[barrkel]

Form designers are editing a data structure. It's not just visual placement of controls; it's the settings on those controls: content, appearance, behaviour, event bindings. And not just controls, also components.

VB and Delphi have components, non-visual controls that live on design surfaces, where their properties can be edited. Things like database connections and table connectors, which can further be linked up with data aware controls. Whole simple form-based CRUD applications can be built without any code at all, merely by wiring together components.

The wiring is data.