NAME
XtInsertEventTypeHandler, XtRemoveEventTypeHandler, XtRegisterExtensionSelector,
XtSetEventDispatcher, XtDispatchEventToWidget - extension event handling
SYNTAX
void
XtInsertEventTypeHandler(Widget widget, int event_type,
XtPointer select_data, XtEventHandler proc, XtPointer
client_data, XtListPosition position);
void
XtRemoveEventTypeHandler(Widget widget, int event_type,
XtPointer select_data, XtEventHandler proc, XtPointer
client_data);
void
XtRegisterExtensionSelector(Display* display, int
min_event_type, int max_event_type, XtExtensionSelectProc
proc, XtPointer client_data);
XtEventDispatchProc
XtSetEventDispatcher(Widget widget, int event_type,
XtEventDispatchProc proc);
Boolean
XtDispatchEventToWidget(Widget widget, XEvent* event);
ARGUMENTS
- widget
- Specifies the widget for this event handler. Must be of
class Core or any subclass thereof.
- event_type
- Specifies the event type.
- select_data
- Specifies data used to select or deselect events from the
server.
- proc
- Specifies the proc.
- client_data
- Specifies additional data to be passed to the event
handler.
- position
- Specifies when the event handler is to be called relative
to other previously registered handlers.
- display
- Specifies the display.
- min_event_type, max_event_type
- Specifies the range of event types for this extension.
- event
- Specifies a pointer to the event to be dispatched.
DESCRIPTION
The
XtInsertEventTypeHandler function registers a procedure with the
dispatch mechanism that is to be called when an event that matches the
specified
event_type is dispatched to the specified
widget.
If
event_type is one of the core X protocol events then
select_data must be a pointer to a value of type
EventMask,
indicating the event mask to be used to select for the desired event. This
event mask will be included in the value returned by
XtBuildEventMask.
If the widget is realized
XtInsertEventTypeHandler calls
XSelectInput if necessary. Specifying NULL for
select_data is
equivalent to specifying a pointer to an event mask containing 0. This is
similar to the
XtInsertRawEventHandler function.
If
event_type specifies an extension event type then the semantics of the
data pointed to by
select_data are defined by the extension selector
registered for the specified event type.
In either case the Intrinsics are not required to copy the data pointed to by
select_data, so the caller must ensure that it remains valid as long as
the event handler remains registered with this value of
select_data.
The
position argument allows the client to control the order of the
invocation of event handlers registered for the same event type. If the client
does not care about the order, it should normally specify
XtListTail,
which registers this event handler after any previously registered handlers
for this event type.
The
XtRemoveEventTypeHandler function unregisters an even handler
registered with
XtInsertEventTypeHandler for the specified event type.
The request is ignored if
client_data does not match the value given
with the handler was registered.
If
event_type specifies on of the core X protocol events,
select_data must be a pointer to a value of type
EventMask,
indicating the mask to be used to deselect for the appropriate event. If the
widget is realized,
XtRemoveEventTypeHandler calls
XSelectInput
if necessary. Specifying NULL for
select_data is equivalent to
specifying a pointer to an event mask containing 0. This is similar to the
XtRemoveRawEventHandler function.
If
event_type specifies an extension event type then the semantics of the
data pointed to by
select_data are defined by the extension selector
registered for the specified event type.
The
XtRegisterExtensionSelector function registers a procedure to arrange
for the delivery of extension events to widgets.
If
min_event_type and
max_event_type match the parameters to a
previous call to
XtRegisterExtensionSelector for the same display, the
proc and
client_data replace the previously registered values.
If the range specified by
min_event_type and
max_event_type
overlaps the range of the parameters to a previous call for the same display
in any other way, an error results.
The
XtSetEventDispatcher function registers the event dispatcher
procedure specified by
proc for events with the type
event_type.
The previously registered dispatcher (or the default dispatcher if there was
no previously registered dispatcher) is returned. If
proc is NULL, the
default procedure is restored for the specified type.
In the future, when
XtDispatchEvent is called with an event of
event_type, the specified
proc (or the default dispatcher) will
be invoked to determine a widget ot which to dispatch the event.
The
XtDispatchEventToWidget function scans the list of registered event
handlers for the specified widget and calls each handler that has been
registered for the specified event type, subject to the
continue_to_dispatch value returned by each handler. The Intrinsics
behave as if event handlers were registered at the head of the list for
Expose,
NoExpose,
GraphicsExpose, and
VisibilityNotify events to invoke the widget's expose procedure
according to the exposure compression rules and to update the widget's
visible field if
visible_interest is
True. These internal
event handlers never set
continue_to_dispatch to
False.
XtDispatchEventToWidget returns
True if any event handler was
called and
False otherwise.
SEE ALSO
XtGetKeyboardFocusWidget(3)
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface