internal/wayland: relocate connection struct

This interface is getting replaced, so relocating it to the deprecated wrapper package before working on its replacement.

Signed-off-by: Ophestra <cat@gensokyo.uk>

system/wayland/deprecated.go

@@ -4,13 +4,89 @@
 package wayland
 
 import (
+	"errors"
+	"net"
+	"os"
+	"runtime"
+	"sync"
+	"syscall"
 	_ "unsafe" // for go:linkname
 
 	"hakurei.app/internal/wayland"
 )
 
 // Conn represents a connection to the wayland display server.
-type Conn = wayland.Conn
+//
+// Deprecated: this interface is being replaced.
+// Additionally, the package it belongs to will be removed in 0.4.
+type Conn struct {
+	conn *net.UnixConn
+
+	done     chan struct{}
+	doneOnce sync.Once
+
+	mu sync.Mutex
+}
+
+// Attach connects Conn to a wayland socket.
+func (c *Conn) Attach(p string) (err error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.conn != nil {
+		return errors.New("socket already attached")
+	}
+
+	c.conn, err = net.DialUnix("unix", nil, &net.UnixAddr{Name: p, Net: "unix"})
+	return
+}
+
+// Close releases resources and closes the connection to the wayland compositor.
+func (c *Conn) Close() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.done == nil {
+		return errors.New("no socket bound")
+	}
+
+	c.doneOnce.Do(func() {
+		c.done <- struct{}{}
+		<-c.done
+	})
+
+	// closed by wayland
+	runtime.SetFinalizer(c.conn, nil)
+	return nil
+}
+
+//go:linkname bindRawConn hakurei.app/internal/wayland.bindRawConn
+func bindRawConn(done chan struct{}, rc syscall.RawConn, p, appID, instanceID string) ([2]int, error)
+
+// Bind binds the new socket to pathname.
+func (c *Conn) Bind(pathname, appID, instanceID string) (*os.File, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.conn == nil {
+		return nil, errors.New("socket not attached")
+	}
+	if c.done != nil {
+		return nil, errors.New("socket already bound")
+	}
+
+	if rc, err := c.conn.SyscallConn(); err != nil {
+		// unreachable
+		return nil, err
+	} else {
+		c.done = make(chan struct{})
+		if closeFds, err := bindRawConn(c.done, rc, pathname, appID, instanceID); err != nil {
+			return nil, err
+		} else {
+			return os.NewFile(uintptr(closeFds[1]), "close_fd"), nil
+		}
+	}
+}
 
 const (
 	// WaylandDisplay contains the name of the server socket