virtualjaguar-libretro/app

Virtual Jaguar app (standalone desktop front end)

A desktop front end for the Virtual Jaguar core: SDL3 for window, audio and input, Dear ImGui for the UI, OpenGL 3.3 core for presentation, on macOS, Linux and Windows. The core stays C89 and is linked statically; the app drives it only through the standard retro_* API, the same one RetroArch uses, so every option and save state behaves exactly as it does there.

Everything lives under app/. The core's own make build is untouched.

Installable packages (macOS zip, Windows installer and portable zip, Linux AppImage and .deb) are built by CI and attached to the releases: see packaging/README.md. To package and sign your own build locally (a Developer ID or Apple Development certificate found in your keychain on macOS, a .pfx or store certificate on Windows, optionally configured in a gitignored .env), run bash app/packaging/local-package.sh --sign [--notarize] [--build-dir DIR]: see "Signing locally" in packaging/README.md.

Build

You need CMake 3.20+, a C99/C++17 toolchain and, on Linux, the SDL3 desktop dev packages (see below). SDL3 (3.4.16), Dear ImGui (1.92.8) and rcheevos (12.5.0) are downloaded at configure time, pinned by SHA256. Nothing is vendored in the repo.

cmake -S app -B app/build -DCMAKE_BUILD_TYPE=Release
cmake --build app/build -j
ctest --test-dir app/build -C Release --output-on-failure   # headless smoke tests

The binary is app/build/virtualjaguar (app/build/Release/virtualjaguar.exe with the Visual Studio generator).

With CMake 3.21+ the same builds have names, run from app/:

cd app
cmake --preset release            # or debug, or nightly (the nightly channel: emulation thread on by default)
cmake --build --preset release -j
ctest --preset release            # headless smoke tests

Each preset builds in its own app/build-<preset>/ and sets its build type and channel on every configure. Any other -D option stays in the build directory's cache until you change it: an earlier -DVJ_APP_FETCH_LIBRASHADER=OFF keeps the librashader runtime out of every later build, and configure warns about that where a prebuilt exists.

-DVJ_TV_DEFAULT=auto|manual|off (default auto) is the TV mode setting a fresh config starts on, so a local build starts on Auto while release packages are built with manual (see TV mode).

FreeType 2.14.1 is the default font rasteriser: it is fetched (pinned, SHA-256 checked), built static with every optional library off, so it needs no system libraries. -DVJ_APP_FREETYPE=OFF uses Dear ImGui's built-in stb_truetype instead (no hinting or anti-aliasing choices); offline builds use -DFETCHCONTENT_SOURCE_DIR_FREETYPE=<dir>.

Use an already installed SDL3 instead of fetching one: -DVJ_APP_SYSTEM_SDL3=ON (Homebrew sdl3, distro libsdl3-dev). For offline builds point -DFETCHCONTENT_SOURCE_DIR_SDL3=<dir> and -DFETCHCONTENT_SOURCE_DIR_IMGUI=<dir> at unpacked sources.

macOS

Xcode command line tools and CMake (brew install cmake). No extra libraries. The host make build of the core needs DEVELOPER_DIR=/Library/Developer/CommandLineTools to avoid App Management prompts; the CMake/C++ build of the app does not, and setting it there can hide the C++ standard library headers.

Linux

sudo apt-get install cmake pkg-config libasound2-dev libpulse-dev libx11-dev \
  libxext-dev libxrandr-dev libxcursor-dev libxfixes-dev libxi-dev libxss-dev \
  libxtst-dev libxkbcommon-dev libdrm-dev libgbm-dev libgl1-mesa-dev \
  libegl1-mesa-dev libdbus-1-dev libudev-dev libwayland-dev wayland-protocols \
  libdecor-0-dev libcurl4-openssl-dev

libcurl4-openssl-dev is only for the game library's box art and database downloads (see Game library); without it the app still builds and runs, it just never downloads anything.

Windows

MinGW-w64 (MSYS2 mingw-w64-x86_64-gcc, cmake, ninja) is the supported toolchain: it is what the core's own Windows release build uses.

cmake -S app -B app/build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build app/build

MSVC (cmake -S app -B app/build then cmake --build app/build --config Release) is wired up and runs in CI as an experimental, non-gating job: the repo's msvc-check job has never compiled about 31 of the core's sources with cl.exe (scripts/check-msvc-sources.sh, issue #679), so full-core MSVC is unproven.

How the core is built here

app/cmake/VJCore.cmake parses the source list out of Makefile.common (the same regexes as scripts/check-package-sources.sh), so adding a .c there needs no change in app/. The flags mirror what make -n passes: -D__LIBRETRO__, -DINLINE=inline, the warning set, -fno-strict-overflow, libchdr's own C99 translation unit. The SIMD blitter variant is chosen by the compiler: all three blitter_simd_<arch>.c are built with -DBLITTER_SIMD_AUTODETECT, exactly as Package.swift does (CI checks that exactly one blitter_simd_ops exists). src/core/version.h is generated at configure time when sh is available.

No -std=gnu89 is forced: make passes no -std either, and gnu89 changes inline linkage. C89 conformance is gated by scripts/c89-lint.sh.

Running

virtualjaguar game.j64            # cartridge (HLE boot, no BIOS needed)
virtualjaguar disc.cue            # or .chd / .cdi
virtualjaguar game.m3u            # a multi-disc set: every disc listed in File > Disc
virtualjaguar --option virtualjaguar_usefastblitter=enabled game.j64
virtualjaguar --help

Open a game with File > Open (Ctrl/Cmd+O), by drag and drop onto the window, or on the command line. File > Open recent keeps the last ten. Loading another game while one is running does a full unload, retro_deinit, retro_init, retro_load_game cycle.

Key	Action
Arrows, Z, X, C, Enter, Right Shift	D-pad, B, A, C, Option, Pause
number row / numpad, - =	Jaguar keypad 0-9, *, #
A S D, Q E	Jaguar Pro Controller X Y Z and left / right shoulder (keypad 9 8 7, 4 6)
F2	keypad overlay
Ctrl/Cmd+Shift+T	toggle TV mode (View > TV mode), with or without a game; the game keeps running. Fixed, not rebindable (see TV mode)
F4, or a Share hold	the "TV menu / TV mode" action (rebindable): with a game it opens the in-game TV menu, without one it toggles TV mode
F3	controls overlay: a cheat sheet of your current bindings (also View menu)
Esc / F10	release the captured mouse; F10 or a click on the picture captures it again (see below)
F5 / F7 / F6	save state / load state / next slot (Shift+F6 previous)
F8, Ctrl/Cmd+R	pause, reset
Tab (hold)	fast-forward
F11, Alt+Enter, Esc	fullscreen, leave fullscreen
F1	pin or hide the menu bar in fullscreen

Gamepads use SDL's standard layout (South/East/West = B/A/C, Back = Pause, Start = Option); the left stick also drives the D-pad. Controller types per Jaguar port (Team Tap, rotary, ...) are under Settings > Input > Devices & players.

Controls and the keypad

Settings > Input edits the bindings: pick a device (the keyboard, every gamepad, or one connected controller model), pick the scope (everywhere, or this game only), then Set / Add a binding and press the key, button or stick direction ("press a button to bind"; Esc cancels), Unbind, or go back to Default. Per control, the first of these that defines it wins: this game and this controller, this game, this controller, everywhere, built-in default. Games are identified by the CRC32 of the cartridge image (the key the core's title database uses; copier headers stripped); discs fall back to the file name. Everything is stored in config.ini as input.* keys. Controllers SDL does not know can be added with a gamecontrollerdb.txt (SDL's format) in the data folder.

The default gamepad layout reaches all twelve keypad keys without the overlay:

pad	keypad
North, L1, R1, L2, R2, L3, R3	0, 1, 2, 3, 4, 5, 6
right stick left / up / right / down	7, 8, 9, * (dominant axis only, never two keys)
Guide	#
Share / Capture, or F2, or View > Keypad overlay	on-screen keypad (D-pad moves, A/B presses, C closes)

How it reaches the core: pad buttons ride the RetroPad bitmask; the RetroPad has no button for keypad 7, 8, 9, *, #, so keypad keys are delivered as the RETRO_DEVICE_KEYBOARD keys libretro.c polls (player 1: 0-9 - =; player 2: p q w e r t y u i o [ ]). The app announces a keyboard after every load, which the core needs before it polls them. This is the core's default input path, so the core's own remapping options (virtualjaguar_alt_inputs, *_numpad_to_kb, *_retropad_* and the per-port device options) are forced to their defaults and hidden: this tab and Devices & players do all of that. Team Tap sockets read only the RetroPad, so there keypad 0-6 ride X, L, R, L2, R2, L3, R3 and keypad 7-9, *, # are unreachable (a limit of the core).

Controller in the desktop library

With TV mode off and no game running (or a paused game with the Game library window open), a pad browses the library: a focus ring follows it over the grid, the Favorites and Recently played strips, and the BIOS and States tabs. Mouse and keyboard work as before.

Pad	Library
D-pad, left stick	move the focus
A (tap)	play the focused game; open a BIOS tile's menu; load a state
A (hold) or X	the tile's menu (D-pad moves, A picks, B closes)
B	close the open menu, or the Game library window
Y	favorite / unfavorite
LB / RB	previous / next tab
LT / RT	previous / next initial letter
Right stick	scroll the grid
View / Back	focus the search box
Share or Guide, held	toggle TV mode (see TV mode)

The buttons follow the controller family, detected automatically: Xbox, PlayStation, Nintendo Switch (A on the right confirms, B on the bottom goes back) and MFi / generic (Xbox layout). A custom layout is under Settings > Input: pick one controller in the device list, then Menu buttons (a Family choice, and Set / Default per button). Reset menu buttons clears that controller's overrides.

TV mode

TV mode is a 10-foot look for a pad and a TV: large tiles and text, one focus ring, and a pad-driven Home, Library, Achievements and Settings, plus an in-game menu (see the rows in the key table above). With a game running it only changes which screen stands behind the game; the game keeps running.

The TV mode setting has three values, under Settings > Interface (and TV Settings > Interface in TV mode itself):

• Off: TV mode never turns on: F4, the Share hold, Ctrl/Cmd+Shift+T and --tv do nothing without a game. With a game running the TV-menu button still opens the in-game menu.
• Manual: only when you ask: View > TV mode, Ctrl/Cmd+Shift+T, the TV-menu button (F4, or a hold of the pad's Share / Capture / Mic button, or of Guide on a pad without one, with no game running) or --tv. The on/off state is remembered for the next start (--tv is not).
• Auto: also on its own, with two checkboxes you can untick, Turn on in fullscreen and Turn on when a controller is used.

Auto in one paragraph: entering fullscreen turns TV mode on and leaving it turns it off; a controller press on a navigation button (D-pad, face buttons, LB / RB, Start) in the library, with no game running, turns it on, and that press does nothing else. A TV mode the controller started is handed back to the desktop by 32 px of mouse movement or by typing (a printable key without Ctrl, Cmd or Alt; F-keys, Esc, Enter and shortcuts never count), unless fullscreen is holding it. Turning it on or off by hand wins until the next fullscreen change or controller press.

Build default. A fresh config starts on the build's default, which is Auto for a local build (the CMake default) and for nightly builds and the other CI packages, and Manual for release packages; -DVJ_TV_DEFAULT=auto|manual|off sets it when configuring. Nothing is stored until you change the setting in the UI, so a build can move its default under people who never chose one; Reset group at the top of Settings > Interface returns to the build default.

First-use hint. Under Manual, the first controller press in the desktop library shows a 6-second toast naming the buttons for this pad, as the pad names the button ("Press Share (hold) or F4 for TV mode" on an Xbox pad; "Mic (hold)" on a DualSense, "Capture (hold)" on a Switch Pro Controller, "Guide (hold)" on a pad without Share). It shows once per install (ui.tv_hint_shown), never under Auto or Off, and Reset group on Settings > Interface shows it once more.

Starting and the hold. --tv starts with TV mode on (when the setting is not Off). The TV-menu button on a pad is a hold of 500 ms, so a short Share tap keeps opening the keypad overlay. Limit: Guide held opens the TV menu on a pad with no Share button, and Guide is also the keypad's #, so a keypad chord that holds # (such as * + #) needs the keypad overlay, a pad with Share, or that binding removed (the controls screen says so next to the binding).

Devices, players and the mouse

Settings > Input > Devices & players (everywhere, or this game only; stored as input.port.N / input.game.<id>.port.N) picks the device in each Jaguar port from the core's own list and calls retro_set_controller_port_device. The Pro Controller is not in that list (the core has it as the option value virtualjaguar_pN_device = pad_pro only): the app offers it after Standard Joypad, claims a standard pad and hands the core pad_pro, so the core's own Pro path turns the RetroPad X / L2 / R2 / L / R into keypad 9 / 8 / 7 / 4 / 6:

device	driven by (defaults, all rebindable under Key / button bindings)
Standard Joypad	the pad and keypad bindings above
Pro Controller (6-button)	the pad bindings above, plus X / Y / Z = Left Shoulder / North / Right Shoulder and L / R = the triggers (rebindable as X (Pro) ... R (Pro)); keypad 0-4 move to the overlay on a gamepad, 5-9, *, # stay where they were; the keyboard keeps A S D / Q E
ST / Amiga mouse (port 2)	the mouse or trackpad (captured); or the right stick / arrows; Z X or South East are the buttons
Rotary (either port)	mouse left / right, or two keys (Left / Right), or the right stick; speed in Tuning
Analog, driving, paddle	left stick or A D W S; driving: Right trigger / E accelerator, Left trigger / Q brake; D = North or V
6D	both sticks (A D W S, J L I K), triggers (Q E), shoulders (U O), A-F, Option = G, Pause = Rezero
Light gun (port 1)	the mouse over the picture, left click fires, right click (or R) fires off-screen to reload; a stick or arrows can aim too
Team Tap	one controller (or the keyboard) per socket, chosen under Players

The Players section lists the active player slots (two, plus three more behind each Team Tap) and which controller plays each: Automatic hands controllers out in plug-in order (the first two play players 1 and 2, as before), or pick one by model and number. The light gun aims with the rectangle the picture is drawn in, so scaling, aspect overrides, integer scaling and HiDPI all land the shot on the pixel under the pointer.

The mouse is captured (SDL relative mode) only while a mouse or rotary is in a port, the game window has focus, the game is running and no menu, popup or Settings window is open. Esc or F10 releases it (F10 may need Fn on a Mac keyboard); click the picture or press F10 to capture again.

The controls overlay (F3, the Touchpad button on a gamepad, or View > Controls overlay) shows the bindings in effect for Player 1's device - the keyboard's or the gamepad's, whichever you last used - and never takes input. A click or tap anywhere, Esc or F3 hides it (the click is not passed to the game). It is not shown by itself: a game that starts with no gamepad on Player 1 gets a short "Press F3 for the controls" hint, once per session. Settings > Interface > Overlays > Show the controls overlay when a game starts (off by default) brings the overlay up at boot instead - for keyboard players every time, for gamepads once per controller model - and hides it again after a few seconds.

Settings > Core options is generated from the core's options v2 definitions, categories and SET_CORE_OPTIONS_DISPLAY visibility included, so a new core option shows up with no change to the app. Changes are saved; options that say "Restart required" apply on Restart game to apply. Every core option category and every other Settings tab has a Reset group button (it skips options the app locks and options a Netplay session or --option pins), and Reset all settings... asks first and leaves library folders, recents, covers, saves, the RetroAchievements login, key and button bindings and per-game overrides alone unless you tick the matching boxes.

Pacing follows the core's reported field rate (60.05445 Hz NTSC, 50.08013 Hz PAL). Audio is opened at the core's rate and resampled by SDL, with a small playback-ratio correction against the buffered amount so it tracks the video.

Shaders

Settings > Video > Shader (or View > Shader) runs the picture through a RetroArch .slangp preset, on the GL 3.3 presenter, unmodified. Presets come from librashader (MPL-2.0), which the app loads at run time: the build needs no Rust and links nothing extra. If the library is missing, the wrong version, or a preset does not compile, the picture is drawn plain and a one-line message says why; it is never a failure.

• Library. At configure time CMake fetches librashader's two MIT-licensed C headers (the tag in app/packaging/librashader/pin.env, pinned by SHA256; -DVJ_LIBRASHADER_INCLUDE_DIR=<dir> for offline builds, -DVJ_APP_SHADERS=OFF to leave it out). At run time the app looks for librashader.dylib / .so / .dll in $VJ_LIBRASHADER (a file or folder; a path that does not exist means "missing"), next to the executable (and ../Frameworks in a macOS bundle), in <data folder>/librashader/, and then the system library path (Homebrew's /opt/homebrew/lib included). The release packages (macOS universal, Windows, AppImage, .deb) ship it: Windows and Apple-silicon dev builds download upstream's pinned prebuilt (-DVJ_APP_FETCH_LIBRASHADER=OFF for offline builds), while the macOS (both architectures) and Linux libraries are built from source in CI (librashader.yml, pinned commit and archive SHA-256 in app/packaging/librashader/pin.env), because upstream's Intel-macOS zip holds an arm64 dylib and it publishes no Linux binary. Any build can be given a library it built itself with -DVJ_LIBRASHADER_LIB=<file>; it is copied beside the executable and installed by cmake --install. When no library can be used, Settings > Video > Shader says why: not bundled in this build (none found anywhere), the bundled runtime is missing, or failed to load: ... with the loader's reason (wrong architecture, wrong ABI version, a missing dependency), and links here. It is informational: the app never installs or downloads anything for you.
• Presets. shaders/ beside the executable holds two small first-party presets (vj-sharp-bilinear, vj-scanlines, also the offline test fixtures) and, by default, a subset of libretro/slang-shaders under shaders/slang-shaders/: the CRT (CRT-Royale, CRT-Geom, CRT-EasyMode, ...), scanline and interpolation families plus every directory they reference (~23 MB, ~900 files). CMake downloads the tarball for one pinned commit at configure time (SHA256-verified; nothing is committed to this repo), extracts those directories untouched and copies them beside the executable. Licensing: slang-shaders has no single licence; each shader states its own (GPL, MIT, public domain, ...) in its header and some directories carry LICENSE/README/THANKS files, all of which travel with the copy together with a NOTICE-virtualjaguar.txt. No network, or a hash mismatch, only means no bundled presets (a warning, never a build failure); -DVJ_APP_BUNDLE_SLANG_SHADERS=OFF skips it for distro/offline builds and -DVJ_SLANG_SHADERS_ARCHIVE=<tarball> supplies a local copy. For the rest of slang-shaders, or a newer copy, set Preset folder to a full checkout; the list is searched recursively and filterable, and preset parameters get sliders.
• Scaling. Integer scaling and the aspect modes are independent of shaders (computePresentRect in present_util.cpp): the chain renders into a texture of exactly the rectangle they pick, so a CRT preset at 3x integer scale looks the same as the plain picture at 3x. Both paths share that one function.
• OpenGL version. The chain compiles to the context's GLSL version (4.10 on macOS, usually 4.60 elsewhere). macOS's OpenGL 4.1 cannot build presets with arrays of arrays (CRT-Geom, CRT-Hyllian and 13 others in the bundle); the list greys them out and says why. Details: packaging/README.md.
• Settings keys. shader.enabled, shader.preset, shader.folder.

Getting the shader runtime

Only needed for a build that does not ship one (a distro or source build, or a package where the file was removed). The app loads any librashader of the right ABI (LIBRASHADER_CURRENT_ABI, currently 2) and CPU architecture; put librashader.so (Linux), librashader.dylib (macOS) or librashader.dll (Windows) next to the executable, in <data folder>/librashader/, or anywhere on the system library path, or point VJ_LIBRASHADER at the file.

• Linux, a system package. librashader's author publishes packages on the openSUSE Build Service (build recipes for RPM and Arch-style packages are in upstream's pkg/obs); pick your distribution on https://software.opensuse.org//download.html?project=home%3Achyyran%3Alibrashader&package=librashader. The package installs librashader.so (and librashader.so.2, whose SONAME is the ABI version) in the system library folder, where the app finds it by name; nothing else to do. If your distribution only has librashader.so.2, add a librashader.so symlink next to the app or set VJ_LIBRASHADER=/path/to/librashader.so.2. There was no Arch User Repository package when this was written (October 2026); build from source, below.

• From source (Linux, macOS, Windows). Needs stable Rust 1.88 or newer, a C/C++ compiler, curl and tar:

  rustup target add <triple>      # e.g. x86_64-unknown-linux-gnu, x86_64-apple-darwin
  bash app/packaging/librashader/build-from-source.sh <triple> ./lr
  # -> ./lr/librashader.so (or .dylib / .dll), built from the pinned, SHA-256-verified source
  cmake -S app -B build -DVJ_LIBRASHADER_LIB="$PWD/lr/librashader.so"   # optional: ship it with your build
  

  This is exactly what CI runs (cargo xtask build --profile optimized --target <triple> -- --locked inside upstream's tree). Upstream's README.md documents the same command.

• macOS. The release .app already includes a universal library. For a source build on Apple silicon the default configure downloads upstream's arm64 library; on an Intel Mac, or to avoid the download, build it as above with x86_64-apple-darwin and pass -DVJ_LIBRASHADER_LIB. A Homebrew or hand-built copy in /opt/homebrew/lib or /usr/local/lib is picked up too (a signed release app additionally needs the library-validation entitlement in app/packaging/macos/entitlements.plist to load a library someone else signed).

vj_shader_tests (CTest shaders_unit, shaders_bundled, shaders_library, shaders_gl) covers the pure logic and the missing-library fallback anywhere; the other two need the library (and a display, for the GL one) and report skipped, not passed, without them. Point VJ_LIBRASHADER at the library, and optionally VJ_TEST_PRESETS="a.slangp;b.slangp" / VJ_TEST_SLANG_DIR=<checkout>, to run them.

Game library

The library is an optional grid of your games. It never replaces the file picker, drag and drop or the command line, which all keep working.

Home screen. With no game loaded the main window is the library: search, filter, size slider, Add folder..., rescan, and a click on a tile launches it. With no folders yet it shows a short welcome with an Add folder... button and the open / drag-and-drop hints. Tile size (0.5x to 2.5x, default 1.0x, library.size) is the slider, and also a trackpad pinch (where SDL reports one: macOS), Ctrl/Cmd+mouse wheel and Ctrl/Cmd + + / - / 0 (reset) while the pointer is over the grid or the library has the keyboard focus; never during gameplay or while typing in a field. Loading a game replaces it with the game; File > Close game brings it back. Settings > Interface > Show the game library on the home screen (ui.home_library, also View > Library on home screen) turns it off for the old plain welcome. The separate Game library window (File > Game library, Ctrl/Cmd+L) stays for in-game use (pick another game without closing this one); on the home screen Ctrl/Cmd+L puts the cursor in the search box instead of opening a second copy of the same view.

Sections. Tabs split the library into Cartridges, Jaguar CD and BIOS & system (plus Favorites, Recently played and Save states, below) (the choice is remembered, library.section). BIOS and system files are not games and are never in the game grids: files are recognized by CRC32 (the Series K and Model M boot ROMs, the two Stubulator developer ROMs, the retail and developer CD BIOS and the Memory Track cartridge: the checksums the core itself checks), by the names the core searches for (jagboot.rom, boot.rom, jagcd.bin, [BIOS] Atari Jaguar ... .j64, ...), by "bios" or "memory track" in the name of a small file (512 KiB or less), or by a [BIOS] entry in the dat. The core's own system folder is always scanned for these too (only BIOS files are kept from it), so the tab shows what the core can read. A BIOS tile says what it is and whether the core's own search finds it where it sits, and a click opens its menu: Use as the Cart boot ROM / CD BIOS (the core runs exactly that file, whatever it is called and wherever it lives, see below), Boot (below) and, for a file the core would find in its system folder under the right name, Copy to the system folder as ... (the fixed names, for RetroArch sharing the folder; never over a file already there). BIOS files are found anywhere under a library folder (any depth the walk reaches, any upper/lower case in the name). The Series K image, the Memory Track and files whose size the core rejects get no copy offer. The core has every standard image built in, so none is required. Loose (Track N).bin files are skipped like the tracks a .cue owns.

Favorites, recently played and save states. Click the star on a tile (or right-click > Add to Favorites) and the game is a favorite; every game that boots, from the library, a drop, File > Open or the command line, goes to the front of Recently played (the last 20; right-click > Remove from Recently Played, or Clear). Where each list shows is up to you, separately, under Favorites & recents... in the library toolbar and in Settings > Interface (library.favorites.show, library.recents.show: 0 hidden, 1 its own tab, 2 a strip at the top of the Cartridges and Jaguar CD tabs, 3 both, the default). A tab lists both media (favorites by title, recents newest first); a strip is one scrolling row at the top of each media tab with that media's games only, under the same search and filter. The Save states tab lists every game that has states, newest first, with the screenshot saved with each state, its slot and when it was saved: click one to start the game from that moment (a state of the game already running just loads into it), Delete asks first and removes the state, its screenshot and its RetroAchievements sidecar. Right-clicking any game tile gives Play, Load state (the game's states with screenshots, newest first), Add/Remove Favorite, Remove from Recently Played, the cover items, Show in Finder / File Explorer / file manager (the containing folder) and Copy path. Lists remember a game by path, checksum and dat name together, so moving a folder or an update that identifies a game does not lose it; a game whose file is away (an unplugged drive) is skipped but not forgotten. A game booted from outside the library folders is not listed. Hardcore RetroAchievements mode refuses a state load before leaving the running game. Resume where I left off. Settings > Interface > Save states: Off / Ask / Always (saves.resume, default Ask). When a game is closed (File > Close game), left for another game, or the app quits, its state is written as an Auto-save: its own slot beside the numbered ones (<file name>.auto.state + .auto.png, one per game, only the latest, written atomically). The next time that game boots, Always loads it right after boot, Ask shows "Resume from ?" with Resume, Start fresh and an "Always resume without asking" box, Off does nothing (and writes nothing). The Save states tab and the tile's Load state list show it as Auto-save, and Delete works on it. Rules: never in RetroAchievements hardcore (state loads are refused, so there is no prompt either) and never during netplay (a state would desynchronise the link); no auto-save for a game that ran under 5 emulated seconds (still the boot logo; a quick open-and-close must not replace a real auto-save with a title screen) or that the crash watchdog flagged (resuming would land in the hang); File > Reload game and headless runs neither keep nor resume one; picking a state in the library skips the offer. Another running copy (instance 2+) keeps its own auto-saves in states/instance-N/ so two windows on one game cannot overwrite each other's; the numbered states stay shared.

The lists live in <data>/library/user.tsv, not in config.ini (rules for several copies in Running several instances). Save states are named <file name>.slotN.state in <data>/states/, as always, so two games whose files share a name share states.

BIOS & boot. The BIOS & system tab starts with the same panel as Settings > BIOS (also File > Boot BIOS > BIOS & boot settings...; the home screen's "BIOS & boot..." button reaches it with no folder added), so a BIOS can be chosen with no game loaded and whatever the loaded game is (the core hides the CD options while a cartridge runs, and the Core options tab is empty before the first load).

• Which file. Each role, the console boot ROM (128 KiB) and the Jaguar CD BIOS (256 KiB), is Auto or one chosen file. Auto is the core's default: a file in the system folder under the names it searches, else the image built into the core (Auto picks = Series K / Model M / Custom for the boot ROM, Retail / Developer for the CD BIOS). A chosen file is handed to the core by path through a private call (VJ_ENV_GET_BIOS_PATH, docs/app-frontend-extension.md), so it needs no copying and no special name. The core still checks it (exact size; a CD BIOS also by checksum or header) and, if it refuses, uses its own choice and the panel says so. The choice is saved per role (bios.cart, bios.cd in config.ini; Auto = no key) and applies when the game starts.
• When it is used. The boot ROM runs when cartridges boot through the Real boot ROM (instead of HLE), for GPU-only demos, and on Boot. The CD BIOS runs when CD games boot through Real BIOS (instead of HLE), for audio CDs and on Boot. These two switches are the core options BIOS (Cartridges) and CD Boot Mode, shown here whatever is loaded. Panel lines say "Running now: ..." from what the core reported staging (built in, system folder file, or your file, with its CRC32) and warn when a chosen file is idle because the matching switch is HLE.
• Boot. Boot the CD BIOS (no disc) / Boot this ROM (empty slot) (panel, tile menu, File > Boot BIOS) starts the console with nothing inserted: the CD BIOS comes up on its disc screen with the Memory Track plugged in; the boot ROM shows the Jaguar logo on an empty slot, as the hardware does. A tile's Boot uses that file for this boot only. The known Memory Track cartridge dump boots as a cartridge (its own manager program); a Memory Track image the core does not recognise, a wrong-sized file or another system file is disabled with the reason in a tooltip. Command line: --boot-bios cart|cd, --cart-bios FILE, --cd-bios FILE.
• Import. Import BIOS file..., or dropping (or File > Open'ing) a boot ROM or CD BIOS on the window, copies it to system/bios/ (never over a different file), chooses it and rescans. A dropped BIOS is imported, not run as a cartridge; the dialog also takes a dump with no recognisable name, by its size.

File > Game library (Ctrl/Cmd+L) opens the window.

1. Add folder... one or more folders. They are walked recursively (8 levels, symlinked folders inside them are not followed) for the formats the core reads: cartridges .j64 .jag .rom .abs .cof .prg .bin and discs .cue .chd .cdi. A .bin that a .cue references is a disc track, not a cartridge, and so is any .bin over 8 MiB. Zip is not scanned: the core cannot load it. An .m3u multi-disc playlist (RetroArch's format: one image per line, relative to the playlist or absolute; # lines and a |label suffix are ignored) is listed in place of the discs it names, and is identified by its first disc. Opening one boots the first disc and puts every disc in File > Disc (the core itself reads no .m3u; the app does). Recents, Restart and the .srm (one per set) follow the playlist; the window title, save states and achievements follow the disc in the tray.
2. Identification by CRC32 against libretro-database (see licences below):
   • cartridges against the No-Intro "Atari - Jaguar" dat, using the whole file first and then the file minus a 512-byte copier header (the same rule as the core's DetectPrependedHeaderSize, so a headered dump of a known game still matches);
   • CD images against the Redump "Atari - Jaguar CD" dat. Redump hashes each track, so a .cue is identified by the CRC32 of the first file it references (Track 1). A .chd is identified the same way: its Track 1 sectors are read back as the Redump .bin has them (the way the core reads them: subcode dropped, audio put back in .bin byte order, a virtual pregap left out). A .chd with several audio tracks and no session metadata (which the core refuses too) is not hashed. A .cdi is hashed best-effort from its Track 1 descriptor; rips whose layout differs from the descriptors (the core repairs these) will not match. This is verified against synthetic images; real Redump CHDs are still to be checked.
   • when the checksum does not match (a bin/cue or .cdi that is not a Redump dump) the disc is matched by name: the file name, then the name of its folder, against the dat's titles with case, punctuation, region and (Track N) / (Disc N) tags ignored. An exact title wins; a file name that is the start of exactly one longer title also matches (file name only, 4+ characters). A name that fits two games (a two-disc set, "Space" for "Space Ace" and "Space Ace Gold") matches neither: it stays unidentified rather than guessing. A name-only match is badged ? (titled and given art from the dat entry), an unidentified file ?? (titled from its file name, no art). Hover a tile for the path, CRC32 and how it was identified (checksum, file name, folder name, or not at all).
3. Box art comes from libretro-thumbnails (thumbnails.libretro.com/Atari - Jaguar/Named_Boxarts/<dat title>.png; the libretro rule replaces & * / : " < > ? \ |with_). It is fetched only for tiles you can see, one title at a time, on a background thread, and cached under /thumbnails/ forever: art you have seen works offline. When there is no box art the title screen, then a snapshot, is used; when upstream has none the tile shows a coloured placeholder and the miss is remembered for 30 days. Upstream coverage is the limit here: of the 209 titles in the cartridge dat, 70 have art under their exact dat name (64 box art); of the 26 Jaguar CD titles, 12 have a snapshot and none a box art. (Measured against libretro-thumbnails at the pinned dat's date.) For Jaguar CD titles libretro-thumbnails is asked first and, on a miss, the project site's mirror (jaguar.provenance-emu.com/thumbnails/Atari - Jaguar CD/..., box art from TheGamesDB plus title screens and snaps made with this emulator, hosted until libretro-thumbnails has a Jaguar CD repository, issue #141 there); each source has its own cache folder, so mirror art never hides upstream art that appears later. A libretro-thumbnails miss is remembered for 30 days; a mirror miss only until the app quits, so art the site gains shows on the next launch. Set library.art_mirrorinconfig.inito another base URL, or to an empty value to turn the mirror off. **Download art and cheat packs** turns all downloading off. **Your own covers.** libretro-thumbnails has no Jaguar CD repository at all, so no disc gets downloaded art. A tile with no art is a drawn card with the game's title and aCD/Cartbadge. Right-click a tile > **Set cover image...** (PNG) to give it one, or drop a PNG onto the tile while the library is showing (a PNG dropped anywhere else is opened as before, and fails as not a game); **Remove cover image** undoes it. The PNG is copied to/covers/custom/.png(the dat title when the game is identified, else a checksum of the disc or of its path). For many at once, put PNGs named after the game in/covers/, e.g. /covers/Myst (USA).png` (dat title first, then the title shown on the tile), then press Rescan. A cover you set beats the folder, which beats a downloaded image, which beats the card. Only PNG is read: SDL3 has no JPEG decoder and the app adds no dependency for one. Covers larger than 8192 px or 32 MB are refused.
4. Launch is a click on the tile; it posts the same "open this path" event as the file dialog. Close on launch hides the window afterwards.

Files: <data>/library/scan.tsv (the hash cache: a rescan only stats files whose size and modification time are unchanged), <data>/library/db/ (databases fetched by Update database), <data>/thumbnails/, <data>/covers/ (your cover art). Settings are the library.* keys in config.ini.

The two dat files are fetched at configure time, pinned to a libretro-database commit and SHA256 (VJ_DB_COMMIT in CMakeLists.txt), and copied next to the executable in libretro-db/. Update database downloads the current files into <data>/library/db/; the newer of the two copies (by the dat's own version) is the one used. Offline build: -DVJ_APP_LIBRETRO_DB_DIR=<folder holding 'Atari - Jaguar.dat' and 'Atari - Jaguar CD.dat'>; -DVJ_APP_BUNDLE_DB=OFF skips them (the library then titles games from file names until Update database).

HTTP is the only network code. SDL3 has no client, so src/http.cpp is a blocking GET with three compile-time backends: libcurl (macOS SDK, libcurl4-openssl-dev on Linux, MinGW if installed), WinHTTP on Windows (part of the OS: no dependency), or none (-DVJ_APP_HTTP=OFF, or libcurl not found), in which case downloads are simply unavailable. It is only ever called from worker threads, never from the UI or emulation loop.

Licences. The dats are CC BY-SA 4.0 (libretro-database, derived from No-Intro and Redump data). They are not committed to this repository, only downloaded and shipped unmodified beside the binary, with attribution here. The box art is the property of its owners; the app downloads it to the user's own machine on demand, as RetroArch does, and never redistributes it. PNGs are decoded with SDL3's own loader (SDL_LoadPNG_IO): no image library was added.

Emulation thread

Settings > Interface > Performance > Emulation thread (ui.emu_thread) runs the emulation on its own thread (#967; design in docs/app-emulation-thread-design.md). The window then only presents. A slow emulated frame or a busy UI no longer stalls the picture. The game runs at the true Jaguar rate (60.05 Hz, PAL 50.08 Hz), paced by the sound card's clock, and the display shows the newest frame (on a 60 Hz panel the true-rate drift alone skips one frame about every 18 s; in this phase frames that finish close to the take point also repeat or skip more often than in the single-thread loop, roughly 1 to 2.5 a second as measured on a 60 Hz panel; Frame pacing: Match display, below, removes both). The setting takes effect at the next start. It is on by default in every build since 4.0 (releases, nightlies and dev builds alike; About shows the build channel, and the log prints [emu] channel=..., emulation thread default on). A stored choice always wins in both directions; Reset group in Settings > Interface returns to the default. To run without it, turn it off in Settings (persistent) or start with --emu-thread off (one run); if the thread cannot start, the app falls back to the single-thread loop and says so in the log. Headless runs stay single-threaded unless --emu-thread on says otherwise.

When it starts, the thread asks the OS to schedule it as the periodic deadline job it is: on macOS the time-constraint (real-time) policy, which runs ahead of every QoS class and on performance cores; on Windows time-critical priority plus the MMCSS "Games" task; on Linux SCHED_RR at a low real-time priority, which the kernel refuses unless RLIMIT_RTPRIO or rtkit allows it. On a loaded host this is the difference between the emulation keeping a core and sharing one (an M2 Max at load 250 ran the same Doom frame in 5.4 ms with a core of its own and 18-20 ms without). The log's [emu] emulation thread on; scheduling ... line says what the thread got; --emu-priority normal skips the request for one run.

With vsync, the window waits until just before each vblank, passing input to the emulation as it arrives, and then shows the newest frame (the late latch, src/late_latch.h). It stays off until it has found where the vblanks are, and lets go by itself if frames keep missing them; the log says [emu] late latch locked / released. --late-latch off turns it off for a measurement. For a dev measurement, virtualjaguar --perf-frames N with VJ_PERF_CSV=path writes one row per measured iteration when the run ends, with the input_lat_ms (event to the emulation's poll) and present_lat_ms (event to the swap that shows it) columns; --perf-input injects a key every 30 iterations so they have samples. VJ_PERF_TRACE=prefix adds prefix-emu.csv (each emulated frame: due, start, end, trim, audio queue, and last the fill_ns the Tools windows' view copy took after it; end_ns is taken before that copy) and prefix-ui.csv (each UI take and swap); python3 app/tests/perf_trace_summary.py prefix counts the frames really shown and splits their timing. With the latch's vblank grid locked, the emulation steps its pacing grid's phase once whenever frame ends would straddle the take point, so each 60.05-on-60 Hz crossing is one skip rather than a burst of repeats and skips; --pace-steer off turns that off for a measurement.

Settings > Video > Frame pacing (video.pacing, #1038) picks the clock the emulation thread follows. Jaguar rate (the default) is the above: the console's own 60.05 / 50.08 Hz, kept by the sound card. Match display runs one emulated frame on every refresh (every second refresh at 120 Hz) where the display's measured rate is within 0.3% of a whole multiple of the game's: 60, 59.94, 120 and 119.88 Hz for NTSC games, 50 and 100 Hz for PAL. The sound plays that much faster or slower (0.09% on a 60 Hz panel, inaudible), the Jaguar rate's periodic repeat or skip goes away, and a frame starts right after the swap that hands it the newest input, so event to present matches the single-thread loop even for heavy games. It needs vsync and the late latch's lock on the vblanks, and settles for about two seconds after the start or a display change. Elsewhere (144 or 75 Hz, a PAL game on 60 Hz, vsync off, a refresh that is not steady), and always during fast-forward and link play, it uses the Jaguar rate; the setting shows why ("Now: ..."), and a lasting fallback shows a message once. The log says [emu] frame pacing: mode B (locked) / mode A (<reason>) at each change. A window that stops swapping (a modal, a sleeping display) does not stop the game: the emulation keeps the display's grid on its own, and returns to the Jaguar rate after a quarter of a second. --pacing jaguar|display chooses for one run without saving. The single-thread loop ignores the setting (it is already display-paced). VJ_PERF_TRACE's emulation rows end with mode, tick_seq, ticks_dropped and lock_reason, which the summary script counts.

While it is on, every Tools window works (their data is copied by the emulation thread after each frame, and their edits run on it), and so do Break, Step, breakpoints and the GDB stub. The halt is served by the emulation thread in 4 ms slices and the window mirrors it once per frame, so the UI keeps drawing while the game is parked (a gdb session holding a halt no longer freezes it); settings and cheats changed meanwhile apply after Continue, and anything that would reload or save the game detaches the debugger first or says why it cannot. With the stub enabled the app keeps a silent debugger host so a gdb halt shows as "HALTED by gdb"; virtualjaguar_gdb_wait parks the boot until the gdb client sends c (connecting alone does not continue it) or F9 continues. RetroAchievements hardcore locks the GDB stub to disabled at load, so turning hardcore on while the stub is enabled reloads the game. A headless run (--headless) ends cleanly on SIGINT or SIGTERM even while gdb holds a halt; a second signal kills it. RetroAchievements and netplay work as usual: achievements are checked on the emulation thread after every frame, and link play's peer waits block only that thread. An action that has to reach the core, such as a Tools-window edit, a load or a state save, waits for the frame in progress to end, including that frame's peer wait, which link play bounds to about one frame. One that takes longer than a quarter of a second shows a spinner instead of freezing the window. A log line [core_host] owner violation: ... means a UI path still called into the core directly: that is a bug, please report it.

Reporting a threading problem

The emulation thread is the default since 4.0 (#1039). If something goes wrong only with it on (stutter, a hang, a crash, lagging input, skipping sound), compare with --emu-thread off, then comment on #1039 or open an issue that links it, with:

• The first line of Help > About: the version and build channel, such as Virtual Jaguar 4.0.0 (nightly build).
• The Now: ... line under Settings > Video > Frame pacing: which clock the thread follows, and why.
• The display's refresh rate, the OS and the GPU.
• Whether it also happens single-threaded: turn the setting off and restart, or run once with --emu-thread off. If it happens both ways it is not a threading problem, but it is still worth reporting; say so.
• If you started the app from a terminal, its lines starting [emu], [core_host] or [stall]. Any owner violation line is a bug on its own.

Running several instances

Run as many copies of the app as you like: to test netplay on one machine (host in one window, join 127.0.0.1 in the other), or for local multiplayer on a big screen. Nothing is locked to a single instance.

• Any platform: File > New window (Ctrl/Cmd+N) starts another copy. On macOS it runs open -n on the app bundle, which is also what you do by hand: a double-click only activates the copy that is already running, so from a shell use open -n "/Applications/Virtual Jaguar.app" (or open -n -a "Virtual Jaguar" --args --data-dir DIR). On Windows and Linux just start the program again (a Linux AppImage starts itself again from $APPIMAGE). A copy started with --data-dir hands the same folder to the copies it opens.
• Numbering. The first copy running on a data folder is instance 1 and behaves exactly as it always did. The next ones are 2, 3, ... (the lowest number nobody holds; an OS file lock on instance-N.lock in the data folder, released automatically when a copy quits or crashes). The number is in the window title ([Instance 2]). Copies with different --data-dir folders, or a portable copy, share nothing and are all instance 1.
• What each copy writes. Instance 2+ never rewrites the shared files:

File	Instance 1	Instance N (2+)
config.ini (settings, bindings, core options, recents, RetroAchievements user name)	read and written as before	read at start (so it has your settings); never written
config-N.ini	not used	its window size and its controller choice only
imgui.ini	imgui.ini	imgui-N.ini
game saves saves/<game>.srm (EEPROM, SRAM, Memory Track) and the GameDrive SD folder	saves/	saves/instance-N/; a game's first run there starts from a copy of instance 1's save (read only)
save states states/, cheat selections cheats/games/	shared	shared: written only when you press save, each file atomically, last save wins. A state saved in one copy loads in another
library cache, box art, database files	shared	shared, written atomically with a per-process temporary name
favorites and recently played library/user.tsv	shared	shared and written by every copy, but as operations: each change re-reads the file, applies that one change (star, play, remove, clear) and writes it atomically, so a copy never replays a stale snapshot over another's list; two changes in the same few milliseconds can lose one. Other copies pick a change up within a second
library display options (library.* in config.ini)	saved with the other settings	read, not saved (like every setting)
netplay address (system/vj_netlink.txt)	written when you join, as before	not written (no copy writes it): the address and port go to the core as per-process option overrides, so two copies can join different hosts

Why: two copies both writing one .srm or one whole-file config.ini would silently lose one side's changes. Settings you change in a second window are therefore not remembered, so make them in the first window. Instance numbers are ordinal slots (the window you opened second), not identities, which is why nothing else is persisted under them.

• Controllers. SDL gives every connected controller to every running copy, so two windows would both answer the same pad. Settings > Input > Devices & players > Controllers used by this window picks All controllers (the default), Keyboard only, or Controller k for each pad, remembered per instance number. Controller numbers follow the order SDL lists them (connection order). A window pinned to one controller keeps reading it while another window has focus (SDL otherwise ignores controllers in the background), so two players can play side by side; the keyboard goes to whichever window has focus. Which Jaguar port or player a controller drives inside a window is still chosen under Devices & players.
• Netplay on one machine: start a game in instance 1 and choose Netplay > Host; in instance 2 start the same game and choose Netplay > Join with address 127.0.0.1 and the same port. Two copies that both host need different ports (the window offers 42171-42174).

Where files go

normal	the OS per-user data folder (SDL_GetPrefPath): ~/Library/Application Support/VirtualJaguar/, %APPDATA%\VirtualJaguar\, ~/.local/share/VirtualJaguar/
portable	data/ next to the executable, when a file named portable.txt sits beside it
override	--data-dir DIR

Inside: config.ini (settings, core option overrides, recents), saves/ (<game>.srm: EEPROM, SRAM, Memory Track), states/ (<game>.slotN.state plus a .png thumbnail), system/ (BIOS files, only if you want real ones), imgui.ini.

Cheats

Emulation > Cheats... lists the cheats of the libretro cheat database for the running game, with a toggle each, plus manual codes (hex ADDRESS:VALUE, + to join several). What is on is remembered per game (<data>/cheats/games/<key>.ini, keyed by the cartridge CRC32; discs by the core's title row or file name) and sent to the core again after every load and state restore.

The cheat files are not committed to this repository (the libretro database is CC BY-SA 4.0), but they are bundled with builds: configure downloads the 41 cht/Atari - Jaguar files of one pinned libretro-database commit (SHA-256 per file) to <build>/cheats/, next to the program, and cmake --install puts them in <prefix>/bin/cheats/ with the database LICENSE and a credit README beside them, so the attribution travels with the files (a packaging step takes them from the install tree). The download is fail-soft: with no network the configure still succeeds, the cheats are then simply not bundled (never without their license). For offline or distro builds: -DVJ_APP_FETCH_CHEATS=OFF. You can always add your own .cht files to <data>/cheats/, or point the window's "Cheat library" box (or --cheats-dir) at a folder of them. A set is picked by name from the core's own title (or the file name); with several matches, or none, you choose. Jaguar cheats are credited to Gent of Emucheats.

Database entries are RetroArch memory cheats (decimal address/value, width in memory_search_size); they become the core's hex codes, value little-endian in memory as RetroArch writes it. cheatN_enable is ignored: nothing starts on.

For community-authored C cheat sources, the optional offline source converter can produce .cht freezes without an emulator binary or SDK. It reports unsupported operations, leaves every cheat disabled, and binds the set to the matching cartridge CRC32. The app blocks revision mismatches and malformed/duplicate guards; legacy unbound .cht files continue to work. No community script pack is bundled.

Community cheats. The Cheats window has a "Community cheats" section for the packs the project publishes at jaguar.provenance-emu.com/cheats/ (converted from jguffer's BigPEmu scripts, credited in the section). Opening the window with a cartridge loaded asks the site for its pack index (at most every 6 hours; Check for updates asks at once); Install downloads the pack named by the cartridge's CRC32, checks its size and SHA-256 and its revision guard, and only then writes it to <data>/cheats/community/packs/<CRC32>.cht (with a .json record beside it). Every cheat starts off, Update keeps the cheats whose text did not change, Remove deletes the pack. Packs cover cartridges only, are found by CRC32 alone (the database set above is independent) and are inert in RetroAchievements hardcore mode. Library > Download art and cheat packs is the single downloads switch (library.art); with it off the section shows only what is installed. cheats.community.url in config.ini points the store at another base URL (a local test server). Headless, --cheats-community-install does the same fetch and install for the loaded cartridge.

RetroAchievements

Achievements > Sign in... takes your RetroAchievements user name and password once, gets a login token from the server and keeps only the token (the password is wiped from memory as soon as the request is built). The user name is ra.user in config.ini; the login token is kept in the system keychain (macOS Keychain, Windows Credential Manager, or the Linux Secret Service through libsecret, loaded at run time) and not in config.ini. A token that an earlier version left in config.ini is moved into the keychain at start-up. Where no keyring is available (no libsecret, no running keyring service, a Flatpak without the secret portal) the token stays in config.ini as ra.token, Settings says "Token stored in the settings file because no system keyring is available", and that file is then a credential: treat it like a password file. Sign out deletes the token from the keychain (and from config.ini). A second copy of the app (see below) reads the keychain and writes it only when you sign in or out there. The menu also has the hardcore toggle, "include unofficial achievements" and the Achievement list, a dashboard with your avatar, badges and the Jaguar games that have achievements (see below). Unlocks, game completion, leaderboard attempts / submissions, progress indicators and server problems show as toasts.

It is built on rcheevos' rc_client (v12.5.0, MIT, fetched at configure time like SDL3):

• Game identification. rc_client hashes the file itself: the whole cartridge file for Atari Jaguar (console 17), the second-session boot executable for a .cue disc (Atari Jaguar CD, console 77, rcheevos' built-in cue/bin reader). .chd and .cdi discs are not identified yet: rcheevos' built-in reader covers cue/bin only and this app has not supplied a CHD/CDI reader (RetroArch installs its own CD reader). The game runs and the app says why. A .bin file is a cartridge for this core and is hashed as one.
• Memory. The core publishes a memory map (RETRO_ENVIRONMENT_SET_MEMORY_MAPS: 2 MB system RAM at $000000). rcheevos' rc_libretro.c, the same code RetroArch builds, maps addresses onto it; nothing is byte-swapped. The RAM is a big-endian image and Jaguar sets use the big-endian operand sizes (0xI 16-bit, 0xG 32-bit).
• Hardcore. While signed in, hardcore is on and a game is being tracked: loading save states is refused (saving works), pausing is rate-limited (rc_client_can_pause), enabling it mid-game (or signing in mid-game with it on) restarts the game for a clean run, core options that rcheevos disallows (today virtualjaguar_pal = enabled) pause hardcore, and Achievements::allowCheats(), allowRewind(), allowSlowMotion() and allowFrameAdvance() are false so those features (cheats, rewind, slow motion and frame advance are separate pieces) must ask. Fast-forward is allowed (it is not slower than real time). Softcore (the default) restricts nothing, and each state file gets a .rcp sidecar so a restored state does not replay stale hit counts.
• Cheats. No cheat reaches the core while hardcore is active: the cheat manager's apply() consults Achievements::allowCheats(), so loads, state restores, the window, manual codes and --cheat/--cheat-on all obey it. Entering hardcore empties the core's list, leaving it (softcore, sign-out, RetroAchievements off) puts the saved per-game selections back; they are never changed on disk meanwhile. The Cheats window stays openable with its controls disabled and says why.
• Network. libcurl (found at configure time; libcurl4-openssl-dev on Linux) or WinHTTP on Windows, on one worker thread; replies are handled on the main thread, so a slow network never delays a frame. Without libcurl the app still builds and the Achievements menu says it is unavailable. Unlocks are retried by rc_client when the network drops.
• Pictures. Your avatar (rc_client_user_get_image_url), the game icon (rc_client_game_get_image_url) and every achievement's badge, earned or greyed (badge_url / badge_locked_url), show in the Achievements window, the menu and the unlock toasts. They download on a worker thread of their own (so they never queue behind rc_client's requests) and are kept in ra-cache/ in the data folder: a badge never changes, so a saved file is reused forever; the avatar is saved per avatar_last_updated. The folder is kept under 48 MB (oldest pictures go first) and at most 256 are held as textures at once (least recently drawn goes first; it comes back from disk when asked for again). They follow the Library's download art switch: with it off, or with Achievements > Download pictures unticked, only pictures already saved are shown and nothing is fetched. Headless runs and --ra-mock sessions never fetch.
• Dashboard. Achievements > Achievement list... is a window with three tabs. This game: icon, title, hardcore / softcore rule in force, progress bar, and the achievement list with badges, points, rarity, earned date and a Hardcore / Softcore marker, with a filter (all, unlocked, locked, unlocked in hardcore, missable), a sort (default, title, points, rarest, recently unlocked, type) and a search box. Jaguar games: every Atari Jaguar (console 17) and Jaguar CD (console 77) game that has achievements (rc_client_begin_fetch_game_list), with icon, achievement count, points and your progress in each (rc_client_begin_fetch_all_user_progress, signed in only); filter by all / in my library / in progress / completed / not started. Games in your library get a Play button: cartridges are matched by the MD5 RetroAchievements lists for the game (hashed on a background thread), everything else by title against the library's names. The list is saved in ra-cache/games-<console>.tsv and refreshed when it is a day old (and only while downloads are on); Refresh fetches it again on request. Profile: avatar, name, hardcore and softcore points, and what you unlocked in this session. rc_client has no call for the account's older unlock history (that needs the web API and its key), so it is not shown. Neither list needs a web API key: both use the login token like the rest.
• Tests never touch the network or an account: --ra-mock DIR answers rc_client's requests from app/tests/ra/<api>.json (<api>_<console>.json first for systemgames and allprogress, one list per console). vj_ra_dash_test covers the picture cache (paths, disk, offline mode, LRU), the games-list parsing and library matching, the cache file, and the filters and sorts; ra_dashboard_mock fetches the lists through the mock server. See cmake/VJAchTests.cmake.

Netplay

The Netplay menu opens a window for the link-cable games (Doom deathmatch, BattleSphere, AirCars, and Ultra Vortek over the Voice Modem) between two computers on a local network (or two windows on one machine, see Running several instances). It configures the core's existing link networking (docs/netlink-user-guide.md) through core options and takes status from the core's event channel (see Core events below; a core that never answers falls back to reading its [NETLINK] log lines); it is not rollback netplay, and play over the Internet or a VPN is not supported. Both players need the same game and the same version of the app, and the same device (JagLink / CatBox cable or Voice Modem).

• Host a game lists this machine's LAN addresses and starts listening on a port: one of the core's four presets (42171-42174) or any port from 1 to 65535 under Custom....
• Join a game finds hosts on the LAN (the core's UDP beacon) or takes a typed host name or IPv4 address, set straight on the core's host option (the core resolves names itself).
• Mode, host and port are session overrides and are never saved, so relaunching the app does not start listening on its own; the link device is an ordinary saved option.
• Command line twin: --netplay host|join|join-discovered|browse|loopback, --netplay-addr, --netplay-port, --netplay-device jaglink|voicemodem. Advanced > Echo test runs the link against itself with no partner.

Platform integration

What the app does so it behaves like a program of the OS it runs on (#833). The code is behind one interface, src/platform/platform.h; every OS-specific file is small and a platform with nothing to add compiles a no-op, so adding a platform feature never touches the others.

	macOS	Windows	Linux
Menu bar	native, with Cmd shortcuts (the in-window bar is hidden)	in-window	in-window
Dock / taskbar menu	Dock menu: recent games, library, open, pause, reset	Jump List: recent games	desktop Actions: Open Game Library, Boot Without Cartridge
Recent games	NSDocumentController (Dock, Open Recent)	Explorer Recent and the Jump List (SHAddToRecentDocs)	not written (no GTK; see below)
File types (double-click, Open With, drop on the icon)	CFBundleDocumentTypes + an exported type for .j64 / .jag	installer task: per-user OpenWithProgids (and the default for .j64 / .jag)	shared-mime-info XML + MimeType=
Window	fullscreen follows the green button / Ctrl+Cmd+F; App Nap held while a game runs	title bar follows the app theme (dark or light), per-monitor-v2 DPI, long paths, one taskbar button with the installer shortcut (AppUserModelID)	the application id is the Wayland app_id / X11 WM_CLASS, so the icon and "pin to dock" match the .desktop file
Tray / menu-bar icon	optional (Settings > Interface > Desktop)	optional	optional where the desktop has a StatusNotifier host (KDE and others; stock GNOME needs an extension)
Screensaver / display sleep	allowed in the library and while paused, blocked while a game runs	same	same (through the portal inside Flatpak)
Show in Finder / Explorer	File > Show in Finder	-	opens the folder

One model, many surfaces. src/platform/commands.cpp builds the menus (File, Emulation, View, Achievements, Netplay, Window, Help, the tray and the Dock menu) from a snapshot of the app state, and every click is posted as an SDL user event and run by the main loop (App::runNativeCommand), never inside Cocoa's menu-tracking loop or SDL's tray callback. The macOS menu bar is built after SDL_Init over SDL's default one and leaves SDL's app delegate alone (it turns Finder's "open" into the drop event the app already handles). Only Cmd-modified shortcuts are bound there; F5 / F7 / F8, Tab and the other hotkeys stay with the app. While a native menu is open the macOS event loop is blocked by Cocoa, so emulation and audio pause for as long as the menu is held open.

File types. The associated extensions are .j64 .jag .rom .abs .cof (games) and .cue .chd .cdi (discs). .bin and .prg open through File > Open and drag and drop but are too generic to claim. The list lives in src/platform/commands.h (VJ_ASSOC_LIST); the CTest platform_assoc_sync fails when the Info.plist, installer, .desktop, mime XML or the application id drift from it. On Windows and Linux a double-clicked game starts a new process, which is a second instance when the app is already running (see "Running several instances": its own save folder, settings not kept); on macOS the running copy opens it.

virtualjaguar --dump-native-menu (macOS) prints the real menu bar and Dock menu and checks every item; exit 77 means no window-server session (ssh) or not macOS.

Windows outside the main window, and the in-window menu bar. Dear ImGui is the -docking build of the same version (v1.92.8-docking; pinned in CMakeLists.txt and the Flatpak manifest), used only for its multi-viewport mode: Settings > Interface > Desktop > "Let windows move outside the main window" lets a Settings / Achievements / Cheats / Netplay / debug-tool window dragged past the edge of the main window become an OS window of its own (real title bar, no Dock / taskbar entry, positions kept in imgui.ini). Breakout windows use only native title-bar controls; the duplicate ImGui title/collapse/close bar returns when they move back inside. Default on for macOS and Windows, off on Linux; it is forced off on Wayland (a client cannot position its own extra windows there; X11 and XWayland are fine), while the window is fullscreen, and in headless runs (src/platform/viewports.*, unit-tested in platform_unit). Docking is left off: it would put tab bars and drop targets on windows people already arranged. The coordinates of the main window are screen coordinates while this is on, so code that mixes them with SDL's window-relative pointer events subtracts GetMainViewport()->Pos. On macOS, "Show the menu bar inside the window" (ui.menubar_in_window, off by default; F1 flips it) keeps the ImGui menu bar as well as the native one.

"Auto-hide the menu bar in fullscreen" (ui.fullscreen_autohide_menu, off by default) unpins the in-window menu on entering fullscreen, including the macOS green-button route. Move the pointer to the top edge to reveal it, or press F1 to pin it. Leaving fullscreen restores the earlier pin state; a temporary F1 reveal on macOS does not change the windowed menu preference. The setting also belongs to Interface's reset group.

VJ_WINDOWED_OK=1 bash app/tests/fullscreen_menu_windowed_check.sh <app> <rom> <out-dir> checks the default and enabled cases on the dedicated display host: fullscreen entry/exit, top-edge hover, F1, saved preference and screenshots. window_chrome_unit drives real ImGui viewports with a fake platform backend to check native close, collapsing, reattachment and decoration-less backends without opening a window.

Discord

Settings > Discord shows what you are playing on your Discord profile (Rich Presence), and the activity doubles as app discovery: friends see "Playing Virtual Jaguar", the game's box art, and a Get Virtual Jaguar button that opens the site's download page (https://jaguar.provenance-emu.com/app.html). Discord has to be running on the same computer; nothing is sent anywhere else, and nothing is installed (the app speaks Discord's local RPC protocol itself, no Discord SDK).

• While playing: the title (dat name without region and revision tags) as the headline; the line below says Atari Jaguar or Jaguar CD plus | Paused, | Netplay: hosting / joined (never an address), | Hardcore and | 12/30 achievements when a RetroAchievements game is tracked; the elapsed time counts from boot. The large picture is the game's box art, a public https address (libretro-thumbnails, or the project site's Jaguar CD mirror) that Discord's media proxy fetches. It is used only when the library already downloaded that picture, so Discord never shows a broken image; otherwise the application's jaguar (cartridge) or jaguarcd (disc) asset is shown. The small picture is the app icon (app) with "Virtual Jaguar ".
• In the library or an empty window: "Browsing the library" with the library picture.
• Buttons: Get Virtual Jaguar, and View on RetroAchievements (the game's page) while a RetroAchievements game is tracked. Discord shows buttons to other people only, so your own profile never shows them.
• Settings: Show what I'm playing on Discord (default on), Show game artwork, Show buttons, and the connection status ("Connected to Discord", "Discord is not running"). Config keys discord.enabled, discord.art, discord.buttons.
• Application ID: the default is the project's "Virtual Jaguar" Discord application, set by the CMake cache string VJ_DISCORD_APP_ID (-DVJ_DISCORD_APP_ID= empty turns the feature off; a fork passes its own). The config key discord.app_id (Settings > Discord > Application ID) overrides it.
• Several windows: only the first copy (instance 1) publishes, so two windows never fight over one status (see Running several instances).
• Behaviour: the connection and every write live on a background thread; if Discord is not running the app looks again every 15 seconds and never waits on it, quitting takes the status down within a quarter of a second, and updates are sent only when something changed and at most 4 per 20 seconds (Discord allows 5).

Maintainer setup (Discord developer portal)

1. Create an application named exactly Virtual Jaguar (Rich Presence cannot set the name; this is what people see after "Playing"). Its Application ID is the number in VJ_DISCORD_APP_ID.
2. Upload these art assets under Rich Presence > Art Assets, with exactly these lowercase keys (at least 512x512): jaguar (cartridge fallback large image), jaguarcd (Jaguar CD fallback), library (browsing), app (the app icon).
3. CI: the repository variable DISCORD_APP_ID (Settings > Secrets and variables > Actions > Variables) overrides the CMake default in app-package.yml; leave it unset to use the default. An application ID is public, not a secret.
4. Test from a second Discord account: buttons are hidden on your own profile.

Neuro API (AI players)

Settings > Neuro connects the app to a Neuro game API server, so Neuro-sama, or any AI backend that speaks the API (the SDK's Randy, Tony and Gary included), can play as Player 1. The app registers the Jaguar controller as actions (press_buttons, button_sequence, hold_buttons, release_all), plus a game profile's own moves (Tempest 2000 is built in; more go in <data folder>/neuro/*.json), asks for the next move whenever the last one has played out, and presses the chosen buttons frame by frame.

• --neuro ws://HOST:PORT turns it on for one run; the default server is $NEURO_SDK_WS_URL, else ws://localhost:8000 (Randy). Only ws://; no TLS.
• Config keys neuro.enabled, neuro.url, neuro.auto_force, neuro.force_interval, neuro.game_name.
• The socket lives on a background thread and reconnects by itself; the game never waits on it.
• Works with the emulation thread on or off: the buttons are played on the thread that polls input (see docs/neuro.md).
• docs/neuro.md has the actions, the profile format and testing with Randy.
• The code is in src/neuro/; -DVJ_APP_NEURO=OFF builds the app without it (no tab, no --neuro).

Tests: ctest -R discord (frame encode/decode, JSON escaping, socket paths per OS, the rate limiter, the activity built from app state, and a loopback test against a fake Discord server on a Unix socket; skipped on Windows).

Typed settings

The core publishes every option as a list, but for a handful it reads any value, so Settings > Core options shows the core's presets plus a Custom... entry that opens a box (applies on Enter or when it loses focus; an invalid value says why in red and is not applied). The keys are in src/typed_options.h, with the range the core actually honours: link port, GDB port (1-65535), GDB halt timeout (1-3600 s), mouse / rotary sensitivity (1-1600%), the per-axis dead zone (0-64), offset (-64..64) and response curve (1-800%), the link host (host name or IPv4, 1-127 characters, no IPv6: the link sockets are IPv4), and the M68K / RISC clock scales (a percentage, 25-400, e.g. 175%). Saved values and --option K=V use the same validators, so --option virtualjaguar_netlink_port=50123 works; every other option stays a strict list. Tested by typed_options (validators, CoreHost, and the real core reading a custom port, host and clock scale).

Core events

The core reports link up/down, link statistics, wire speed and crash-watchdog hits to the app through a private libretro environment call that only this app answers (src/core/vj_frontend_ext.h, docs/app-frontend-extension.md); under RetroArch it is a no-op. CoreHost answers the handshake and hands each event to onEvent; Netplay consumes them instead of scraping log text (the log parser remains the fallback), and a crash-watchdog hit shows as an on-screen message naming the signature.

Debug tools

The Tools menu is a set of developer windows over a private debug interface the core hands only to this app (src/debug/vj_debug_iface.h, docs/app-frontend-extension.md); RetroArch never sees it. Full reference: docs/app-debug-tools.md.

• Memory viewer (hex / ASCII grid over every bus region, go-to, search, change highlighting, edits, "Add as cheat") with a raw Bitmap mode (width/depth hints, live or staged CLUT, PNG export), and Palette (CLUT) (256 swatches as CRY or RGB16, with an editor).
• Cheat scanner: find an address by narrowing (changed / increased / equal to ...), then keep it as an ordinary cheat.
• Object list: the whole display list the Object Processor walks, decoded, with a bitmap preview, an outline over the game picture, PNG export and a pixel painter (RAM only).
• Blitter log: the last 256 blits with their decoded command and registers.
• Textures: browse the core's texture dump, export a tile, replace its art with your own PNG.
• Audio scope: waveforms and peak meters of the audio the core produces.
• F9 breaks into the game (continue when halted), F10 steps while halted; a "HALTED" bar shows over the picture. The CPU debugger covers the 68000, GPU and DSP, with registers, disassembly, breakpoints and step-over.

Writes go to RAM freely; hardware registers need "Allow register writes"; the CD registers ($DFFF00-$DFFFFF) and B_CMD, G_CTRL, D_CTRL, OLP, LTXD, RTXD are never written from here. Everything greys out (and closes) while RetroAchievements hardcore is on. Extra app instances keep their own windows but do not dump textures. Developers can open one at start-up: --show-window memory|bitmap|palette|scanner|objects|blitter|textures|scope (with --screenshot).

Smoke tests

virtualjaguar --headless runs with SDL's dummy video and audio drivers: no window, no GL. Each game is delivered as a drop event (the same handler the window uses), run for --frames frames, and reported as an FNV-1a frame hash (the same hash test/harness/harness.c uses). CTest runs:

• smoke_yarc: boot test/roms/yarc.j64 under HLE with no BIOS, check the hash.

• smoke_reload: yarc, jagniccc, yarc in one process; the two yarc runs must match, which proves a different game in between left no static state behind. The number of visible core options must match too (it differs between a cartridge and a disc, so a stale visibility table would show).

• smoke_state: save state and thumbnail, run on, load, run on; both runs match.

• smoke_bad_option: an --option the core does not register is rejected, not silently ignored.

• smoke_cd: load the synthetic CD image by path (no BIOS).

• smoke_boot_cd_bios / smoke_boot_cart_rom: boot the CD BIOS with no disc, and the boot ROM with an empty slot, from the images built into the core (no files needed); both must draw (no blank frame) and match a hash.

• bios_unit (vj_bios_tests): scanning BIOS files in nested folders with upper and mixed case names, what may be chosen (size), what Boot does and why not, the saved choice, importing (reuse, never overwrite, refusals), and how the running BIOS is described. Synthetic files only.

• bios_e2e (vj_bios_e2e): the real core and the private BIOS channel: a chosen CD BIOS / boot ROM file is the image that runs (checksum, source), a refused or vanished file falls back, a frontend without the capability is never asked, and a no-content boot enters the boot ROM or the CD BIOS as asked.

• library_unit (vj_library_tests): dat parsing, CRC identification of synthetic files (copier-headered and plain carts, a .cue set), thumbnail naming against known libretro examples, cache paths, a scan of a temp folder with the hash cache, and on POSIX the whole art pipeline (scan, identify, download, cache, decode, texture; database update; then offline) against a loopback HTTP server; favorites / recents (persistence, ordering, matching by path, checksum and name, the shared file under two simulated copies), the favorites / recents display options and tab layout, and save-state naming, listing and deletion over synthetic state files. No internet, no GL. vj_library_tests --scan DIR --db DIR prints identification counts for a folder (dev tool).

• remap_unit: the remapping logic with no core (bindings, precedence, config round trip, keypad translation, overlay, bind capture, content identity).

• input_e2e: drives the real core with every Jaguar control on both ports and reads back the console's joypad matrix; keypad 7-9, *, # included.

• devices_unit / devices_e2e: the non-pad devices (kinds, per-game persistence, Team Tap player slots, light-gun geometry, mouse-capture policy, locked core options, the Pro Controller keyboard layout, the controls cheat sheet and its auto-show rule), then the same host-input routing driving the real core and reading back the mouse / rotary quadrature state, analog / driving / 6D values decoded off $F14000 as a game does, the paddle ADC at $F17C00, the light gun's aim point and the Team Tap socket slots. Every group has a negative control (no host input reads the rest value).

• theme_unit (vj_theme_test): the theme choice (System / Dark / Light, the OS's answer, the theme-changed event) and WCAG contrast of every palette and style colour in both themes, and of the in-game overlays on white and black frames; the custom-theme files (round trip, import validation, the themes folder, read-only secondary copies) and the editor's contrast warnings.

• controls_overlay_*: the overlay through the real app: hidden by default (with the F3 hint), shown for a keyboard player when the setting is on, hidden when it is off, text follows a saved rebinding. devices_unit covers the show / hide policy (click, tap, Esc, F3, timeout).

• debug_*: the debug tools. debug_session_unit and the per-tool unit tests (debug_memory_unit, debug_scan_unit, debug_op_unit, debug_bitmap_unit, debug_texture_unit, debug_blitter_unit) run the pure logic against a fake core (tests/debug_mock.h); debug_memory_ui_smoke and debug_scan_ui_smoke draw the windows headlessly over it; debug_e2e, debug_scan_e2e and debug_op_e2e drive the real core on yarc.j64 (halt / step / continue, a found counter kept as a working cheat, the display list captured by the core).

To regenerate the expected hash after an intentional emulation change: virtualjaguar --headless --frames 300 test/roms/yarc.j64 and update VJ_SMOKE_YARC_HASH in app/cmake/VJSmokeTests.cmake.

Window sizing and UI screenshots

Settings > Interface > Appearance picks the colour theme: System (the default) follows the OS and switches live when it does, or Dark / Light / a custom theme made in Customize... and kept as <data>/themes/<name>.ini (--theme system|dark|light|custom:NAME sets it for one run); the palettes are in src/theme.cpp.

The UI scale follows the display's content scale (200% on a 4K Windows/Linux display; 1.0 on a Retina Mac, where ImGui renders at the pixel density by itself). ui.scale in config.ini (default 1.0) multiplies it.

Fonts

Settings > Interface > Font picks the typeface and its size (11-24 pt, default 13): Retro (Dear ImGui's embedded pixel font, the look the app always had, still the default), System UI (San Francisco on macOS, Segoe UI on Windows, the desktop's sans-serif on Linux through fc-match, with DejaVu / Noto / Liberation as fallbacks), Monospace (SF Mono / Menlo, Consolas, DejaVu Sans Mono) or Custom file... (a .ttf / .otf / .ttc; it is checked, then copied to <data>/fonts/). Changes apply at once and persist as ui.font.* in config.ini. Text is rasterised at the display's pixel density (Dear ImGui 1.92's dynamic atlas), so it is crisp on Retina and at 125-200% Windows scaling; it is grayscale anti-aliased with sub-pixel glyph positioning. LCD (RGB) sub-pixel anti-aliasing is not possible: the glyph atlas is a single coverage channel (and macOS dropped LCD smoothing in Mojave). A missing or unreadable font falls back to Retro with a note in the Font section. Debug windows use fonts::mono() / fonts::pushMono() (src/fonts_imgui.h), a monospace face whatever the UI font is. Glyphs the chosen font lacks (arrows, star, check mark) come from a symbols font or the built-in vector face. The typeface list shows every choice in its own typeface: the built-in ones, then any font installed on the computer (the standard font folders are scanned on a worker thread the first time the list is shown, reading only each file's name / OS/2 / post tables: /System/Library/Fonts, /Library/Fonts, ~/Library/Fonts on macOS, %WINDIR%\Fonts and %LOCALAPPDATA%\Microsoft\Windows\Fonts on Windows, /usr/share/fonts, ~/.local/share/fonts and $XDG_DATA_DIRS on Linux; src/fonts_system.*). A search box filters it, the star keeps a font in Favorites, and the last eight picks are listed under Recent; they persist as ui.font.fav.N / ui.font.recent.N, the chosen OS font as ui.font.os (path|face). The previews load lazily: only rows on screen ask for their face, a few per frame, at most 48 faces / 48 MB stay loaded (least recently used go first), and a face that cannot draw its own name (no Latin letters, damaged, over 8 MB) is shown in the UI font with the reason. Debugger font picks the monospace face of the debug windows from the fixed-pitch fonts, each sample drawn in its own face (ui.font.debug; Automatic = the system monospace font). --font installed:/path/Font.ttf[|FACE] selects an installed font for one run. FreeType is the default renderer (FreeType License, fetched and pinned, built static) and provides the Hinting (none / light / full) and Smooth edges choices. -DVJ_APP_FREETYPE=OFF builds with Dear ImGui's stb_truetype instead, which hides those two choices; the Retro pixel font always uses stb_truetype.

Every window opens at a size in font heights (so it scales with DPI), at most 80% of the main window, is constrained to 95% of it each frame (a size saved in imgui.ini by a bigger window never overflows a smaller one) and is pulled back on screen. Long text wraps, tables stretch, controls take a share of the width that is left (src/ui_util.h). To check a layout:

# window size comes from window.w / window.h in <data>/config.ini; --ui-scale 2 stands in for a HiDPI display
virtualjaguar --data-dir /tmp/d --ui-scale 2 --screenshot out.png --screenshot-frame 40 \
  --show-window settings-input game.j64

--low-dpi opens a 1x window even on a Retina display (screenshots of a standard-density screen).

--show-window takes settings[-video|-input|-audio|-storage|-interface][:FILTER], states, about, cheats, library, login, achievements, keypad and theme-editor.

The tests labelled emu_thread (ctest -L emu_thread) cover the emulation thread, including every smoke_*_threaded run with --emu-thread on; CI also runs them under ThreadSanitizer.

Layout

file	job
cmake/VJCore.cmake	core + libchdr static libraries from Makefile.common
cmake/VJSmokeTests.cmake	CTest smoke tests
src/core_host.*	libretro host: environment calls, options, SRAM, states, discs, the core's private event channel
src/typed_options.h, src/typed_ui.h	which options take a typed value and their validators; the Custom... combo and box
src/app.*	window, GL, main loop, pacing, events, save-state slots, headless runner
src/video.*	XRGB8888 texture and presentation (plain, or through the shader chain)
src/present_util.*	GL-free: where the picture goes (aspect / integer / stretch), .slangp parsing and folder scan
src/shaders.*, src/shaders_ui.cpp	librashader loader and GL filter chain; the Shader section of Settings > Video
shaders/	first-party presets copied beside the executable
cmake/VJShaders.cmake	pinned header fetch, optional prebuilt runtime, shader tests
src/audio.*	SDL3 audio stream with dynamic rate control
src/emu_thread.*, src/emu_commands.h	the emulation thread (#967): its loop, post / call / advance, the ordered command queue
src/pacing_clock.h	the emulation thread's pacing: mode A, the core's period trimmed by the audio queue (the sound card as master clock); mode B, a frame every k display ticks with owed ticks dropped
src/display_lock.h	Frame pacing's lock verdict (mode B, #1038): which displays lock at which k, the fallback reasons, the hysteresis
src/frame_exchange.h, src/frame.h	finished frames from the emulation thread to the UI (triple buffer, content epochs)
src/emu_snapshot.h	what the emulation thread publishes for the UI: the per-frame snapshot and the core-event stream (log lines, events, option writes)
src/ach_event.*	an rc_client event copied, so it can be applied on the UI thread
src/precise_sleep.h	short sleeps that honour sub-tick durations (a high-resolution waitable timer on Windows)
src/input_snapshot.h	the newest input from the UI thread to the core's poll (pointer motion exactly once)
src/debug/debug_core.*	the emulation-thread half of the debug session: the debug interface's wrappers and, in the next phase, the halt
src/debug/debug_views.*	the per-window requests (memory range, registers, disassembly, OP list, blit log) the emulation thread fills after each frame, and the buffers the windows read
src/late_latch.h	the late latch: when the threaded window loop stops waiting before a vblank (vblank tracking, UI build budget)
src/input.*	keyboard and gamepad snapshots to libretro input
src/remap.*, src/remap_ui.cpp	profiles, per-game overrides, keypad delivery, overlay, bind capture, and their UI
src/devices.*	device kinds, per-port / per-game selection, player slots (Team Tap), light-gun geometry, mouse-capture policy, locked core options
src/router.*	host input to what the core reads for every device (SDL-free, tested against the real core)
src/devices_ui.*	Settings > Input > Devices & players, claiming devices with the core, per-frame mouse capture
src/cheatsheet.*, src/cheatsheet_ui.cpp	the controls cheat sheet: text, auto-show rule, window
src/ui.*	ImGui: menu bar, settings, options menu, state manager, OSD
src/fonts.*, src/fonts_system.*	UI fonts with no ImGui: ui.font.* settings, favorites / recents, per-OS system font lookup, installed-font enumeration, custom file validation + import, glyph ranges (unit tested)
src/fonts_imgui.*, src/fonts_ui.cpp	the live font atlas (typeface, size, FreeType flags, mono(), the lazy preview cache), and Settings > Interface > Font (font list, debugger font)
src/platform/	native-OS integration: menu model + dispatch (commands.*, no OS), per-OS files (platform_macos.mm, platform_windows.cpp, platform_other.cpp), tray (tray.cpp); src/desktop.cpp is the app side
src/library.*	game library logic: dat parser, CRC identification, folder scan + hash cache, libretro-thumbnails names
src/library_lists.*	favorites, recently played, display options, tab layout, save-state listing (pure)
src/library_service.*	scan / decode / download worker threads, art cache and texture handover
src/library_ui.cpp	the Game library: the home screen and the window
src/ui_util.h	layout helpers every window uses: sizes in em clamped to the main window, width fractions, wrapped rows
src/http.*	blocking HTTP(S) GET: libcurl, WinHTTP or nothing
src/cheats.*	.cht parsing, conversion to core codes, per-game cheat state (no SDL, unit tested)
src/cheats_core.cpp, src/cheats_ui.cpp	core glue (retro_cheat_*, title identity, CLI) and the Cheats window
cmake/VJCheatData.cmake, cmake/VJCheatManifest.cmake, cmake/VJCheatTests.cmake	pinned optional database download, cheat tests
src/paths.*, src/config.*	data folders (portable mode) and the settings file
src/achievements.*	RetroAchievements: rc_client glue, memory, hardcore policy, mock server for tests
src/achievements_ui.cpp	ImGui: sign-in, the dashboard window (this game / Jaguar games / profile), toasts, trackers
src/achievements_games.cpp	dashboard data: picture URLs, achievement rows, the games list and progress, library matching
src/ra_dash.*	dashboard logic with no ImGui or network: games parsing and matching, cache file, filters and sorts
src/ra_images.*	the avatar / icon / badge cache: disk files, bounded textures, offline mode
src/ach_http.*	libcurl / WinHTTP worker for rc_client's requests
cmake/VJRcheevos.cmake, cmake/VJAchTests.cmake	rcheevos fetch + static lib; headless achievement tests

Not supported yet

General rollback netplay for any game (#864); the Netplay window covers the link-cable games only. Microphone and netpacket are reported unsupported.