/* Move iterator IT backward by a specified y-distance DY, DY >= 0.
- If DY > 0, move IT backward at least that many pixels. DY = 0
- means move IT backward to the preceding line start or BEGV. This
- function may move over more than DY pixels if IT->current_y - DY
- ends up in the middle of a line; in this case IT->current_y will be
- set to the top of the line moved to. */
+ If DY > 0, move IT backward that many pixels.
+ DY = 0 means move IT backward to the preceding line start or to BEGV.
+ This function may move over less or more than DY pixels if
+ IT->current_y - DY ends up in the middle of a line; in this case
+ IT->current_y will be set to the top of the line either before or
+ after the exact pixel coordinate. */
void
move_it_vertically_backward (struct it *it, int dy)