cs349 - s10 - Lecture 10

CS349 - Implementing User Interfaces - Spring 2010

Public Service Annoucements

All of the following are problematic

Controllability
- Can you get there from here?
Observability
- Is information available allowing the user to find out how to get there from here?
Freedom from modes
- User can do anything anywhere
Freedom from state chains
Undo capability
Consistency
- enables learning transfer
- consistency of appearance
- consistency of action
- positive & negative consistency
  - Similar things look similar
  - Different things look different
- Classic `not the way I think' blunders

A collection of components that are assembled into an interface.

Apple, for example, controlled the look-and-feel of third party applications by providing a UI toolkit.

Strongly encouraged developers to use it
Lots of other things along the same line
- books
- sample code
- Macintosh University

Important properties of a UI toolkit

Containers
- hold other components, including other containers
  - containers form a tree with non-containers at the leaves
- usually have a layout policy
Canvases
- hold uneditable pictures and text
Selectors
- choose one of many
- selection aspect
- `now' aspect
Changers
- change a value
Text editors
- enter & edit text
- shows very clearly the importance of reuse
  - and the difficulty of innovation
  - "include the previous interface" has all sorts of problems (Exercise for the reader. List six. Yes, `all sorts' is really right. Think concretely.)

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