Encoding

Important: Keysyms are 32-bit integers whoose 3 most significant bits are always set to zero. Thus valid keysyms are in the range 0 – 0x1fffffff = XKB_KEYSYM_MAX.

Note

Throughout this documentation, keysyms values are viewed as four bytes, numbered from most significant to least significant:

Byte 1: The most significant 8 bits: 3 zero bits and the most-significant 5 bits of the 29-bit effective value.
Byte 2: The next most-significant 8 bits
Byte 3: The next most-significant 8 bits
Byte 4: The least-significant 8 bits

Categories

There are 6 categories:

Special keysyms
Latin-1 keysyms
Legacy keysyms
Function keysyms
Unicode keysyms
Vendor keysyms

Overview

Category	Subcategory	Byte 1	Byte 2	Byte 3	Byte 4	First keysym	Last keysym
Special keysyms		0	0	0	0	NoSymbol
Latin-1 keysyms	ASCII non-control characters	0	0	0	0x20 – 0x7e	space	asciitilde
Latin-1 keysyms	Latin-1 Supplement	0	0	0	0xa0 – 0xff	nobreakspace	ydiaeresis
Legacy keysyms	Latin-2	0	0	0x01	0x00 – 0xff	Aogonek	abovedot
	Latin-3			0x02		Hstroke	scircumflex
	Latin-4			0x03		kra	umacron
	Kana			0x04		overline	semivoicedsound
	Arabic			0x05		Arabic_comma	Arabic_sukun
	Cyrillic			0x06		Serbian_dje	Cyrillic_HARDSIGN
	Greek			0x07		Greek_ALPHAaccent	Greek_omega
	Technical			0x08		leftradical	downarrow
	Special			0x09		blank	vertbar
	Publishing			0x0a		emspace	cursor
	APL			0x0b		leftcaret	righttack
	Hebrew			0x0c		hebrew_doublelowline	hebrew_taf
	Thai			0x0d		Thai_kokai	Thai_lekkao
	Korean			0x0e		Hangul_Kiyeog	Korean_Won
	Latin-5			0x0f
	Latin-6			0x10
	Latin-7			0x11
	Latin-8			0x12
	Latin-9			0x13		OE	Ydiaeresis
	Currency			0x20		EuroSign
Function keysyms	IBM 3270 terminals	0	0	0xfd	0x00 – 0xff	3270_Duplicate	3270_Enter
	Keyboard (XKB) Extension			0xfe		ISO_Lock	Pointer_Drag5
	Keyboard			0xff		BackSpace	Delete
Special keysyms		0	0xff	0xff	0xff	VoidSymbol
Unicode keysyms		0x01	0x00 – 0x10	0x00 – 0xff	0x00 – 0xff	0x01000100	0x0110ffff
Vendor keysyms	DEC, HP, misc.	0x10	0x00	0x00 – 0xff	0x00 – 0xff	0x10000000	0x1000ffff
		0x10	0x01 – 0x03			0x10010000	0x1003ffff
	OSF	0x10	0x04			0x10040000	0x1004ffff
	Sun	0x10	0x05			0x10050000	0x1005ffff
		0x10	0x06 – 0x07			0x10060000	0x1007ffff
	XFree86	0x10	0x08			0x10080000	0x1008ffff
		0x10 – 0x1f	0x09 – 0xff			0x10090000	0x1fffffff

Special keysyms

There are 2 special values: NoSymbol and VoidSymbol. They are used to indicate the absence of symbols.

Byte 1	Byte 2	Byte 3	Byte 4	Hex. value	Name
0	0	0	0	0x00000000	NoSymbol
0	255	255	255	0x00ffffff	VoidSymbol

See also: Appendix A “Special keysyms” of the X Window System Protocol.

Latin-1 keysyms

The Latin-1 keysyms occupy the range 0x0020 – 0x007E and 0x00a0 – 0x00ff and represent the ISO 10646 / Unicode characters U+0020 – U+007E and U+00A0 – U+00FF, respectively.

See also: ISO/IEC 8859-1 character encoding; Appendix A “Latin-1 keysyms” of the X Window System Protocol.

Legacy keysyms

Legacy keysyms date from the time before ISO 10646 / Unicode was available. They represent characters from a number of different older 8-bit coded character sets and have zero values for bytes 1 and 2. Byte 3 indicates a coded character set and byte 4 is the 8-bit value of the particular character within that set.

Byte 3
Value	Character set	Comment
1	Latin-2
2	Latin-3
3	Latin-4
4	Kana
5	Arabic
6	Cyrillic
7	Greek
8	Technical	Based on DEC Technical‌: add 0x880 to the original code point
9	Special	Based on DEC Special Graphics‌: add 0x980 to the original code point
10	Publishing
11	APL
12	Hebrew
13	Thai
14	Korean
15	Latin-5
16	Latin-6
17	Latin-7
18	Latin-8
19	Latin-9
32	Currency

Each character set contains gaps where codes have been removed that were duplicates with codes in previous character sets (that is, character sets with lesser byte 3 value).

Todo: Legacy keysyms

See also: Latin-1 keysyms; Appendix A “Legacy keysyms” of the X Window System Protocol.

Function keysyms

Function keysyms represent keycap symbols that do not directly represent elements of a coded character set. Instead, they typically identify a software function, mode, or operation (e.g., cursor up, caps lock, insert) that can be activated using a dedicated key. Function keysyms have zero values for bytes 1 and 2. Byte 3 distinguishes between several 8-bit sets within which byte 4 identifies the individual function key.

Byte 1	Byte 2	Byte 3		Byte 4
Value	Value	Value	Function set	Value
0	0	253	IBM 3270 terminals	(individual function key)
		254	Keyboard (XKB) Extension
		255	Keyboard

Todo: Function keysyms

See also: Appendix A “Function keysyms” of the X Window System Protocol.; Appendix C “New keysyms” of the XKB Protocol Specification.

Unicode keysyms

The Unicode keysyms occupy the range 0x01000100 – 0x0110FFFF and represent the ISO 10646 / Unicode characters U+0100 – U+10FFFF, respectively. The numeric value of a Unicode keysym is the Unicode code point of the corresponding character plus 0x01000000. In the interest of backwards compatibility, clients should be able to process both the Unicode keysym and the legacy keysym for those characters where both exist.

Note: Dead keys, which place an accent on the next character entered, shall be encoded as function keysyms, and not as the Unicode keysym corresponding to an equivalent combining character.; Where a keycap indicates a specific function with a graphical symbol that is also available in Unicode (e.g., an upwards arrow for the cursor up function), the appropriate function keysym should be used, and not the Unicode keysym corresponding to the depicted symbol.

See also: Appendix A “Unicode keysyms” of the X Window System Protocol.; Unicode technical website.

Vendor keysyms

Vendor keysyms are vendor-specific extentions in the range 0x10000000 – 0x1fffffff. Among these, the range 0x11000000 – 0x1100ffff is designated for keypad keysyms.

See also: Appendix A “Vendor keysyms” of the X Window System Protocol.