Provided by: libx11-doc_1.6.3-1ubuntu2.2_all 
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)