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. 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 Chapter 10). 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. 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. 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 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. 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. 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 To ring the bell on an X input extension device or the default keyboard, use XkbDeviceBell. Bool XkbDeviceBell ( display, window, device_id, bell_class, bell_id, percent, name ) Display * display ; /* connection to the X server */ Window window ; /* window for which the bell is generated, or None */ unsigned int device_spec ; /* device ID, or XkbUseCoreKbd */ unsigned int bell_class ; /* X input extension bell class of the bell to be rung */ unsigned int bell_id ; /* X input extension bell ID of the bell to be rung */ int percent ; /* bell volume, from -100 to 100 inclusive */ Atom 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, window, percent, name ) Display * display ; /* connection to the X server */ Window window ; /* event window, or None*/ int percent ; /* relative volume, which can range from -100 to 100 inclusive */ Atom 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. 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, window, device_spec, bell_class, bell_id, percent, name ) Display * display ; /* connection to the X server */ Window window ; /* event window, or None*/ unsigned int device_spec ; /* device ID, or XkbUseCoreKbd */ unsigned int bell_class; /* input extension bell class for the event */ unsigned int bell_id ; /* input extension bell ID for the event */ int percent ; /* volume for the bell, which can range from -100 to 100 inclusive */ Atom 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, window, percent, name ) Display * display ; /* connection to the X server */ Window window ; /* the event window, or None */ int percent ; /* relative volume, which can range from -100 to 100 inclusive */ Atom 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. To ring the bell on any keyboard, overriding user preference settings for audible bells, use XkbForceDeviceBell. Bool XkbForceDeviceBell ( display, window, device_spec, bell_class, bell_id, percent ) Display * display ; /* connection to the X server */ Window window ; /* event window, or None */ unsigned int device_spec ; /* device ID, or XkbUseCoreKbd */ unsigned int bell_class ; /* input extension class of the bell to be rung */ unsigned int bell_id ; /* input extension ID of the bell to be rung */ int 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, percent) Display * display ; /* connection to the X server */ int 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. 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 XkbAllBellNotifyMask 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.