We thus
added a property ???Blinking??? to State, making it a list where the user could choose
from Hours, Minutes, or Seconds. This also ?¬?tted well with choosing a Display
Function in each state: the actual display thread would need to know both the
function and any blinking time unit to be able to keep the display updated. Having
the blinking property in the Display Function itself would not have helped, as it would
mean having to create duplicate Display Functions differing only in which time unit
was blinking.
Display Functions were also the source of the third addition to the modeling
language. We realized that the mapping of the different time units of a time value to
actual digit pairs on the watch display could be different in different physical watches,
and also different between two watch applications in the same physical watch. For
instance, in a lady??™s watch there are often only two digit pairs. In the normal time
display these are used for hours and minutes, but in a Stopwatch and possibly in a
Countdown Timer, they should show minutes and seconds. However, editing a
Countdown Timer generally only allows choosing hour and minute values, so while
editing those should clearly be shown. Specifying a hard mapping in a watch
application from time units to digit pairs would not work though, since it would mean
the application would not work so well in a different watch model with a different
number of digit pairs.
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