Provides a framework for connecting document regions with annotations and for displaying those annotations in combination with an `ITextViewer`. `ISourceViewer` combines annotation support and all text viewer add-ons.

## Package Specification

`ISourceViewer` defines the concept of a document based, editable viewer supporting visual annotations. `ISourceViewer` supports document-specific and viewer-specific annotations attached to the viewer's input document. An `ISourceViewer` uses an `IAnnotationModel` to manage annotations and to inform implementers of `IAnnotationModelListener` about changes in respect to annotations. An `IVerticalRuler` represents an `IAnnotationModel` access adapter for an SWT widget capapble of display annotations. This package also provides default implementations for all defined interfaces.