XtAddGrab(3Xt) XT FUNCTIONS XtAddGrab(3Xt)NAME
XtAddGrab, XtRemoveGrab - redirect user input to a modal
widget
SYNTAX
void XtAddGrab(w, exclusive, spring_loaded)
Widget w;
Boolean exclusive;
Boolean spring_loaded;
void XtRemoveGrab(w)
Widget w;
ARGUMENTS
exclusive Specifies whether user events should be dis-
patched exclusively to this widget or also to
previous widgets in the cascade.
spring_loaded
Specifies whether this widget was popped up
because the user pressed a pointer button.
w Specifies the widget to add to or remove from
the modal cascade.
DESCRIPTION
The XtAddGrab function appends the widget (and associated
parameters) to the modal cascade and checks that exclusive
is True if spring_loaded is True. If these are not True,
XtAddGrab generates an error.
The modal cascade is used by XtDispatchEvent when it tries
to dispatch a user event. When at least one modal widget
is in the widget cascade, XtDispatchEvent first determines
if the event should be delivered. It starts at the most
recent cascade entry and follows the cascade up to and
including the most recent cascade entry added with the
exclusive parameter True.
This subset of the modal cascade along with all descen-
dants of these widgets comprise the active subset. User
events that occur outside the widgets in this subset are
ignored or remapped. Modal menus with submenus generally
add a submenu widget to the cascade with exclusive False.
Modal dialog boxes that need to restrict user input to the
most deeply nested dialog box add a subdialog widget to
the cascade with exclusive True. User events that occur
within the active subset are delivered to the appropriate
widget, which is usually a child or further descendant of
the modal widget.
Regardless of where on the screen they occur, remap events
are always delivered to the most recent widget in the
active subset of the cascade that has spring_loaded True,
X Version 11 Release 6.4 1
XtAddGrab(3Xt) XT FUNCTIONS XtAddGrab(3Xt)
if any such widget exists.
The XtRemoveGrab function removes widgets from the modal
cascade starting at the most recent widget up to and
including the specified widget. It issues an error if the
specified widget is not on the modal cascade.
SEE ALSO
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface
X Version 11 Release 6.4 2