XtVaSetValues()XtVaSetValues()NameXtVaSetValues - set resource values for a widget, using varargs argu‐
ment style.
Synopsis
void XtVaSetValues(object, ..., NULL)
Widget object;
Inputs
object Specifies the object whose resources are to be modified; may
be of class Object or any subclass thereof.
..., NULL A NULL-terminated variable-length list of resource name/value
pairs to override any other resource specifications.
Availability
Release 4 and later.
DescriptionXtVaSetValues() sets the resources of object named in the variable-
length argument list to the values specified in the same list. It is
identical to XtSetValues() except that the args array of resource names
and values and the num_args argument of that function are replaced with
a NULL-terminated variable-length argument list.
The "Background" section below explains how to specify resource names
and values in a variable-length argument list. See XtSetValues() for
more information on setting widget resources.
Usage
Using variable-length argument lists is usually much more convenient
than passing an ArgList which must be declared and initialized. Note
that the varargs interface is less efficient than the ArgList inter‐
face, because each varargs function converts its argument list into an
ArgList and calls the corresponding ArgList function. Unless you are
setting or querying resources repeatedly, however, this overhead is not
generally significant.
Variable-length argument lists cannot be type-checked by the compiler,
and so using XtVaSetValues() and other varargs functions can be a
source of bugs. Be sure to end all of your argument lists with NULL,
and be sure that the type of each argument is as expected. If you
specify only a single name/value pair per line, it will be easy to
delete or comment out resources, and to insert new resources at an
acceptable place.
Example
You can use XtVaSetValues() as in the following example:
XtVaSetValues(w,
XtNlabel, "Enter a value:",
XtNjustify, XtJustifyRight,
XtVaTypedArg, XtNforeground, XtRString, "red", 4,
NULL);
Background
This function and the other XtVa functions have resource names and val‐
ues specified in a NULL-terminated variable-length argument list,
rather than an ArgList array. Generally, the argument list to these
functions will consist of resource names (of type String) followed by
resource values (these are of type XtArgVal, but because varargs lists
cannot be type-checked, you do not have to cast your values). There
are two special symbols which can be used in place of a resource name,
however. Each symbol modifies the interpretation of the following
arguments.
XtVaNestedList
If you specify a resource name of XtVaNestedList, the following argu‐
ment will be interpreted as an XtVarArgsList value, as returned by
XtVaCreateArgsList(). The resource names and values on this nested
list will be treated exactly as if they were specified at the current
point in the original list. Nested lists may contain other nested
lists, to any depth of nesting.
XtVaTypedArg
If you specify a resource name of XtVaTypedArg, then the following
four arguments will be interpreted specially as instructions to
invoke a resource converter and set a resource to the result of the
conversion. The first following argument is the name of the resource
to be set, and must be of type String. The second following argument
is also a String, the resource type of the following value. This
type, plus the type of the named resource identify the resource con‐
verter to be invoked. This argument is usually XtRString, or one of
the other XtR types predefined by the Intrinsics. The third follow‐
ing argument is the value to be converted. It is of the type speci‐
fied by the previous argument, usually a String. If the type is not
XtRString, then if the value fits in an XtArgVal, it is passed
directly in the argument list, otherwise a pointer to the value is
passed. Finally, the forth following argument is the size in bytes
of the type. If the type is XtRString, however, then type should be
the length of the string plus one, not sizeof(String).
The example above show a use of the XtVaTypedArg value. See XtVaCre‐
ateArgsList() for an example of XtVaNestedList.
See AlsoXtSetValues(1), XtVaCreateArgsList(1).
Xt - Resource Management XtVaSetValues()
