Contains the list of active dates.
Only the dates in this list will be activated.
In week/month granularity each entry activates the whole unit
containing it.
Number of tiles rendered from startDate, where each tile is one
granularity unit — days by default (the historical meaning), weeks
or months otherwise.
The calendar unit each tile represents: one day (the default), one
week, or one month. Tapping a week/month tile selects and emits the
unit's start date. In week/month granularity the first tile is the
unit CONTAINING startDate, so it may begin before startDate, and
daysCount counts tiles (weeks/months), not days.
Gregorian calendar only.
Contains the list of inactive dates.
All the dates defined in this List will be deactivated.
In week/month granularity each entry deactivates the whole unit
containing it.
Called with the whole selection after every tap, in every mode.
In SelectionMode.range it fires with one date after the first tap
(the pending start) and two after the second ([start, end]).
Seeds the selection, and adopts the list again whenever its contents
change between builds (pass the value received in onSelectionChange
back in to drive the picker as a controlled component). null means
the picker owns its selection; pass [] to clear it.
In SelectionMode.range it holds [start] or [start, end].
When true, the timeline also shows past dates: half of daysCount
units falls before the unit containing startDate, which is treated
as the anchor ("today").
The picker opens with the selected date (or the anchor) in the center
of the viewport, and all DatePickerController methods scroll dates
to the center instead of the leading edge.
