Values that depend on other values

Many forms work things out as the person types: a plan's total from the seats, a schedule's next runs from its rule, a run's cost and time from its inputs. Each number on the screen should be the one that follows from the inputs now, and a person using a screen reader should hear the result without hearing every step on the way.

Each changed number or word is a value moment keyed on its value: it changes in place, at once, and the motion only shows that it changed. A control that is swapped for another is a reveal. A list that is rebuilt (the next runs) is arrive for what is new and pop out for what went. Nothing moves for a value the person didn't change, such as a run that passes with time or the figures drawn with the page, and a burst of key presses moves things once, not per key.

Screen readers hear the result once, politely, after the person stops changing the input (Candor's items wait 600 ms), from a live region that was there before: useAnnouncer gives you one.