Extensions

Most interesting X functionality lives in protocol extensions. node-x11 loads them at runtime with X.require(name, callback). The callback receives an extension object carrying the extension's requests, enums and version info; any extension events are registered on the client automatically:

X.require('randr', (err, Randr) => {
  if (err) throw err; // extension missing on this server
  Randr.GetScreenResources(display.screen[0].root, (err, res) => {
    console.log(res.outputs);
  });
});

name is the module name below (the file in lib/ext/), not the on-the-wire extension name. Requiring an extension twice returns the cached instance.

An absent extension gives you an err rather than throwing, so the callback is also where you put your fallback. This demo requires RENDER and uses it to do something the core protocol cannot — blend two translucent rectangles:

Loading live demo…

The in-page X server implements three of these

The live demos on this site run against the pure-JavaScript X server in lib/xserver, which registers BIG-REQUESTS, XC-MISC and RENDER (plus GLX in the browser build, backed by WebGL). X.require('randr') and friends will report the extension as missing here — the client supports all of them, but you need a real server to talk to.

Available extensions

module	X name	what it does
`apple-wm`	Apple-WM	XQuartz window-manager integration
`big-requests`	BIG-REQUESTS	requests larger than 256 KiB (enabled automatically at connect)
`composite`	Composite	redirect window rendering off-screen
`damage`	DAMAGE	be notified when drawables change
`dbe`	DOUBLE-BUFFER	flicker-free double buffering
`dpms`	DPMS	monitor power management
`fixes`	XFIXES	regions, cursor names, selection tracking
`ge`	Generic Event Extension	framing for extensions with large events
`glx`	GLX	OpenGL rendering over the X protocol
`present`	Present	vsynced pixmap presentation
`randr`	RANDR	outputs, CRTCs, modes, rotation
`record`	RECORD	record/replay of the protocol stream
`render`	RENDER	anti-aliased compositing, gradients, glyphs
`res`	X-Resource	per-client server resource usage
`screen-saver`	MIT-SCREEN-SAVER	screen-saver control and notification
`shape`	SHAPE	non-rectangular windows
`shm`	MIT-SHM	shared-memory images
`sync`	SYNC	counters, alarms, fences
`xc-misc`	XC-MISC	XID range recycling
`xinerama`	XINERAMA	multi-head screen layout
`xinput`	XInputExtension	input devices beyond core pointer/keyboard
`xkb`	XKEYBOARD	keyboard maps, controls, indicators
`xtest`	XTEST	synthesize input events for testing
`xv`	XVideo	video output adaptors

Each extension has its own reference page with every request, event and enum — see the Extensions section of the API reference.

Available extensions​

Available extensions