Audio and input drivers

Audio drivers

Each audio driver subclasses AudioDriver (core/os/audio_driver.h) and exposes itself via AudioDriverManager::add_driver on the platform that owns it.

Driver	Directory	Platforms	Notes
AudioDriverPulseAudio	drivers/pulseaudio/	Linux/BSD	Default Linux backend; works alongside PipeWire's PulseAudio compatibility
AudioDriverALSA	drivers/alsa/	Linux/BSD	Direct hardware access, lower latency for specialized setups
AudioDriverWASAPI	drivers/wasapi/	Windows	Default Windows backend; supports shared + exclusive modes
AudioDriverXAudio2	drivers/xaudio2/	Windows / GDK	Fallback / console-friendly
AudioDriverCoreAudio	drivers/coreaudio/	macOS / iOS / visionOS	Apple's primary audio API
AudioDriverDummy	servers/audio/audio_driver_dummy.cpp	All	No-op (headless / disabled audio)
AudioDriverOpenSL	platform/android/audio_driver_opensl.cpp	Android	OpenSL ES
AudioDriverWeb	platform/web/audio_driver_web.cpp	Web	Web Audio API (AudioWorklet)

The selection happens at startup: AudioServer consults the project setting audio/driver/driver (default Default picks the platform's native driver) and the CLI flag --audio-driver.

How an audio driver runs

1. AudioDriver::init() opens the device with the configured channel count, sample rate, and latency.
2. AudioDriver::start() spawns a callback thread (or registers a callback with the OS audio API).
3. On each callback, the driver requests a chunk of frames from AudioServer::_driver_process.
4. AudioServer mixes the active streams and bus graph into the chunk and returns it.
5. The driver presents the chunk to the OS.

The audio thread runs concurrent with the main thread; AudioServer::lock()/unlock() is used to safely modify bus state from the main thread.

MIDI

Three MIDI drivers ship:

Driver	Directory	Platforms
MIDIDriverALSAMidi	drivers/alsamidi/	Linux/BSD
MIDIDriverCoreMidi	drivers/coremidi/	macOS / iOS
MIDIDriverWinMidi	drivers/winmidi/	Windows

They poll attached MIDI input devices and turn MIDIIn events into InputEventMIDI instances, which then flow through the standard input pipeline.

Input / joypad

Joypad handling lives mostly under each platform's directory because Linux uses evdev, Windows uses XInput/DirectInput, macOS uses GameController, and Android/iOS use platform APIs. Cross-platform pieces:

• drivers/sdl/joypad_sdl.{cpp,h} — SDL3-based joypad implementation. Linux can use this as an alternative to the evdev-based JoypadLinux. Brings SDL's mature gamepad mapping ecosystem (gamecontrollerdb.txt).
• Per-platform implementations:
  • platform/linuxbsd/joypad_linux.cpp — evdev / udev.
  • platform/windows/joypad_windows.cpp — XInput + DirectInput.
  • platform/macos/joypad_macos.mm and platform/apple_embedded/... (shared joypad_apple.mm for iOS / visionOS) — GameController.framework + IOHIDManager.
  • platform/android/android_input_handler.cpp — Android InputDevice API.
  • platform/web/display_server_web.cpp — Web Gamepad API.

Input (core/input/input.cpp) aggregates joypad state from whichever driver is active, applies the user's InputMap, and exposes actions to scripts.

Accessibility

drivers/accesskit/ integrates AccessKit — a cross-platform accessibility tree library — with Godot's AccessibilityServer. It bridges Godot's UI to:

• UI Automation on Windows.
• AT-SPI on Linux.
• NSAccessibility on macOS.
• TalkBack on Android (where applicable).

The integration is per-platform; accesskit provides the cross-platform trees while platform-specific code activates the OS-side a11y service.

Backtrace bridges

drivers/backtrace/ includes libbacktrace-style bridges used by the platform crash handlers to symbolicate stack traces. The actual symbol resolution depends on the platform — DWARF on Linux, PDB on Windows (via DbgHelp), Mach-O on macOS.

Key abstractions

Abstraction	File	Role
AudioDriver	core/os/audio_driver.h	Audio backend interface
AudioDriverManager	core/os/audio_driver.h	Driver registry
MIDIDriver	core/os/midi_driver.h	MIDI input interface
JoypadSDL	drivers/sdl/joypad_sdl.cpp	Cross-platform SDL3 joypad driver
AccessibilityDriver	drivers/accesskit/accessibility_driver_accesskit.cpp	Accessibility tree bridge
OS::ensure_user_data_dir, file/dir access	drivers/unix/, drivers/windows/	Cross-platform POSIX/Win32 file helpers

Entry points for modification

• Switching the default audio driver per platform → adjust AudioDriverManager::add_driver order and the project setting defaults.
• New audio backend → subclass AudioDriver, register from the relevant platform's register_driver_types.cpp.
• New joypad mapping → update gamecontrollerdb.txt (vendored SDL mappings); the driver re-reads it at startup.