The main interface of this package is the {@link Tool
} interface.
It represents a graphical tool with which a user can select, move, manipulate or draw figures
on a drawing surface of the type {@link org.esa.beam.framework.ui.ImageDisplay
}.
The {@link Tool
} interface in conjunction with the
{@link org.esa.beam.framework.ui.ImageDisplay
} class implements the GoF 'State' pattern:
An image display can have a tool assigned to which it delegates all user inputs. The tool itself
can change at any time. Neew tools can be developed without changing the ImageDisplay
implementation.