think-cell technical report TC2003/01 A GUI-based Interaction ...

4.2 Interaction Toolbox INTERACTION CONCEPT
of different needs is served, but also the need to switch frequently between mouse
and keyboard is reduced. This is especially important for optimal performance of
expert users because the frequent relocation of the hands from mouse to keyboard
and back requires additional attention.
Modifier Keys. Usual modifier keys are shift, ctrl and alt. When held down
while another key is pressed, the modifier keys modify the function of that other
key. Modifier keys are used with alphanumeric keys and function keys as well as
sometimes with mouse interaction. Although it often appears convenient to assign
multiple – usually similar – functions to the same key with different modifier keys,
the multiplicity of key combinations usually does not allow single handed input and
also may confuse users.
Shortcut Keys. There is a number of common shortcut keys – actually, key
combinations – that should be supported by all Microsoft Windows applications
(refer to [Micb] for a complete list). In particular, those common shortcut keys
should not take on other functions than the standardized ones. This idea supports
the principles of consistency, familiarity and predictability and thus enhances the
learnability of the system.
Function Keys. To the function keys f1 through f12, similar considerations
apply as to shortcut keys. Moreover, while shortcut keys usually have at least one
character as a reminder of their function – e. g., ctrl-c for copy – the assignment
of features to function keys appears entirely arbitrary and is therefore especially
hard to learn. In addition, function keys are usually located along the upper brim
of the keyboard and often are especially small on laptop computers, meaning that
additional effort and attention is required to reach them. For these reasons, the use
of function keys for application specific features is generally discouraged, although
the default functions that are suggested by [Micb] should be implemented.
4.2.3 Mouse-based Interaction
The mouse is a standard input device for personal computers just as much as the
keyboard. While the keyboard is ideal for discrete input, the mouse is convenient
to interact with a (pseudo) continuum in 2-dimensional space. The most commonly
used mouse interaction patterns are point-and-click and drag-and-drop. The mouse-
over pattern, that occurs when the mouse is moved and then rests with no buttons
pressed, is often used to support learnability: An on-screen control at the current
mouse pointer position highlights and sometimes a short explanation of the control’s
function is given by a tooltip.
In Microsoft Windows, there are always at least two mouse buttons that can
be used in the user interface. Some mice have additional buttons and a wheel,
that can be used to provide shortcuts to frequently used functions. However, it
must remain possible to access an application’s full functionality with only two
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