fix: correct Katakana composition

strans.c

@@ -27,7 +27,7 @@ backmap(Im *im)
 Lang langs[] = {
 	{LangEN,    "english", nil,      transmap, backmap, dictqmap, nil, nil},
 	{LangJP,    "hira",    "kanji",  transmap, backjp,  dictqjp,  nil, nil},
-	{LangJPK,   "kata",    "kanji",  transmap, backjp,  dictqjp,  nil, nil},
+	{LangJPK,   "kata",    nil,      transmap, backjp,  dictqjp,  nil, nil},
 	{LangKO,    "hangul",  nil,      transko,  backko,  dictqmap, nil, nil},
 	{LangEMOJI, nil,       "emoji",  nil,      nil,     nil,      nil, nil},
 	{LangVI,    "telex",   nil,      transvi,  backvi,  dictqmap, nil, nil},
@@ -213,6 +213,23 @@ backjp(Im *im)
 		spopr(&im->pre);
 }
 
+static int
+issmalltsu(Str *s)
+{
+	return s->n == 1 && (s->r[0] == L'っ' || s->r[0] == L'ッ');
+}
+
+static void
+keeptail(Str *s)
+{
+	int i;
+
+	for(i = 1; i < s->n; i++)
+		s->r[i-1] = s->r[i];
+	if(s->n > 0)
+		s->n--;
+}
+
 static int
 dotransjp(Rune c, Str *com)
 {
@@ -228,8 +245,13 @@ dotransjp(Rune c, Str *com)
 	key = im.raw;
 	if(key.n < Maxrunes)
 		sputr(&key, c);
+	sclear(&mapped);
 	if(maplookup(im.l->map, &key, &mapped)){
 		im.raw = key;
+		if(issmalltsu(&mapped)){
+			sappend(&im.pre, &mapped);
+			keeptail(&im.raw);
+		}
 		dictqjp(&im);
 		return 1;
 	}