ZDM Zero Default Mode
Whether a parameter of 0 means zero or the default.
CSI 22 h/l
Mode 22 decides what a parameter of 0 means. Reset, it means the number zero; set, it means the default, so CSI 0 C moves one column like CSI C. The first edition of ECMA-48 treated 0 as the default, and the mode was kept for implementations of it; the fifth edition deprecates it and moved it to an annex.
| State | ECMA-48 calls it | Meaning |
|---|---|---|
Reset, CSI 22 l | ZERO | 0 is the number zero |
Set, CSI 22 h | DEFAULT | 0 is the default value |
Terminals behave as if the mode were set. In xterm and libghostty-vt a 0 given to a count, as in CUF or ICH, means one, the same as leaving it out, whatever the mode says.
Neither xterm nor libghostty-vt implements it. Both ignore CSI 22 h and CSI 22 l, and both answer DECRQM with 0, not recognized: the mode is not among the ones xterm’s do_ansi_rqm answers for.
Support
| Terminal | Version | Support | Notes |
|---|---|---|---|
| VT220 | manual, 2nd ed., 1984 | No | not in the manual, whose table of ANSI modes has only KAM, IRM, SRM and LNM |
| VT510 | manual, 1st ed., 1993 | No | not in the manual |
| xterm | patch 412, xterm-411a | No | ignored; DECRQM answers 0 |
| libghostty-vt | 0f171f6 | No | ignored; DECRQM answers 0 |
| ConEmu | build 230724, its documentation | No | not in its ANSI escape codes |
Validation
ZDM-1: Not recognized
\e[22$p
|_____|
reply \e[22;0$y
ZDM-2: Not recognized after it is set, either
\e[22h
\e[22$p
|_____|
reply \e[22;0$y
ZDM-3: A zero is still the default
\e[22l # zero means zero: ignored
A
\e[0C # moves one column
B
|A_B__|
cursor 1,4