fix: fly_to in overlay/interleaved basemap mode

[tylere]

Summary

• Fix fly_to() having no effect when the basemap mode is "overlaid" or "interleaved" (the default). The OverlayRenderer passes initialViewState to react-map-gl's <MapGL>, which only reads that prop on initial mount and ignores subsequent updates.
• Use a MapGL ref to call MapLibre's native map.flyTo() API directly when a fly-to request arrives, keeping the existing uncontrolled view state management unchanged for normal pan/zoom.
• Filter out transition_* fields from view state dicts sent by the frontend before constructing Python ViewState dataclasses, preventing TypeError on unexpected keyword arguments like transition_duration.

Test plan

• npm run build completes without errors
• In a notebook with default basemap (overlay mode): m = viz(gdf) then m.fly_to(longitude=..., latitude=..., zoom=...) — verify the map animates
• Verify deck-first mode still works (no basemap): m = Map(layers=[...]) then m.fly_to(...)
• Verify normal pan/zoom still syncs view state back to Python in overlay mode

🤖 Generated with Claude Code

[tylere]

Fixes #1064.

[Copilot]

Pull request overview

Fixes fly_to() not animating the map when using the default basemap modes (“overlaid” / “interleaved”) by routing fly-to requests through MapLibre’s native map.flyTo() in the overlay renderer, and hardens Python view state validation against frontend transition* fields.

Changes:

• Add flyToRequest plumbing to the overlay renderer and invoke map.flyTo() via a MapGL ref.
• Route "fly-to" custom messages to the overlay renderer in overlaid/interleaved basemap modes; keep existing deck-first behavior.
• Filter out transition* keys from frontend-sent view state dicts before constructing Python ViewState dataclasses.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/renderers/types.ts	Extends overlay renderer prop types to accept a fly-to request and completion callback.
src/renderers/overlay.tsx	Uses a MapGL ref + effect to call MapLibre flyTo() in overlay mode.
src/index.tsx	Stores fly-to requests in React state for overlay/interleaved modes and passes them to OverlayRenderer.
lonboard/traits/_map.py	Drops transition* fields from view state dict inputs to avoid dataclass constructor errors.

Comments suppressed due to low confidence (1)

src/index.tsx:183

• model.on("msg:custom", ...) is being called during render, which will register a new event handler on every re-render and can cause duplicated fly-to handling and memory leaks. Move this subscription into a useEffect with a stable handler and cleanup via model.off("msg:custom", handler) in the effect's return function.

  // Handle custom messages
  model.on("msg:custom", (msg: Message) => {
    switch (msg.type) {
      case "fly-to":
        if (
          basemapState?.mode === "overlaid" ||
          basemapState?.mode === "interleaved"
        ) {
          setFlyToRequest(msg);
        } else {
          flyTo(msg, setViewState);
        }
        break;

      default:
        break;
    }
  });

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[Copilot]

React.useRef<MapRef>(null) is a TypeScript error under strictNullChecks because the initial value is null but the ref type is non-nullable. Make the ref type nullable (e.g., MapRef | null) or omit the explicit generic so the inferred type matches the null initializer.

Suggested change

	const mapRef = React.useRef<MapRef>(null);
	const mapRef = React.useRef<MapRef | null>(null);

[Copilot]

This new filtering of transition* keys should be covered by a unit test to prevent regressions (e.g., ensure a camelCase transitionDuration/transitionInterpolator key in an incoming view_state dict is ignored rather than raising TypeError). There are already view_state validation tests in tests/test_map.py that could be extended for this case.