XkbForceBell(3)
NAME
XkbForceBell - Overrides user preference settings for audible bells to ring the bell on the default keyboard
SYNOPSIS
Bool XkbForceBell (Display *display, int percent);
ARGUMENTS
- display
connection to the X server
- percent
volume for the bell, which can range from -100 to 100 inclusive
DESCRIPTION
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 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. 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. 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.
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. These named bells are shown
in the Table 1; the name is included in any bell event sent to clients
that have requested to receive XkbBellNotify events.
Table 1 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 AX_SlowKeysWarning
turned on or off
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. 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. 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.
Audible bells are also part of the per-client auto-reset controls.
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 2 shows the conditions that cause a bell to sound or an
XkbBellNotifyEvent to be generated when a bell function is called.
Table 2 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
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.
RETURNS VALUES
False The XkbForceBell function returns False when a
compatible keyboard extension isn't present in the X
server.
STRUCTURES
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.
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.
SEE ALSO
XBell(3), XkbBell(3), XkbChangeEnabledControls(3), XkbForceDeviceBell(3), XkbSelectEventDetails(3), XkbSelectEvents(3)
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