Input Devices

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Input Devices
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Agenda

• Questions
• Revisions of syllabus
• feedback on pace of lectures homework
• Khai on Damage Management in Swing
• Khai on HW 2
• Traditional input devices
• Text-entry, valuator, locator
• Card et al. paper
• Modeling and analyzing input device space

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Input Agenda

• Similar to how we handled output
• Devices / Technology
• Input modeling or event handling
• Olsen, Ch. 4
• Input handling in Swing

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Traditional input devices

• keyboards
• Text entry
• Related to single-button devices
• Valuators
• Single value in some range
• Locators (or pointing devices)
• many different kinds
• mouse most familiar

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Keyboards

• How they work
• http//www.howstuffworks.com/keyboard.htm
• Issues
• Key layout (QWERTY, DVORAK, etc.)
• RSI
• 1-handed options
• Half-keyboard
• Twiddler (chorded)

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Buttons

• Work like a keyboard key, but not for text
• Function keys
• Hard (e.g., Xerox Star)
• Soft (e.g, NCR salvation)
• On a mouse

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Valuators

• Return a single value in range
• Potentiometer (variable resistor)
• similar to typical volume control
• bounded range, keeps residual position
• Shaft encoders
• sense incremental movements
• unbounded range
• no residual position remembered

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Locators (or pointing devices)

• Returns a location (2-D or 3-D)
• 2 (or 3) values in given ranges
• Usually denotes a screen position (cursor)
• Examples
• mice, track balls, joysticks, tablets, touch
  panels, etc.
• Types
• Absolute or relative
• Clutched or not

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Absolute Locators

• 1-1 mapping from device movement to input
• example pen tablet
• fast but less accurate (for same range of
  physical movement)
• doesnt scale past fixed distances

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Relative Locators

• Maps movement into rate of change of input
• example joystick or trackpoint
• more accurate
• not bounded
• Harder to develop motor skills

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The Mouse

• Invented by Douglas Engelbart et al. 1967
• How it works
• http//www.howstuffworks.com/mouse.htm
• Shaft encoders vs. fully optical mouse

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Is a mouse a relative or absolute locator?

• answer neither
• third major type clutched absolute
• within a range its absolute
• can disengage movement (pick it up) to extend
  beyond range
• picking up clutch mechanism

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Clutched absolute locators

• get one-to-one mapping when in range (easy to
  learn, fast, etc.)
• clutch gives some of benefits of a relative
  device (e.g., unbounded)

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Lots of other devices

• Any favorites?

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Some interesting ones

• Thumb Wheel
• DataGlove
• Motion detectors (and other sensors)
• Accelerometers
• Fingerprint readers
• RF tags (physical objects as tokens for
  data/action)
• Sub-gram resolution scales

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Modelling Input Device Space

• Card et al.
• Lets discuss.
• What is the model of input device?
• Why relevant?
• What modeling/analytic power?

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Fitts Law

• What is it?
• Why is it important for an input device?
• Where to find out more?