Debian 9 Xresources xsessionrc

# Make ~/.notify folder executable
export PATH="${PATH}:$HOME/.exec"

RANGER_LOAD_DEFAULT_RC=FALSE

# Disable GTK CSD
if [ -n "$STARTUP" ]; then
    BASESTARTUP=${STARTUP%% *}
    BASESTARTUP=${BASESTARTUP##*/}
    if [ "$BASESTARTUP" = x-session-manager ]; then
      BASESTARTUP=$(basename $(readlink /etc/alternatives/x-session-manager))
    fi
    if [ x"$BASESTARTUP" = x"${BASESTARTUP#gnome-session}" ] ; then
      export GTK_CSD=0
      STARTUP="env LD_PRELOAD=/path/to/libgtk3-nocsd.so.0 $STARTUP"
    fi
  fi

https://github.com/PCMan/gtk3-nocsd

export GTK_CSD=0
export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libgtk3-nocsd.so.0

#!/usr/bin/env bash

if [ -d /etc/X11/xinit/xinitrc.d ]; then
    for f in /etc/X11/xinit/xinitrc.d/*; do
        [ -x "$f" ] && . "$f"
    done
    unset f
fi

if [ -n "$STARTUP" ]; then
    BASESTARTUP=${STARTUP%% *}
    BASESTARTUP=${BASESTARTUP##*/}
    if [ "$BASESTARTUP" = x-session-manager ]; then
      BASESTARTUP=$(basename $(readlink /etc/alternatives/x-session-manager))
    fi
    if [ x"$BASESTARTUP" = x"${BASESTARTUP#gnome-session}" ] ; then
      export GTK_CSD=0
      STARTUP="env LD_PRELOAD=libgtk3-nocsd.so.0 $STARTUP"
    fi
fi


xrdb -merge ~/.Xresources &
dbus-launch --exit-with-session openbox-session

#cat /etc/X11/Xsession.d/51gtk3-nocsd-detect

# This file is sourced by Xsession(5), not executed.

# Check if /usr/bin/gtk3-nocsd is executable, to make sure that the
# case where gtk3-nocsd is removed but not yet purged is also
# handled properly.
if [ -x /usr/bin/gtk3-nocsd ] && ( [ -z "$GTK3_NOCSD_IGNORE" ] || [ x"$GTK3_NOCSD_IGNORE"x = x"0"x ] ) ; then
    BASESTARTUP=${STARTUP%% *}
    BASESTARTUP=${BASESTARTUP##*/}
    if [ "$BASESTARTUP" = x-session-manager ]; then
        BASESTARTUP=$(basename $(readlink /etc/alternatives/x-session-manager))
    fi
    case "$BASESTARTUP" in
      gnome-session*)
          # This is GNOME, make sure GTK_CSD is not set to 0
          if [ x"$GTK_CSD"x = x"0"x ] ; then
              unset GTK_CSD
          fi
          ;;
      *)
          # not GNOME, and the user didn't specify GTK_CSD
          # themselves, so set it to 0
          if [ -z "$GTK_CSD" ] ; then
              GTK_CSD=0
          fi
          export GTK_CSD
          if [ x"$GTK_CSD"x = x"0"x ] ; then
              export LD_PRELOAD="libgtk3-nocsd.so.0${LD_PRELOAD:+:$LD_PRELOAD}"
          fi
          ;;
    esac
fi

#cat /etc/X11/Xsession.d/70gtk3-nocsd-propagate-LD_PRELOAD

# This file is sourced by Xsession(5), not executed.

# Some other startup programs may drop LD_PRELOAD as environment
# variable (ssh-agent is known for this), so make sure it's set
# explicitly again AFTER ssh-agent has been called.
if [ -n "$LD_PRELOAD" ] ; then
    STARTUP="env LD_PRELOAD=$LD_PRELOAD $STARTUP"
fi