browser-entry/playback/snapshot

Snapshot synchronization helpers for playback.

The worker streams packed typed-array snapshots, while the browser renderer wants stable mutable arrays of pipes and birds. This module performs that translation in place so playback can stay fast and allocation-light.

The design goal is stable browser-side state with minimal churn: allocate when the population grows, then mutate in place for the steady-state render loop.

Snapshot flow:

flowchart LR
    Worker["worker snapshot\npacked typed arrays"] --> Hydrate["applyPlaybackSnapshot"]
    Hydrate --> Pipes["sync pipes in place"]
    Hydrate --> Birds["sync birds in place"]
    Pipes --> RenderState["stable PopulationRenderState"]
    Birds --> RenderState

Minimal example:

applyPlaybackSnapshot(renderState, payload.snapshot);

browser-entry/playback/snapshot/playback.snapshot.services.ts

applyPlaybackSnapshot

applyPlaybackSnapshot(
  renderState: PopulationRenderState,
  snapshot: EvolutionPlaybackStepSnapshot,
): void

Applies worker snapshot data to the mutable playback render state.

This is the top-level hydration step for one frame: copy scalar frame fields, then synchronize packed pipe and bird arrays into reusable browser-side objects.

Parameters:

• renderState - Mutable render state mirror used by the browser.
• snapshot - Worker playback snapshot for the current render tick.

Returns: Nothing.

PlaybackRenderStateWithWinnerStream

Render state extended with the streamed winner activation fields.

PopulationRenderState is owned by the simulation types module, so the winner stream fields surface through this local intersection until the simulation type gains them natively. Assigning undefined when a snapshot omits the stream intentionally clears stale winner state from previous frames.

syncPlaybackSnapshotBirds

syncPlaybackSnapshotBirds(
  renderState: PopulationRenderState,
  snapshot: EvolutionPlaybackStepSnapshot,
): void

Synchronizes packed bird snapshot fields into the reusable render-state bird array.

This mirrors the pipe strategy: keep a stable array shape when possible and update fields in place from the packed worker buffers.

Parameters:

• renderState - Mutable render state mirror used by the browser.
• snapshot - Packed worker playback snapshot for the current render tick.

Returns: Nothing.

syncPlaybackSnapshotPipes

syncPlaybackSnapshotPipes(
  renderState: PopulationRenderState,
  snapshot: EvolutionPlaybackStepSnapshot,
): void

Synchronizes packed pipe snapshot fields into the reusable render-state pipe array.

Instead of recreating pipe objects every frame, the browser grows the array as needed and then mutates the existing records in place.

Parameters:

• renderState - Mutable render state mirror used by the browser.
• snapshot - Packed worker playback snapshot for the current render tick.

Returns: Nothing.

syncPlaybackSnapshotWinnerStream

syncPlaybackSnapshotWinnerStream(
  renderState: PopulationRenderState,
  snapshot: EvolutionPlaybackStepSnapshot,
): void

Surfaces the winner activation stream fields onto the render state.

Snapshots that omit the stream (legacy worker builds) clear any stale winner state from earlier frames, so the visualization never renders activations from a previous generation.

Parameters:

• renderState - Mutable render state mirror used by the browser.
• snapshot - Worker playback snapshot for the current render tick.

Returns: Nothing.

browser-entry/playback/snapshot/playback.snapshot.summary.utils.ts

Small summary helpers derived from hydrated playback render state.

Once a packed snapshot has been synchronized into the browser render state, these helpers compute simple aggregate values needed by the HUD and playback reporting flow.

resolveLeaderFramesSurvived

resolveLeaderFramesSurvived(
  renderState: PopulationRenderState,
): number

Resolves the maximum survived-frame count in the current render state.

This is the "leader frames survived" view of the current frame: the best raw frame count among all birds currently represented in the render state.

Parameters:

• renderState - Current render state.

Returns: Maximum frames survived by any bird.