RI Reverse Index

The mirror image of a line feed: move the cursor up one line, keeping its column. If the cursor is on the top margin, the lines of the scrolling region move down by one instead: the bottom line leaves the region, and a blank line appears at the top.

This is how a full-screen program scrolls backwards, a line at a time, without redrawing what is already on the screen.

Validation

RI-1: Up one line

\e[3;2H
\eM
X

|_____|
|_X___|
|_____|

RI-2: Scrolls down at the top

A\r\nB\r\nC
\e[1;1H
\eM
X

|X____|
|A____|
|B____|

RI-3: Within a scrolling region

1\r\n2\r\n3\r\n4
\e[2;3r   # region is lines 2 and 3; homes the cursor
\e[2;1H
\eM
X

|1____|
|X____|
|2____|
|4____|