[gnome-session/benzea/systemd-new-session-config] tools: Add generator for session configuration drop-in

[Benjamin Berg <bberg src gnome org>]

commit 8bb264e6961c9062576888fa6cd361f555c9fd8b
Author: Benjamin Berg <bberg redhat com>
Date:   Thu Feb 13 17:30:49 2020 +0100

    tools: Add generator for session configuration drop-in
    
    This simply generates Wants= entries for every RequiredComponent. We
    generate Wants for the application ID directly, and also ones for the
    wayland/x11 session with a -wayland/-x11 postfix added. This means that
    applications can provide either a unit without any postfix, or a unit
    with a session type specific postfix.
    
    The session type specific postfix is solely intend to be used by
    gnome-shell.

 meson.build                            |   2 +
 tools/gnome-session-config-generator.c | 179 +++++++++++++++++++++++++++++++++
 tools/meson.build                      |   1 +
 3 files changed, 182 insertions(+)
---
diff --git a/meson.build b/meson.build
index 65d530b1..0a197752 100644
--- a/meson.build
+++ b/meson.build
@@ -133,6 +133,8 @@ if enable_systemd or enable_consolekit
     systemd_dep = dependency('systemd', version: '>= 242', required: true)
     systemd_userunitdir = systemd_dep.get_pkgconfig_variable('systemduserunitdir',
                                                              define_variable: ['prefix', prefix])
+    systemd_usergeneratordir = systemd_dep.get_pkgconfig_variable('systemdusergeneratordir',
+                                                                  define_variable: ['prefix', prefix])
 
     libsystemd_dep = dependency('libsystemd', version: '>= 209', required: false)
     session_bin_deps += libsystemd_dep
diff --git a/tools/gnome-session-config-generator.c b/tools/gnome-session-config-generator.c
new file mode 100644
index 00000000..fb280cbe
--- /dev/null
+++ b/tools/gnome-session-config-generator.c
@@ -0,0 +1,179 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*-
+ * gnome-session-config-genreator.c - Generator to create systemd definition from session descriptions
+
+   Copyright (C) 2006, 2010 Novell, Inc.
+   Copyright (C) 2008,2020 Red Hat, Inc.
+
+   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 2, 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 <http://www.gnu.org/licenses/>.
+*/
+
+#include <config.h>
+
+#include <glib.h>
+#include <glib/gstdio.h>
+
+#define GSM_KEYFILE_SESSION_GROUP "GNOME Session"
+#define GSM_KEYFILE_REQUIRED_COMPONENTS_KEY "RequiredComponents"
+
+static void
+try_generate_session_config (const char *path, const char *output_dir_prefix, const char *output_dir_postfix)
+{
+        const char * session_types[] = { "", "-x11", "-wayland", NULL };
+        const char **type;
+        g_autoptr(GKeyFile) keyfile = NULL;
+        g_auto(GStrv) list = NULL;
+        gsize      len;
+
+        g_debug ("fill: *** Looking if %s is a valid session file", path);
+
+        keyfile = g_key_file_new ();
+
+        if (!g_key_file_load_from_file (keyfile, path, G_KEY_FILE_NONE, NULL)) {
+                g_debug ("Cannot use session '%s': non-existing or invalid file.", path);
+                return;
+        }
+
+        if (!g_key_file_has_group (keyfile, GSM_KEYFILE_SESSION_GROUP)) {
+                g_warning ("Cannot use session '%s': no '%s' group.", path, GSM_KEYFILE_SESSION_GROUP);
+                return;
+        }
+
+        list = g_key_file_get_string_list (keyfile,
+                                           GSM_KEYFILE_SESSION_GROUP,
+                                           GSM_KEYFILE_REQUIRED_COMPONENTS_KEY,
+                                           &len, NULL);
+        if (len == 0) {
+                g_warning ("Session '%s': no component in the session.", path);
+                return;
+        }
+
+        for (type = session_types; *type != NULL; type++) {
+                g_autoptr(GError) error = NULL;
+                g_autoptr(GPtrArray) lines = NULL;
+                g_autofree char *output_dir = NULL;
+                g_autofree char *output_file = NULL;
+                g_autofree char *contents = NULL;
+                gsize i;
+
+                lines = g_ptr_array_new_with_free_func (g_free);
+
+                g_ptr_array_add (lines, g_strdup ("[Unit]"));
+                g_ptr_array_add (lines, g_strdup ("# Auto-generated for gnome-session"));
+                for (i = 0; i < len; i++)
+                        g_ptr_array_add (lines, g_strdup_printf ("Wants=%s%s.target", list[i], *type));
+                g_ptr_array_add (lines, NULL);
+
+                contents = g_strjoinv("\n", (GStrv) lines->pdata);
+
+                output_dir = g_strconcat (output_dir_prefix, *type, output_dir_postfix, NULL);
+                g_mkdir (output_dir, 0777);
+
+                output_file = g_build_filename (output_dir, "session.conf", NULL);
+
+                if (!g_file_set_contents (output_file, contents, -1, &error)) {
+                        g_warning ("Could not write generated configuration to %s: %s",
+                                   output_file, error->message);
+                } else {
+                        g_debug ("Generated %s", output_file);
+                }
+        }
+}
+
+
+/**
+ * find_valid_session_keyfile:
+ *
+ * We look for the session file in XDG_CONFIG_HOME, XDG_CONFIG_DIRS and
+ * XDG_DATA_DIRS. This enables users and sysadmins to override a specific
+ * session that is shipped in XDG_DATA_DIRS.
+ *
+ * Copied from find_valid_session_keyfiles()
+ */
+static void
+find_valid_session_keyfiles (const char *generator_dir)
+{
+        g_autoptr(GPtrArray) dirs = NULL;
+        const char * const *system_config_dirs;
+        const char * const *system_data_dirs;
+        int                 i;
+
+        dirs = g_ptr_array_new ();
+
+        g_ptr_array_add (dirs, (gpointer) g_get_user_config_dir ());
+
+        system_config_dirs = g_get_system_config_dirs ();
+        for (i = 0; system_config_dirs[i]; i++)
+                g_ptr_array_add (dirs, (gpointer) system_config_dirs[i]);
+
+        system_data_dirs = g_get_system_data_dirs ();
+        for (i = 0; system_data_dirs[i]; i++)
+                g_ptr_array_add (dirs, (gpointer) system_data_dirs[i]);
+
+        /* Iterate backwards so that earlier directories are prefered
+         * (resulting in the same priority as gnome-session opening the files). */
+        for (i = dirs->len - 1; i >= 0; i--) {
+                GDir *dir = NULL;
+                g_autofree char *dir_path = NULL;
+                const char *session_file;
+
+                dir_path = g_build_filename (dirs->pdata[i], "gnome-session", "sessions", NULL);
+                dir = g_dir_open (dir_path, 0, NULL);
+                if (dir == NULL)
+                        continue;
+
+                while ((session_file = g_dir_read_name (dir))) {
+                        g_autofree char *path = NULL;
+                        g_autofree char *session_name = NULL;
+                        g_autofree char *output_dir_prefix = NULL;
+                        g_autofree char *output_dir_postfix = NULL;
+
+                        if (!g_str_has_suffix (session_file, ".session"))
+                                continue;
+
+                        /* Session name is the file name with the last 8 characters chopped off */
+                        session_name = g_strndup (session_file, strlen(session_file) - 8);
+
+                        path = g_build_filename (dir_path, session_file, NULL);
+                        output_dir_prefix = g_build_filename (generator_dir, "gnome-session", NULL);
+                        output_dir_postfix = g_strdup_printf ("@%s.target.d", session_name);;
+
+                        try_generate_session_config (path, output_dir_prefix, output_dir_postfix);
+                }
+
+                g_dir_close (dir);
+        }
+}
+
+int
+main (int argc, char *argv[])
+{
+        const char *generator_normal G_GNUC_UNUSED;
+        const char *generator_early;
+        const char *generator_late G_GNUC_UNUSED;
+
+        if (argc != 4) {
+                g_warning ("Need exactly three directory arguments!");
+                return 1;
+        }
+
+        generator_normal = argv[1];
+        generator_early = argv[2];
+        generator_late = argv[3];
+
+        /* NOTE: We don't bother to initialise i18n */
+
+        find_valid_session_keyfiles (generator_early);
+
+        return 0;
+}
diff --git a/tools/meson.build b/tools/meson.build
index 68be8a4a..2cf22459 100644
--- a/tools/meson.build
+++ b/tools/meson.build
@@ -18,6 +18,7 @@ programs = [
 
 if enable_systemd_session
   programs += [['gnome-session-ctl', session_bin_deps, cflags, session_libexecdir]]
+  programs += [['gnome-session-config-generator', session_bin_deps, cflags, systemd_usergeneratordir]]
 endif
 
 if enable_session_selector