The range of text that is still being composed.
Composing regions are created by input methods (IMEs) to indicate the text within a certain range is provisional. For instance, the Android Gboard app's English keyboard puts the current word under the caret into a composing region to indicate the word is subject to autocorrect or prediction changes.
Composing regions can also be used for performing multistage input, which is typically used by IMEs designed for phonetic keyboard to enter ideographic symbols. As an example, many CJK keyboards require the user to enter a Latin alphabet sequence and then convert it to CJK characters. On iOS, the default software keyboards do not have a dedicated view to show the unfinished Latin sequence, so it's displayed directly in the text field, inside of a composing region.
The composing region should typically only be changed by the IME, or the user via interacting with the IME.
If the range represented by this property is TextRange.empty, then the text is not currently being composed.
final TextRange composing;