Flutter + Rust FFI via flutter_rust_bridge

Raw FFI requires manually writing C-compatible bindings. flutter_rust_bridge auto-generates Dart bindings from Rust function signatures — handles async, enums, and complex types without boilerplate.

Frame Timing — Detecting Jank

Flutter exposes frame timings via SchedulerBinding.addTimingsCallback. Each callback gives you build duration and raster duration per frame.

Thresholds: >16ms = jank (drops below 60fps), >32ms = severe jank (drops below 30fps).

Ring Buffer — Bounded Memory in Production SDKs

Fixed-capacity circular buffer — new events overwrite the oldest. Prevents unbounded heap growth in long-running apps. Shared safely across threads using Arc<Mutex<RingBuffer<T>>>.

Dart Zone-Based Log Interception

Override ZoneSpecification.print inside runZoned to intercept all print() calls without the host app changing a single line. Capture the message, then pass it through so normal logging still works.

HttpClient Interceptor — Capturing All Network

Wrap Dart’s base HttpClient to capture all HTTP traffic regardless of which package the app uses. For Dio, use a Dio Interceptor — same concept, different hook point.

Event Correlation — Tying Network + Logs to Frames

Tag each network call and log entry with the active frame ID at the time it was recorded. Answers: “which network call caused this jank?” — without needing a separate trace.

OpenTelemetry Mapping

Flutter Event	OTel Concept
Frame timing	Histogram metric
Network call	HTTP client span
Log entry	Log record
Memory snapshot	Gauge metric

OTLP/HTTP has the widest compatibility — Grafana, SigNoz, Datadog, and Jaeger all support it.

OverlayEntry for Non-Intrusive Debug UI

OverlayEntry sits above the entire route stack — survives navigation and works with any router (GoRouter, Navigator 1.0, etc). Good pattern for debug HUDs that need to persist across screens.

Event Bus via Dart Streams

Use a broadcast StreamController to fan out from multiple collectors (frames, network, logs) into a single processing layer. Broadcast streams let multiple listeners tap the same flow without blocking each other.

Architecture Flow

Flutter App
  └── Dart SDK Layer
        ├── Frame Tracker (SchedulerBinding)
        ├── Network Monitor (HttpClient interceptor)
        └── Log Sink (Zone override)
              │
              ▼ (Dart Streams event bus)
        FFI Bridge (flutter_rust_bridge)
              │
              ▼
        Rust Engine
              ├── Ring Buffer (bounded storage)
              └── OTel Metric Mapper
                    │
                    ▼
              Exporters
                    ├── OTLP/HTTP → Grafana / Datadog
                    ├── JSON → local report
                    └── Overlay HUD → in-app