Cell
Handle given to a column's DataTableHeader.editorContent, for editors that are not plain text.
A custom editor renders whatever control it likes — a dropdown, a date picker, a lookup field — and calls commit or cancel when the user is done. It is composed in place of the cell's normal content and is expected to take keyboard focus itself.
Properties
The text the cell holds now, whatever began the edit. Differs from initialText only when the user typed over the cell.
Message from DataTableHeader.validateEdit rejecting the last attempted commit, or null when nothing has been rejected. Show it, and stay open.
The text the editor should start with: the cell's current value, or the character the user typed if the edit began by typing over the cell.