The Model-View-Controller Architecture

• Model
  • Represents the state of the component
  • Data is independant of the component's visual representation
• View
  • How the component is represented on the screen (LnFs)
• Controller
  • Describes how the component interacts with the user

The scrollbar uses the information in the model to determine how far into the scrollbar to render the thumb and how winde the thumb should be. Note that it only contains information about the minimum and maximum, not the current position.