fedora/lib/session.sh

# shellcheck shell=bash
#------------------------------------------
# lib/session.sh — display manager and graphical session wiring
#
# DM policy:
#   * A DE module leaves its native DM alone (GNOME→gdm, Plasma→sddm, XFCE→sddm).
#   * A TWM module enforces SDDM, because SDDM is the only DM that presents both
#     Wayland compositors and X11 sessions in one menu. One greeter, no surprises.
#------------------------------------------

if [[ -n "${_SB_SESSION_LOADED:-}" ]]; then
    return 0
fi
_SB_SESSION_LOADED=1

# Name of the active display manager ("sddm", "gdm", "lightdm"), or "" if none.
detect_display_manager() {
    local link=/etc/systemd/system/display-manager.service
    if [[ -L "$link" ]]; then
        basename "$(readlink "$link")" | sed 's/\.service$//'
    else
        echo ""
    fi
}

enable_graphical_target() {
    sudo systemctl set-default graphical.target
}

# Make $1 the display manager, disabling whatever is active now.
switch_display_manager() {
    local target="$1"
    local current
    current=$(detect_display_manager)

    if [[ "$current" == "$target" ]]; then
        ok "Display manager already $target."
    else
        if [[ -n "$current" ]]; then
            info "Disabling current display manager: $current"
            # disable may fail if the unit vanished; that is not fatal
            sudo systemctl disable "$current" 2>/dev/null || true
        fi
        info "Enabling display manager: $target"
        sudo systemctl enable "$target"
    fi

    enable_graphical_target
}

# Register a Wayland session so the DM can list it.
# $1 = identifier, $2 = display name, $3 = command
write_wayland_session() {
    local id="$1" name="$2" exec_cmd="$3"
    local file="/usr/share/wayland-sessions/${id}.desktop"
    if [[ -f "$file" ]]; then
        ok "Wayland session already registered: $id"
        return 0
    fi
    info "Registering Wayland session: $id"
    sudo mkdir -p "$(dirname "$file")"
    printf '[Desktop Entry]\nName=%s\nComment=%s\nExec=%s\nType=Application\nDesktopNames=%s\n' \
        "$name" "$name session" "$exec_cmd" "$id" | sudo tee "$file" >/dev/null
    sudo chmod 644 "$file"
}

# Register an X11 session so the DM can list it.
write_x11_session() {
    local id="$1" name="$2" exec_cmd="$3"
    local file="/usr/share/xsessions/${id}.desktop"
    if [[ -f "$file" ]]; then
        ok "X11 session already registered: $id"
        return 0
    fi
    info "Registering X11 session: $id"
    # A bare Fedora has no X session yet, so the directory may not exist.
    sudo mkdir -p "$(dirname "$file")"
    printf '[Desktop Entry]\nName=%s\nComment=%s\nExec=%s\nType=Application\n' \
        "$name" "$name session" "$exec_cmd" | sudo tee "$file" >/dev/null
    sudo chmod 644 "$file"
}

# Common login-time plumbing every Wayland compositor wants on a bare install.
install_session_prereqs() {
    # polkit-kde ships the agent (polkit-gnome is orphaned, EPEL-only).
    # BUT Fedora's autostart .desktop carries X-systemd-skip=true (and a
    # OnlyShowIn on some versions): niri starts apps via systemd's
    # xdg-desktop-autostart.target, which honors those flags -> agent never
    # starts in a niri session (VM-proven twice). Fighting .desktop semantics
    # is fragile, so we ship our own user unit bound to
    # graphical-session.target, which niri/Hyprland/MangoWC all bring up.
    install_packages \
        xdg-desktop-portal \
        polkit \
        polkit-kde \
        pipewire \
        pipewire-pulseaudio \
        wireplumber

    local unit_dir="/etc/systemd/user"
    if [[ ! -f "$unit_dir/polkit-agent.service" ]]; then
        info "Installing polkit-agent user unit (compositor-safe)..."
        sudo mkdir -p "$unit_dir"
        sudo tee "$unit_dir/polkit-agent.service" >/dev/null <<'UNIT'
[Unit]
Description=PolicyKit Authentication Agent (for bare compositors)
PartOf=graphical-session.target

[Service]
# polkit-kde's binary on Fedora (kf6 path). Restart in case the agent dies
# before the session settles.
ExecStart=/usr/libexec/kf6/polkit-kde-authentication-agent-1
Restart=on-failure
RestartSec=2

[Install]
WantedBy=graphical-session.target
UNIT
    fi

    # Enable per-user: preset-all would also do, but be explicit. This is a
    # global unit dir; each user links it at first login via the preset.
    if [[ ! -f /etc/systemd/user/graphical-session.target.wants/polkit-agent.service ]]; then
        sudo mkdir -p /etc/systemd/user/graphical-session.target.wants
        sudo ln -sf ../polkit-agent.service \
            /etc/systemd/user/graphical-session.target.wants/polkit-agent.service
    fi

    # libvirt group: members manage qemu:///system without a polkit prompt.
    # Without this, virt-manager dies on "access denied by policy" even with
    # a working agent (VM-proven). Idempotent; applies after re-login.
    if pkg_installed libvirt; then
        local real_user="${SUDO_USER:-$USER}"
        if ! id -nG "$real_user" 2>/dev/null | grep -qw libvirt; then
            info "Adding $real_user to the libvirt group (re-login to apply)..."
            sudo usermod -aG libvirt "$real_user"
        fi
    fi
}