int bell_id int percent Atom name

display

  connection to the X server

window

  window for which the bell is generated, or None

device_spec

  device ID, or XkbUseCoreKbd

bell_class

  X input extension bell class of the bell to be rung

bell_id

  X input extension bell ID of the bell to be rung

percent

  bell volume, from −100 to 100 inclusive

name

  a name for the bell, or NULL

Set percent to be the volume relative to the base volume for the keyboard as described for `XBell`.

Note that bell_class and bell_id indicate the bell to physically ring. name is simply an arbitrary moniker for the client application’s use.

To determine the current feedback settings of an extension input device, use `XGetFeedbackControl`. See the X input extension documentation for more information on `XGetFeedbackControl` and related data structures.

If a compatible keyboard extension is not present in the X server, `XkbDeviceBell` immediately returns False. Otherwise, `XkbDeviceBell` rings the bell as specified for the display and keyboard device and returns True. If you have disabled the audible bell, the server does not ring the system bell, although it does generate a XkbBellNotify event.

You can call `XkbDeviceBell` without first initializing the keyboard extension.

As a convenience function, Xkb provides a function to ring the bell on the default keyboard: `XkbBell`.

Bool `XkbBell` Display *display Window window int percent Atom name

display

  connection to the X server

window

  event window, or None

percent

  relative volume, which can range from −100 to 100 inclusive

name

  a bell name, or NULL

If a compatible keyboard extension isn’t present in the X server, `XkbBell` calls `XBell` with the specified display and percent, and returns False. Otherwise, `XkbBell` calls `XkbDeviceBell` with the specified display, window, percent, and name, a device_spec of XkbUseCoreKbd, a bell_class of XkbDfltXIClass, and a bell_id of XkbDfltXIId, and returns True.

If you have disabled the audible bell, the server does not ring the system bell, although it does generate a XkbBellNotify event.

You can call `XkbBell` without first initializing the keyboard extension.

XkbDeviceBell
XkbBell

### Generating Named Bell Events

Using Xkb, you can also generate a named bell event that does not ring any bell. This allows you to do things such as generate events when your application starts.

For example, if an audio client listens for these types of bells, it can produce a whoosh sound when it receives a named bell event to indicate a client just started. In this manner, applications can generate start-up feedback and not worry about producing annoying beeps if an audio server is not running.

To cause a bell event for an X input extension device or for the keyboard, without ringing the corresponding bell, use `XkbDeviceBellEvent`.

Bool `XkbDeviceBellEvent` Display *display Window window unsigned int device_spec unsigned int bell_class unsigned int bell_id int percent Atom name

display

  connection to the X server

window

  event window, or None

device_spec

  device ID, or XkbUseCoreKbd

bell_class

  input extension bell class for the event

bell_id

  input extension bell ID for the event

percent

  volume for the bell, which can range from −100 to 100 inclusive

name

  a bell name, or NULL

If a compatible keyboard extension isn’t present in the X server, `XkbDeviceBellEvent` immediately returns False. Otherwise, `XkbDeviceBellEvent` causes an XkbBellNotify event to be sent to all interested clients and returns True. Set percent to be the volume relative to the base volume for the keyboard as described for `XBell`.

In addition, `XkbDeviceBellEvent` may generate Atom protocol errors as well as XkbBellNotify events. You can call `XkbBell` without first initializing the keyboard extension.

As a convenience function, Xkb provides a function to cause a bell event for the keyboard without ringing the bell: `XkbBellEvent`.

Bool `XkbBellEvent` Display *display Window window int percent Atom name

display

  connection to the X server

window

  the event window, or None

percent

  relative volume, which can range from −100 to 100 inclusive

name

  a bell name, or NULL

If a compatible keyboard extension isn’t present in the X server, `XkbBellEvent` immediately returns False. Otherwise, `XkbBellEvent` calls `XkbDeviceBellEvent` with the specified display, window, percent, and name, a device_spec of XkbUseCoreKbd, a bell_class of XkbDfltXIClass, and a bell_id of XkbDfltXIId, and returns what `XkbDeviceBellEvent` returns.

`XkbBellEvent` generates a XkbBellNotify event.

You can call `XkbBellEvent` without first initializing the keyboard extension.

XkbDeviceBellEvent
XkbBellEvent

### Forcing a Server-Generated Bell

To ring the bell on any keyboard, overriding user preference settings for audible bells, use `XkbForceDeviceBell`.

Bool `XkbForceDeviceBell` Display *display Window window unsigned int device_spec unsigned int bell_class unsigned int bell_id int percent

display

  connection to the X server

window

  event window, or None

device_spec

  device ID, or XkbUseCoreKbd

bell_class

  input extension class of the bell to be rung

bell_id

  input extension ID of the bell to be rung

percent

  relative volume, which can range from −100 to 100 inclusive

If a compatible keyboard extension isn’t present in the X server, `XkbForceDeviceBell` immediately returns False. Otherwise, `XkbForceDeviceBell` rings the bell as specified for the display and keyboard device and returns True. Set percent to be the volume relative to the base volume for the keyboard as described for `XBell`. There is no name parameter because `XkbForceDeviceBell` does not cause an XkbBellNotify event.

You can call `XkbBell` without first initializing the keyboard extension.

To ring the bell on the default keyboard, overriding user preference settings for audible bells, use `XkbForceBell`.

Bool `XkbForceBell` Display *display int percent

display

  connection to the X server

percent

  volume for the bell, which can range from −100 to 100 inclusive

If a compatible keyboard extension isn’t present in the X server, `XkbForceBell` calls `XBell` with the specified display and percent and returns False. Otherwise, `XkbForceBell` calls `XkbForceDeviceBell` with the specified display and percent, device_spec = XkbUseCoreKbd, bell_class = XkbDfltXIClass, bell_id = XkbDfltXIId, window = None, and name = NULL, and returns what `XkbForceDeviceBell` returns.

`XkbForceBell` does not cause an XkbBellNotify event.

You can call `XkbBell` without first initializing the keyboard extension.

XkbForceDeviceBell
XkbForceBell

## Detecting Bells

Xkb generates XkbBellNotify events for all bells except for those resulting from calls to `XkbForceDeviceBell` and `XkbForceBell`. To receive XkbBellNotify events under all possible conditions, pass XkbBellNotifyMask in both the bits_to_change and values_for_bits parameters to `XkbSelectEvents` (see section 4.3).

The XkbBellNotify event has no event details. It is either selected or it is not. However, you can call `XkbSelectEventDetails` using XkbBellNotify as the event_type and specifying XkbAllBellEventsMask in bits_to_change and values_for_bits. This has the same effect as a call to `XkbSelectEvents`.

The structure for the XkbBellNotify event type contains:

    typedef struct _XkbBellNotify {
        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;    /* XkbBellNotify */
        unsigned int    device;      /* Xkb device ID, will not be XkbUseCoreKbd */
        int             percent;     /* requested volume as % of max */
        int             pitch;       /* requested pitch in Hz */
        int             duration;    /* requested duration in microseconds */
        unsigned int    bell_class;  /* X input extension feedback class */
        unsigned int    bell_id;     /* X input extension feedback ID */
        Atom            name;        /* "name" of requested bell */
        Window          window;      /* window associated with event */
        Bool            event_only;  /* False → the server did not produce a beep */
    } XkbBellNotifyEvent;

If your application needs to generate visual bell feedback on the screen when it receives a bell event, use the window ID in the XkbBellNotifyEvent, if present.

bell