- Undo texts of 4 KiB or more (Insert/Paste from the buffer, Delete from
the spans the piece table remembers for its last large deletion) are
held as TextSpan references into the piece table's append-only
storage, after checking they hold exactly the recorded bytes. Undo and
redo insert them with Buffer::insert_spans, which adds pieces over the
stored bytes instead of copying them into storage again (the journal
still gets the bytes, as one record). A replace-all session on a 26 MB
file peaks at 181 MB instead of 332 MB; undo/redo cycles of a 6.6 MB
kill no longer grow memory by 6.6 MB each.
- UndoSystem keeps a byte budget (default max(64 MiB, twice the buffer
size); SetByteBudget). Over it, history is pruned to 75% of the budget:
branches off the current path, then the oldest edits (an undo group
goes whole, and never the current state's group), then the redo line.
When the saved state is dropped the buffer stays modified until saved.
- replace_all_bytes clears undo history, which was recorded against (and
may reference the storage of) the previous content.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015rcVQiiWyTzoNrsvLSaAfB
