After commit c018f5fd29 Fenrir is being switched over to go. If you do not want to be part of the testing process, please switch to master.

internal/clipboard/display.go

@@ -0,0 +1,121 @@
+// Fenrir console screen reader.
+// Copyright (c) 2026 Storm Dragon
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// this program. If not, see <https://www.gnu.org/licenses/gpl-3.0.html>.
+
+package clipboard
+
+import (
+	"fmt"
+	"os"
+	"os/user"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+type Target struct{ Display, Authority string }
+
+// Display_candidates never falls through an explicit setting or DISPLAY to a
+// different session. Discovery uses existing local sockets, not a fixed :0..:9.
+func Display_candidates(configured, current, authority, home, socketDirectory string) ([]Target, error) {
+	if authority == "" {
+		authority = filepath.Join(home, ".Xauthority")
+	}
+	if configured != "" {
+		return []Target{{configured, authority}}, nil
+	}
+	if current != "" {
+		return []Target{{current, authority}}, nil
+	}
+	entries, err := os.ReadDir(socketDirectory)
+	if err != nil {
+		return nil, err
+	}
+	var targets []Target
+	for _, entry := range entries {
+		name := entry.Name()
+		if !strings.HasPrefix(name, "X") {
+			continue
+		}
+		number, err := strconv.Atoi(name[1:])
+		if err != nil || number < 0 {
+			continue
+		}
+		info, err := entry.Info()
+		if err == nil && info.Mode()&os.ModeSocket != 0 {
+			targets = append(targets, Target{fmt.Sprintf(":%d", number), authority})
+		}
+	}
+	sort.Slice(targets, func(i, j int) bool { return targets[i].Display < targets[j].Display })
+	if len(targets) == 0 {
+		return nil, fmt.Errorf("no local X display")
+	}
+	// Multiple desktops require an explicit choice; do not silently mix users.
+	if len(targets) > 1 {
+		return nil, fmt.Errorf("multiple X displays; set clipboard.sync_display")
+	}
+	return targets, nil
+}
+
+func system_targets(configured string) ([]Target, error) {
+	home, _ := os.UserHomeDir()
+	if os.Geteuid() == 0 && os.Getenv("SUDO_UID") != "" {
+		if caller, err := user.LookupId(os.Getenv("SUDO_UID")); err == nil {
+			home = caller.HomeDir
+		}
+	}
+	targets, err := Display_candidates(configured, os.Getenv("DISPLAY"), os.Getenv("XAUTHORITY"), home, "/tmp/.X11-unix")
+	if err != nil {
+		return nil, err
+	}
+	if os.Getenv("XAUTHORITY") == "" {
+		// Console services may lack a desktop environment. Xorg's -auth names
+		// the actual cookie file, including display-manager runtime locations.
+		// Read command-line metadata only; never log or copy cookie contents.
+		paths, _ := filepath.Glob("/proc/[0-9]*/cmdline")
+		for _, path := range paths {
+			data, err := os.ReadFile(path)
+			if err != nil {
+				continue
+			}
+			args := strings.Split(strings.TrimRight(string(data), "\x00"), "\x00")
+			if len(args) == 0 {
+				continue
+			}
+			switch filepath.Base(args[0]) {
+			case "Xorg", "X", "Xwayland":
+			default:
+				continue
+			}
+			display, auth := "", ""
+			for i, arg := range args {
+				if strings.HasPrefix(arg, ":") {
+					display = arg
+				}
+				if arg == "-auth" && i+1 < len(args) {
+					auth = args[i+1]
+				}
+			}
+			for i := range targets {
+				if display != "" && strings.SplitN(targets[i].Display, ".", 2)[0] == display && auth != "" {
+					targets[i].Authority = auth
+				}
+			}
+		}
+	}
+	return targets, nil
+}