Add Sources Toggle

[jonahadkins]

Feature Description

Add a control for filtering by all sources (OSM, Google, FSQ, etc)

Use Case

i want to look at all the features on the map in either mode by only one source.

Which area of the Explorer does this relate to?

Search / filtering

[jonahadkins]

follow the existing LanguageSwitcher pattern (MUI Button + Menu dropdown) for the UI, and use MapLibre's map.setFilter() to apply
runtime filter expressions based on the selected dataset.

Since sources is stringified JSON in the tiles, we'll use MapLibre's index-of expression to match dataset names within the string (same
technique used for $extract:categories.primary).

Files to Modify

1. app/page.jsx — Add state

• Add sourceFilter / setSourceFilter state (null = show all, string = dataset name)
• Pass sourceFilter and setSourceFilter to Header and MapView

2. components/nav/SourceFilter.jsx — New component (similar to LanguageSwitcher)

• MUI Button + Menu dropdown
• "All Sources" option (clears filter) + list of dataset names (provided by user)
• Receives sourceFilter, setSourceFilter, and mode as props
• Follows LanguageSwitcher CSS/styling pattern

3. components/nav/Header.jsx — Add SourceFilter to toolbar

• Import and render SourceFilter component in the toolbar (before the inspect mode toggle)
• Pass through sourceFilter and setSourceFilter props

4. lib/LayerManager.js — Apply source filter to map layers

• Add applySourceFilter(map, datasetName) function
  • Iterates all Overture layers (both explore and inspect specs)
  • For each layer, retrieves its current filter and wraps it:
    • If datasetName is null: restore original filter (remove source constraint)
    • If datasetName is set: combine original filter with [">=", ["index-of", datasetName, ["get", "sources"]], 0] using ["all", ...]
  • Store original filters in a module-level Map on first call so they can be restored

5. components/MapView.jsx — React to sourceFilter changes

• Add a useEffect that calls applySourceFilter(map, sourceFilter) when sourceFilter changes
• Depends on sourcesAdded being true (same pattern as other effects)

Implementation Notes

• The sources property is a stringified JSON array, so index-of on the raw string with the dataset name is sufficient (dataset names are
  unique enough to avoid false substring matches)
• The filter is additive — it combines with existing per-layer filters via ["all", existingFilter, sourceCheck]
• When "All Sources" is selected, original filters are restored exactly
• This works for both explore and inspect mode layers