UI controls fall in one of two basic categories: visual or non-visual.

  • Visual controls appear on the application's user interface and generally allow user interaction, display data, or both. Examples include buttons, combo boxes, and data grids.
  • Non-visual controls do not appear on the user interface at run time; instead, they support visual controls or provide other services such as logging. Non-visual controls typically hold data, formatting, or other information needed by one or more interactive controls. An example is the ProBindingSource, which serves as an intermediary between an actual ABL data source and the control, such as a grid, that displays the data.
Visual controls can be placed and manipulated on the Design Canvas. Non-visual controls appear in a separate area at the bottom of the Design Canvas; you can select them for the purpose of setting their properties, but since they have no visual characteristics, you cannot resize or format them.
Note: In the context of .NET development, non-visual controls are often referred to as components.