Respect group integrity when removing stuff from the Undo stack.

Fixes: #9079

diff --git a/src/Undo.cpp b/src/Undo.cpp
index a335873d7cced6173849d818f02536ef152d34b1..31eaec3dbd84977ee7d52e3dca4c86b3726df7f9 100644 (file)
--- a/src/Undo.cpp
+++ b/src/Undo.cpp
@@ -160,13 +160,17 @@ public:
        /// Push an item on to the stack, deleting the bottom group on
        /// overflow.
        void push(UndoElement const & v) {
-               c_.push_front(v);
-               if (c_.size() > limit_) {
+               // Remove some entries if the limit has been reached.
+               // However, if the only group on the stack is the one
+               // we are currently populating, do nothing.
+               if (c_.size() >= limit_
+                   && c_.front().group_id != v.group_id) {
                        // remove a whole group at once.
                        const size_t gid = c_.back().group_id;
                        while (!c_.empty() && c_.back().group_id == gid)
                                c_.pop_back();
                }
+               c_.push_front(v);
        }
 
        /// Mark all the elements of the stack as dirty