vte/console: implement CSI 'M' (DL: delete line)

The 'M' CSI mode is used to delete lines. This implements this mode
similar to the "INSERT LINES" CSI.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

src/console.c

@@ -891,6 +891,41 @@ void kmscon_console_insert_lines(struct kmscon_console *con, unsigned int num)
 	con->cursor_x = 0;
 }
 
+void kmscon_console_delete_lines(struct kmscon_console *con, unsigned int num)
+{
+	unsigned int i, j, max;
+
+	if (!con || !num)
+		return;
+
+	if (con->cursor_y < con->margin_top ||
+	    con->cursor_y > con->margin_bottom)
+		return;
+
+	max = con->margin_bottom - con->cursor_y + 1;
+	if (num > max)
+		num = max;
+
+	struct line *cache[num];
+
+	for (i = 0; i < num; ++i) {
+		cache[i] = con->lines[con->cursor_y + i];
+		for (j = 0; j < con->size_x; ++j)
+			cell_init(con, &cache[i]->cells[j]);
+	}
+
+	if (num < max) {
+		memmove(&con->lines[con->cursor_y],
+			&con->lines[con->cursor_y + num],
+			(max - num) * sizeof(struct line*));
+
+		memcpy(&con->lines[con->cursor_y + (max - num)],
+		       cache, num * sizeof(struct line*));
+	}
+
+	con->cursor_x = 0;
+}
+
 void kmscon_console_erase_cursor(struct kmscon_console *con)
 {
 	unsigned int x;

src/console.h

@@ -85,6 +85,7 @@ void kmscon_console_move_right(struct kmscon_console *con, unsigned int num);
 void kmscon_console_move_line_end(struct kmscon_console *con);
 void kmscon_console_move_line_home(struct kmscon_console *con);
 void kmscon_console_insert_lines(struct kmscon_console *con, unsigned int num);
+void kmscon_console_delete_lines(struct kmscon_console *con, unsigned int num);
 void kmscon_console_erase_cursor(struct kmscon_console *con);
 void kmscon_console_erase_cursor_to_end(struct kmscon_console *con);
 void kmscon_console_erase_home_to_cursor(struct kmscon_console *con);

src/vte.c

@@ -1099,6 +1099,13 @@ static void do_csi(struct kmscon_vte *vte, uint32_t data)
 			num = 1;
 		kmscon_console_insert_lines(vte->con, num);
 		break;
+	case 'M': /* DL */
+		/* delete lines */
+		num = vte->csi_argv[0];
+		if (num <= 0)
+			num = 1;
+		kmscon_console_delete_lines(vte->con, num);
+		break;
 	default:
 		log_debug("unhandled CSI sequence %c", data);
 	}