Drawings and persistence
Enable drawings for drawing tools, selection, handles, undo/redo and persistence.
DrawingToolType identifies a tool and its interaction mode. The ui feature
also provides a drawing toolbar for a host-composed layout.
Save through the chart
Section titled “Save through the chart”Use Chart::save_drawings, then validate and serialize the returned drawing file
before replacing a previous save. Restore with Chart::load_drawings after setting
the matching symbol. Chart-level persistence retains timestamped anchors, so
prepending history does not move a saved drawing to another bar.
The builder guide includes a tested round trip. Unreadable files and symbol mismatches leave current drawings intact; report skipped records to the user rather than silently discarding them.
Keep durable storage in the host
Section titled “Keep durable storage in the host”Store the JSON in your own file or service. Implement services::Storage and
attach it with Chart::set_storage for automatic per-symbol persistence.
With ui, Chart::snapshot and Chart::restore additionally preserve settings,
studies and the view.
The drawing persistence example shows save/load and error handling. Drawing types and programmatic construction are documented in the API reference.