Add an environment generator

This is a script that program that gets run by systemd
before every user service to set up the environment.

See systemd.environment-generator(7) for details.

Closes: #2122
Approved by: matthiasclasen

Makefile.am

@@ -159,6 +159,9 @@ flatpak.env: env.d/flatpak.env.in
 	$(AM_V_GEN) $(SED) -e "s|\@localstatedir\@|$(localstatedir)|" \
 		-e "s|\@sysconfdir\@|$(sysconfdir)|" $< > $@
 
+envgendir = $(systemduserenvgendir)
+envgen_DATA = env.d/60-flatpak
+
 dbussnippetdir = $(systemduserunitdir)/dbus.service.d
 dbussnippet_DATA = flatpak.conf
 EXTRA_DIST += dbus.service.d/flatpak.conf.in

configure.ac

@@ -121,6 +121,15 @@ AC_ARG_WITH([systemdsystemunitdir],
     [with_systemdsystemunitdir='${prefix}/lib/systemd/system'])
 AC_SUBST([systemdsystemunitdir], [$with_systemdsystemunitdir])
 
+AC_ARG_WITH([systemduserenvgendir],
+            [AS_HELP_STRING([--with-systemduserenvgendir=DIR],
+                            [Directory for systemd user environment generators (default=PREFIX/lib/systemd/user-environment-generators)])],
+    [],
+    dnl This is deliberately not ${libdir}: systemd units always go in
+    dnl .../lib, never .../lib64 or .../lib/x86_64-linux-gnu
+    [with_systemduserenvgendir='${prefix}/lib/systemd/user-environment-generators'])
+AC_SUBST([systemduserenvgendir], [$with_systemduserenvgendir])
+
 AC_ARG_WITH(system_fonts_dir,
 		AS_HELP_STRING([--with-system-fonts-dir=PATH],[Directory where system fonts are, [default=/usr/share/fonts]]),
             with_system_fonts_dir="$withval", with_system_fonts_dir=/usr/share/fonts)

env.d/60-flatpak

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+new_dirs=
+while read -r install_path
+do
+    share_path=$install_path/exports/share
+    case ":$XDG_DATA_DIRS:" in
+        *":$share_path:"*) :;;
+        *":$share_path/:"*) :;;
+        *) new_dirs=${new_dirs:+${new_dirs}:}$share_path;;
+    esac
+done < <(echo "${XDG_DATA_HOME:-"$HOME/.local/share"}/flatpak"; flatpak  --installations)
+
+XDG_DATA_DIRS="${new_dirs:+${new_dirs}:}${XDG_DATA_DIRS:-/usr/local/share:/usr/share}"
+echo "XDG_DATA_DIRS=$XDG_DATA_DIRS"