menuconfig: Extend dialog_textbox so that it can return to a scrolled position

We can now display other UI elements (menus) "on top" of a textbox and then
seemingly come back to it in the same state it was left.

Signed-off-by: Benjamin Poirier <bpoirier@suse.de>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/kconfig/lxdialog/textbox.c b/scripts/kconfig/lxdialog/textbox.c
index eb4ee92a..506a095 100644
--- a/scripts/kconfig/lxdialog/textbox.c
+++ b/scripts/kconfig/lxdialog/textbox.c
@@ -51,7 +51,7 @@
  * keys is a null-terminated array
  */
 int dialog_textbox(const char *title, const char *tbuf, int initial_height,
-		   int initial_width, int *keys)
+		   int initial_width, int *keys, int *_vscroll, int *_hscroll)
 {
 	int i, x, y, cur_x, cur_y, key = 0;
 	int height, width, boxh, boxw;
@@ -65,6 +65,15 @@
 	buf = tbuf;
 	page = buf;	/* page is pointer to start of page to be displayed */
 
+	if (_vscroll && *_vscroll) {
+		begin_reached = 0;
+
+		for (i = 0; i < *_vscroll; i++)
+			get_line();
+	}
+	if (_hscroll)
+		hscroll = *_hscroll;
+
 do_resize:
 	getmaxyx(stdscr, height, width);
 	if (height < 8 || width < 8)
@@ -275,6 +284,19 @@
 	}
 	delwin(box);
 	delwin(dialog);
+	if (_vscroll) {
+		const char *s;
+
+		s = buf;
+		*_vscroll = 0;
+		back_lines(page_length);
+		while (s < page && (s = strchr(s, '\n'))) {
+			(*_vscroll)++;
+			s++;
+		}
+	}
+	if (_hscroll)
+		*_hscroll = hscroll;
 	return key;
 }