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x11

Go Reference

The foundation every X11 client needs before it can say anything of its own: the wire codec, the .Xauthority parser, the connection-setup exchange, the anonymous shared-memory segment MIT-SHM attaches, and the unix-domain transport that hands the server a descriptor over SCM_RIGHTS. Pure Go, CGO_ENABLED=0, standard library only — no Xlib, no XCB, no cgo.

It is the one module here that is not a freedesktop specification. It is the byte layer underneath one, and it exists because two clients needed the identical answer: screencast asks the server to write into a shared segment, and go-widgets/window writes into one and asks the server to read. Two copies of a wire-protocol parser drift silently until something fails on one back-end only.

Scope — deliberately, the bytes and nothing above them

There is no connection type, no event loop and no widget here. What there is:

  • request/reply/error framing in both wire orders,
  • .Xauthority parsing and MIT-MAGIC-COOKIE-1 selection,
  • the setup exchange, including the screen, visual and depth tables,
  • NewSegment, the shared-memory segment MIT-SHM 1.2 attaches by descriptor,
  • DialUnix, and the SCM_RIGHTS descriptor pass.

The one thing above the bytes is Monitors: RANDR 1.5 and XINERAMA enumeration, because "which display is where" is not a capture question — a toolkit putting a window full screen on a chosen panel needs the same answer.

Install

go get github.com/go-freedesktop/x11

Platforms
linux (amd64, arm64, riscv64, loong64, ppc64le, s390x) everything, against real syscalls
darwin, freebsd, other unix codec + xauth + setup + the unix transport; no shared memory
windows, js/wasm codec + xauth + setup; DialUnix reports ErrNoTransport

Both wire orders are exercised, and the big-endian path is executed on real big-endian — s390x under qemu — rather than merely compiled.

Coverage

100% of statements, on Linux, darwin and Windows, with no exemptions. Every line is either protocol arithmetic or a syscall behind a package variable a test can fail on purpose, so a figure below 100 means a branch nobody tested rather than a platform getting in the way.

The full API is on pkg.go.dev. Source: github.com/go-freedesktop/x11.