PKsinew Devlog # 8: Embedding mGBA and Switching Between Game and Sinew

By this point, Sinew could do a lot — but the experience still felt fractured.

Launching games externally meant context switching:

• Alt-tabbing

• Separate controller configs

• No clean way to jump between the game and Sinew

I wanted a fast, console-like way to switch between Sinew and whatever game was running — something closer to a Home button than a desktop workflow.

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The External mGBA Problem

Using external mGBA, this is technically possible via its scripting API.
The idea would be:

• Run mGBA as a separate process

• Use its scripting hooks

• Spin up a Node.js server

• Listen for controller button combinations

• Send commands back to mGBA

It works — but it’s messy.

It adds:

• Extra services

• Network plumbing

• More failure points

And it didn’t feel right for what Sinew was becoming.

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Thinking Like RetroArch

That’s when I started thinking about how RetroArch does things.

RetroArch embeds emulators directly using libretro cores, which expose:

• Video frame buffers

• Audio buffers

• Input callbacks

So I wondered:

What if I embed the mGBA libretro core directly inside Sinew?

In theory, Python could do this.

In practice… it was rough.

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First Attempts (and Shelving It)

I’d played around with this earlier while I was out of Claude tokens, using ChatGPT.

I managed to:

• Get the frame buffer rendering into a Pygame surface after some trial and error

• Get input mostly working

• Get audio, but it was extremely choppy

• Break save handling completely

It worked, but it didn’t feel stable or shippable — so I shelved it.

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Claude to the Rescue (Again)

Later on, I dropped the same code into Claude and asked it to take a look.

Within minutes:

• The audio bitrate was corrected

• Audio became silky smooth immediately

• Save handling was fixed

That was all I needed.

At that point, embedding the emulator directly into Sinew became viable.

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Embedding mGBA Into Sinew

Once embedded, everything started to fall into place:

• The emulator now uses Sinew’s ROM paths and save paths

• A unified button mapper controls both:

  • Sinew UI

  • The running game

I wired in a Start + Select combo that instantly switches between:

• The game

• The Sinew menu

From there, I added guardrails:

• You can’t launch another game while one is running

• Sinew offers:

  • Return to game

  • Stop game

• The button combo works globally

At this point, Sinew finally felt cohesive.

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Catching Up to Today

This devlog is now starting to catch up to the present.

Today, I added:

• An option to change the button combo

• Support for using a single custom “Home” button

This matters because:

• GBA doesn’t have many buttons

• Many controllers do have Home buttons

• Some only have just enough buttons

Flexibility here was important.

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The Bug You Only Find by Playing

After all that, I did the sensible thing.

I kicked back, loaded up FireRed, and relaxed before heading to a Christmas party.

Five minutes in — the audio died.

Turns out the issue was subtle:

• The emulator was producing audio faster than it was being consumed

• Unused audio chunks were queuing up

• Once the queue filled, audio playback crashed

The fix was simple but necessary:

• Keep a small audio buffer

• If more than a few chunks are waiting, discard the oldest unused audio data

In other words:

Better to drop stale audio than let it pile up and kill sound entirely.

Problem solved.

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Where This Leaves Sinew

At this point, Sinew can:

• Launch games internally

• Switch instantly between game and UI

• Share controller mappings across both

• Enforce safe rules around save access

• Recover gracefully from real-world edge cases

This is the point where Sinew stopped feeling like a tool and started feeling like a system.

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Next Up

• Settings

• Themes

• Mass Pokémon storage

And then… polishing.

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