screencast

Capture the pixels of displays and windows on Linux, in pure Go, CGO_ENABLED=0, without shelling out to anything — no xwd, no import, no grim, no ffmpeg, and no Xlib or XCB. It speaks the X11 wire protocol itself through x11, and lets the X server write captured frames straight into shared memory it handed over with SCM_RIGHTS.

It is the Linux sibling of go-macos/screencapture and presents deliberately the same shape, so one consumer drives both platforms through near-identical adapters.

Install

go get github.com/go-freedesktop/screencast

Usage

content, err := screencast.Shareable(ctx)
d, err := content.MainDisplay()

s, err := screencast.CaptureDisplay(ctx, d, screencast.Options{FPS: 60})
defer s.Close()

for {
    f, fresh := s.Frame()      // borrowed BGRA bytes; no allocation
    if fresh {
        upload(f.Pix, f.Width, f.Height, f.Stride)   // index with Stride
    }
}

Backends, and what is not implemented

Backend	State
X11	works — MIT-SHM 1.2 with AttachFd, core GetImage fallback, MIT-MAGIC-COOKIE-1, RANDR 1.5 and XINERAMA, XFIXES cursor, every TrueColor/DirectColor visual at 16, 24 and 32 bpp
Wayland	not implemented. A wlroots compositor exposing wlr-screencopy-unstable-v1 could be driven the same way; it is not done here. Under Wayland, capture works only through Xwayland
xdg-desktop-portal	deliberately not started. The sanctioned GNOME/KDE route hands back a PipeWire stream, and there is no pure-Go PipeWire client here. Diagnose() detects that situation and says so, rather than failing obscurely — it only looks, and never opens a session or prompts anyone

Proof, not assertion

"The frame is not all zeroes" is a weak claim: a capture that read the wrong drawable, swapped red and blue, or sheared every row would pass it. So the integration suite and sccheck -selftest paint — they cover the display with a colour built from the visual's own channel masks, and then require every captured pixel to be exactly that colour, in that byte order, at the declared stride, and then require the next colour to be seen. It passes identically on a 5-6-5 visual, an 8-8-8 one and a 10-10-10 one.

Everything measured so far was measured against Xvfb on a VM with no GPU. The repository's README says which figures that qualifies and which it does not.

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