wreadln: support wide characters

wreadln() didn't distinguish narrow from wide characters, which
resulted in display corruption.  This patch adds a lot of internal
conversions between byte positions, screen positions and character
position, which hopefully fixes all these bugs.  Since these
conversions are quite expensive, the code should be revised and
optimized.

1 files changed, 190 insertions, 17 deletions

diff --git a/src/wreadln.c b/src/wreadln.c
index 08ba991f2..7abfc4ac2 100644
--- a/src/wreadln.c
+++ b/src/wreadln.c
@@ -76,35 +76,208 @@ void *wrln_completion_callback_data = NULL;
 wrln_gcmp_pre_cb_t wrln_pre_completion_callback = NULL;
 wrln_gcmp_post_cb_t wrln_post_completion_callback = NULL;
 
+/** converts a byte position to a screen column */
+static unsigned
+byte_to_screen(const gchar *data, size_t x)
+{
+#ifdef ENABLE_WIDE
+	gchar *dup;
+	char *p;
+	unsigned width;
+
+	assert(x <= strlen(data));
+
+	dup = g_strdup(data);
+	dup[x] = 0;
+	p = locale_to_utf8(dup);
+	g_free(dup);
+
+	width = utf8_width(p);
+	g_free(p);
+
+	return width;
+#else
+	(void)data;
+
+	return (unsigned)x;
+#endif
+}
+
+/** finds the first character which doesn't fit on the screen */
+static size_t
+screen_to_bytes(const gchar *data, unsigned width)
+{
+#ifdef ENABLE_WIDE
+	size_t length = strlen(data);
+	gchar *dup = g_strdup(data);
+	char *p;
+	unsigned p_width;
+
+	while (true) {
+		dup[length] = 0;
+		p = locale_to_utf8(dup);
+		p_width = utf8_width(p);
+		g_free(p);
+		if (p_width <= width)
+			break;
+
+		--length;
+	}
+
+	g_free(dup);
+
+	return length;
+#else
+	(void)data;
+
+	return (size_t)width;
+#endif
+}
+
+/** returns the screen colum where the cursor is located */
+static unsigned
+cursor_column(const struct wreadln *wr)
+{
+	return byte_to_screen(wr->line + wr->start,
+			      wr->cursor - wr->start);
+}
+
+/** returns the offset in the string to align it at the right border
+    of the screen */
+static inline size_t
+right_align_bytes(const gchar *data, size_t right, unsigned width)
+{
+#ifdef ENABLE_WIDE
+	gchar *dup;
+	size_t start = 0;
+
+	assert(right <= strlen(data));
+
+	dup = g_strdup(data);
+	dup[right] = 0;
+
+	while (dup[start] != 0) {
+		char *p = locale_to_utf8(dup + start), *q;
+		unsigned p_width = utf8_width(p);
+		gunichar c;
+
+		if (p_width < width) {
+			g_free(p);
+			break;
+		}
+
+		c = g_utf8_get_char(p);
+		p[g_unichar_to_utf8(c, NULL)] = 0;
+		q = utf8_to_locale(p);
+		g_free(p);
+
+		start += strlen(q);
+		g_free(q);
+	}
+
+	g_free(dup);
+
+	return start;
+#else
+	(void)data;
+
+	return right >= width ? right + 1 - width : 0;
+#endif
+}
+
+/** returns the size (in bytes) of the next character */
+static inline size_t
+next_char_size(const gchar *data)
+{
+#ifdef ENABLE_WIDE
+	char *p = locale_to_utf8(data), *q;
+	gunichar c;
+	size_t size;
+
+	c = g_utf8_get_char(p);
+	p[g_unichar_to_utf8(c, NULL)] = 0;
+	q = utf8_to_locale(p);
+	g_free(p);
+
+	size = strlen(q);
+	g_free(q);
+
+	return size;
+#else
+	(void)data;
+
+	return 1;
+#endif
+}
+
+/** returns the size (in bytes) of the previous character */
+static inline size_t
+prev_char_size(const gchar *data, size_t x)
+{
+#ifdef ENABLE_WIDE
+	char *p = locale_to_utf8(data), *q;
+	gunichar c;
+	size_t size;
+
+	assert(x > 0);
+
+	q = p;
+	while (true) {
+		c = g_utf8_get_char(q);
+		size = g_unichar_to_utf8(c, NULL);
+		if (size > x)
+			size = x;
+		x -= size;
+		if (x == 0) {
+			g_free(p);
+			return size;
+		}
+
+		q += size;
+	}
+#else
+	(void)data;
+	(void)x;
+
+	return 1;
+#endif
+}
+
 /* move the cursor one step to the right */
 static inline void cursor_move_right(struct wreadln *wr)
 {
+	size_t size;
+
 	if (wr->line[wr->cursor] == 0)
 		return;
 
-	++wr->cursor;
-	if (wr->cursor >= (size_t)wr->width &&
-	    wr->start < wr->cursor - wr->width + 1)
-		++wr->start;
+	size = next_char_size(wr->line + wr->cursor);
+	wr->cursor += size;
+	if (cursor_column(wr) >= wr->width)
+		wr->start = right_align_bytes(wr->line, wr->cursor, wr->width);
 }
 
 /* move the cursor one step to the left */
 static inline void cursor_move_left(struct wreadln *wr)
 {
+	size_t size;
+
 	if (wr->cursor == 0)
 		return;
 
-	if (wr->cursor == wr->start && wr->start > 0)
-		--wr->start;
-	--wr->cursor;
+	size = prev_char_size(wr->line, wr->cursor);
+	assert(wr->cursor >= size);
+	wr->cursor -= size;
+	if (wr->cursor < wr->start)
+		wr->start = wr->cursor;
 }
 
 /* move the cursor to the end of the line */
 static inline void cursor_move_to_eol(struct wreadln *wr)
 {
 	wr->cursor = strlen(wr->line);
-	if (wr->cursor >= wr->width)
-		wr->start = wr->cursor - wr->width + 1;
+	if (cursor_column(wr) >= wr->width)
+		wr->start = right_align_bytes(wr->line, wr->cursor, wr->width);
 }
 
 /* draw line buffer and update cursor position */
@@ -115,11 +288,12 @@ static inline void drawline(const struct wreadln *wr)
 	whline(wr->w, ' ', wr->width);
 	/* print visible part of the line buffer */
 	if (wr->masked)
-		whline(wr->w, '*', utf8_width(wr->line) - wr->start);
+		whline(wr->w, '*', utf8_width(wr->line + wr->start));
 	else
-		waddnstr(wr->w, wr->line + wr->start, wr->width);
+		waddnstr(wr->w, wr->line + wr->start,
+			 screen_to_bytes(wr->line, wr->width));
 	/* move the cursor to the correct position */
-	wmove(wr->w, wr->y, wr->x + wr->cursor - wr->start);
+	wmove(wr->w, wr->y, wr->x + cursor_column(wr));
 	/* tell ncurses to redraw the screen */
 	doupdate();
 }
@@ -185,19 +359,18 @@ wreadln_insert_byte(struct wreadln *wr, gint key)
 #endif
 
 	wr->cursor += length;
-	if (wr->cursor >= (size_t)wr->width &&
-	    wr->start < wr->cursor - wr->width + 1)
-		wr->start += length;
+	if (cursor_column(wr) >= wr->width)
+		wr->start = right_align_bytes(wr->line, wr->cursor, wr->width);
 }
 
 static void
 wreadln_delete_char(struct wreadln *wr, size_t x)
 {
-	size_t rest;
-	const size_t length = 1;
+	size_t rest, length;
 
 	assert(x < strlen(wr->line));
 
+	length = next_char_size(&wr->line[x]);
 	rest = strlen(&wr->line[x + length]) + 1;
 	memmove(&wr->line[x], &wr->line[x + length], rest);
 }