Linux / BSD

Purpose

platform/linuxbsd/ is the Linux and BSD platform layer. It supplies an OS_LinuxBSD subclass, two display server implementations (X11 and Wayland), Linux-specific exporters, and crash handler / joypad / accessibility integration. The same codebase covers Linux distros and BSD variants where supported toolchains exist.

Layout

platform/linuxbsd/
├── godot_linuxbsd.cpp          Application entry: instantiate OS, create DisplayServer, run Main
├── os_linuxbsd.{cpp,h}         OS_LinuxBSD subclass (file system, environment, processes)
├── x11/                        X11 display server (DisplayServerX11 + key codes + DnD + IME)
├── wayland/                    Wayland display server (DisplayServerWayland + EGL/Vulkan integration)
├── crash_handler_linuxbsd.{cpp,h}  Backtrace via libbacktrace + signal handler
├── joypad_linux.{cpp,h}        evdev-based joypad / gamepad
├── freedesktop_screensaver.{cpp,h}  D-Bus calls to inhibit the screen saver
├── freedesktop_portal_desktop.{cpp,h}  XDG Desktop Portal integration (file dialogs, inhibitors)
├── tts_linux.{cpp,h}           speech-dispatcher TTS bindings
├── export/                     Linux exporter (binary stripping + AppImage-style packaging)
├── detect.py                   Build options (use_pulseaudio, use_alsa, use_dbus, …)
└── SCsub

Display server choices

DisplayServer for Linux comes in two flavours selected at runtime by --display-driver:

• X11 (x11/display_server_x11.cpp) — the historical Linux backend. Mature, ubiquitous, good fallback. Handles XInput2 for tablet / multi-touch, XRandR for screen enumeration, the X clipboard primary/secondary distinction, and IME via XIM/IBus.
• Wayland (wayland/display_server_wayland.cpp) — the modern Linux compositor protocol. Uses xdg-shell, xdg-decoration, wlr-output-management, fractional-scale-v1 where compositors expose them. Builds against wayland-client + the auto-generated protocol marshalling.

The default is X11 on legacy distros, Wayland where the compositor advertises support; the user can override with DISPLAY / WAYLAND_DISPLAY and --display-driver.

Both servers create graphics contexts:

• Vulkan via VK_KHR_xlib_surface / VK_KHR_wayland_surface.
• OpenGL ES 3 via EGL on both backends, or GLX on X11.

OS_LinuxBSD

OS_LinuxBSD (os_linuxbsd.cpp) implements:

• File system root (/), user data dir (~/.local/share/godot/), config dir (~/.config/godot/).
• Process spawning via execvp + posix_spawn.
• Environment variables, command-line argument parsing, locale detection (setlocale, nl_langinfo).
• Dynamic library loading via dlopen.
• Power management (battery info via UPower or /sys).
• Stack-trace capture for crash handler via libbacktrace.

The implementation often falls back gracefully when optional libraries (D-Bus, speech-dispatcher, libudev) are absent; build flags in detect.py control whether they are linked at all.

D-Bus integration

Two D-Bus integrations:

• Screensaver inhibition (freedesktop_screensaver.cpp) — calls org.freedesktop.ScreenSaver.Inhibit so games don't get blanked.
• XDG Desktop Portal (freedesktop_portal_desktop.cpp) — calls portals for native file dialogs (in flatpak / sandboxed environments where direct fs access is restricted), and for accessibility / inhibitor APIs.

Joypad

joypad_linux.cpp walks /dev/input/event* via libevdev, probes capabilities (axes, buttons, force feedback), and reports devices to Input. The Steam controller and most Bluetooth gamepads work out of the box; SDL game controller mappings (gamecontrollerdb.txt) are honored.

TTS / accessibility

tts_linux.cpp integrates speech-dispatcher when present so the engine can speak text via DisplayServer::tts_*. The accesskit module (cross-platform) plus AT-SPI provides the screen-reader bridge.

Audio

Linux ships with two audio drivers, both under drivers/:

• PulseAudio — default; works alongside PipeWire's PulseAudio compatibility layer.
• ALSA — direct hardware access; lower latency for users with non-Pulse setups.
• MIDI — ALSA MIDI (drivers/alsamidi/).

Export

export/export_plugin.cpp packages a Linux build:

• Strips the binary if requested.
• Bundles the PCK alongside (or appends it to the binary).
• Optionally embeds an icon via PNG metadata for desktop environments that read it.

Toolchain

detect.py configures GCC / Clang, with optional cross-compilation via MinGW (Linux → Windows) handled by the Windows platform's detect.py.

Key abstractions

Abstraction	File	Role
OS_LinuxBSD	platform/linuxbsd/os_linuxbsd.cpp	OS subclass
DisplayServerX11	platform/linuxbsd/x11/display_server_x11.cpp	X11 backend
DisplayServerWayland	platform/linuxbsd/wayland/display_server_wayland.cpp	Wayland backend
JoypadLinux	platform/linuxbsd/joypad_linux.cpp	evdev gamepad input
CrashHandlerLinuxBSD	platform/linuxbsd/crash_handler_linuxbsd.cpp	Stack trace on signals
EditorExportPlatformLinuxBSD	platform/linuxbsd/export/export_plugin.cpp	Linux exporter

Entry points for modification

• New display protocol → drop a new directory next to x11/ and wayland/, implement DisplayServer, register in os_linuxbsd.cpp.
• New exporter feature → export/export_plugin.cpp.
• Joypad mapping fixes → joypad_linux.cpp or update gamecontrollerdb.txt.