remove most explicit Txt* params, fix some utf-8 problems

3 files changed, 246 insertions, 210 deletions

diff --git a/main.c b/main.c
index 0fe9513..91ef1dc 100644
--- a/main.c
+++ b/main.c
@@ -27,37 +27,37 @@ int is_space(u32 c) {
 
 u32 move_word_back(Txt *t, u32 cur) {
 	TxtLoc l = txt_at(t, cur);
-	while (!txt_at_start(t,l)) {
-		TxtLoc n = txt_prev(t, l);
-		if (!is_space(txt_chr(t, n))) break;
+	while (!at_start(l)) {
+		TxtLoc n = bprev(l);
+		if (!is_space(txt_chr(n))) break;
 		l = n;
 	}
-	while (!txt_at_start(t,l)) {
-		TxtLoc n = txt_prev(t, l);
-		if (is_space(txt_chr(t, n))) break;
+	while (!at_start(l)) {
+		TxtLoc n = bprev(l);
+		if (is_space(txt_chr(n))) break;
 		l = n;
 	}
-	return txt_ofs(t, l);
+	return txt_ofs(l);
 }
 
 u32 move_word_fwd(Txt *t, u32 cur) {
 	TxtLoc l = txt_at(t, cur);
-	while (!txt_at_end(t,l) && is_space(txt_chr(t, l))) l = txt_next(t, l);
-	while (!txt_at_end(t,l) && !is_space(txt_chr(t, l))) l = txt_next(t, l);
-	return txt_ofs(t, l);
+	while (!at_end(l) && is_space(txt_chr(l))) l = cnext(l);
+	while (!at_end(l) && !is_space(txt_chr(l))) l = cnext(l);
+	return txt_ofs(l);
 }
 
 u32 move_char_back(Txt *t, u32 cur) {
 	while (cur > 0) {
 		cur--;
-		u8 c = txt_byte(t, txt_at(t, cur));
+		u8 c = txt_byte(txt_at(t, cur));
 		if ((c & 0xc0) != 0x80) break;
 	}
 	return cur;
 }
 
 u32 move_char_fwd(Txt *t, u32 cur) {
-	u8 b = txt_byte(t, txt_at(t, cur));
+	u8 b = txt_byte(txt_at(t, cur));
 	u32 n = stdc_leading_ones(b);
 	if (cur + n >= t->len) return t->len;
 	return cur + n + !n;
@@ -66,91 +66,40 @@ u32 move_char_fwd(Txt *t, u32 cur) {
 u32 del_between(Txt *t, u32 a, u32 b) {
 	if (b < a) { u32 t = a; a = b; b = t; }
 	//if (b - a > 10) TRAP();
-	return txt_delete(t, b, b - a);
-}
-
-TxtLoc next_newline(Txt *t, TxtLoc l) {
-	do l = txt_next(t, l);
-	while (!txt_at_end(t, l) && txt_byte(t, l) != '\n');
-	return l;
-}
-
-TxtLoc prev_newline(Txt *t, TxtLoc l) {
-	do l = txt_prev(t, l);
-	while (!txt_at_start(t, l) && txt_byte(t, l) != '\n');
-	return l;
-}
-
-TxtLoc start_of_line(Txt *t, TxtLoc l) {
-	l = prev_newline(t, l);
-	if (!txt_at_start(t,l) && txt_byte(t, l) == '\n') l = txt_next(t, l);
-	return l;
-}
-
-TxtLoc end_of_line(Txt *t, TxtLoc l) {
-	TxtLoc start = start_of_line(t, l);
-	return txt_byte(t, start) == '\n' ? start : next_newline(t, start);
-}
-
-u32 get_col(Txt *t, TxtLoc l) {
-	u32 n = 0;
-	for (TxtLoc tmp = start_of_line(t, l); txt_before(tmp, l); txt_chr_next(t, &tmp)) n++;
-	return n;
-}
-
-TxtLoc at_col(Txt *t, TxtLoc l, u32 col) {
-	l = start_of_line(t, l);
-	while (col--) {
-		if (txt_chr_next(t, &l) == '\n') {
-			l = txt_prev(t, l);
-			break;
-		}
-	}
-	return l;
-}
-
-TxtLoc prev_line(Txt *t, TxtLoc l) {
-	TxtLoc start = start_of_line(t, l);
-	return at_col(t, txt_prev(t, start), get_col(t, l));
-}
-
-TxtLoc next_line(Txt *t, TxtLoc l) {
-	TxtLoc end = end_of_line(t, l);
-	if (txt_at_end(t, end)) return end;
-	return at_col(t, txt_next(t, end), get_col(t, l));
+	return txt_ofs(txt_delete(txt_at(t, b), b - a));
 }
 
 u32 move_line_up(Txt *t, u32 cur) {
-	return txt_ofs(t, prev_line(t, txt_at(t, cur)));
+	return txt_ofs(prev_line(txt_at(t, cur)));
 }
 
 u32 move_line_down(Txt *t, u32 cur) {
-	return txt_ofs(t, next_line(t, txt_at(t, cur)));
+	return txt_ofs(next_line(txt_at(t, cur)));
 }
 
-int empty_line(Txt *t, TxtLoc l) {
-	u8 b = txt_byte(t, start_of_line(t, l));
+int empty_line(TxtLoc l) {
+	u8 b = txt_byte(start_of_line(l));
 	return b == '\n' || b == 0 /* last line of buffer */;
 }
 
-TxtLoc next_par(Txt *t, TxtLoc l) {
-	while (!txt_at_end(t, l) && empty_line(t, l)) l = next_line(t, l);
-	while (!txt_at_end(t, l) && !empty_line(t, l)) l = next_line(t, l);
+TxtLoc next_par(TxtLoc l) {
+	while (!at_end(l) && empty_line(l)) l = next_line(l);
+	while (!at_end(l) && !empty_line(l)) l = next_line(l);
 	return l;
 }
 
-TxtLoc prev_par(Txt *t, TxtLoc l) {
-	while (!txt_at_start(t, l) && empty_line(t, l)) l = prev_line(t, l);
-	while (!txt_at_start(t, l) && !empty_line(t, l)) l = prev_line(t, l);
+TxtLoc prev_par(TxtLoc l) {
+	while (!at_start(l) && empty_line(l)) l = prev_line(l);
+	while (!at_start(l) && !empty_line(l)) l = prev_line(l);
 	return l;
 }
 
 u32 move_par_up(Txt *t, u32 cur) {
-	return txt_ofs(t, prev_par(t, txt_at(t, cur)));
+	return txt_ofs(prev_par(txt_at(t, cur)));
 }
 
 u32 move_par_down(Txt *t, u32 cur) {
-	return txt_ofs(t, next_par(t, txt_at(t, cur)));
+	return txt_ofs(next_par(txt_at(t, cur)));
 }
 
 /* main */
@@ -162,12 +111,12 @@ void find_view_window(Txt *t, u32 curs, TxtLoc *start, TxtLoc *end) {
 	TxtLoc l = txt_at(t, curs);
 	u32 u = LINES / 2;
 	TxtLoc a = l;
-	for (u32 i = 0; i < u; i++) a = prev_newline(t, a);
+	for (u32 i = 0; i < u; i++) a = prev_newline(a);
 	u32 n = 0;
 	TxtLoc b = a;
-	while (!txt_at_end(t, b) && n++ < LINES) b = next_newline(t, b);
-	while (!txt_at_start(t, a) && n++ < LINES) a = prev_newline(t, a);
-	if (!txt_at_start(t,a) && txt_byte(t,a) == '\n') a = txt_next(t, a);
+	while (!at_end(b) && n++ < LINES) b = next_newline(b);
+	while (!at_start(a) && n++ < LINES) a = prev_newline(a);
+	if (!at_start(a) && txt_byte(a) == '\n') a = bnext(a);
 	*start = a;
 	*end = b;
 }
@@ -193,7 +142,7 @@ void draw(void *ctx) {
 			cur_found = 1;
 			vui_curs_pos(x, y);
 		}
-		u32 c = txt_chr_next(&txt, &start);
+		u32 c = txt_chr_next(&start);
 		if (c == '\n') {
 			x = 0;
 			y++;
@@ -206,7 +155,7 @@ void draw(void *ctx) {
 	}
 	ASSERT(start.i <= txt.ptbl.v[start.p].n);
 	if (!cur_found) vui_curs_pos(x, y);
-	u32 c = txt_chr(&txt, l);
+	u32 c = txt_chr(l);
 	vui_printf(-1, -4, "%u", count);
 	vui_aprintf(-1, -3, mode ? FG_BCYAN : FG_CYAN, "%s", mode ? "INSERT" : "NORMAL");
 	vui_printf(-1, -1, "%u - %u.%u - %02x (%c)", cur, l.p, l.i, c, (c < 0x20 || c > 0x7e) ? ' ' : c);
@@ -259,11 +208,11 @@ loop:
 	case KEY_HOME:
 	case '^':
 	case '0':
-		cur = txt_ofs(&txt, start_of_line(&txt, txt_at(&txt, cur)));
+		cur = txt_ofs(start_of_line(txt_at(&txt, cur)));
 		break;
 	case KEY_END:
 	case '$':
-		cur = txt_ofs(&txt, next_newline(&txt, txt_at(&txt, cur)));
+		cur = txt_ofs(next_newline(txt_at(&txt, cur)));
 		break;
 	case KEY_HOME | KEY_CTRL_BIT:
 	case 'g':
@@ -275,12 +224,12 @@ loop:
 		break;
 	case 'f': {
 		u32 n = vui_key();
-		TxtLoc l = txt_next(&txt, txt_at(&txt, cur));
+		TxtLoc l = cnext(txt_at(&txt, cur));
 		for (TxtLoc t = l;;) {
-			u32 c = txt_chr_next(&txt, &t);
+			u32 c = txt_chr_next(&t);
 			if (c == '\n') break;
 			if (c == n) {
-				cur = txt_ofs(&txt, l);
+				cur = txt_ofs(l);
 				break;
 			}
 			l = t;
@@ -288,15 +237,15 @@ loop:
 	} break;
 	case 'F': {
 		u32 n = vui_key();
-		TxtLoc l = txt_prev(&txt, txt_at(&txt, cur));
+		TxtLoc l = bprev(txt_at(&txt, cur));
 		for (;;) {
-			u32 c = txt_chr(&txt, l);
+			u32 c = txt_chr(l);
 			if (c == '\n') break;
 			if (c == n) {
-				cur = txt_ofs(&txt, l);
+				cur = txt_ofs(l);
 				break;
 			}
-			l = txt_prev(&txt, l);
+			l = bprev(l);
 		}
 	} break;
 	default:
@@ -343,25 +292,25 @@ int main(int argc, const char **argv) {
 			case 'a': {
 				mode = 1;
 				TxtLoc l = txt_at(&txt, cur);
-				TxtLoc e = end_of_line(&txt, l);
-				l = txt_before(l, e) ? txt_next(&txt, l) : e;
-				cur = txt_ofs(&txt, l);
+				TxtLoc e = end_of_line(l);
+				l = txt_before(l, e) ? cnext(l) : e;
+				cur = txt_ofs(l);
 			} break;
 			case 'I':
 				mode = 1;
-				cur = txt_ofs(&txt, start_of_line(&txt, txt_at(&txt, cur)));
+				cur = txt_ofs(start_of_line(txt_at(&txt, cur)));
 				break;
 			case 'A':
 				mode = 1;
-				cur = txt_ofs(&txt, end_of_line(&txt, txt_at(&txt, cur)));
+				cur = txt_ofs(end_of_line(txt_at(&txt, cur)));
 				break;
 			case 'o':
 				mode = 1;
-				cur = txt_ofs(&txt, end_of_line(&txt, txt_at(&txt, cur)));
+				cur = txt_ofs(end_of_line(txt_at(&txt, cur)));
 				goto ins_newline;
 			case 'O':
 				mode = 1;
-				cur = txt_ofs(&txt, txt_prev(&txt, start_of_line(&txt, txt_at(&txt, cur))));
+				cur = txt_ofs(bprev(start_of_line(txt_at(&txt, cur))));
 				goto ins_newline;
 			case 'd': {
 				u32 before = cur;
@@ -371,19 +320,19 @@ int main(int argc, const char **argv) {
 				}
 			} break;
 			case 'D': {
-				u32 end = txt_ofs(&txt, end_of_line(&txt, txt_at(&txt, cur)));
+				u32 end = txt_ofs(end_of_line(txt_at(&txt, cur)));
 				del_between(&txt, cur, end);
 			} break;
 			case 'C': {
-				u32 end = txt_ofs(&txt, end_of_line(&txt, txt_at(&txt, cur)));
+				u32 end = txt_ofs(end_of_line(txt_at(&txt, cur)));
 				del_between(&txt, cur, end);
 				mode = 1;
 			} break;
 			case 'S': {
-				TxtLoc l = start_of_line(&txt, txt_at(&txt, cur));
-				u32 end = txt_ofs(&txt, end_of_line(&txt, l));
-				del_between(&txt, txt_ofs(&txt, l), end);
-				cur = txt_ofs(&txt, l);
+				TxtLoc l = start_of_line(txt_at(&txt, cur));
+				u32 end = txt_ofs(end_of_line(l));
+				del_between(&txt, txt_ofs(l), end);
+				cur = txt_ofs(l);
 				mode = 1;
 			} break;
 			case 'c': {
@@ -396,10 +345,10 @@ int main(int argc, const char **argv) {
 				break;
 			}
 			case 'x':
-				txt_delete_c(&txt, txt_ofs(&txt, txt_next(&txt, txt_at(&txt, cur))));
+				cur = txt_ofs(txt_delete_c(cnext(txt_at(&txt, cur))));
 				break;
 			case 's':
-				txt_delete_c(&txt, txt_ofs(&txt, txt_next(&txt, txt_at(&txt, cur))));
+				cur = txt_ofs(txt_delete_c(cnext(txt_at(&txt, cur))));
 				mode = 1;
 				break;
 			case '1': case '2': case '3': case '4':
@@ -420,11 +369,13 @@ add_to_count:
 		case 1:
 			switch (c) {
 			case KEY_ESC:
-				if (txt_after(txt_at(&txt, cur), start_of_line(&txt, txt_at(&txt, cur)))) cur--;
+				if (txt_after(txt_at(&txt, cur), start_of_line(txt_at(&txt, cur)))) {
+					cur = txt_ofs(cprev(txt_at(&txt, cur)));
+				}
 				mode = 0;
 				break;
 			case KEY_BKSP:
-				cur = txt_delete_c(&txt, cur);
+				cur = txt_ofs(txt_delete_c(txt_at(&txt, cur)));
 				break;
 			case 0x17 /* ^W */:
 				cur = del_between(&txt, move_word_back(&txt, cur), cur);
@@ -434,19 +385,21 @@ add_to_count:
 				break;
 			case '\r': {
 ins_newline:;
+	    /*
 				u32 tabs = 0;
-				TxtLoc start = start_of_line(&txt, txt_at(&txt, cur));
-				for (TxtLoc l = start; txt_byte(&txt, l) == '\t'; l = txt_next(&txt, l))
+				TxtLoc start = start_of_line(txt_at(&txt, cur));
+				for (TxtLoc l = start; txt_byte(l) == '\t'; l = bnext(l))
 					tabs++;
-				while (txt_byte(&txt, txt_at(&txt, cur - 1)) == '\t') {
-					cur = txt_delete(&txt, cur, 1);
+				while (txt_byte(txt_at(&txt, cur - 1)) == '\t') {
+					cur = txt_ofs(txt_delete(txt_at(&txt, cur), 1));
 				}
-				cur = txt_insert_c(&txt, cur, '\n');
-				while (tabs--) cur = txt_insert_c(&txt, cur, '\t');
+				*/
+				cur = txt_ofs(txt_insert_c(txt_at(&txt, cur), '\n'));
+				//while (tabs--) cur = txt_ofs(txt_insert_c(txt_at(&txt, cur), '\t'));
 			} break;
 
 			default:
-				if ((c == '\t' || c >= ' ') && c <= KEY_UTF8_MAX) cur = txt_insert_c(&txt, cur, c);
+				if ((c == '\t' || c >= ' ') && c <= KEY_UTF8_MAX) cur = txt_ofs(txt_insert_c(txt_at(&txt, cur), c));
 				break;
 			}
 			break;
diff --git a/txt.c b/txt.c
index 38f34c4..b2dc2d8 100644
--- a/txt.c
+++ b/txt.c
@@ -56,7 +56,7 @@ static void txt_buf_append(Txt *b, TxtBufIdx bi, const char *s, u32 n) {
 	buf->n += n;
 }
 
-u32 txt_add_piece(Txt *b, TxtLoc l) {
+TxtLoc txt_add_piece(Txt *b, TxtLoc l) {
 	if (l.p > 0 && !l.i) {
 		l.p--;
 		l.i = b->ptbl.v[l.p].n;
@@ -76,24 +76,24 @@ insert:
 			txt_insert_piece(b, l.p, TXT_ADD, b->buf[TXT_ADD].n, 0);
 		}
 	}
-	return l.p;
+	return l;
 }
 
-u32 txt_insert(Txt *b, u32 cur, const char *s, u32 n) {
-	TxtLoc l = txt_at(b, cur);
-	l.p = txt_add_piece(b, l);
-	TxtPiece *p = &b->ptbl.v[l.p];
-	txt_buf_append(b, p->buf, s, n);
+TxtLoc txt_insert(TxtLoc l, const char *s, u32 n) {
+	l = txt_add_piece(l.t, l);
+	TxtPiece *p = &l.t->ptbl.v[l.p];
+	txt_buf_append(l.t, p->buf, s, n);
 	p->n += n;
-	b->len += n;
-	return cur + n;
+	l.t->len += n;
+	l.i = p->n;
+	return l;
 }
 
-u32 txt_insert_c(Txt *b, u32 cur, u32 ch) {
+TxtLoc txt_insert_c(TxtLoc l, u32 ch) {
 	char buf[6];
 	u32 n = utf8_encode_len(&ch, 1);
 	utf8_encode(buf, &ch, 1);
-	return txt_insert(b, cur, buf, n);
+	return txt_insert(l, buf, n);
 }
 
 static int txt_are_pieces_adjacent(Txt *t, u32 a, u32 b) {
@@ -102,46 +102,46 @@ static int txt_are_pieces_adjacent(Txt *t, u32 a, u32 b) {
 	return pa->buf == pb->buf && pa->ofs + pa->n == pb->ofs;
 }
 
-static void txt_join_or_kill(Txt *b, u32 pi) {
-	if (b->ptbl.v[pi].n == 0 && !(pi == 0 && b->ptbl.n == 1)) {
-		txt_remove_piece(b, pi);
+static TxtLoc txt_join_or_kill(TxtLoc l) {
+	Txt *b = l.t;
+	if (l.t->ptbl.v[l.p].n == 0 && !(l.p == 0 && b->ptbl.n == 1)) {
+		txt_remove_piece(b, l.p);
 	}
-	if (pi + 1 < b->ptbl.n && txt_are_pieces_adjacent(b, pi, pi + 1)) {
-		b->ptbl.v[pi].n += b->ptbl.v[pi+1].n;
-		txt_remove_piece(b, pi + 1);
+	if (l.p + 1 < b->ptbl.n && txt_are_pieces_adjacent(b, l.p, l.p + 1)) {
+		b->ptbl.v[l.p].n += b->ptbl.v[l.p+1].n;
+		txt_remove_piece(b, l.p + 1);
 	}
+	return l;
 }
 
-u32 txt_delete(Txt *b, u32 cur, u32 n) {
-	TxtLoc l = txt_at(b, cur);
-	u32 pi = txt_split_piece(b, l.p, l.i);
+TxtLoc txt_delete(TxtLoc l, u32 n) {
+	u32 pi = txt_split_piece(l.t, l.p, l.i);
 	if (pi > 0) pi--;
-	if (n > cur) n = cur;
-	cur -= n;
-	b->len -= n;
+	l.p = pi;
+	l.i = l.t->ptbl.v[l.p].n;
 	for (;;) {
-		TxtPiece *p = &b->ptbl.v[pi];
-		if (n >= p->n) {
-			n -= p->n;
-			p->n = 0;
-			if (pi > 0 || b->ptbl.n > 1) txt_remove_piece(b, pi);
-		} else {
-			p->n -= n;
-			n = 0;
+		ASSERT(l.i == l.t->ptbl.v[l.p].n);
+		if (l.i >= n) {
+			l.i -= n;
+			l.t->ptbl.v[l.p].n -= n;
 			break;
+		} else {
+			l.t->ptbl.v[l.p].n -= l.i;
+			n -= l.i;
+			l.i = 0;
+			if (l.p == 0) break;
+			l.p = l.p - 1;
+			l.i = l.t->ptbl.v[l.p].n;
 		}
-		if (pi == 0) break;
-		pi--;
 	}
-	txt_join_or_kill(b, pi);
-	return cur;
+	return txt_join_or_kill(l);
 }
 
-u32 txt_delete_c(Txt *b, u32 cur) {
-	while (cur > 0 && (txt_byte(b, txt_at(b, cur-1)) & 0xc0) == 0x80) 
-		cur = txt_delete(b, cur, 1);
-	cur = txt_delete(b, cur, 1);
-	return cur;
+TxtLoc txt_delete_c(TxtLoc l) {
+	while (!at_start(l) && (txt_byte(l) & 0xc0) == 0x80) 
+		l = txt_delete(l, 1);
+	l = txt_delete(l, 1);
+	return l;
 }
 
 int txt_load(Txt *b, const char *path) {
@@ -195,44 +195,37 @@ void txt_free(Txt *t) {
 	free(t->ptbl.v);
 }
 
-/* reading individual chars */
+/* navigation */
 
-u8 txt_byte(Txt *t, TxtLoc l) {
-	TxtPiece *p = &t->ptbl.v[l.p];
-	TxtBuf *b = &t->buf[p->buf];
-	if (l.i >= p->n) return 0;
-	return b->s[p->ofs + l.i];
-}
-
-u32 txt_chr(Txt *t, TxtLoc l) {
-	TxtPiece *p = &t->ptbl.v[l.p];
-	TxtBuf *b = &t->buf[p->buf];
-	return utf8_decode_at(b->s, p->ofs + l.i, p->ofs + p->n);
-}
-
-/* cursor manipulation */
-
-TxtLoc txt_at(Txt *b, u32 cur) {
+TxtLoc txt_at(Txt *b, u32 ofs) {
 	for (u32 i = 0; i < b->ptbl.n; i++) {
-		if (cur < b->ptbl.v[i].n) {
-			return (TxtLoc) { b, i, cur };
+		if (ofs < b->ptbl.v[i].n) {
+			return (TxtLoc) { b, i, ofs };
 		}
-		cur -= b->ptbl.v[i].n;
+		ofs -= b->ptbl.v[i].n;
 	}
 	return (TxtLoc) { b, b->ptbl.n - 1, b->ptbl.v[b->ptbl.n - 1].n };
 }
 
-u32 txt_ofs(Txt *b, TxtLoc l) {
+u32 txt_ofs(TxtLoc l) {
 	u32 r = 0;
 	for (u32 i = 0; i < l.p; i++) {
-		r += b->ptbl.v[i].n;
+		r += l.t->ptbl.v[i].n;
 	}
 	return r + l.i;
 }
 
-TxtLoc txt_next(Txt *b, TxtLoc l) {
-	TxtPiece *p = &b->ptbl.v[l.p];
-	if (l.p + 1 < b->ptbl.n) {
+int txt_before(TxtLoc a, TxtLoc b) {
+	return a.p < b.p || (a.p == b.p && a.i < b.i);
+}
+
+int txt_after(TxtLoc a, TxtLoc b) {
+	return a.p > b.p || (a.p == b.p && a.i > b.i);
+}
+
+TxtLoc bnext(TxtLoc l) {
+	TxtPiece *p = &l.t->ptbl.v[l.p];
+	if (l.p + 1 < l.t->ptbl.n) {
 		if (l.i + 1 < p->n) l.i++;
 		else l.p++, l.i = 0;
 	} else {
@@ -242,37 +235,106 @@ TxtLoc txt_next(Txt *b, TxtLoc l) {
 	return l;
 }
 
-TxtLoc txt_prev(Txt *b, TxtLoc l) {
+TxtLoc bprev(TxtLoc l) {
 	if (l.i > 0) {
-		return (TxtLoc) { b, l.p, l.i - 1 };
-	} else if (l.p > 0) {
-		return (TxtLoc) { b, l.p - 1, b->ptbl.v[l.p - 1].n - 1 };
+		return (TxtLoc) { l.t, l.p, l.i - 1 };
+	} else if (l.p > 0 && l.t->ptbl.v[l.p - 1].n > 0) {
+		return (TxtLoc) { l.t, l.p - 1, l.t->ptbl.v[l.p - 1].n - 1 };
 	} else {
-		return (TxtLoc) { b, 0, 0 };
+		return (TxtLoc) { l.t, 0, 0 };
 	}
 }
 
-int txt_at_start(Txt *b, TxtLoc l) {
-	(void)b;
+TxtLoc cnext(TxtLoc l) {
+	l = bnext(l);
+	while ((txt_byte(l) & 0xc0) == 0x80) l = bnext(l);
+	return l;
+}
+
+TxtLoc cprev(TxtLoc l) {
+	l = bprev(l);
+	while ((txt_byte(l) & 0xc0) == 0x80) l = bprev(l);
+	return l;
+}
+
+int at_start(TxtLoc l) {
 	return l.p == 0 && l.i == 0;
 }
 
-int txt_at_end(Txt *b, TxtLoc l) {
-	return l.p + 1 == b->ptbl.n && l.i == b->ptbl.v[l.p].n;
+int at_end(TxtLoc l) {
+	return l.p + 1 == l.t->ptbl.n && l.i == l.t->ptbl.v[l.p].n;
 }
 
-int txt_before(TxtLoc a, TxtLoc b) {
-	return a.p < b.p || (a.p == b.p && a.i < b.i);
+TxtLoc next_newline(TxtLoc l) {
+	do l = cnext(l);
+	while (!at_end(l) && txt_byte(l) != '\n');
+	return l;
 }
 
-int txt_after(TxtLoc a, TxtLoc b) {
-	return a.p > b.p || (a.p == b.p && a.i > b.i);
+TxtLoc prev_newline(TxtLoc l) {
+	do l = cprev(l);
+	while (!at_start(l) && txt_byte(l) != '\n');
+	return l;
+}
+
+TxtLoc start_of_line(TxtLoc l) {
+	l = prev_newline(l);
+	if (!at_start(l) && txt_byte(l) == '\n') l = cnext(l);
+	return l;
+}
+
+TxtLoc end_of_line(TxtLoc l) {
+	TxtLoc start = start_of_line(l);
+	return txt_byte(start) == '\n' ? start : next_newline(start);
+}
+
+u32 get_col(TxtLoc l) {
+	u32 n = 0;
+	for (TxtLoc tmp = start_of_line(l); txt_before(tmp, l); txt_chr_next(&tmp)) n++;
+	return n;
+}
+
+TxtLoc at_col(TxtLoc l, u32 col) {
+	l = start_of_line(l);
+	while (col--) {
+		if (txt_chr_next(&l) == '\n') {
+			l = bprev(l);
+			break;
+		}
+	}
+	return l;
+}
+
+TxtLoc prev_line(TxtLoc l) {
+	TxtLoc start = start_of_line(l);
+	return at_col(cprev(start), get_col(l));
+}
+
+TxtLoc next_line(TxtLoc l) {
+	TxtLoc end = end_of_line(l);
+	if (at_end(end)) return end;
+	return at_col(cnext(end), get_col(l));
+}
+
+/* reading chars */
+
+u32 txt_chr(TxtLoc l) {
+	TxtPiece *p = &l.t->ptbl.v[l.p];
+	TxtBuf *b = &l.t->buf[p->buf];
+	return utf8_decode_at(b->s, p->ofs + l.i, p->ofs + p->n);
+}
+
+u8 txt_byte(TxtLoc l) {
+	TxtPiece *p = &l.t->ptbl.v[l.p];
+	TxtBuf *b = &l.t->buf[p->buf];
+	if (l.i >= p->n) return 0;
+	return b->s[p->ofs + l.i];
 }
 
-u32 txt_chr_next(Txt *t, TxtLoc *l) {
-	if (txt_at_end(t, *l)) return 0;
-	u32 c = txt_chr(t, *l);
+u32 txt_chr_next(TxtLoc *l) {
+	if (at_end(*l)) return 0;
+	u32 c = txt_chr(*l);
 	u32 n = UTF8_CP_LEN(c);
-	for (u32 i = 0; i < n; i++) *l = txt_next(t, *l);
+	for (u32 i = 0; i < n; i++) *l = bnext(*l);
 	return c;
 }
diff --git a/txt.h b/txt.h
index 3af9970..b33599b 100644
--- a/txt.h
+++ b/txt.h
@@ -29,29 +29,50 @@ typedef struct {
 	u32 p, i;
 } TxtLoc;
 
+/* text buffer manipulation */
+
 u32 txt_split_piece(Txt *b, u32 pi, u32 i);
 void txt_remove_piece(Txt *b, u32 pi);
 void txt_insert_piece(Txt *b, u32 pi, TxtBufIdx buf, u32 ofs, u32 n);
 
-u32 txt_insert(Txt *b, u32 cur, const char *s, u32 n);
-u32 txt_delete(Txt *b, u32 cur, u32 n);
-u32 txt_insert_c(Txt *b, u32 cur, u32 ch);
-u32 txt_delete_c(Txt *b, u32 cur);
 int txt_load(Txt *b, const char *path);
 int txt_save(Txt *b, const char *path);
 void txt_free(Txt *b);
 
-TxtLoc txt_at(Txt *b, u32 cur);
-u32 txt_ofs(Txt *b, TxtLoc l);
-TxtLoc txt_next(Txt *b, TxtLoc l);
-TxtLoc txt_prev(Txt *b, TxtLoc l);
-int txt_at_start(Txt *b, TxtLoc l);
-int txt_at_end(Txt *b, TxtLoc l);
+/* insertion & deletion */
+
+TxtLoc txt_insert(TxtLoc l, const char *s, u32 n);
+TxtLoc txt_delete(TxtLoc l, u32 n);
+TxtLoc txt_insert_c(TxtLoc l, u32 ch);
+TxtLoc txt_delete_c(TxtLoc l);
+
+/* navigation */
+
+TxtLoc txt_at(Txt *b, u32 ofs);
+u32 txt_ofs(TxtLoc l);
 int txt_before(TxtLoc a, TxtLoc b);
 int txt_after(TxtLoc a, TxtLoc b);
 
-u32 txt_chr(Txt *b, TxtLoc l);
-u8 txt_byte(Txt *b, TxtLoc l);
-u32 txt_chr_next(Txt *b, TxtLoc *l);
+TxtLoc bnext(TxtLoc l);
+TxtLoc bprev(TxtLoc l);
+TxtLoc cnext(TxtLoc l);
+TxtLoc cprev(TxtLoc l);
+int at_start(TxtLoc l);
+int at_end(TxtLoc l);
+
+TxtLoc next_newline(TxtLoc l);
+TxtLoc prev_newline(TxtLoc l);
+TxtLoc start_of_line(TxtLoc l);
+TxtLoc end_of_line(TxtLoc l);
+TxtLoc prev_line(TxtLoc l);
+TxtLoc next_line(TxtLoc l);
+TxtLoc at_col(TxtLoc l, u32 col);
+u32 get_col(TxtLoc l);
+
+/* reading */
+
+u32 txt_chr(TxtLoc l);
+u8 txt_byte(TxtLoc l);
+u32 txt_chr_next(TxtLoc *l);
 
 #endif