support line-by-line undo in text mode

1 files changed, 5 insertions, 0 deletions

diff --git a/lineset.c b/lineset.c
index 75ae1d3..4b5ad8c 100644
--- a/lineset.c
+++ b/lineset.c
@@ -171,3 +171,8 @@ void copy_lines_to_ring(int y1, int y2, int which){
 	}
 #endif	
 }
+
+void invalidate_undo(){
+	if (undo_lst > undo_cur)
+		undo_lst = undo_cur;
+}