GUI Design

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GUI Design
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HMI design

• There are entire college courses taught on HMI
  (Human-Machine Interface) design
• This is just a very brief presentation on some of
  the points that I consider most essential
• The goal is (usually) to make the design
• Intuitive It behaves as the user expects
• Simple Not cluttered
• Complete It lets the user do everything that the
  program is capable of doing
• From CIT591, day one A program is elegant if it
  combines power with simplicity

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Different needs

• Someone who uses the program only occasionally
  wants to be able to figure out how to use it
• Simple controls
• Clear, descriptive labels
• Help files
• Frequent users want to minimize effort
• Few button clicks, little typing
• No long sentences that must be read
• You should know what audience you are designing
  for
• Compromises may be necessary, but with care you
  can design an interface that isnt too bad for
  either group

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Intuitive design

• An interface is intuitive if a new user grasps
  immediately how to use it
• It is impossible to make a very specialized task
  intuitive to someone who doesnt understand the
  underlying principles
• For example, 3D animation programs
• Very few programs are of this nature
• What is intuitive varies from person to person
• However, most computer users have some common
  expectations as to how common controls work

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Principle of Least Surprise

• The Principle of Least Surprise says that the GUI
  should do the least surprising ( most expected)
  thing
• Users have strong expectations about how GUI
  elements, such as Buttons, work
• Users also have strong expectations about how and
  when files are opened and saved, and a host of
  other things
• Anything that we take for granted in an
  interface should not be violated without very
  good reason

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Passive GUI elements

• When text is entered, it just sits there until
  the user does something moreentering text does
  not cause something to happen
• For example, there may be an OK button to use the
  text
• Exception Very simple forms with only a text
  field may respond to the Enter key (even if an OK
  button is present)
• Checkboxes (squares) and radio buttons (circles)
  accept information from the user but dont take
  any actions
• Selection lists (for example, to choose a
  language) accept information but dont themselves
  do anything with it
• Exception Lists that modify the view (such as
  the font or the alignment) may have an immediate,
  visible effect

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Active GUI elements

• The most common active GUI element is the Button
• When you click a button, you expect something to
  happen
• Buttons that only make settings for future use
  should not be Buttons
• Menu items may be either active or passive
• Menu items that are just settings should have a
  checkmark in front of them when turned on
• Menu items that change their labels (such as On
  or Off) are just confusing
• Does On mean the feature is on, or you have to
  click it to turn it on?
• Menu items that open a dialog box to get more
  information should end in an ellipsis (...), for
  example, Font...

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Feedback

• Everything the user does in a GUI should result
  in feedback as to whether it worked
• Example Checkboxes get checked, radio buttons
  get pushed, typing shows up in text areas, etc.
• Clicking a button should either show the results,
  display a message that the action occurred, start
  a progress bar going, or pop up a dialog box
  that says what went wrong
• Items that cannot be used at the moment should be
  made inactive (so that they are visibly grayed
  out)
• This also solves the problem of what to do if the
  user clicks on oneit cant happen
• Items that cannot be used at the moment should
  not be removed, which will cause the user to
  waste time looking for them

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Minimize effort

• One common measure of the effort required to do
  something is mouse clicks
• Example Compiling a program in BlueJ vs. Dr.
  Java
• For example, if the users action is successful,
  provide feedback, but dont pop up a dialog box
  with a message such as Your file has been saved.
  OK
• If the users action is not successful, make sure
  that the feedback is highly visible
• This is a good place to use a dialog box

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Simple design

• Windows that do everything are too cluttered to
  use easily
• For example, you should not put your preferences
  and your working elements in the same window
• One ambulance company used a single window for
  maintenance information, keeping track of which
  employees were on duty, and dispatching
  ambulances
• Separate concernspresent windows that give the
  user the right tools for what they are working on
  now

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Progressive disclosure

• Simple design does not mean less control
• The Principle of Progressive Disclosure says to
  hide complexity until it is needed
• For example, look at the Preferences... menu on
  almost any large program
• You dont see all the possible settings at once
• Settings are grouped according to what the user
  is probably trying to dochange the appearance,
  set security levels, etc.

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User testing

• Most important in GUI design, even for
  experienced designers, is user testing
• Have a classmate or friend try out your program
• Watch as they do it
• Do not tell them how to use it let them figure
  it out
• If your test user cannot figure something out,
  explain how to do it but make a note of the
  problem, and fix it
• Even a minimal amount of user testing can greatly
  improve the design

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The End