Play overlay (FPS, TURBO, volume, save states) and savestates over the link (1.1)

[TechnicallyComputers]

What

retro_overlay (overlay/) is what a host draws over a running core. It looks and behaves the same whichever core is running.

• FPS, top left. It counts emulated frames over the time they span, not a mean of 1/dt, which reads high when frames arrive unevenly.
• >> TURBO, top right.
• Volume meter on the right edge, for 1.5 s after a change.
• Toasts.
• Save-state browser, centre: twelve slots with thumbnails.
  • Opened by SELECT+R1 or the host's hotkey.
  • Face buttons are read and drawn by position, not one console's letters.
• It depends on no SDL, GL or clock. place() puts every layer in the same spot on every host.
• The font, boxes and browser layout are the ones psxrecomp, snesrecomp and n64lle already share.

retro_state (state/) implements the savestate envelope CORE_ABI.md "Savestates" specifies.

• check_state() is its load rule, applied in order. It names both values of the first mismatch.
• The thumbnail is inside the envelope.

Link 1.1 adds SaveState / LoadState / StateDone, taken between frames.

• The runner's StateKeeper writes and checks envelopes, and hashes content on a background thread.
• --load-state checks an envelope and still accepts bare states (n64lle's gates).
• as_msg now implements the minor rule: it ignores a longer packet's tail and zero-fills a shorter one. LINK_TRANSPORTS.md §10 required that fix before the first minor bump.
• A 1.0 runner never receives the new messages: CoreLink::states_supported() checks first.

Design and hotkeys: docs/OVERLAY.md. The consumer is Retro Launcher PR (hub feat/runtime-overlay).

Checked

• ctest: 13/13.
  • New overlay test: FPS method, layers, place(), the browser, InputGuard, every load-rule mismatch, corruption, truncation.
  • New link_savestates test (fake core, which now has a 12-byte state): save after frame 4, load after frame 8, last picture 6; refused on other content; headless load.
• The hub's real PlaySession, driven offscreen with injected keys against n64lle 0.375.0 / Pokémon Stadium, with framebuffers read back:
  • overlay layers drawn in place;
  • a 2.97 MB state saved in about 40 ms, with a thumbnail of the game frame, and loaded back;
  • events.tsv empty.

Not checked

A real screen, a real controller (the chord, stick repeat), sound and volume by ear. Those verdicts are Alex's.

🤖 Generated with Claude Code