Profile-driven performance optimization for SvelteBoy AssemblyScript/WASM backend. Use when asked to optimize emulator performance, profile hotspots, or reduce CPU usage.

2026-04-244

audio

vizigr0u/svelteboy

Prime context for working on the SvelteBoy APU — architecture, channel implementations, register layout, event queue, render pipeline, and test patterns

2026-04-194

backend

vizigr0u/svelteboy

Prime context for working on the AssemblyScript/WASM GameBoy emulator backend in /assembly/

2026-04-194

backend-tests

vizigr0u/svelteboy

Guide for writing AssemblyScript backend tests in assembly/tests/ — patterns, helpers, ROM setup, and wiring

2026-04-194

gameboy-docs

vizigr0u/svelteboy

Complete Game Boy DMG hardware reference — all registers, timing, opcodes, PPU modes, APU circuits, MBC banking. Authoritative inline spec for emulator implementation.

2026-04-194

emulator-architecture

vizigr0u/svelteboy

Prime context for architectural discussions about SvelteBoy's design patterns, component interactions, timing model, and trade-offs vs. general emulator approaches

2026-04-194

File/Dir

Purpose

src/emulator/index.ts

Emulator+Debug facades, re-exports AudioSuspended/FrameStats/RenderFrames

src/emulator/wasmBridge.ts

re-export build/backend, frame/audio typed-array views

src/emulator/loop.ts

requestAnimationFrame loop, pre/postRun, FrameStats, callbacks

src/emulator/audio.ts

AudioContext, queue, fade, mute subs, suspendAudio/resumeAudio

src/emulator/lifecycle.ts

pause/unpause/reset/runUntilBreak, visibility, HMR

src/emulator/saveState.ts

QuickSave/QuickLoad + thumbnails

src/emulator/rom.ts

playRom, getRomBuffer, loadSaveGame

src/inputs.ts

Keyboard → joypad bitmask → setJoypad() WASM call

src/types.ts

TypeScript types mirroring WASM-exported shapes

src/stores/playStores.ts

GameFrames, KeyPressMap, emulator running state

src/stores/debugStores.ts

Breakpoints, logs, debug info reactive state

src/stores/optionsStore.ts

Volume, pixel size, FPS target

src/stores/romStores.ts

Loaded cartridge reference

src/lib/Player.svelte

Top-level game player container

src/lib/PlayCanvas.svelte

160×144 <canvas> — receives Uint8ClampedArray frame, calls putImageData

src/lib/PlayerControls.svelte

Play/Pause/Reset buttons

src/lib/debug/Debugger.svelte

Full debugger UI container

src/lib/debug/CpuDebugInfo.svelte

Registers, flags display

src/lib/debug/Disassembler.svelte

Disassembly view using getCartLines()

src/lib/debug/HexView.svelte

Memory hex dump using hexDump()

src/lib/debug/LogView.svelte

Serial/debug log viewer

// inside src/emulator/* import { initEmulator, runEmulator, setJoypad, getDebugInfo, loadCartridgeRom, getGameFrameView, getCgbGameFrameView, getAudioBufferView, backendMemory } from "./wasmBridge"; // Pass data TO wasm (bindings handle pointer/length automatically) loadCartridgeRom(new Uint8Array(romArrayBuffer)); // Zero-copy frame view (helper wraps backendMemory + ptr) const frame = getGameFrameView(); // Uint8Array(160*144) palette indices // or RGBA (CGB): getCgbGameFrameView() — Uint16Array RGB555 // Get managed objects (copy via bindings) const info = getDebugInfo(); // → plain JS object matching DebugInfo shape

// Called in postRun after each emulation step const count = getAudioBuffersToReadCount(); for (let i = 0; i < count; i++) { const leftPtr = getAudioBufferToReadPointer(0); const rightPtr = getAudioBufferToReadPointer(1); const size = getAudioBuffersSize(); // Zero-copy typed array views const left = new Float32Array(backendMemory.buffer, leftPtr, size); const right = new Float32Array(backendMemory.buffer, rightPtr, size); // Feed to Web Audio API const buf = audioCtx.createBuffer(2, size, getAudioSampleRate()); buf.copyToChannel(left, 0); buf.copyToChannel(right, 1); const src = audioCtx.createBufferSource(); src.buffer = buf; src.connect(audioCtx.destination); src.start(nextAudioTime); nextAudioTime += buf.duration; } markAudioBuffersRead(count);

// loop.ts function run(time: number) { accumulator += wallDt * get(EmulatorSpeed); while (accumulator >= GB_FRAME_MS && framesThisTick < MAX_CATCHUP) { preRun(); // setJoypad(inputBits) LastStopReason.set(runEmulator(GB_FRAME_MS)); postRun(); // fetchLogs, GameFrames++, debug snapshot, AutoSave, postRunCallbacks accumulator -= GB_FRAME_MS; framesThisTick++; } if (framesThisTick > 0) renderCallbacks.forEach(cb => cb()); if (!get(EmulatorPaused)) requestAnimationFrame(run); }

<script lang="ts"> // Reactive state (replaces writable store in component) let frame = $state<Uint8ClampedArray | null>(null); // Derived (replaces $: reactive declaration) let isRunning = $derived(frame !== null); // Side effects (replaces onMount + $: with cleanup) $effect(() => { const unsub = someStore.subscribe(v => { ... }); return () => unsub(); }); </script>

Store

Use for

playStores.ts

Emulator running state, current frame, key press map

debugStores.ts

Debug info snapshot, logs, breakpoints list

optionsStore.ts

User settings (volume, scale) — persisted to localStorage

romStores.ts

Currently loaded cartridge metadata

File/Dir

Purpose

src/emulator/index.ts

Emulator+Debug facades, re-exports AudioSuspended/FrameStats/RenderFrames

src/emulator/wasmBridge.ts

re-export build/backend, frame/audio typed-array views

src/emulator/loop.ts

requestAnimationFrame loop, pre/postRun, FrameStats, callbacks

src/emulator/audio.ts

AudioContext, queue, fade, mute subs, suspendAudio/resumeAudio

src/emulator/lifecycle.ts

pause/unpause/reset/runUntilBreak, visibility, HMR

src/emulator/saveState.ts

QuickSave/QuickLoad + thumbnails

src/emulator/rom.ts

playRom, getRomBuffer, loadSaveGame

src/inputs.ts

Keyboard → joypad bitmask → setJoypad() WASM call

src/types.ts

TypeScript types mirroring WASM-exported shapes

src/stores/playStores.ts

GameFrames, KeyPressMap, emulator running state

src/stores/debugStores.ts

Breakpoints, logs, debug info reactive state

src/stores/optionsStore.ts

Volume, pixel size, FPS target

src/stores/romStores.ts

Loaded cartridge reference

src/lib/Player.svelte

Top-level game player container

src/lib/PlayCanvas.svelte

160×144 <canvas> — receives Uint8ClampedArray frame, calls putImageData

src/lib/PlayerControls.svelte

Play/Pause/Reset buttons

src/lib/debug/Debugger.svelte

Full debugger UI container

src/lib/debug/CpuDebugInfo.svelte

Registers, flags display

src/lib/debug/Disassembler.svelte

Disassembly view using getCartLines()

src/lib/debug/HexView.svelte

Memory hex dump using hexDump()

src/lib/debug/LogView.svelte

Serial/debug log viewer

Store

Use for

playStores.ts

Emulator running state, current frame, key press map

debugStores.ts

Debug info snapshot, logs, breakpoints list

optionsStore.ts

User settings (volume, scale) — persisted to localStorage

romStores.ts

Currently loaded cartridge metadata

name	frontend
description	Prime context for working on the Svelte 5 frontend in /src/ — components, stores, WASM bridge, audio, canvas rendering
argument-hint	optional: specific area, e.g. debugger, audio, canvas, stores

name	frontend
description	Prime context for working on the Svelte 5 frontend in /src/ — components, stores, WASM bridge, audio, canvas rendering
argument-hint	optional: specific area, e.g. debugger, audio, canvas, stores

frontend

Key Facts

File Map

Calling WASM from the Frontend

Audio Pipeline

Emulation Loop Pattern

Svelte 5 Runes Patterns Used Here

Stores: When to Use Which

InputType Bitmask (src/inputs.ts)

Key Facts

File Map

Calling WASM from the Frontend

Audio Pipeline

Emulation Loop Pattern

Svelte 5 Runes Patterns Used Here

Stores: When to Use Which

InputType Bitmask (src/inputs.ts)