fix: correct Katakana composition

tests/engine_test.c

@@ -481,6 +481,41 @@ engine_japanese_backspace_and_boundaries(struct ct *t)
 	}
 }
 
+void
+engine_katakana_sequences(struct ct *t)
+{
+	static const struct {
+		char *keys;
+		char *want;
+	} cases[] = {
+		{ "kitte", "キッテ" },
+		{ "katta", "カッタ" },
+		{ "gakkou", "ガッコウ" },
+		{ "matcha", "マッチャ" },
+		{ "xu", "ゥ" },
+		{ "vu", "ヴ" },
+	};
+	Dictreq req;
+	Str com, shown;
+	int i;
+
+	newestrequest(&req);
+	for(i = 0; i < nelem(cases); i++){
+		init();
+		im.l = getlang(LangJPK);
+		sclear(&com);
+		if(!typekeys(t, cases[i].keys, &com))
+			continue;
+		checkstr(t, cases[i].keys, "", &com);
+		shown = shownpre(&im);
+		checkstr(t, cases[i].keys, cases[i].want, &shown);
+		CT_CHECK(t, keystroke(Kret, 0, &com));
+		checkstr(t, "committed Katakana", cases[i].want, &com);
+	}
+	CT_EQ_INT(t, 0, newestrequest(&req));
+	CT_EQ_PTR(t, nil, getlang(LangJPK)->dictname);
+}
+
 void
 engine_emoji_single_candidate(struct ct *t)
 {