Whenever an indicator changes state, the server sends XkbIndicatorStateNotify events to all interested clients. Similarly, whenever an indicator's map changes, the server sends XkbIndicatorMapNotify events to all interested clients.
To receive XkbIndicatorStateNotify events, use XkbSelectEvents with both the bits_to_change and values_for_bits parameters containing XkbIndicatorStateNotifyMask. To receive XkbIndicatorMapNotify events, use XkbSelectEvents with XkbIndicatorMapNotifyMask.
To receive events for only specific indicators, use XkbSelectEventDetails. Set the event_type parameter to XkbIndicatorStateNotify or XkbIndicatorMapNotify, and set both the bits_to_change and values_for_bits detail parameters to a mask where each bit specifies one indicator, turning on those bits that specify the indicators for which you want to receive events.
Both types of indicator events use the same structure:
typedef struct _XkbIndicatorNotify {
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; /* specifies state or map notify */
int device; /* Xkb device ID, will not be XkbUseCoreKbd */
unsigned int changed; /* mask of indicators with new state or map */
unsigned int state; /* current state of all indicators */
} XkbIndicatorNotifyEvent;
xkb_type
is either XkbIndicatorStateNotify or XkbIndicatorMapNotify, depending on whether the event is
a kbIndicatorStateNotify event or kbIndicatorMapNotify event.
The changed parameter is a mask that is the bitwise inclusive OR of the indicators that have changed. If the event is of type XkbIndicatorMapNotify, changed reports the maps that changed. If the event is of type XkbIndicatorStateNotify, changed reports the indicators that have changed state. state is a mask that specifies the current state of all indicators, whether they have changed or not, for both XkbIndicatorStateNotify and IndicatorMapNotify events.
When your client application receives either a XkbIndicatorStateNotify event or XkbIndicatorMapNotify event, you can note the changes in a changes structure by calling XkbNoteIndicatorChanges.
XkbGetIndicatorChanges examines the changes parameter, pulls over the necessary information from the server, and copies the results into the xkb keyboard description. If any bits are set in the state_changes field of changes, XkbGetIndicatorChanges also places the state of those indicators in state. If the indicators field of xkb is NULL, XkbGetIndicatorChanges allocates and initializes it. To free the indicators field, use XkbFreeIndicators.