"/home/yossef/notes/git/projects/maplibra/modules/Map Rendering.md"

path: maplibra/modules/Map Rendering.md

- **fileName**: Map Rendering
- **Created on**: 2026-06-16 00:48:42

Map Rendering

Purpose: Loads, prepares, caches, and renders floor-specific geometry on demand.

Related: ../Home.md, ../Architecture.md, ./Layer Management.md, ./MVF Loading.md, ./UI Components.md, ../flows/Map Render.md

What It Does

FloorDataManager (src/app/floor-data.js) is responsible for the complete floor render pipeline: loading raw floor data from the MVF bundle, optionally preparing it via a Web Worker, and painting it on the map.

Fast Render Strategy

The render pipeline uses a two-phase approach to keep floor changes responsive:

1. Fast render — Paint raw geometry immediately without waiting for worker preparation
2. Prepared swap — Once the geo-prep worker finishes, swap in precomputed style buckets, door features, and label features

This ensures the user sees floor geometry within milliseconds while the richer prepared version arrives shortly after.

Floor Data Cache

• LRU cache with configurable max size (default 4 floors)
• Memory pressure monitoring via performance.memory (if available)
• Eviction drops oldest floors when threshold exceeded
• Object URL cleanup on eviction

Memory Pressure

• memoryThreshold — configurable byte limit (default 100MB)
• jsHeapSizeLimit check — evict when heap usage > 80%
• checkMemoryPressure runs on a 30-second interval

Geo Preparation

src/app/geo-prep.js (via Web Worker src/workers/geo-worker.js) precomputes:

• styleLayers — bucketed features by style name
• doorFeatures — door geometry for rendering
• labelFeatures — text labels and icons
• prepared form is faster to paint and update than raw geometry

Floor Request Cancellation

Only the latest floor request is allowed to paint the map. Older requests are cancelled via AbortController:

• activeFloorRequest counter increments on each request
• requestId !== activeFloorRequest aborts stale callbacks
• AbortController per floor for signal-based cancellation

Important Files

• src/app/floor-data.js — FloorDataManager (load, cache, render, memory)
• src/app/geo-prep.js — Geometry preparation (style buckets, doors, labels)
• src/app/geo-prep-sync.js — Synchronous geo-prep fallback
• src/workers/geo-worker.js — Web Worker for geo-prep
• src/layer-manager.js — LayerManager.renderFloorData()

How It Connects

• FloorDataManager is created in script.js with references to mvfLoader and layerManager

• UIManager dispatches floor-change-requested → script.js calls floorDataManager.loadAndRenderFloor()

• LayerManager receives both raw and prepared data via renderFloorData()

• SearchBox receives onLocationsAdded callback when new floor locations are discovered

• Adjacent floor prefetching happens in startup tasks after the first render

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