Constraint set_values() Constraint set_values()Name
Constraint set_values - Constraint class method called to handle
changes to constraint resources.
Synopsis
typedef Boolean (*XtSetValuesFunc)(Widget, Widget, Widget, ArgList,
Cardinal *);
Widget current;
Widget request;
Widget set;
ArgList args;
Cardinal *num-args;
Inputs
current Specifies a copy of the child widget (and that widget's con‐
straint record) made by XtSetValues() before any resources
are changed or any class methods are called.
request Specifies a copy of the child widget (and that widget's con‐
straint record) made by XtSetValues() after the constraint
and normal resources are changed as requested, but before any
class set_values() methods are called.
set Specifies the child widget with constraint and normal
resources set and as modified by any superclass methods that
have been called by XtSetValues().
args Specifies the argument list passed to XtSetValues().
num_args Specifies the number of arguments in the args.
Returns
True if the resource changes require the child widget to be redrawn;
False otherwise.
Description
The Constraint set_values() method is registered on the set_value field
of the Constraint class part structure. It is invoked when XtSetVal‐
ues() is called on a child of the constraint widget to do any process‐
ing necessary to handle resource changes in the child's constraint
record.
The arguments to the Constraint set_values() method are the same as
those passed to the child's Object, RectObj, or Core set_values()
method. The constraints field of each of the widget arguments points
to a copy of the child's constraints procedure made at the appropriate
point by XtSetValues(). The Constraint set_values() procedure must
perform the same sort of processing on this record as the normal
set_values() method performs on the widget instance record itself.
The Constraint set_values() method will deal primarily with the fields
of the constraint record, but may also modify widget instance fields as
necessary. If the constraint for the maximum height of a child is
changed to a value that is less than the current height of the child,
for example, the Constraint set_values() method may change the height
instance field of the child widget. If the parent needs to change the
geometry of the child, it needn't call XtConfigureWidget() directly; if
any child geometry fields are changed by this or other set_values()
methods, XtSetValues() will call XtMakeGeometryRequest(), which will
invoke the parent's geometry_manager() method, which can do any neces‐
sary processing.
As with the Object set_values() method, the Constraint set_values()
method should return True if the widget should be redrawn. Unless this
method actually modifies fields in the widget instance structure
itself, however, a redraw will never be useful because the child's
expose() method cannot take constraint fields into account.
The Constraint set_values() method should not assume that the child
widget is realized.
The args and num_args arguments were added in Release 4.
The Constraint set_values() method is chained in superclass-to-subclass
order, and cannot be inherited. If none of the resources in a class's
constraint record need special processing when their values are
changed, this method may be NULL.
See set_values(4) for information on the arguments to this function,
and a discussion of the typical tasks of a set_values() method. See
XtSetValues(1) for full details on the widget creation process.
Example
The following procedure is the Constraint set_values() method, lightly
edited, of the Xaw Paned widget class. Note that it obtains the con‐
straint records of the current and set arguments (which are named old
and new here) and compares their fields to determine what has changed.
Note also that "new" is a reserved word in C++, and your C code will be
more portable if you avoid using it as an argument name.
#define PaneInfo(w) ((Pane)(w)->core.constraints)
/* ARGSUSED */
static Boolean
PaneSetValues(old, request, new, args, num_args)
Widget old, request, new;
ArgList args;
Cardinal *num_args;
{
Pane old_pane = PaneInfo(old);
Pane new_pane = PaneInfo(new);
/* Check for new min and max. */
if (old_pane->min != new_pane->min old_pane->max != new_pane->max)
XawPanedSetMinMax(new, (int)new_pane->min, (int)new_pane->max);
/* Check for change in XtNshowGrip. */
if (old_pane->show_grip != new_pane->show_grip)
if (new_pane->show_grip == TRUE) {
CreateGrip(new);
if (XtIsRealized(XtParent(new))) {
if (XtIsManaged(new)) /* if paned is unrealized this will
happen automatically at realize time.*/
XtManageChild(PaneInfo(new)->grip); /* manage the grip. */
CommitNewLocations( (PanedWidget) XtParent(new) );
}
}
else if ( HasGrip(old) ) {
XtDestroyWidget( old_pane->grip );
new_pane->grip = NULL;
}
return(False);
}
See AlsoXtSetValues(1),
Constraint(3), Core(3),
set_values(4).
Xt - Intrinsics Methods Constraint set_values()
