affinity property

If the offset has more than one visual location (e.g., occurs at a line break), which of the two locations is represented by this position.

For example, if the text 'AB' had a forced line break between the A and the B, then the downstream affinity at offset 1 represents the cursor being just after the A on the first line, while the upstream affinity at offset 1 represents the cursor being just before the B on the first line.