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.