In environments where computers are shared, features such as SlowKeys present a problem: if SlowKeys is on, the keyboard can appear to be unresponsive because keys are not accepted until they are held for a certain period of time. To help solve this problem, Xkb provides an AccessXTimeout control to automatically change the enabled/disabled state of any boolean controls and to change the value of the AccessXKeys and AccessXFeedback control attributes if the keyboard is idle for a specified period of time.
When a timeout as specified by AccessXTimeout occurs and a control is consequently modified, Xkb generates an XkbControlsNotify event. For more information on XkbControlsNotify events.
timeout specifies the number of seconds the
keyboard must be idle before the controls are modified. ctrls_mask specifies
what controls are to be enabled or disabled, and ctrls_values specifies
whether those controls are to be enabled or disabled. The bit values correspond
to those for enabling and disabling boolean controls using XkbChangeEnabledControls.
The
opts_mask field specifies which attributes of the AccessXKeys and AccessXFeedback
controls are to be changed, and opts_values specifies the new values
for those options. The bit values correspond to those for the ax_options
field of an XkbDescRec.
XkbSetAccessXTimeout sends a request to configure the AccessXTimeout control to the server. It does not wait for a reply, and normally returns True. If a compatible version of the Xkb extension is not available in the server, XkbSetAccessXTimeout returns False.
The complete description of an Xkb keyboard is given by an XkbDescRec. The component structures in the XkbDescRec represent the major Xkb components.
typedef struct {
struct _XDisplay * display; /* connection to X server */
unsigned short flags; /* private to Xkb, do not modify */
unsigned short device_spec; /* device of interest */
KeyCode min_key_code; /* minimum keycode for device */
KeyCode max_key_code; /* maximum keycode for device */
XkbControlsPtr ctrls; /* controls */
XkbServerMapPtr server; /* server keymap */
XkbClientMapPtr map; /* client keymap */
XkbIndicatorPtr indicators; /* indicator map */
XkbNamesPtr names; /* names for all components */
XkbCompatMapPtr compat; /* compatibility map */
XkbGeometryPtr geom; /* physical geometry of keyboard */
} XkbDescRec, *XkbDescPtr;
The display field points to an X display structure. The flags field is
private to the library: modifying flags may yield unpredictable results.
The device_spec field specifies the device identifier of the keyboard
input device, or XkbUseCoreKeyboard, which specifies the core keyboard
device. The min_key_code and max_key_code fields specify the least and
greatest keycode that can be returned by the keyboard.
Each structure component has a corresponding mask bit that is used in function calls to indicate that the structure should be manipulated in some manner, such as allocating it or freeing it. These masks and their relationships to the fields in the XkbDescRec are shown in Table 1.
| Table 1 Mask Bits for XkbDescRec |
| Mask Bit XkbDescRec Field Value |
| XkbControlsMask ctrls (1L<<0) |
| XkbServerMapMask server (1L<<1) |
| XkbIClientMapMask map (1L<<2) |
| XkbIndicatorMapMask indicators (1L<<3) |
| XkbNamesMask names (1L<<4) |
| XkbCompatMapMask compat (1L<<5) |
| XkbGeometryMask geom (1L<<6) |
| XkbAllComponentsMask All Fields (0x7f) |
The structure for the XkbControlsNotify event is defined 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; /* XkbCompatMapNotify */
int device; /* Xkb device ID, will not be XkbUseCoreKbd
*/
unsigned int changed_ctrls; /* bits indicating which controls
data have changed*/
unsigned int enabled_ctrls; /* controls currently enabled in server
*/
unsigned int enabled_ctrl_changes; /* bits indicating enabled/disabled
controls */
int num_groups; /* current number of keyboard groups
*/
KeyCode keycode; /* != 0 => keycode of key causing change
*/
char event_type; /* Type of event causing change */
char req_major; /* major event code of event causing
change */
char req_minor; /* minor event code of event causing
change */
} XkbControlsNotifyEvent;