Add native i3 desktop announcements

internal/i3ipc/protocol.go

@@ -0,0 +1,76 @@
+// Copyright (c) 2026 Storm Dragon
+// Authors: Storm Dragon, Angus Kola
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// Package i3ipc observes i3 without issuing window-management commands.
+package i3ipc
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"errors"
+	"io"
+)
+
+const (
+	workspaces            = 1
+	subscribe             = 2
+	tree                  = 4
+	eventBit       uint32 = 1 << 31
+	workspaceEvent        = eventBit
+	modeEvent             = eventBit | 2
+	windowEvent           = eventBit | 3
+	// A corrupt peer cannot cause an unbounded allocation or event backlog.
+	maxPayload = 16 << 20
+	maxPending = 256
+)
+
+type message struct {
+	kind uint32
+	body []byte
+}
+
+func readMessage(r io.Reader) (message, error) {
+	var header [14]byte
+	if _, err := io.ReadFull(r, header[:]); err != nil {
+		return message{}, err
+	}
+	if string(header[:6]) != "i3-ipc" {
+		return message{}, errors.New("invalid i3 magic")
+	}
+	size := binary.NativeEndian.Uint32(header[6:10])
+	if size > maxPayload {
+		return message{}, errors.New("i3 payload too large")
+	}
+	body := make([]byte, int(size))
+	if _, err := io.ReadFull(r, body); err != nil {
+		return message{}, err
+	}
+	if len(body) != 0 && !json.Valid(body) {
+		return message{}, errors.New("invalid i3 JSON")
+	}
+	return message{binary.NativeEndian.Uint32(header[10:]), body}, nil
+}
+
+func writeMessage(w io.Writer, kind uint32, body []byte) error {
+	if len(body) > maxPayload {
+		return errors.New("i3 payload too large")
+	}
+	var header [14]byte
+	copy(header[:], "i3-ipc")
+	binary.NativeEndian.PutUint32(header[6:10], uint32(len(body)))
+	binary.NativeEndian.PutUint32(header[10:], kind)
+	for _, part := range [][]byte{header[:], body} {
+		for len(part) > 0 {
+			n, err := w.Write(part)
+			if err != nil {
+				return err
+			}
+			if n == 0 {
+				return io.ErrShortWrite
+			}
+			part = part[n:]
+		}
+	}
+	return nil
+}