"Browse Files" button does nothing on Wayland compositors (missing WAYLAND_DISPLAY and XDG_RUNTIME_DIR in exec_user_async)

Bug Description

The "Browse Files" button (and "View Timeshift Logs") does nothing on Wayland compositors. The file manager (Thunar, Nautilus, etc.) silently fails and never appears.

This is a different root cause from the issues previously closed (#517, #520). While PR #518 fixed those by switching from exec_script_async() to exec_user_async() to drop root privileges, exec_user_async() itself does not pass the Wayland-specific environment variables needed for GTK apps to connect to the compositor.

Root Cause

1. TeeJee.Process.vala — exec_user_async() missing Wayland env vars

In src/Utility/TeeJee.Process.vala, the exec_user_async() function constructs this pkexec command:

cmd = "pkexec --user %s env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS ".printf(user) + cmd;

It passes X11 variables (DISPLAY, XAUTHORITY) and DBUS_SESSION_BUS_ADDRESS, but does NOT pass:

• WAYLAND_DISPLAY (e.g., wayland-1)
• XDG_RUNTIME_DIR (e.g., /run/user/1000)

Without these, GTK apps launched via pkexec cannot connect to the Wayland compositor socket. The file manager silently fails because it has no display to connect to.

2. Main.vala — setup_env() breaks Wayland variable resolution

In src/Core/Main.vala, the setup_env() function has an additional problem:

if (wayland_display != null && xdg_runtime_dir != null) {
    string path = "%s/%s".printf(xdg_runtime_dir, wayland_display);
    GLib.Environment.set_variable("WAYLAND_DISPLAY", path, true);
    GLib.Environment.set_variable("XDG_RUNTIME_DIR", "/run/user/0", true);
}

This code:

• Changes WAYLAND_DISPLAY from the normal value wayland-1 to the full path /run/user/1000/wayland-1
• Overwrites XDG_RUNTIME_DIR to /run/user/0 (root's runtime dir)

This breaks the standard Wayland resolution where GTK apps combine XDG_RUNTIME_DIR/WAYLAND_DISPLAY to find the compositor socket. After this transformation, the Wayland socket can't be found because the path construction becomes nonsensical (/run/user/0/wayland-1 doesn't exist, and /run/user/1000/wayland-1 is now unreachable via normal variable resolution).

Steps to Reproduce

1. Use a Wayland compositor (e.g., Niri, Hyprland, Sway, GNOME on Wayland)
2. Start Timeshift
3. Select a snapshot
4. Click "Browse Files"
5. Nothing happens — no file manager window appears, no error dialog

Environment

• OS: Arch Linux
• Compositor: Niri (Wayland)
• Timeshift Version: 24.06.5
• File Manager: Thunar (also confirmed on Nautilus)

Suggested Fix

Fix 1: Add Wayland env vars to exec_user_async() in TeeJee.Process.vala

cmd = "pkexec --user %s env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS WAYLAND_DISPLAY=$WAYLAND_DISPLAY XDG_RUNTIME_DIR=$XDG_RUNTIME_DIR ".printf(user) + cmd;

Fix 2: Correct setup_env() in Main.vala

The setup_env() function should not mangle the WAYLAND_DISPLAY value or override XDG_RUNTIME_DIR for the root process in a way that breaks child process resolution. The Wayland socket needs to remain accessible. Possible approaches:

• Keep WAYLAND_DISPLAY as the socket name (e.g., wayland-1) and preserve the original XDG_RUNTIME_DIR so child processes can resolve the socket path correctly
• Or, if the full path must be set for the root process's own use, ensure the original variables are restored/passed correctly when launching user processes via exec_user_async()

Workaround

Create a wrapper script for your file manager at /usr/local/bin/thunar (or equivalent for your file manager) that forces X11 fallback when Wayland is unavailable:

#!/bin/bash
if [ -z "$WAYLAND_DISPLAY" ] && [ -n "$DISPLAY" ]; then
    export GDK_BACKEND=x11
fi
exec /usr/bin/thunar "$@"

This works because DISPLAY is still passed through by exec_user_async(), so the file manager can fall back to XWayland.

Related Issues

• #520 — "Browse button does nothing" (closed as duplicate of #517, but this is a different root cause specific to Wayland)
• #338 — "Browse does not open Dolphin in KDE" (mentions XDG_RUNTIME_DIR not set but on X11)
• #206 — "Cannot launch timeshift on wayland" (about app launch failure, not Browse Files)
• #517 — "View TimeShift Logs button doesn't work" (fixed by PR #518 which introduced exec_user_async(), but the Wayland env passthrough was missed)

Start with exec_user_async() in src/Utility/TeeJee.Process.vala and setup_env() in src/Core/Main.vala, comparing the current DISPLAY, WAYLAND_DISPLAY, XDG_RUNTIME_DIR, and DBUS_SESSION_BUS_ADDRESS handling. Reproduce the Browse Files and View Timeshift Logs actions under a Wayland compositor; done means both launch the expected file manager or log viewer.