set-gdm-theme

#!/bin/bash

# SPDX-FileCopyrightText: 2017 - 2024 sudorook <daemon@nullcodon.com>
#
# 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/>.

set -euo pipefail

ROOT="$(dirname "${0}")"

source "${ROOT}"/globals

! check_command glib-compile-resources gsettings sed && exit 3

# Check that GDM is installed.
command -v pacman > /dev/null 2>&1 && {
  if ! pacman -Qi gdm > /dev/null 2>&1; then
    show_error "GDM is not installed. Exiting."
    exit 3
  fi
}

command -v apt > /dev/null 2>&1 && {
  if ! dpkg -s gdm3 > /dev/null 2>&1; then
    show_error "GDM is not installed. Exiting."
    exit 3
  fi
}

# Get the current GTK theme.
case ${XDG_CURRENT_DESKTOP} in
  X-Cinnamon)
    GTKTHEME=$(gsettings get org.cinnamon.desktop.interface gtk-theme | sed -e "s/'//g")
    ;;
  GNOME | ubuntu:GNOME)
    GTKTHEME=$(gsettings get org.gnome.desktop.interface gtk-theme | sed -e "s/'//g")
    ;;
  *)
    show_error "${XDG_CURRENT_DESKTOP@Q} environment not supported."
    exit 3
    ;;
esac

GNOMESHELLDIR="/usr/share/gnome-shell"
GNOMESHELLBAK="/usr/share/gnome-shell-$(date +%Y%m%d-%I%M%S)"

if [[ -d "/usr/share/themes/${GTKTHEME}" ]]; then
  THEMEDIR="/usr/share/themes"
elif [[ -d "/usr/local/share/themes/${GTKTHEME}" ]]; then
  THEMEDIR="/usr/local/share/themes"
elif [[ -d "${HOME}/.local/share/themes/${GTKTHEME}" ]]; then
  THEMEDIR="${HOME}/.local/share/themes/"
fi

show_header "Setting GDM login theme to ${GTKTHEME@Q}."
show_info "Backing up current GDM settings to ${GNOMESHELLBAK@Q}."
sudo cp -r "${GNOMESHELLDIR}" "${GNOMESHELLBAK}"

if [[ "${GTKTHEME}" =~ ^Adapta ]] || [[ "${GTKTHEME}" =~ ^Plata ]]; then
  show_info "Copying over ${GTKTHEME@Q} GDM theme."
  sudo cp -rf "${THEMEDIR}/${GTKTHEME}"/gnome-shell/* "${GNOMESHELLDIR}"
  sudo cp -vf \
    "${THEMEDIR}/${GTKTHEME}"/gnome-shell/extensions/window-list/{classic.css,stylesheet.css} \
    "${GNOMESHELLDIR}"/extensions/window-list@gnome-shell-extensions.gcampax.github.com/
elif [[ "${GTKTHEME}" =~ ^Materia ]]; then
  show_info "Building ${GTKTHEME@Q} GDM theme from GResource file."
  sudo glib-compile-resources \
    --target="/usr/share/gnome-shell/gnome-shell-theme.gresource" \
    --sourcedir="${THEMEDIR}/${GTKTHEME}/gnome-shell" \
    "${THEMEDIR}/${GTKTHEME}/gnome-shell/gnome-shell-theme.gresource.xml"
elif [[ "${GTKTHEME}" =~ ^Arc ]]; then
  show_info "Copying over ${GTKTHEME@Q} GDM gresource file."
  if [[ "${GTKTHEME}" =~ Dark ]]; then
    [ -f "${THEMEDIR}/Arc-Dark/gnome-shell/gnome-shell-theme-dark.gresource" ] &&
      sudo cp -f \
        "${THEMEDIR}/Arc-Dark/gnome-shell/gnome-shell-theme-dark.gresource" \
        "/usr/share/gnome-shell/gnome-shell-theme.gresource"
  else
    [ -f "${THEMEDIR}/Arc/gnome-shell/gnome-shell-theme.gresource" ] &&
      sudo cp -f \
        "${THEMEDIR}/Arc/gnome-shell/gnome-shell-theme.gresource" \
        "/usr/share/gnome-shell/gnome-shell-theme.gresource"
  fi
else
  show_error "${GTKTHEME@Q} is unsupported."
  exit 3
fi

show_success "Done."