App preferences were spread across six flat plain-text files (settings.txt,
recent.txt, recent_limit.txt, statusbar.txt, ribbon.txt, plot.txt), each with a
bespoke line parser and no grouping. Replace them with a single grouped JSON,
serialized via serde (enabling the derive feature; serde_json was already a
dependency).
- New app/config.rs: AppConfig { settings, recent, statusbar, ribbon, plot } →
<config>/settings.json (pretty JSON), load()/save().
- Make UserSettings, StatusBarConfig/StatusPill, CollapseMode and
PlotDialogState serde-derived; #[serde(skip)] marks the plot dialog's runtime
fields so only print preferences persist. Their bespoke .txt load/save is
removed.
- App gains current_config/apply_config/save_config: one AppConfig::load at
startup distributes into live state; every settings-change site
(persist_settings_if_changed, recent add/remove/limit, status-bar pill
toggle, ribbon density, plot commit) routes through save_config, which diffs
against the last write to avoid thrashing.
- Clean start: the old flat files are ignored (no migration). ocad.pgp stays a
separate hand-editable file.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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