Add getters for scrollback buffer line count and line pos

This functionality is needed to implement a scrollbar

src/tsm/libtsm-int.h

@@ -140,6 +140,7 @@ struct tsm_screen {
 	struct line *sb_last;		/* last line; was moved last*/
 	unsigned int sb_max;		/* max-limit of lines in sb */
 	struct line *sb_pos;		/* current position in sb or NULL */
+	unsigned int sb_pos_num;	/* current numeric position in sb */
 	uint64_t sb_last_id;		/* last id given to sb-line */
 
 	/* cursor: positions are always in-bound, but cursor_x might be

src/tsm/libtsm.h

@@ -201,6 +201,8 @@ void tsm_screen_sb_down(struct tsm_screen *con, unsigned int num);
 void tsm_screen_sb_page_up(struct tsm_screen *con, unsigned int num);
 void tsm_screen_sb_page_down(struct tsm_screen *con, unsigned int num);
 void tsm_screen_sb_reset(struct tsm_screen *con);
+unsigned int tsm_screen_sb_get_line_count(struct tsm_screen *con);
+unsigned int tsm_screen_sb_get_line_pos(struct tsm_screen *con);
 
 void tsm_screen_set_def_attr(struct tsm_screen *con,
 			     const struct tsm_screen_attr *attr);

src/tsm/libtsm.sym

@@ -129,4 +129,6 @@ global:
 	tsm_vte_get_mouse_mode;
 	tsm_vte_get_mouse_event;
 	tsm_vte_handle_mouse;
+	tsm_screen_sb_get_line_count;
+	tsm_screen_sb_get_line_pos;
 } LIBTSM_4;

src/tsm/tsm-screen.c

@@ -230,10 +230,13 @@ static void link_to_scrollback(struct tsm_screen *con, struct line *line)
 		if (con->sb_pos) {
 			if (con->sb_pos == tmp ||
 			    !(con->flags & TSM_SCREEN_FIXED_POS)) {
-				if (con->sb_pos->next)
+				if (con->sb_pos->next) {
 					con->sb_pos = con->sb_pos->next;
-				else
+					++con->sb_pos_num;
+				} else {
 					con->sb_pos = line;
+					con->sb_pos_num = 0;
+				}
 			}
 		}
 
@@ -253,12 +256,17 @@ static void link_to_scrollback(struct tsm_screen *con, struct line *line)
 	line->sb_id = ++con->sb_last_id;
 	line->next = NULL;
 	line->prev = con->sb_last;
-	if (con->sb_last)
+	if (con->sb_last) {
 		con->sb_last->next = line;
-	else
+	} else {
 		con->sb_first = line;
+	}
 	con->sb_last = line;
 	++con->sb_count;
+
+	if (con->sb_pos == NULL) {
+		con->sb_pos_num = con->sb_count;
+	}
 }
 
 static void screen_scroll_up(struct tsm_screen *con, unsigned int num)
@@ -832,6 +840,7 @@ void tsm_screen_clear_sb(struct tsm_screen *con)
 	con->sb_last = NULL;
 	con->sb_count = 0;
 	con->sb_pos = NULL;
+	con->sb_pos_num = 0;
 
 	if (con->sel_active) {
 		if (con->sel_start.line) {
@@ -861,10 +870,12 @@ void tsm_screen_sb_up(struct tsm_screen *con, unsigned int num)
 				return;
 
 			con->sb_pos = con->sb_pos->prev;
+			--con->sb_pos_num;
 		} else if (!con->sb_last) {
 			return;
 		} else {
 			con->sb_pos = con->sb_last;
+			con->sb_pos_num = con->sb_count - 1;
 		}
 	}
 }
@@ -880,8 +891,10 @@ void tsm_screen_sb_down(struct tsm_screen *con, unsigned int num)
 	con->age = con->age_cnt;
 
 	while (num--) {
-		if (con->sb_pos)
+		if (con->sb_pos) {
 			con->sb_pos = con->sb_pos->next;
+			++con->sb_pos_num;
+		}
 		else
 			return;
 	}
@@ -918,6 +931,25 @@ void tsm_screen_sb_reset(struct tsm_screen *con)
 	con->age = con->age_cnt;
 
 	con->sb_pos = NULL;
+	con->sb_pos_num = 0;
+}
+
+unsigned int tsm_screen_sb_get_line_count(struct tsm_screen *con)
+{
+	if (!con) {
+		return 0;
+	}
+
+	return con->sb_count;
+}
+
+unsigned int tsm_screen_sb_get_line_pos(struct tsm_screen *con)
+{
+	if (!con) {
+		return 0;
+	}
+
+	return con->sb_pos_num;
 }
 
 SHL_EXPORT

test/test_screen.c

@@ -194,11 +194,80 @@ START_TEST(test_screen_resize_alt_colors)
 }
 END_TEST
 
+START_TEST(test_screen_sb_get_line_pos)
+{
+	struct tsm_screen *screen;
+	int r;
+
+	r = tsm_screen_new(&screen, NULL, NULL);
+	ck_assert_int_eq(r, 0);
+
+	r = tsm_screen_resize(screen, 5, 5);
+	ck_assert_int_eq(r, 0);
+
+	tsm_screen_set_max_sb(screen, 5);
+
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 0);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 0);
+
+	/* fill up screen */
+	tsm_screen_newline(screen);
+	tsm_screen_newline(screen);
+	tsm_screen_newline(screen);
+	tsm_screen_newline(screen);
+
+	/* create first entry in scrollback buffer */
+	tsm_screen_newline(screen);
+
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 1);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 1);
+
+	tsm_screen_newline(screen);
+
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 2);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 2);
+
+	tsm_screen_newline(screen);
+
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 3);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 3);
+
+	/* scroll up by one (third line of sb) */
+	tsm_screen_sb_up(screen, 1);
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 3);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 2);
+
+	/* scroll up by one (second line of sb) */
+	tsm_screen_sb_up(screen, 1);
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 3);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 1);
+
+	/* scroll up by one (first line of sb) */
+	tsm_screen_sb_up(screen, 1);
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 3);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 0);
+
+	/* scroll up beyond top end of buffer */
+	tsm_screen_sb_up(screen, 1);
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 3);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 0);
+
+	/* scroll out of scrollback buffer */
+	tsm_screen_sb_down(screen, 3);
+	ck_assert_int_eq(tsm_screen_sb_get_line_count(screen), 3);
+	ck_assert_int_eq(tsm_screen_sb_get_line_pos(screen), 3);
+
+	tsm_screen_unref(screen);
+	screen = NULL;
+}
+END_TEST
+
 
 TEST_DEFINE_CASE(misc)
 	TEST(test_screen_init)
 	TEST(test_screen_null)
 	TEST(test_screen_resize_alt_colors)
+	TEST(test_screen_sb_get_line_pos)
 TEST_END_CASE
 
 TEST_DEFINE(