Design Intuition

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Preferences ​

A small wrapper around the browser's local storage. Reads and writes named values that survive across page reloads.

Location ​

src/lib/ts/managers/Preferences.ts

What it does ​

Stores typed values in the browser's local storage under a project-specific prefix. Provides four basic operations and two store-builders.

Operations ​

  • Read. Pull a value out by name. Returns the stored value or null if no value has been stored.
  • Write. Save a value under a name. The value is JSON-encoded.
  • Remove. Delete one stored value.
  • Clear. Delete every stored value owned by this project.
  • Reset. Delete every stored value except the saved scene and the saved library — used by the "factory reset" button.
  • Dump. Print every stored value to the browser console for debugging.

Builders ​

  • persistent. Returns a writable store seeded with the value last saved under a key, and saves the value on every change.
  • persistent_set. Same shape, but the value is a Set of strings, stored as a JSON array.

Stored values ​

The set of names that can be stored is fixed by an enum. As of today the names cover:

  • Layout: whether the side panel is open, which sub-panels are open.
  • Colors: background, accent, text, edge.
  • Units: imperial or metric.
  • View: decorations bitmask, edge thickness, precision, view mode, solid flag, grid visibility, grid opacity.
  • Rotation: rotation-snap on or off.
  • Render: orientation, scale.
  • Parts table: which tab is active, whether the parts list is shown, whether the givens are shown, the set of collapsed-row ids.
  • Mode: editing-lock flag.
  • Persistence: the saved scene, the saved library, the active library folder.

Citation: src/lib/ts/managers/Preferences.ts lines 11-60 — the T_Preference enum.

Storage format ​

All values are JSON-encoded and stored under the prefix di:. So a key called showDetails lives in local storage at di:showDetails.

Read failure ​

A read that finds no value, or finds an undecodable string, returns null. The caller is expected to fall back to a default.

  • src/lib/ts/managers/Stores.ts — many session-and-persistent values are built using the persistent helpers in this module.
  • Any module that calls persistent or persistent_set to back a store with local storage.