1 The rules file 2 ============== 3 4 The purpose of the rules file is to map between configuration values 5 that are easy for a user to specify and understand, and the 6 configuration values xkbcomp uses and understands. 7 8 xkbcomp uses the xkb_component_names struct, which maps directly to 9 include statements of the appropriate sections, called for short 10 KcCGST (see doc/keymap-format-text-v1.txt; 'G' stands for "geometry", 11 which is not supported). These are not really intuitive or straight- 12 forward for the uninitiated. 13 14 Instead, the user passes in a xkb_rule_names struct, which consists 15 of the name of a rules file (in Linux this is usually "evdev"), a 16 keyboard model (e.g. "pc105"), a set of layouts (which will end up 17 in different groups, e.g. "us,fr"), variants (used to alter/augment 18 the respective layout, e.g. "intl,dvorak"), and a set of options 19 (used to tweak some general behavior of the keyboard, e.g. 20 "ctrl:nocaps,compose:menu" to make the Caps Lock key act like Ctrl 21 and the Menu key like Compose). We call these RMLVO. 22 23 Format of the file 24 ------------------ 25 The file consists of rule sets, each consisting of rules (one per 26 line), which match the MLVO values on the left hand side, and, if 27 the values match to the values the user passed in, results in the 28 values on the right hand side being added to the resulting KcCGST. 29 Since some values are related and repeated often, it is possible 30 to group them together and refer to them by a group name in the 31 rules. 32 33 Along with matching values by simple string equality, and for 34 membership in a group defined previously, rules may also contain 35 "wildcard" values - "*" - which always match. These usually appear 36 near the end. 37 38 Grammar 39 ------- 40 (It might be helpful to look at a file like rules/evdev along with 41 this grammer. Comments, whitespace, etc. are not shown.) 42 43 File ::= { "!" (Group | RuleSet) } 44 45 Group ::= GroupName "=" { GroupElement } "\n" 46 GroupName ::= "$"<ident> 47 GroupElement ::= <ident> 48 49 RuleSet ::= Mapping { Rule } 50 51 Mapping ::= { Mlvo } "=" { Kccgst } "\n" 52 Mlvo ::= "model" | "option" | ("layout" | "variant") [ Index ] 53 Index ::= "[" 1..XKB_NUM_GROUPS "]" 54 Kccgst ::= "keycodes" | "symbols" | "types" | "compat" | "geometry" 55 56 Rule ::= { MlvoValue } "=" { KccgstValue } "\n" 57 MlvoValue ::= "*" | GroupName | <ident> 58 KccgstValue ::= <ident> 59 60 Notes: 61 62 - The order of values in a Rule must be the same as the Mapping it 63 follows. The mapping line determines the meaning of the values in 64 the rules which follow in the RuleSet. 65 66 - If a Rule is matched, %-expansion is performed on the KccgstValue, 67 as follows: 68 69 %m, %l, %v: 70 The model, layout or variant, if only one was given (e.g. 71 %l for "us,il" is invalid). 72 73 %l[1], %v[1]: 74 Layout or variant for the specified group Index, if more than 75 one was given (e.g. %l[1] for "us" is invalid). 76 77 %+m, %+l, %+v, %+l[1], %+v[1] 78 As above, but prefixed with '+'. Similarly, '|', '-', '_' may be 79 used instead of '+'. 80 81 %(m), %(l), %(l[1]), %(v), %(v[1]): 82 As above, but prefixed by '(' and suffixed by ')'. 83 84 In case the expansion is invalid, as described above, it is 85 skipped (the rest of the string is still processed); this includes 86 the prefix and suffix (that's why you shouldn't use e.g. "(%v[1])"). 87
