How the text should be aligned vertically.
Determines the alignment of the baseline within the available space of the input (typically a TextField). For example, TextAlignVertical.top will place the baseline such that the text, and any attached decoration like prefix and suffix, is as close to the top of the input as possible without overflowing. The heights of the prefix and suffix are similarly included for other alignment values. If the height is greater than the height available, then the prefix and suffix will be allowed to overflow first before the text scrolls.
final TextAlignVertical? textAlignVertical;