xdg-autostart-generator: Add a generator for XDG autostart files

This generator can be used by desktop environments to launch autostart
applications and services. The feature is an opt-in, triggered by
xdg-desktop-autostart.target being activated.

Also included is the new binary xdg-autostart-condition. This binary is
used as an ExecCondition to test the OnlyShowIn and NotShowIn XDG
desktop file keys. These need to be evaluated against the
XDG_CURRENT_DESKTOP environment variable which may not be known at
generation time.

Co-authored-by: Henri Chain <henri.chain@enioka.com>

man/systemd.special.xml

@@ -1150,6 +1150,16 @@
             <filename>gnome-session.target</filename>.</para>
           </listitem>
         </varlistentry>
+
+        <varlistentry>
+          <term><filename>xdg-desktop-autostart.target</filename></term>
+          <listitem>
+            <para>The XDG specification defines a way to autostart applications using XDG desktop files.
+            systemd ships a generator for the XDG desktop files in autostart directories.
+            Desktop Environments can opt-in to use this service by adding a <varname>Wants=</varname>
+            dependency on <literal>xdg-desktop-autostart.target</literal></para>.
+          </listitem>
+        </varlistentry>
       </variablelist>
     </refsect2>
   </refsect1>

meson.build

@@ -1417,6 +1417,7 @@ foreach term : ['utmp',
                 'tmpfiles',
                 'hwdb',
                 'rfkill',
+                'xdg-autostart',
                 'ldconfig',
                 'efi',
                 'tpm',
@@ -1520,6 +1521,7 @@ includes = include_directories('src/basic',
                                'src/libudev',
                                'src/core',
                                'src/shutdown',
+                               'src/xdg-autostart-generator',
                                'src/libsystemd/sd-bus',
                                'src/libsystemd/sd-device',
                                'src/libsystemd/sd-event',
@@ -2301,6 +2303,27 @@ if conf.get('HAVE_SYSV_COMPAT') == 1
                 install_dir : systemgeneratordir)
 endif
 
+if conf.get('ENABLE_XDG_AUTOSTART') == 1
+        executable(
+                'systemd-xdg-autostart-generator',
+                'src/xdg-autostart-generator/xdg-autostart-generator.c',
+                'src/xdg-autostart-generator/xdg-autostart-service.c',
+                include_directories : includes,
+                link_with : [libshared],
+                install_rpath : rootlibexecdir,
+                install : true,
+                install_dir : usergeneratordir)
+
+        executable(
+                'systemd-xdg-autostart-condition',
+                'src/xdg-autostart-generator/xdg-autostart-condition.c',
+                include_directories : includes,
+                link_with : [libshared],
+                install_rpath : rootlibexecdir,
+                install : true,
+                install_dir : rootlibexecdir)
+endif
+
 if conf.get('ENABLE_HOSTNAMED') == 1
         executable(
                 'systemd-hostnamed',
@@ -3566,6 +3589,7 @@ foreach tuple : [
         ['randomseed'],
         ['backlight'],
         ['rfkill'],
+        ['xdg-autostart'],
         ['logind'],
         ['machined'],
         ['portabled'],

meson_options.txt

@@ -142,6 +142,8 @@ option('hwdb', type : 'boolean',
        description : 'support for the hardware database')
 option('rfkill', type : 'boolean',
        description : 'support for the rfkill tools')
+option('xdg-autostart', type : 'boolean',
+       description : 'install the xdg-autostart-generator and unit')
 option('man', type : 'combo', choices : ['auto', 'true', 'false'],
        value : 'false',
        description : 'build and install man pages')

src/xdg-autostart-generator/xdg-autostart-condition.c

@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "main-func.h"
+#include "strv.h"
+
+/*
+ * This binary is intended to be run as an ExecCondition= in units generated
+ * by the xdg-autostart-generator. It does the appropriate checks against
+ * XDG_CURRENT_DESKTOP that are too advanced for simple ConditionEnvironment=
+ * matches.
+ */
+
+static int run(int argc, char *argv[]) {
+        _cleanup_strv_free_ char **only_show_in = NULL, **not_show_in = NULL, **desktops = NULL;
+        const char *xdg_current_desktop;
+        char **d;
+
+        if (argc != 3)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Wrong argument count. Expected the OnlyShowIn= and NotShowIn= sets, each colon separated.");
+
+        xdg_current_desktop = getenv("XDG_CURRENT_DESKTOP");
+        if (xdg_current_desktop) {
+                desktops = strv_split(xdg_current_desktop, ":");
+                if (!desktops)
+                        return log_oom();
+        }
+
+        only_show_in = strv_split(argv[1], ":");
+        not_show_in = strv_split(argv[2], ":");
+        if (!only_show_in || !not_show_in)
+                return log_oom();
+
+        /* Each desktop in XDG_CURRENT_DESKTOP needs to be matched in order. */
+        STRV_FOREACH(d, desktops) {
+                if (strv_contains(only_show_in, *d))
+                        return 0;
+                if (strv_contains(not_show_in, *d))
+                        return 1;
+        }
+
+        /* non-zero exit code when only_show_in has a proper value */
+        return !strv_isempty(only_show_in);
+}
+
+DEFINE_MAIN_FUNCTION_WITH_POSITIVE_FAILURE(run);

src/xdg-autostart-generator/xdg-autostart-generator.c

@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "generator.h"
+#include "hashmap.h"
+#include "log.h"
+#include "main-func.h"
+#include "nulstr-util.h"
+#include "path-lookup.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "xdg-autostart-service.h"
+
+DEFINE_PRIVATE_HASH_OPS_WITH_VALUE_DESTRUCTOR(xdgautostartservice_hash_ops, char, string_hash_func, string_compare_func, XdgAutostartService, xdg_autostart_service_free);
+
+static int enumerate_xdg_autostart(Hashmap *all_services) {
+        _cleanup_strv_free_ char **autostart_dirs = NULL;
+        _cleanup_strv_free_ char **config_dirs = NULL;
+        _unused_ _cleanup_strv_free_ char **data_dirs = NULL;
+        _cleanup_free_ char *user_config_autostart_dir = NULL;
+        char **path;
+        int r;
+
+        r = xdg_user_config_dir(&user_config_autostart_dir, "/autostart");
+        if (r < 0)
+                return r;
+        r = strv_extend(&autostart_dirs, user_config_autostart_dir);
+        if (r < 0)
+                return r;
+
+        r = xdg_user_dirs(&config_dirs, &data_dirs);
+        if (r < 0)
+                return r;
+        r = strv_extend_strv_concat(&autostart_dirs, config_dirs, "/autostart");
+        if (r < 0)
+                return r;
+
+        STRV_FOREACH(path, autostart_dirs) {
+                _cleanup_closedir_ DIR *d = NULL;
+                struct dirent *de;
+
+                d = opendir(*path);
+                if (!d) {
+                        if (errno != ENOENT)
+                                log_warning_errno(errno, "Opening %s failed, ignoring: %m", *path);
+                        continue;
+                }
+
+                FOREACH_DIRENT(de, d, log_warning_errno(errno, "Failed to enumerate directory %s, ignoring: %m", *path)) {
+                        _cleanup_free_ char *fpath = NULL, *name = NULL;
+                        _cleanup_(xdg_autostart_service_freep) XdgAutostartService *service = NULL;
+                        struct stat st;
+
+                        if (fstatat(dirfd(d), de->d_name, &st, 0) < 0) {
+                                log_warning_errno(errno, "stat() failed on %s/%s, ignoring: %m", *path, de->d_name);
+                                continue;
+                        }
+
+                        if (!S_ISREG(st.st_mode))
+                                continue;
+
+                        name = xdg_autostart_service_translate_name(de->d_name);
+                        if (!name)
+                                return log_oom();
+
+                        if (hashmap_contains(all_services, name))
+                                continue;
+
+                        fpath = path_join(*path, de->d_name);
+                        if (!fpath)
+                                return log_oom();
+
+                        service = xdg_autostart_service_parse_desktop(fpath);
+                        if (!service)
+                                return log_oom();
+                        service->name = TAKE_PTR(name);
+
+                        r = hashmap_put(all_services, service->name, service);
+                        if (r < 0)
+                                return log_oom();
+                        TAKE_PTR(service);
+                }
+        }
+
+        return 0;
+}
+
+static int run(const char *dest, const char *dest_early, const char *dest_late) {
+        _cleanup_(hashmap_freep) Hashmap *all_services = NULL;
+        XdgAutostartService *service;
+        Iterator j;
+        int r;
+
+        assert_se(dest_late);
+
+        all_services = hashmap_new(&xdgautostartservice_hash_ops);
+        if (!all_services)
+                return log_oom();
+
+        r = enumerate_xdg_autostart(all_services);
+        if (r < 0)
+                return r;
+
+        HASHMAP_FOREACH(service, all_services, j)
+                (void) xdg_autostart_service_generate_unit(service, dest_late);
+
+        return 0;
+}
+
+DEFINE_MAIN_GENERATOR_FUNCTION(run);

src/xdg-autostart-generator/xdg-autostart-service.h

@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+#include "macro.h"
+
+typedef struct XdgAutostartService {
+        char *name;
+        char *path;
+        char *description; /* Name in XDG desktop file */
+
+        char *type; /* Purely as an assertion check */
+        char *exec_string;
+
+        char **only_show_in;
+        char **not_show_in;
+
+        char *try_exec;
+        char *autostart_condition; /* This is mostly GNOME specific */
+        char *kde_autostart_condition;
+
+        char *gnome_autostart_phase;
+
+        bool hidden;
+        bool systemd_skip;
+
+} XdgAutostartService;
+
+
+XdgAutostartService * xdg_autostart_service_free(XdgAutostartService *s);
+DEFINE_TRIVIAL_CLEANUP_FUNC(XdgAutostartService*, xdg_autostart_service_free);
+
+char *xdg_autostart_service_translate_name(const char *name);
+int xdg_autostart_format_exec_start(const char *exec, char **ret_exec_start);
+
+XdgAutostartService *xdg_autostart_service_parse_desktop(const char *path);
+int xdg_autostart_service_generate_unit(XdgAutostartService *service, const char *dest);

units/user/meson.build

@@ -20,6 +20,10 @@ units = [
         'timers.target',
 ]
 
+if conf.get('ENABLE_XDG_AUTOSTART') == 1
+        units += [ 'xdg-desktop-autostart.target', ]
+endif
+
 foreach file : units
         install_data(file,
                      install_dir : userunitdir)

units/user/xdg-desktop-autostart.target

@@ -0,0 +1,14 @@
+#  SPDX-License-Identifier: LGPL-2.1+
+#
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=Startup of XDG autostart applications
+Documentation=man:systemd.special(7)
+RefuseManualStart=yes
+StopWhenUnneeded=yes