The common fields for all object classes are defined in the ObjectClassPart structure. The class record initialization must fill all objn fields with NULL or zero as appropriate to the type. ObjectPartStructure The common fields for all object instances are defined in the ObjectPart structure. All fields have the same meaning as the corresponding fields in CorePart . The prototypical type Object is defined with only this set of fields.
Various routines can cast object pointers, as needed, to specific object types.
All fields in ObjectPart have the same default values as the corresponding fields in CorePart . The Object class exists to enable programmers to use the Intrinsics' classing and resource-handling mechanisms for things smaller and simpler than widgets. Composite widget classes that wish to accept nonwidget children must set the accepts objects field in the CompositeClassExtension structure to True . XtCreateWidget will otherwise generate an error message on an attempt to create a nonwidget child. Of the classes defined by the Intrinsics, ApplicationShell and SessionShell accept nonwidget children, and the class of any nonwidget child must not be rectObjClass or any subclass.