H

Keysyms

This appendix provides a list of keysyms and a brief description of each keysym. Keysyms, as you may remember, are the portable representation of the symbols on the caps of keys.

The normal way to process a keyboard event is to use XLookupKeysym to determine the keysym or, if the application allows remapping of keys to strings, it may use XLookupString to get the ASCII string mapped to the key or keys pressed. This allows the application to treat keys in a simple and portable manner, and places the responsibility of tailoring the mapping between keys and keysyms on the server vendor.*

Many keysyms do not have obvious counterparts on the keyboard, but may be generated with certain key combinations. You will need a table for each particular model of hardware you intend the program to work on, to tell you what key combination results in each keysym that is not present on the caps of the keyboard. For real portability, you will want to use only the keysyms that are supported on all vendors equipment you intend the program to be displayed on.

The keysyms are defined in two standard include files: <X11/keysym.h> and <X11/keysymdef.h>. There are several families of keysyms defined in <X11/keysymdef.h>; LATIN1, LATIN2, LATIN3, LATIN4, KATAKANA, ARABIC, CYRILLIC, GREEK, TECHNICAL, SPECIAL, PUBLISHING, APL, HEBREW, and MISCELLANY. The <X11/keysym.h> file specifies which families are enabled. Only the LATIN1, LATIN2, LATIN3, LATIN4, GREEK, and MISCELLANY families are enabled in the standard <X11/keysym.h> file, probably because some compilers have an upper limit on the number of defined symbols that are allowed.

The developers of X at MIT say that to the best of their knowledge the Latin, Kana, Arabic, Cyrillic, Greek, Technical, APL, and Hebrew keysym sets are from the appropriate ISO (International Standards Organization) and/or ECMA international standards. There are no Technical, Special nor Publishing international standards, so these sets are based on Digital Equipment Corporation standards.

Keysyms are four byte long values. In the standard keysyms, the least significant 8 bits indicate a particular character within a set. and the next 8 bits indicate a particular keysym set. The order of the sets is important since not all the sets are complete. Each character set contains gaps where codes have been removed that were duplicates with codes in previous (that is, with lesser keysym set) character sets.

The 94 and 96 character code sets have been moved to occupy the right hand quadrant (decimal 129 - 256), so the ASCII subset has a unique encoding across the least significant byte which corresponds to the ASCII character code. However, this cannot be guaranteed in the keysym sets of future releases and does not apply to all of the MISCELLANY set.

As far as possible, keysym codes are the same as the character code. In the LATIN1 to LATIN4 sets, all duplicate glyphs occupy the same position. However, duplicates between GREEK and TECHNICAL do not occupy the same code position. Thus, applications wishing to use the TECHNICAL character set must transform the keysym using an array.

The MISCELLANY set is a miscellaneous collection of commonly occurring keys on keyboards. Within this set, the keypad symbols are generally duplicates of symbols found on keys on the alphanumeric part of the keyboard but are distinguished here because they often have distinguishable keycodes associated with them.

There is a difference between European and US usage of the names Pilcrow, Paragraph, and Section, as shown in Table H-1.

Table H-1. European vs. US usage of Pilcrow, Paragraph, and Section symbol names

X has adopted the names used by both the ISO and ECMA standards. Thus, XK_paragraph is what Europeans call the pilcrow sign, and XK_section is what they would call the paragraph sign. This favors the US usage.

Keysyms and Description

Tables H-2 through H-7 list the six commonly available sets of keysyms (MISCELLANY, LATIN1 through LATIN4, and GREEK) and describe each keysym briefly. When necessary and possible, these tables show a representative character or characters that might appear on the cap of the key or on the screen when the key or keys corresponding to the keysym were typed.

Table H-2. MISCELLANY

Table H-3. LATIN1

Table H-4. LATIN2

Table H-5. LATIN3

Table H-6. LATIN4

Table H-7. GREEK