Retro Boy: simple Game Boy emulator written in Rust, can be played on the web

I feel like the GB/GBC/GBA are pretty much what the VT102 is to writing grid-cell software. The demo scene keeps cranking. Chiptune is still in love with the hardware - especially with the OG DMG, with a pro sound mod. Writing new software for the GBA feels a lot like targeting a tiny, modern ARM microcontroller. The hardware is well documented and understood by the enthusiasts, and it's a stable target.

Plus there are plenty of emulators focusing on different aspects: one is focusing on perfect emulation; another will try to squeeze out performance; another might offer memory inspection and "cheat codes"; this one makes it available on the web. There's beauty in all of that.

A gameboy emulator is a very popular project. There are plenty of guides on how to get started. Checkout "build your own x" repo for some project ideas

Why does almost every project written in rust have "written in rust" advertised in the title/description?

What a clean repo, great job!

For me it runs at full speed in both stable and developer versions of Firefox (but even then, audio is bad at times). But still, I looked at performance out of curiosity.

After running it under FF's profiler for a moment, it looks like a sync executed after every opcode recalculates the framebuffer (`step_until_next_audio_buffer -> cpu::microops::read_byte_from_memory -> emulator::sync -> gpu::scanline::write_scanlines`) and uploads it to the canvas with `putImageData`, which takes ~35% of execution time. Sounds like that could be redundant work, since I'm pretty sure the canvas isn't actually redrawn until the wasm execution yields back to the browser.

EDIT: also, the emulator can't really be ran in debug mode, since 1. it blows the wasm stack (presumably when creating the huge `Emulator` struct, a not uncommon issue in Rust; I had to hack in bigger stack size with linker args), and 2. is panics on int overflows `apu::step`.