SIMD Select Implicit Movement Direction

In ECMA-48, CSI Ps ^ chooses which way the active position moves after a character is written: 0 the same way as the character path, 1 the opposite way, for text that runs right to left. It belongs with the standard’s other functions for bidirectional text, listed on the rest of ECMA-48 page, which no terminal on this site implements.

xterm does something else with it. Its parser sends a final ^ to SD (VTPrsTbl.c), and the handler says it is there to “cater to ECMA-48’s typographical error” (CASE_SD). xterm’s control sequence documentation lists CSI Ps ^ as “Scroll down Ps lines”, and calls it a publication error in the 1991 edition of ECMA-48 that was corrected in 2003. The copy of the fifth edition this site links to already gives SD as CSI Pn 05/04, that is CSI Pn T, in §8.3.113, p. 59 and puts SIMD at 05/14 in its table of final bytes (Table 3, p. 11), so the error was presumably in another printing.

Either way, a default xterm scrolls: CSI Ps ^ moves the scrolling region down Ps lines exactly as CSI Ps T does, with 0 taken as 1, and the parameter’s ECMA-48 meaning plays no part. The cases follow xterm. libghostty-vt has no case for ^ in its CSI dispatch and ignores the sequence, so they are marked as known differences.

Validation

SIMD-1: xterm scrolls down one line

ABC\r\n
DEF\r\n
GHI
\e[^

|____|
|ABC_|
|DEF_|
cursor 3,4

SIMD-2: The ECMA-48 parameter is a count

ABC\r\n
DEF\r\n
GHI
\e[1^     # ECMA-48: the opposite direction

|____|
|ABC_|
|DEF_|
cursor 3,4

SIMD-3: Two lines

ABC\r\n
DEF\r\n
GHI
\e[2^

|____|
|____|
|ABC_|
cursor 3,4

SIMD-4: Within the scrolling region

ABC\r\n
DEF\r\n
GHI\r\n
JKL
\e[2;3r
\e[^

|ABC_|
|____|
|DEF_|
|JKL_|
cursor 1,1