classNames is used to attribute containers and widgets to certain classes in order to ensure the necessary runtime behavior of this container or widget as a member of a certain class:

property set in lycia form designer

For the first Label (identifier=lb1), classNames=first_class:

For the second Label (identifier=lb2), classNames=second_class:

properties applied to the class in lycia theme designer

runtime behavior

At runtime, you can use ui methods to specify the application behavior:

LET widget_var = ui.<widget>.ForName("widget_id")

CALL widget_var.setClassNames(...)

DISPLAY widget_var.getClassNames()

4gl code sample	DEFINE lb_1, lb_2 ui.Label ... LET lb_1 = ui.Label.ForName("f1") LET lb_2 = ui.Label.ForName("f2") ... DISPLAY "With lb1, classNames=", lb_1.getClassNames() DISPLAY "With lb2, classNames=", lb_2.getClassNames() ... CALL lb_1.setClassNames("first_class") CALL lb_2.setClassNames("second_class")
runtime behavior
runtime behavior

The example above were taken from the example program.