core: Make sound player feature optional

Mutter can play sounds in some contexts and also provides an API
for libmutter users to do so using libcanberra internally.

In some specific use cases of Mutter, we would like to not depend
on libcanberra and not have any sound playing feature by default.

The changes keeps the sound player API but make it no-op if the
sound_player feature is disabled to not make it possible to break
a gnome-shell build.

See https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2270
for relevant discussion

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2375>

config.h.meson

@@ -61,6 +61,9 @@
 /* Defined if gnome-desktop is enabled */
 #mesondefine HAVE_GNOME_DESKTOP
 
+/* Defined if sound player is enabled */
+#mesondefine HAVE_SOUND_PLAYER
+
 /* Building with SM support */
 #mesondefine HAVE_SM
 

meson.build

@@ -124,7 +124,6 @@ json_glib_dep = dependency('json-glib-1.0', version: json_glib_req)
 xkbcommon_dep = dependency('xkbcommon', version: xkbcommon_req)
 ice_dep = dependency('ice')
 atk_dep = dependency('atk', version: atk_req)
-libcanberra_dep = dependency('libcanberra', version: libcanberra_req)
 dbus_dep = dependency('dbus-1')
 colord_dep = dependency('colord', version: colord_req)
 lcms2_dep = dependency('lcms2', version: lcms2_req)
@@ -170,6 +169,11 @@ if have_gnome_desktop
   gnome_desktop_dep = dependency('gnome-desktop-3.0')
 endif
 
+have_sound_player = get_option('sound_player')
+if have_sound_player
+  libcanberra_dep = dependency('libcanberra', version: libcanberra_req)
+endif
+
 have_gl = get_option('opengl')
 if have_gl
   gl_dep = dependency('gl')
@@ -500,6 +504,7 @@ cdata.set('HAVE_LIBSYSTEMD', have_libsystemd)
 cdata.set('HAVE_NATIVE_BACKEND', have_native_backend)
 cdata.set('HAVE_REMOTE_DESKTOP', have_remote_desktop)
 cdata.set('HAVE_GNOME_DESKTOP', have_gnome_desktop)
+cdata.set('HAVE_SOUND_PLAYER', have_sound_player)
 cdata.set('HAVE_EGL_DEVICE', have_egl_device)
 cdata.set('HAVE_WAYLAND_EGLSTREAM', have_wayland_eglstream)
 cdata.set('HAVE_LIBGUDEV', have_libgudev)
@@ -658,6 +663,7 @@ summary('Native Backend', have_native_backend, section: 'Options')
 summary('EGL Device', have_egl_device, section: 'Options')
 summary('Remote desktop', have_remote_desktop, section: 'Options')
 summary('libgnome-desktop', have_gnome_desktop, section: 'Options')
+summary('Sound player', have_sound_player, section: 'Options')
 summary('gudev', have_libgudev, section: 'Options')
 summary('Wacom', have_libwacom, section: 'Options')
 summary('SM', have_sm, section: 'Options')

meson_options.txt

@@ -93,6 +93,12 @@ option('libwacom',
   description: 'Enable libwacom support'
 )
 
+option('sound_player',
+  type: 'boolean',
+  value: true,
+  description: 'Enable sound player support using libcanberra',
+)
+
 option('pango_ft2',
   type: 'boolean',
   value: true,

src/core/meta-sound-player.c

@@ -21,24 +21,31 @@
 
 #include "config.h"
 
+#ifdef HAVE_SOUND_PLAYER
 #include <canberra.h>
+#endif
 
 #include "meta/meta-sound-player.h"
 
 #define EVENT_SOUNDS_KEY "event-sounds"
 #define THEME_NAME_KEY   "theme-name"
 
-typedef struct _MetaPlayRequest MetaPlayRequest;
 
 struct _MetaSoundPlayer
 {
   GObject parent;
   GThreadPool *queue;
   GSettings *settings;
+#ifdef HAVE_SOUND_PLAYER
   ca_context *context;
+#endif
   uint32_t id_pool;
 };
 
+#ifdef HAVE_SOUND_PLAYER
+
+typedef struct _MetaPlayRequest MetaPlayRequest;
+
 struct _MetaPlayRequest
 {
   ca_proplist *props;
@@ -48,6 +55,8 @@ struct _MetaPlayRequest
   MetaSoundPlayer *player;
 };
 
+#endif
+
 const char * const cache_allow_list[] = {
   "bell-window-system",
   "desktop-switch-left",
@@ -59,6 +68,31 @@ const char * const cache_allow_list[] = {
 
 G_DEFINE_TYPE (MetaSoundPlayer, meta_sound_player, G_TYPE_OBJECT)
 
+static void
+meta_sound_player_finalize (GObject *object)
+{
+  MetaSoundPlayer *player = META_SOUND_PLAYER (object);
+
+  g_object_unref (player->settings);
+  g_thread_pool_free (player->queue, FALSE, TRUE);
+
+#ifdef HAVE_SOUND_PLAYER
+  ca_context_destroy (player->context);
+#endif
+
+  G_OBJECT_CLASS (meta_sound_player_parent_class)->finalize (object);
+}
+
+static void
+meta_sound_player_class_init (MetaSoundPlayerClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->finalize = meta_sound_player_finalize;
+}
+
+#ifdef HAVE_SOUND_PLAYER
+
 static MetaPlayRequest *
 meta_play_request_new (MetaSoundPlayer *player,
                        ca_proplist     *props,
@@ -82,26 +116,6 @@ meta_play_request_free (MetaPlayRequest *req)
   g_free (req);
 }
 
-static void
-meta_sound_player_finalize (GObject *object)
-{
-  MetaSoundPlayer *player = META_SOUND_PLAYER (object);
-
-  g_object_unref (player->settings);
-  g_thread_pool_free (player->queue, FALSE, TRUE);
-  ca_context_destroy (player->context);
-
-  G_OBJECT_CLASS (meta_sound_player_parent_class)->finalize (object);
-}
-
-static void
-meta_sound_player_class_init (MetaSoundPlayerClass *klass)
-{
-  GObjectClass *object_class = G_OBJECT_CLASS (klass);
-
-  object_class->finalize = meta_sound_player_finalize;
-}
-
 static void
 cancelled_cb (GCancellable    *cancellable,
               MetaPlayRequest *req)
@@ -204,9 +218,21 @@ create_context (GSettings *settings)
   return context;
 }
 
+static void
+build_ca_proplist (ca_proplist *props,
+                   const char  *event_property,
+                   const char  *event_id,
+                   const char  *event_description)
+{
+  ca_proplist_sets (props, event_property, event_id);
+  ca_proplist_sets (props, CA_PROP_EVENT_DESCRIPTION, event_description);
+}
+#endif /* HAVE_SOUND_PLAYER */
+
 static void
 meta_sound_player_init (MetaSoundPlayer *player)
 {
+#ifdef HAVE_SOUND_PLAYER
   player->queue = g_thread_pool_new ((GFunc) play_sound,
 				     player, 1, FALSE, NULL);
   player->settings = g_settings_new ("org.gnome.desktop.sound");
@@ -214,17 +240,9 @@ meta_sound_player_init (MetaSoundPlayer *player)
 
   g_signal_connect (player->settings, "changed",
                     G_CALLBACK (settings_changed_cb), player);
+#endif
 }
 
-static void
-build_ca_proplist (ca_proplist  *props,
-                   const char   *event_property,
-                   const char   *event_id,
-                   const char   *event_description)
-{
-  ca_proplist_sets (props, event_property, event_id);
-  ca_proplist_sets (props, CA_PROP_EVENT_DESCRIPTION, event_description);
-}
 
 /**
  * meta_sound_player_play_from_theme:
@@ -241,6 +259,7 @@ meta_sound_player_play_from_theme (MetaSoundPlayer *player,
                                    const char      *description,
                                    GCancellable    *cancellable)
 {
+#ifdef HAVE_SOUND_PLAYER
   MetaPlayRequest *req;
   ca_proplist *props;
 
@@ -258,6 +277,7 @@ meta_sound_player_play_from_theme (MetaSoundPlayer *player,
 
   req = meta_play_request_new (player, props, cancellable);
   g_thread_pool_push (player->queue, req, NULL);
+#endif
 }
 
 /**
@@ -275,6 +295,7 @@ meta_sound_player_play_from_file (MetaSoundPlayer *player,
                                   const char      *description,
                                   GCancellable    *cancellable)
 {
+#ifdef HAVE_SOUND_PLAYER
   MetaPlayRequest *req;
   ca_proplist *props;
   char *path;
@@ -293,4 +314,5 @@ meta_sound_player_play_from_file (MetaSoundPlayer *player,
 
   req = meta_play_request_new (player, props, cancellable);
   g_thread_pool_push (player->queue, req, NULL);
+#endif
 }

src/meson.build

@@ -27,7 +27,6 @@ mutter_pkg_private_deps = [
   gmodule_no_export_dep,
   gnome_settings_daemon_dep,
   json_glib_dep,
-  libcanberra_dep,
   xkbcommon_dep,
 ]
 
@@ -37,6 +36,12 @@ if have_gnome_desktop
   ]
 endif
 
+if have_sound_player
+  mutter_pkg_private_deps += [
+    libcanberra_dep,
+  ]
+endif
+
 if have_gl
   mutter_pkg_deps += [
     gl_dep,