cterm.txt

$Id$

CTerm terminal characteristics:
------------------------------

End of line behaviour (wrapping):
The cursor is moved to the first character of the next line
as soon as a character is written to the last column of the
current line, not on the next character.  A tab will wrap
to the next line only if the current cursor position is the
last character on the line.

I'm often asked why I don't use VT semantics for wrapping.
The primary reason is that the person asking almost certainly
doesn't know what the VT semantics are, they just want
SyncTERM to behave the same as some other terminal they like.

Not only have the VT semantics never been properly
implemented in any terminal, they even varied between
different actual hardware VT terminals.  Luckily, everything
is on the internet now, so you can see the details and results
here: https://github.com/mattiase/wraptest

Control characters:

0x00 - NUL:
	In doorway mode, indicates that the next character is
	a literal character.  The IBM CP437 character will
	be displayed.  This allows ESC and other control
	characters to be placed on the screen.

0x07 - BEL:
	Beep

0x08 - BS:
	Non-destructive backspace.  Moves cursor position to
	the previous column unless the current column is the
	first, in which case no operation is performed.

0x09 - HT:
	Moves to the next horizontal tab stop.  Does not overwrite
	any characters in between.  If the starting position is
	last column, advances to next line.  If starting
	position is the last column of the last line, performs
	a scroll, filling the new line at bottom with the
	current attribute and moves to the first character in
	the new line.

0x0A - LF:
	Move cursor position to same column of the next row.
	If current row is the last row, scrolls the screen up
	and fills the new row with the current attribute.

0x0D - CR:
	Move cursor position to column 1 of the current line

Control Codes:
--------------

Control codes are in the following format:
ESC {'0' (ZERO) to '~'}
	Legal combinations which are not handled are silently dropped.

ESC E	Next Line (NEL)
	Moves to the line home position of the next line.
	(Same as CR LF)

ESC H	Set Tab (HTS)
	Sets a tab stop at the current column

	SOURCE: http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-048.pdf

ESC M	Reverse Line Feed (RI)
	Move up one line

	SOURCE: http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-048.pdf

ESC P	Device Control String (DCS)
	Begins a string consisting of the characters 0x08 - 0x0d and
	0x20-0x7e, terminated by a String Terminator (ST)
	Supported OSC values:
		"CTerm:Font:p1:<b64>"
		Indicates the string is a loadable font. (CTerm 1.213)

		p1 is a font slot number, which must be higher than the last
		default defined font (See CSI sp D for list of predefined
		fonts). <b64> is the base64 encoded font data.  Font size is
		deduced from the size of the data.  This replaces the now
		deprecated CSI = Ps1 ; Ps2 {


		[ p1 [ ; p2 ] ] q
		Defaults:  p1 = 0  p2 = 0
		Indicates the string is a sixel sequence.

		p1 selects the vertical height of a single pixel.  This
		may be overridden by the raster attributes command, and
		is deprecated.  Supported values
		
			Value      Vertical Size
			-----      -------------
			0,1,5,6    2 pixels
			2          5 pixels
			3,4        3 pixels
			7,8,9      1 pixel

		p2 indicates if unset sixels should be set to the current
		background colour.  If p2 is 1, positions specified as 0
		remain at their current colour.

		Any additional parameters are ignored.

		The rest of the string is made up of sixel data characters and
		sixel control functions.  Sixel data characters are in the
		rage of '?' (0x3f) to '~' (0x7e).  Each sixel data character
		represents six vertical pixels.  The data is extracted by
		subtracting 0x3f from the ASCII value of the character.
		The least significant bit is the topmost pixel.

                Sixel Control Functions
                ! Pn X
			Graphics Repeat Introducer
			The character X is repeated Pn times.
		" p1 ; p2 [ ; p3 [ ; p4 ] ]
			Raster Attributes
			p1 indicates the vertical size in pixels of each
			sixel.  p2 indicates the horizontal size in pixels.
			p3 and p4 define the height and width (in sixels)
			respectively of a block to fill with the background
			colour.  This block may not extend past the current
			bottom of the screen.  If any pixel data characters
			proceed this command, it is ignored.
		# p1
			Colour Select
			Selects the current foreground colour from the
			sixel palette.
		# p1 ; p2 ; p3 ; p4 ; p5
			Palette map
			Defines sixel palette entry p1 and sets it as the
			current foreground colour.  p2 specifies the colour
			space to define the colour in, the only supported
			value is 2.  p3, p4, and p5 specify the red, green,
			and blue content as a percentage (0-100).
		$
			Graphics Carriage Return
			Returns the active position to the left border of
			the same sixel row.  Generally, one pass per colour
			is used.  In passes after the first one, sixels
			with a value of zero are not overwritten with the
			background colour.
		-
			Graphics New Line
			Moves the active position to the left border of the
			next sixel row.


		$ q pt
		Request Status String (DECRQSS)

		pt is the intermediate and/or final characters of a control
		function to query the status of.  The terminal will send a
		response in the format

		DCS p1 $ r pt ST

		p1 is 1 if the terminal supports querying the control
		function and 0 if it does not.

		pt is the characters in the control function except the CSI
		characters.

		Currently supported values of p1:

		m	Request SGR parameters
		r	Request top and bottom margins
		s	Request left and right margins
		t	Request height in lines
		$|	Request width in columns
		*|	Request height in lines


		p1 [ ; p2 [ ; p3 ] ! z
		Define Macro (DECDMAC)
		Defaults: p2 = 0  p3 = 0
		
		Sets a macro to be replayed using CSI Pn * z

		p1 is the macro number to set, and make be between 0 and
		63 inclusive.

		If p2 is zero, the macro numbered p1 will be deleted. If
		p2 is one, all macros are deleted.
		
		If p3 is zero, the macro is defined using ASCII characters
		(0x20 - 0x7e and 0xa0 - 0xff only) if p3 is one, the macro
		is defined using hex pairs.
		
		When the macro is defined using hex pairs, a repeat
		sequence may be included in the format of ! Pn ; D..D ;
		Pn specifies the number of repeats (default of one instance)