engine: a Hanja reading answers with the words it begins

hanjaquery matched the reading exactly, so a word was reachable only
once every syllable of it had been typed, and the popup went blank on
the way there.  Measured over map/hanja.dict's 187,304 readings:
95,024 proper prefixes of a word answer with nothing today, and 66,731
of those are the keystroke just before the word completes -- 대한민 is
one, so 대한민국 looks absent until the last key lands.

dictprefix walks the entry at a node before its children, so the
reading's own conversions keep their place and the words follow: 34,441
readings gain candidates and none of the 187,304 has its existing order
changed.  A jamo reading is untouched, since the two keyspaces do not
meet and ㅁ has no children.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -56,7 +56,9 @@ emoji's CLDR name and keywords in English, Korean and Japanese, and against
 ASCII aliases such as `->` and `<=`. `Ctrl+H` takes the syllable being
 composed as its query and composes on from it, converting a word as well as
 a syllable — 한자 gives 漢字, 대한민국 gives 大韓民國 — and `Esc` gives the
-syllable back. A lone consonant is a reading too, and answers with the
+syllable back. A reading is also the start of the longer words it begins,
+whose conversions follow its own, so 대한 answers 大寒 first and 大韓民國
+further down. A lone consonant is a reading too, and answers with the
 symbol table a Korean keyboard's 한자 key has always offered: ㅁ gives ※ ○
 △ ㈜, ㄴ the brackets 「」『』, ㄹ the units ℃ ㎏ ℓ, ㅇ the circled numbers
 ①②③. Text already committed belongs to the application and cannot be

strans.c

@@ -627,13 +627,18 @@ emojiquery(void)
 	selectfirst();
 }
 
-/* The keys typed since Ctrl+H go on composing from the seed. */
+/*
+ * The keys typed since Ctrl+H go on composing from the seed.  A reading
+ * is also the start of the longer words it begins, so its own
+ * conversions come first and theirs follow: 대한 answers 大寒 and, past
+ * them, 大韓民國.
+ */
 static void
 hanjaquery(void)
 {
 	transstr(im.l, &search.seed, &search.raw, &search.text);
 	clearkouho();
-	im.nkouho = dictlookup(getlang(LangHANJA)->dict, &search.text,
+	im.nkouho = dictprefix(getlang(LangHANJA)->dict, &search.text,
 		im.kouho, Maxkouho);
 	selectfirst();
 }

tests/engine_test.c

@@ -1104,6 +1104,8 @@ hanjabegin(Searchfix *f, int lang)
 	f->dictlang->dict = trienew();
 	setdict(f->dictlang->dict, "한", "漢 韓");
 	setdict(f->dictlang->dict, "가", "家");
+	setdict(f->dictlang->dict, "민", "民");
+	setdict(f->dictlang->dict, "민국", "民國");
 	init();
 	im.l = getlang(lang);
 }
@@ -1933,6 +1935,32 @@ cleanup:
 	searchend(&f);
 }
 
+/*
+ * A reading is the start of the longer words it begins: its own
+ * conversions come first, and past them theirs.
+ */
+void
+engine_hanja_word_prefix(struct ct *t)
+{
+	Searchfix f;
+	Str com;
+
+	hanjabegin(&f, LangKO);
+	sclear(&com);
+	if(!CT_CHECK(t, keystroke('h', Mctrl, &com)) ||
+	   !typekeys(t, "als", &com))
+		goto cleanup;
+	checkstr(t, "the reading typed so far", "민", &search.text);
+	CT_EQ_INT(t, 2, im.nkouho);
+	checkstr(t, "the reading's own conversion", "民", &im.kouho[0]);
+	checkstr(t, "the word it begins", "民國", &im.kouho[1]);
+	CT_CHECK(t, keystroke(Kdown, 0, &com));
+	CT_CHECK(t, keystroke(Kret, 0, &com));
+	checkstr(t, "a word longer than the reading", "民國", &com);
+cleanup:
+	searchend(&f);
+}
+
 void
 engine_hanja_korean_keys(struct ct *t)
 {

tests/test.h

@@ -86,6 +86,7 @@ void	engine_emoji_preedit_languages(struct ct*);
 void	engine_emoji_start_and_unknown(struct ct*);
 void	engine_hanja_search(struct ct*);
 void	engine_hanja_unknown_and_cancel(struct ct*);
+void	engine_hanja_word_prefix(struct ct*);
 void	engine_hanja_korean_keys(struct ct*);
 void	engine_hanja_backspace(struct ct*);
 void	engine_hanja_input_languages(struct ct*);

tests/unit_test.c

@@ -107,6 +107,7 @@ static const struct ct_test tests[] = {
 	{ "engine/emoji-start-and-unknown", engine_emoji_start_and_unknown },
 	{ "engine/hanja-search", engine_hanja_search },
 	{ "engine/hanja-unknown-cancel", engine_hanja_unknown_and_cancel },
+	{ "engine/hanja-word-prefix", engine_hanja_word_prefix },
 	{ "engine/hanja-korean-keys", engine_hanja_korean_keys },
 	{ "engine/hanja-backspace", engine_hanja_backspace },
 	{ "engine/hanja-input-languages", engine_hanja_input_languages },