From: handa Date: Thu, 1 Feb 2007 04:20:41 +0000 (+0000) Subject: New file. X-Git-Tag: REL-1-4-0~148 X-Git-Url: http://git.chise.org/gitweb/?a=commitdiff_plain;h=e554aba4b1da8b7b73813e18b08e34ec25d07f30;p=m17n%2Fm17n-db.git New file. --- diff --git a/FORMATS/IM-tut.txt b/FORMATS/IM-tut.txt new file mode 100644 index 0000000..89fd0d6 --- /dev/null +++ b/FORMATS/IM-tut.txt @@ -0,0 +1,367 @@ +An input method is defined in a *.mim file with this format. + +(input-method LANG NAME) + +(description (_ "DESCRIPTION")) + +(title "TITLE-STRING") + +(map + (MAP-NAME + (KEYSEQ MAP-ACTION ...) <- rule + ...) + ...) + +(state + (STATE-NAME + (MAP-NAME BRANCH-ACTION ...) <- branch + ...)) + +KEYSEQ specifies a sequence of keys in this format: + (SYMBOLIC-KEY ...) + +For instance "(n i)" represents a key sequence of and . If all +SYMBOLIC-KEYs are ASCII characters, you can use the short form "ni". + +MAP-ACTION and BRANCH-ACTION are a sequence of actions of this format: + + (ACTION ARG ...) + +The most common action is "insert" which can be written as this: + + (insert "TEXT") + +But as it is very frequently used, you can use the short form "TEXT". +And if "TEXT" actually contains just one character "C", you can write +as "(insert ?C)" or just "?C". So the shortest notation for an action +of inserting "a" is "?a". + +Here is a simple example: + +---upcase.mim--------------------------------------------------------- +(input-method en upcase) +(description (_ "Upcase all lowercase letters")) +(title "a->A") +(map + (toupper ("a" "A") ("b" "B") ... ("z" "Z"))) +(state + (init (toupper))) +---------------------------------------------------------------------- + +When this input method is activated, it is in the initial condition of +the first state (in this case, it is "init"). In initial conditions, +no key is being processed and no action is suspended. When it +receives a key event , it searches branches of the current state +for a rule that matches with and finds one in the map "toupper". +Then it executes MAP-ACTIONs (in this case, just inserting "A" in the +preedit buffer). After all MAP-ACTIONSs are executed, the input +method shift to the initial condition of the current state. + +The shifting to "the initial condition of the first state" has a +special meaning. It commits all characters in the preedit buffer and +clears it. + +As a result, "A" is given to an application program. + +A German user may want to extend the above example for "ß". As "ß" is +an uppercase of "ss", he surely want to type "ss" to input "ß". So, he +will add this rule in "toupper". + + ("ss" "ß") + +But we already have this rule too: + + ("s" "S") + +What happens when a key event is sent to the input method? + +No problem. When the input method receives , it inserts "S" in the +preedit buffer. But, as it detects that there is another rule that may +match with the additional key event . So, after inserting "S", it +suspends the normal behavior of shifting to the initial condition, and +waits for another key. Thus, a user may see "S" with underline that +indicates it is not yet committed. + +When the input method receives the next , it cancels the effects +done by the rule for "s" (in this case, the preedit buffer is +cleared), and executes MAP-ACTIONs of the rule for "ss". So, "ß" is +inserted in the preedit buffer. This time, as there is no other rules +that matches with an addition key, it shifts to the initial condition +of the current state, and commit "ß". + +Then, what happens when the next key event is instead of ? + +No problem too. + +The input method knows that there is no rule matching key +sequence. So, when it receives the next , it executes the +suspended behavior (i.e. shifting to the initial condition) which +leads to committing of "S", then try to handle in the current +state which leads to committing of "A". + +So far, we have explained about MAP-ACTION but not about +BRANCH-ACTION. The format of BRANCH-ACTION is the same as MAP-ACTION. +It is executed only after a matching rule is determined and the +corresponding MAP-ACTIONs are executed. A typical use of +BRANCH-ACTION is to shift to a different state. + +To see this effect, let us modify the current input method to upcase a +letter only at a beginning of a word (i.e. "capitalizing"). For that purpose, +we modify the "init" state as this: + + (init + (toupper (shift non-upcase))) + +Here "(shift non-upcase)" is an action to shift to the state +"non-upcase" which has two branches as below: + + (non-upcase + (lower) + (nil (shift init))) + +The first branch is simple. We can define the map "lower" as this to +insert lower letters as is. + +(map + ... + (lower ("a" "a") ("b" "b") ... ("z" "z"))) + +The second branch has a special meaning. The map name "nil" means +that it matches with any key event that does not match any rules of the +other maps in the same state. In addition, it does not eat (or +consume) the key event. We will show the full code of the new input +method before explaining how it works. + +---titlecase.mim------------------------------------------------------ +(input-method en titlecase) +(description (_ "Titlecase letters")) +(title "abc->Abc") +(map + (toupper ("a" "A") ("b" "B") ... ("z" "Z") ("ss" "ß")) + (lower ("a" "a") ("b" "b") ... ("z" "z"))) +(state + (init + (toupper (shift non-upcase))) + (non-upcase + (lower (commit)) + (nil (shift init)))) +---------------------------------------------------------------------- + +Let us see what happens when a user types keys < >. + +Upon , "A" is committed and the state is changed to "non-upcase". +So, the next is handled in "non-upcase" state. As it matches with a +rule in the map "lower", "b" is inserted in the preedit buffer and it +is committed by the explicit "commit" command of BRANCH-ACTION. After +that the input method is still in "non-upcase" state. So the next < > +is also handled in "non-upcase". This time, as no rule in this state +matches with it, the branch "(nil (shift init))" is selected, and the +state is changed to init. Please note that < > is not yet handled. +So, the input method tries to handle it in "init" state. Again no +rule matches with it. So that event is given back to an application +program which usually inserts a space for that. + +So, when you type "a quick blown fox" with this input method, you get +"A Quick Blown Fox". OK, you find a typo in "blown", it should be +"brown". To correct it, perhaps you move a cursor after "l" and type +Backspace and . But, if you forget to turn off the current input +method, "R" is inserted. It is not a sophisticated behavior. + +To make the input method work well also in such a case, we must use a +"surrounding text support". It is a way to check characters around +the inputting spot and delete them if necessary. Please note that +this facility is provided only with Gtk+ applications and Qt +applications. You cannot use it with such an application that uses XIM +to communicate with an input method. + +Before explaining how to utilize "surrounding text support", you must +understand how to use variables, arithmetic comparison, and +a conditional action. + +At first, any symbol (except for several preserved ones) used as ARG +of an action is treated as a variable. For instance, + + (set X 32) (insert X) + +sets the variable "X" to integer value 32, and insert a character +whose Unicode character code is 32 (i.e. SPACE). + +The second argument of "set" action can be an expression of this form: + + (OPERAND ARG1 [ARG2]) + +And both ARG1 and ARG2 can be an expression. So, + + (set X (+ (* Y 32) Z)) --- set "X" to the value of "Y*32+Z" + +We have these arithmetic/bitwise OPERANDs (require two arguments): + + + - * / & | + +these relational OPERANDs (require two arguments): + + == <= >= < > + +and this logical OPERAND (require one argument): + + ! + +For surrounding text support, we have these preserved variables: + + @-0, @-N, @+N (N is a natural number) + +The values of them are predefined as below and can not be altered. + + @-0 -- -1 if surrounding text is supported, -2 if not. + @-N -- N previous character of the preedit buffer. If there is only + M previous characters in it, the value is (N-M) previous + character of the inputting spot. + @+N -- N following character of the preedit buffer. If there is only + M following characters in it, the value is (N-M) following + character of the inputting spot. + +So, provided that you have this context ("def" is in the preedit +buffer, 2 "|"s just indicate borders between the preedit buffer and +the surrounding text): + + ABC|def|GHI + +and your current position in the preedit buffer is just after "d", we +have these values: + + @-3 -- ?B + @-2 -- ?C + @-1 -- ?d + @+1 -- ?e + @+2 -- ?f + @+3 -- ?G + +Next, you have to understand a conditional action of this form: + + (cond + (EXPR1 ACTION ...) + (EXPR2 ACTION ...) + ...) + +where EXPRn are expression. When an input method executes this +action, it resolves values of EXPRn one by one from the first branch. +If the value of EXPRm is resolved into nonzero, the corresponding +actions are executed. + +Now you are ready to write a new version of input method. + +---titlecase2.mim------------------------------------------------------ +(input-method en titlecase) +(description (_ "Titlecase letters")) +(title "abc->Abc") +(map + (toupper ("a" "A") ("b" "B") ("c" "C") ("d" "D") ("e" "E") + ("f" "F") ("g" "G") ("h" "H") ("i" "I") ("j" "J") + ("k" "K") ("l" "L") ("m" "M") ("n" "N") ("o" "O") + ("p" "P") ("q" "Q") ("r" "R") ("s" "S") ("t" "T") + ("u" "U") ("v" "V") ("w" "W") ("x" "X") ("y" "Y") + ("z" "Z") ("ss" "ß"))) +(state + (init + (toupper + + ;; Now we have one character in the preedit buffer. So, "@-2" is + ;; the character just before the inputting spot. + + (cond ((| (& (>= @-2 ?A) (<= @-2 ?Z)) (& (>= @-2 ?a) (<= @-2 ?z))) + + ;; If that character is A..Z or a..z, remember the + ;; character in the preedit in X and delete it. + + (set X @-1) (delete @-) + + ;; Then insert a proper lower case version of X. + + (cond ((= X ?ß) "ss") + (1 (set X (+ X 32)) (insert X)))))))) +---------------------------------------------------------------------- + +Above example contains a new action "delete". So, it is time to +explain more about the preedit buffer. The preedit buffer is a +temporary place to store a sequence of character. In the buffer, an +input method keep one position called "current position". The current +position exist between characters, at the head of the buffer, or at +the tail of the buffer. The "insert" action inserts characters before +the current position. For instance, when your preedit +buffer contains "ab.c" ("." indicates the current position), + + (insert "xyz") + +changes the buffer to "abxyz.c". + +There are several predefined variables that hold a position in the +preedit buffer. They are: + + @<, @=, @> -- the first, current, and last positions + @-, @+ -- the previous and the next positions + +The format of "delete" action is this: + + (delete POS) + +and the meaning is to delete characters between the position POS and +the current position. So, "(delete @-)" deletes one character before +the current position. The other examples of "delete" actions are: + + (delete @+) -- delete the next character + (delete 0<) -- delete all preceding characters in the buffer + (delete @>) -- delete all following characters in the buffer + +You can change the current position by "move" action as below: + + (move @-) -- move the current position to the position before the + previous character + (move @<) -- move to the first position + + +Let us see how our new example works. Whatever a key event is, the +input method is in its only state, "init". An event is first handled +by MAP-ACTIONs, so that every key is shifted to upcase and put into +the preedit area. The character now put into the preedit buffer and +can be retrieved by @-1. + +How can we determine if the new character should be in its lower case? +We have to check the character before it, that is, @-2. +BRANCH-ACTIONs in the "init" state do the job. + +It first checks if the character @-2 is between A to Z, or between a +to z, by the conditional below. + + (cond ((| (& (>= @-2 ?A) (<= @-2 ?Z)) (& (>= @-2 ?a) (<= @-2 ?z))) + +If not, the work with this key event is done. If so, our new key +should be changed back to lowercase. The upcase character is already +in the preedit buffer and we have to retrieve and remember it in the +variable X by + + (set X @-1) + +and then delete the character by + + (delete @-) + +Lastly we insert back the character in its lowercase form. The +problem here is that ß must be changed to "ss", so we need another +conditional. The first branch means that "if the character remembered +in X is ß, "ss" is inserted". + +The second branch + + (1 (set X (+ X 32)) (insert X)) + +starts with "1" that is always resolved into nonzero, so this branch +is catchall. Actions in this branch shifts up X by 32 and then insert +it, that is, they make A...Z into a...z respectively and inserts the +lower case character to the preedit buffer. As the input method +reached the end of the BRANCH-ACTIONs, the character is commited. + +This new input method always checks the character before the current +position, so "A Quick Blown Fox" will be successfully fixed to "A +Quick Brown Fox" by a backspace and . + +