modules: implement logind module and integrate with bluez monitor

This copies the logic of media-session's logind module and allows
the bluez monitor to be active in only one user session at a time.
This is especially useful to avoid interference between the gdm
session and the actual user session, which momentarily both have
wireplumber running when logging in/out.

Fixes #54

meson.build

@@ -79,6 +79,11 @@ else
 endif
 summary({'Lua version': lua_dep.version() + (system_lua ? ' (system)' : ' (built-in)')})
 
+systemd = dependency('systemd', required: get_option('systemd'))
+libsystemd_dep = dependency('libsystemd',required: get_option('systemd'))
+summary({'systemd conf data': systemd.found(),
+         'libsystemd': libsystemd_dep.found()}, bool_yn: true)
+
 gnome = import('gnome')
 pkgconfig = import('pkgconfig')
 fs = import('fs')

meson_options.txt

@@ -9,7 +9,7 @@ option('system-lua-version',
        description: 'The system lua version to use or "auto" for auto-detection')
 option('systemd',
        type: 'feature', value: 'auto',
-       description: 'Enable installing systemd units')
+       description: 'Enable installing systemd units & logind integration')
 option('systemd-system-service',
        type : 'boolean', value : false,
        description: 'Install systemd system service file')

modules/meson.build

@@ -176,3 +176,16 @@ shared_library(
   install_dir : wireplumber_module_dir,
   dependencies : [wp_dep, pipewire_dep],
 )
+
+if libsystemd_dep.found()
+  shared_library(
+    'wireplumber-module-logind',
+    [
+      'module-logind.c',
+    ],
+    c_args : [common_c_args, '-DG_LOG_DOMAIN="m-logind"'],
+    install : true,
+    install_dir : wireplumber_module_dir,
+    dependencies : [wp_dep, pipewire_dep, libsystemd_dep],
+  )
+endif

modules/module-logind.c

@@ -0,0 +1,142 @@
+/* WirePlumber
+ *
+ * Copyright © 2021 Collabora Ltd.
+ *    @author George Kiagiadakis <george.kiagiadakis@collabora.com>
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <wp/wp.h>
+#include <glib-unix.h>
+
+#include <systemd/sd-login.h>
+
+#include <spa/utils/result.h>
+#include <spa/utils/string.h>
+
+#define NAME "logind"
+
+struct _WpLogind
+{
+  WpPlugin parent;
+  sd_login_monitor *monitor;
+  GSource *source;
+  char *state;
+};
+
+enum {
+  ACTION_GET_STATE,
+  SIGNAL_STATE_CHANGED,
+  N_SIGNALS
+};
+
+static guint signals[N_SIGNALS] = {0};
+
+G_DECLARE_FINAL_TYPE (WpLogind, wp_logind, WP, LOGIND, WpPlugin)
+G_DEFINE_TYPE (WpLogind, wp_logind, WP_TYPE_PLUGIN)
+
+static void
+wp_logind_init (WpLogind * self)
+{
+}
+
+static gchar *
+wp_logind_get_state (WpLogind *self)
+{
+  return g_strdup (self->state);
+}
+
+static gboolean
+wp_logind_source_ready (gint fd, GIOCondition condition, gpointer user_data)
+{
+  WpLogind *self = WP_LOGIND (user_data);
+  sd_login_monitor_flush (self->monitor);
+  {
+    char *state = NULL;
+    sd_uid_get_state (getuid(), &state);
+    if (g_strcmp0 (state, self->state) != 0) {
+      char *tmp = state;
+      state = self->state;
+      self->state = tmp;
+      g_signal_emit (self, signals[SIGNAL_STATE_CHANGED], 0, self->state);
+    }
+    free (state);
+  }
+  return G_SOURCE_CONTINUE;
+}
+
+static void
+wp_logind_enable (WpPlugin * plugin, WpTransition * transition)
+{
+  WpLogind *self = WP_LOGIND (plugin);
+  int res = 0;
+
+  if ((res = sd_login_monitor_new (NULL, &self->monitor)) < 0) {
+    wp_transition_return_error (transition, g_error_new (G_IO_ERROR,
+            g_io_error_from_errno (-res),
+            "failed to start systemd logind monitor: %d (%s)",
+            res, spa_strerror(res)));
+    return;
+  }
+
+  if ((res = sd_uid_get_state (getuid(), &self->state)) < 0) {
+    wp_transition_return_error (transition, g_error_new (G_IO_ERROR,
+            g_io_error_from_errno (-res),
+            "failed to get systemd login state: %d (%s)",
+            res, spa_strerror(res)));
+    g_clear_pointer (&self->monitor, sd_login_monitor_unref);
+    return;
+  }
+
+  self->source = g_unix_fd_source_new (
+      sd_login_monitor_get_fd (self->monitor),
+      sd_login_monitor_get_events (self->monitor));
+  g_source_set_callback (self->source, G_SOURCE_FUNC (wp_logind_source_ready),
+      self, NULL);
+
+  g_autoptr (WpCore) core = wp_object_get_core (WP_OBJECT (plugin));
+  GMainContext *context = wp_core_get_g_main_context (core);
+  g_source_attach (self->source, context);
+
+  wp_object_update_features (WP_OBJECT (self), WP_PLUGIN_FEATURE_ENABLED, 0);
+}
+
+static void
+wp_logind_disable (WpPlugin * plugin)
+{
+  WpLogind *self = WP_LOGIND (plugin);
+
+  g_clear_pointer (&self->state, free);
+  g_source_destroy (self->source);
+  g_clear_pointer (&self->source, g_source_unref);
+  g_clear_pointer (&self->monitor, sd_login_monitor_unref);
+}
+
+static void
+wp_logind_class_init (WpLogindClass * klass)
+{
+  WpPluginClass *plugin_class = (WpPluginClass *) klass;
+
+  plugin_class->enable = wp_logind_enable;
+  plugin_class->disable = wp_logind_disable;
+
+  signals[ACTION_GET_STATE] = g_signal_new_class_handler (
+      "get-state", G_TYPE_FROM_CLASS (klass),
+      G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
+      (GCallback) wp_logind_get_state,
+      NULL, NULL, NULL, G_TYPE_STRING, 0);
+
+  signals[SIGNAL_STATE_CHANGED] = g_signal_new (
+      "state-changed", G_TYPE_FROM_CLASS (klass),
+      G_SIGNAL_RUN_LAST, 0, NULL, NULL, NULL, G_TYPE_NONE, 1, G_TYPE_STRING);
+}
+
+WP_PLUGIN_EXPORT gboolean
+wireplumber__module_init (WpCore * core, GVariant * args, GError ** error)
+{
+  wp_plugin_register (g_object_new (wp_logind_get_type (),
+          "name", NAME,
+          "core", core,
+          NULL));
+  return TRUE;
+}

src/config/bluetooth.lua.d/30-bluez-monitor.lua

@@ -7,4 +7,6 @@ function bluez_monitor.enable()
     properties = bluez_monitor.properties,
     rules = bluez_monitor.rules,
   })
+
+  load_module("logind")
 end

src/scripts/monitors/bluez.lua

@@ -125,13 +125,39 @@ function createDevice(parent, id, type, factory, properties)
   end
 end
 
-local monitor_props = config.properties or {}
-monitor_props["api.bluez5.connection-info"] = true
+function createMonitor()
+  local monitor_props = config.properties or {}
+  monitor_props["api.bluez5.connection-info"] = true
 
-monitor = SpaDevice("api.bluez5.enum.dbus", monitor_props)
-if monitor then
-  monitor:connect("create-object", createDevice)
+  local monitor = SpaDevice("api.bluez5.enum.dbus", monitor_props)
+  if monitor then
+    monitor:connect("create-object", createDevice)
+  else
+    Log.message("PipeWire's BlueZ SPA missing or broken. Bluetooth not supported.")
+    return nil
+  end
   monitor:activate(Feature.SpaDevice.ENABLED)
-else
-  Log.message("PipeWire's BlueZ SPA missing or broken. Bluetooth not supported.")
+
+  return monitor
+end
+
+logind_plugin = Plugin.find("logind")
+if logind_plugin then
+  -- if logind support is enabled, activate
+  -- the monitor only when the seat is active
+  function startStopMonitor(seat_state)
+    Log.info(logind_plugin, "Seat state changed: " .. seat_state)
+
+    if seat_state == "active" then
+      monitor = createMonitor()
+    elseif monitor then
+      monitor:deactivate(Feature.SpaDevice.ENABLED)
+      monitor = nil
+    end
+  end
+
+  logind_plugin:connect("state-changed", function(p, s) startStopMonitor(s) end)
+  startStopMonitor(logind_plugin:call("get-state"))
+else
+  monitor = createMonitor()
 end

src/systemd/meson.build

@@ -1,6 +1,3 @@
-systemd = dependency('systemd', required: get_option('systemd'))
-summary({'systemd conf data': systemd.found()}, bool_yn: true)
-
 if systemd.found()
   systemd_config = configuration_data()
   systemd_config.set('WP_BINARY', wireplumber_bin_dir / 'wireplumber')