641: Mainline

Both subpanes and top panes are views. In Smalltalk Express, views are managed by a view manager.

A view manager serves as a command center, enabling information to flow from one subpane to another:

• Instance methods defined for the view manager respond to requests for action forwarded from top pane and subpane views in response to events.
• Instance methods defined for the view manager send messages to subpanes asking for action.