VT features

NOTE: WORK IN PROGRESS

Supported VT features by xterm.js

Version: 3.14.0

Table of Contents

• General notes
• C0
• C1
• CSI
• DCS
• ESC
• OSC

General notes

This document lists xterm.js' support of typical VT commands. The commands are grouped by their type:

• C0: single byte command (7bit control characters, byte range \x00 .. \x1f)
• C1: single byte command (8bit control characters, byte range \x80 .. \x9f)
• ESC: sequence starting with ESC (\x1b)
• CSI - Control Sequence Introducer: sequence starting with ESC [ (7bit) or CSI (\x9b 8bit)
• DCS - Device Control String: sequence starting with ESC P (7bit) or DCS (\x90 8bit)
• OSC - Operating System Command: sequence starting with ESC ] (7bit) or OSC (\x9d 8bit)

Application Program Command (APC), Privacy Message (PM) and Start of String (SOS) are not supported, any sequence of these types will be ignored.

Note that the list only contains commands implemented in xterm.js' core codebase. Missing commands are either not supported or unstable/experimental. Furthermore addons can provide additional commands.

To denote the sequences the lists use the same abbreviations as xterm does:

• Ps: A single (usually optional) numeric parameter, composed of one or more decimal digits.
• Pm: A multiple numeric parameter composed of any number of single numeric parameters, separated by ; character(s), e.g. Ps ; Ps ; ....
• Pt: A text parameter composed of printable characters. Note that for most commands with Pt only ASCII printables are specified to work. Additionally xterm.js will let any character >C1 pass as printable.

C0

Mnemonic	Name	Sequence	Short Description	Status
BEL	Bell	\a	Ring the bell. more	supported
BS	Backspace	\b	Move the cursor one position to the left.	supported
SO	Shift Out	\x0e	Switch to an alternative character set. more	partly
FF	Form Feed	\f	Treated as LF.	supported
SI	Shift In	\x0f	Return to regular character set after Shift Out.	supported
LF	Line Feed	\n	Move the cursor one row down, scrolling if needed.	supported
CR	Carriage Return	\r	Move the cursor to the beginning of the row.	supported
HT	Horizontal Tabulation	\t	Move the cursor to the next character tab stop.	supported
VT	Vertical Tabulation	\v	Treated as LF.	supported

Bell

The behavior of the bell is further customizable with ITerminalOptions.bellStyle and ITerminalOptions.bellSound.

Shift Out

TODO: document supported native character sets and support limitations ...

C1

Mnemonic	Name	Sequence	Short Description	Status
IND	Index	\x84	Move the cursor one line down scrolling if needed.	supported
NEL	Next Line	\x85	Move the cursor to the beginning of the next row.	supported
HTS	Horizontal Tabulation Set	\x88	Places a tab stop at the current cursor position.	supported

CSI

Mnemonic	Name	Sequence	Short Description	Status
ECH	Erase Character	CSI Ps X	Erase Ps characters from current cursor position to hte right (default=1).	supported
SL	Scroll Left	CSI Ps SP @	Scroll viewport Ps times to the left.	unsupported
HPA	Horizontal Position Absolute	CSI Ps `	Same as CHA.	supported
SCORC	Restore Cursor	CSI u	Restore cursor position, charmap and text attributes.	partly
CUU	Cursor Up	CSI Ps A	Move cursor Ps times up (default=1).	supported
CUD	Cursor Down	CSI Ps B	Move cursor Ps times down (default=1).	supported
CUF	Cursor Forward	CSI Ps C	Move cursor Ps times forward (default=1).	supported
CUB	Cursor Backward	CSI Ps D	Move cursor Ps times backward (default=1).	supported
CNL	Cursor Next Line	CSI Ps E	Move cursor Ps times down (default=1) and to the first column.	supported
CPL	Cursor Backward	CSI Ps F	Move cursor Ps times up (default=1) and to the first column.	supported
CHA	Cursor Horizontal Absolute	CSI Ps G	Move cursor to Ps-th column of the active row (default=1).	supported
CUP	Cursor Position	CSI Ps ; Ps H	Set cursor to position [Ps, Ps].	supported
CHT	Cursor Horizontal Tabulation	CSI Ps I	Move cursor Ps times tabs forward (default=1).	supported
ED	Erase In Display	CSI Ps J	Erase various parts of the viewport. more	supported
DECSED	Selective Erase In Display	CSI ? Ps J	Currently the same as ED.	partly
EL	Erase In Line	CSI Ps K	Erase various parts of the active row. more	supported
DECSEL	Selective Erase In Line	CSI ? Ps K	Currently the same as EL.	partly
IL	Insert Line	CSI Ps L	Insert Ps blank lines at active row (default=1).	supported
DL	Delete Line	CSI Ps M	Delete Ps lines at active row (default=1).	supported
DCH	Delete Character	CSI Ps P	Delete Ps characters in the active row (default=1).	supported
SU	Scroll Up	CSI Ps S	Scroll Ps lines up (default=1).	supported
SD	Scroll Down	CSI Ps T	Scroll Ps lines down (default=1).	supported
SR	Scroll Right	CSI Ps SP A	Scroll viewport Ps times to the right.	unsupported
SCOSC	Save Cursor	CSI s	Save cursor position, charmap and text attributes.	partly
HPR	Horizontal Position Relative	CSI Ps a	Same as CUF.	supported
REP	Repeat Preceding Character	CSI Ps b	Repeat preceding character Ps times (default=1). more	supported
DA1	Primary Device Attributes	CSI c	Send primary device attributes. more	supported
DA2	Secondary Device Attributes	CSI > c	Send primary device attributes. more	supported
VPA	Vertical Position Absolute	CSI Ps d	Move cursor to Ps-th row (default=1).	supported
VPR	Vertical Position Relative	CSI Ps e	Move cursor Ps times down (default=1).	supported
HVP	Horizontal and Vertical Position	CSI Ps ; Ps f	Same as CUP.	supported
TBC	Tab Clear	CSI Ps g	Clear tab stops at current position (0) or all (3) (default=0).	supported
SM	Set Mode	CSI Pm h	Set various terminal attributes. more	partly
DECSET	DEC Private Set Mode	CSI ? Pm h	Set various terminal attributes. more	partly
RM	Reset Mode	CSI Pm l	Set various terminal attributes. more	partly
DECRST	DEC Private Reset Mode	CSI ? Pm l	Reset various terminal attributes. more	partly
SGR	Select Graphic Rendition	CSI Pm m	Reset various text attributes. more	partly
DSR	Device Status Report	CSI Ps n	Request cursor position (CPR) with Ps = 6.	supported
DECDSR	DEC Device Status Report	CSI ? Ps n	Only CPR is supported (same as DSR).	partly
DECSTR	Soft Terminal Reset	CSI ! p	Reset several terminal attributes to initial state. more	supported
DECSCUSR	Set Cursor Style	CSI Ps SP q	Set cursor style. more	supported
DECSTBM	Set Top and Bottom Margin	CSI Ps ; Ps r	Set top and bottom margins of the viewport [top;bottom] (default = viewport size). more	supported
DECIC	Insert Columns	CSI Ps ' }	Insert Ps columns at cursor position.	unsupported
DECDC	Delete Columns	CSI Ps ' ~	Delete Ps columns at cursor position.	unsupported

Erase In Display

TODO: document different modes...

Erase In Line

TODO: document different modes...

Repeat Preceding Character

Has no effect if the sequence does not follow a printed character (NOOP for any other sequence in between). TODO: document character limitations due to xterm compliance

Primary Device Attributes

TODO: Describe response...

Secondary Device Attributes

TODO: Describe response...

Set Mode

TODO: Describe all supported attributes.

DEC Private Set Mode

TODO: Describe all supported attributes.

Reset Mode

TODO: Describe all supported attributes.

DEC Private Reset Mode

TODO: Describe all supported attributes.

Select Graphic Rendition

Detailed description goes here...

Soft Terminal Reset

There are two terminal reset sequences - RIS and DECSTR. While RIS performs almost a full terminal bootstrap, DECSTR only resets certain attributes. For most needs DECSTR should be sufficient. Attributes reset to default values:

• TODO: list attributes here ...

Set Cursor Style

Supported cursor styles (note that most renderers dont implement the blink feature, thus will show the steady variant instead):

• empty, 0 or 1: steady block
• 2: blink block
• 3: steady underline
• 4: blink underline
• 5: steady bar
• 6: blink bar

Set Top and Bottom Margin

TODO: document specialties like dependent cursor commands and scrolling...

DCS

Mnemonic	Name	Sequence	Short Description	Status
SIXEL	SIXEL Graphics	DCS Ps ; Ps ; Ps ; q Pt ST	Draw SIXEL image starting at cursor position.	unsupported
DECRQSS	Request Selection or Setting	DCS $ q Pt ST	Request several the terminal settings. more	partly

Request Selection or Setting

Supported:

• Graphic Rendition (SGR): DCS $ q m ST (always reporting 0m)
• Top and Bottom Margins (DECSTBM): DCS $ q m ST
• Cursor Style (DECSCUSR): DCS $ q SP q ST

ESC

Mnemonic	Name	Sequence	Short Description	Status
SC	Save Cursor	ESC 7	Save cursor position, charmap and text attributes.	supported
RC	Restore Cursor	ESC 8	Restore cursor position, charmap and text attributes.	supported
DECALN	Screen Alignment Pattern	ESC # 8	Fill viewport with a test pattern (E).	supported
IND	Index	ESC D	Move the cursor one line down scrolling if needed.	supported
NEL	Next Line	ESC E	Move the cursor to the beginning of the next row.	supported
HTS	Horizontal Tabulation Set	ESC H	Places a tab stop at the current cursor position.	supported
IR	Reverse Index	ESC M	Move the cursor one line up scrolling if needed.	supported

OSC

Identifier	Sequence	Short Description	Status
0	OSC 0 ; Pt BEL	Set window title and icon name. more	partly
1	OSC 1 ; Pt BEL	Set icon name.	unsupported
2	OSC 2 ; Pt BEL	Set window title. more	supported

Set Windows Title and Icon Name

Icon name is not supported. For Window Title see below.

Set Windows Title

xterm.js does not manipulate the title directly, instead exposes changes via the event Terminal.onTitleChange.

TODO

• improve table sorting:
  • sort C0/C1 in byte order
  • sort OSC in numerical order
  • sort CSI/ESC/DCS in final byte order
• references