Keyboard Support in Microsoft Windows

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Keyboard Support in Microsoft Windows

• John Murphy

Windows International Microsoft (European
Development Centre, Dublin)
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What is a Keyboard Layout?

• A collection of data for each keystroke and shift
  state combination within a particular keyboard
  driver
• In other words, it is not the keyboard hardware
  but the software that connects the hardware to
  the system

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Anatomy of a keystroke

• User presses a key
• Key contains a scan code
• Keyboard layout driver maps the scan code to a
  virtual key (VK)
• OS sends the VK to the application
• If asked, the driver maps the VK/shift state to
  characters (if they are assigned)

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The User perspective

• User requirements are obviously critical
  considerations
• User expectations are fundamental to
  successful adoption
• When I press AltGr and K I always get k
• Some potential user considerations\challenges
• Backwards compatibility is always preferable
• Users in different countries are pre-conditioned
  to different keyboard layouts
• Commonly used characters should always be most
  easily accessible

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The Application perspective

• Applications can prevent a keystroke ever
  becoming a character
• All Virtual Keys are processed by the active
  application
• The application decides if it wants to query the
  keyboard layout for a character value
• This has always been the case and we are
  powerless to change this reality
• Consideration/Challenge
• Chance of encountering an application assigned
  function is directly proportional to the number
  of shift state character assignments

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Dead Keys in Windows

• Dead key A combination of keystrokes to insert
  a single character
• Windows architecture requires defined dead key
  pairs
• Each keystroke in a dead key pair must correspond
  to a single UTF-16 code point
• Chained dead key support to add double diacritics
  is limited and problematic
• Final output character cannot be bigger than a
  single UTF-16 code point

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Sample Approach

• UK-English keyboard layout supported needs of
  English, Scots-Gaelic and Irish
• Requirement to add language support to support
  Welsh version of Windows
• Also required by users throughout the UK to type
  Welsh names etc
• Used existing UK English keyboard layout and
  appended with required extensions

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Sample Approach contd

• Added tilde to also support Breton.
• Result Users who traditionally used the
  UK-English keyboard could seamlessly switch to UK
  Extended
• Everything worked as it did before, but now also
  able to type in
• Welsh, Irish, Scots Gaelic, Breton, Cornish ,
  French, Spanish, Italian, Estonian
• There are some risks!
• Reported usability issues with US International
  and Canadian National Standard keyboards
• For example Unexpected behaviour resulting in
  increased typing mistakes

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Microsoft Perspective

• New features added to our products are driven by
  customer demand.
• Often the official requirement is different from
  what customers actually want.
• Adding anything new to the in box Windows system
  is increasingly hard.
• The future of market-specific content will be
  downloads from the internet.

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MSKLCMicrosoft Keyboard Layout Creator

• Create new keyboard layouts from scratch
• Base a new layout on an existing one
• Modify an existing keyboard layout and build a
  new layout from it
• Package the resulting keyboard layouts for
  subsequent delivery and installation.
• Available from http//go.microsoft.com/fwlink/?Lin
  kId82315
• Does not support Chained dead key definition

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MSKLCMicrosoft Keyboard Layout Creator

• UK Extended default view

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MSKLCMicrosoft Keyboard Layout Creator

• UK Extended AltGr shift state view

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Summary

• Users expectations and existing usage are
  critical considerations
• Applications may interfere with expected output
  from overloaded Shift state character assignments
• Chained dead key combinations should be avoided
• Where possible build on what users are already
  using