pipewire: Check for the audio service when determining driver preference

Wireplumber now exposes a list of session services, so check the "session.services" property for an "audio" entry to determine whether Pipewire is configured for audio playback/capture.

src/audio/pipewire/SDL_pipewire.c

@@ -256,6 +256,8 @@ static int hotplug_init_seq_val;
 static bool hotplug_init_complete;
 static bool hotplug_events_enabled;
 
+static bool pipewire_have_session_services;
+static bool pipewire_have_audio_service;
 static int pipewire_version_major;
 static int pipewire_version_minor;
 static int pipewire_version_patch;
@@ -438,7 +440,7 @@ static void core_events_interface_callback(void *object, uint32_t id, int seq)
     }
 }
 
-static void core_events_metadata_callback(void *object, uint32_t id, int seq)
+static void core_events_generic_callback(void *object, uint32_t id, int seq)
 {
     struct node_object *node = object;
 
@@ -449,7 +451,7 @@ static void core_events_metadata_callback(void *object, uint32_t id, int seq)
 
 static const struct pw_core_events hotplug_init_core_events = { PW_VERSION_CORE_EVENTS, .info = core_events_hotplug_info_callback, .done = core_events_hotplug_init_callback };
 static const struct pw_core_events interface_core_events = { PW_VERSION_CORE_EVENTS, .done = core_events_interface_callback };
-static const struct pw_core_events metadata_core_events = { PW_VERSION_CORE_EVENTS, .done = core_events_metadata_callback };
+static const struct pw_core_events generic_core_events = { PW_VERSION_CORE_EVENTS, .done = core_events_generic_callback };
 
 static void hotplug_core_sync(struct node_object *node)
 {
@@ -652,6 +654,35 @@ static int metadata_property(void *object, Uint32 subject, const char *key, cons
 
 static const struct pw_metadata_events metadata_node_events = { PW_VERSION_METADATA_EVENTS, .property = metadata_property };
 
+// Client info node callback.
+static void client_info(void *data, const struct pw_client_info *info)
+{
+    // If WirePlumber lists the session services, check to see if audio is enabled.
+    const char *services = spa_dict_lookup(info->props, "session.services");
+    if (services) {
+        pipewire_have_session_services = true;
+
+        // Services are in a JSON array.
+        struct spa_json iter[2];
+        spa_json_init(&iter[0], services, SDL_strlen(services));
+        if (spa_json_enter_array(&iter[0], &iter[1]) > 0) {
+            char element[PW_MAX_IDENTIFIER_LENGTH];
+            while (spa_json_get_string(&iter[1], element, sizeof(element)) > 0) {
+                if (SDL_strcmp(element, "audio") == 0) {
+                    pipewire_have_audio_service = true;
+                    break;
+                }
+            }
+        }
+    }
+}
+
+static const struct pw_client_events client_node_events = {
+    .version = PW_VERSION_CLIENT_EVENTS,
+    .info = client_info,
+    .permissions = NULL
+};
+
 // Global registry callbacks
 static void registry_event_global_callback(void *object, uint32_t id, uint32_t permissions, const char *type, uint32_t version,
                                            const struct spa_dict *props)
@@ -714,12 +745,21 @@ static void registry_event_global_callback(void *object, uint32_t id, uint32_t p
             }
         }
     } else if (!SDL_strcmp(type, PW_TYPE_INTERFACE_Metadata)) {
-        node = node_object_new(id, type, version, &metadata_node_events, &metadata_core_events);
+        node = node_object_new(id, type, version, &metadata_node_events, &generic_core_events);
         if (!node) {
             SDL_SetError("Pipewire: Failed to allocate metadata node");
             return;
         }
 
+        // Update sync points
+        hotplug_core_sync(node);
+    } else if (!SDL_strcmp(type, PW_TYPE_INTERFACE_Client)) {
+        node = node_object_new(id, type, version, &client_node_events, &generic_core_events);
+        if (!node) {
+            SDL_SetError("Pipewire: Failed to allocate client info node");
+            return;
+        }
+
         // Update sync points
         hotplug_core_sync(node);
     }
@@ -1282,6 +1322,8 @@ static void PIPEWIRE_Deinitialize(void)
     if (pipewire_initialized) {
         hotplug_loop_destroy();
         deinit_pipewire_library();
+        pipewire_have_session_services = false;
+        pipewire_have_audio_service = false;
         pipewire_initialized = false;
     }
 }
@@ -1335,7 +1377,8 @@ static bool PIPEWIRE_PREFERRED_Init(SDL_AudioDriverImpl *impl)
 
     PIPEWIRE_pw_thread_loop_unlock(hotplug_loop);
 
-    if (no_devices || !pipewire_core_version_at_least(1, 0, 0)) {
+    if ((pipewire_have_session_services && !pipewire_have_audio_service) ||
+        (!pipewire_have_session_services && (no_devices || !pipewire_core_version_at_least(1, 0, 0)))) {
         PIPEWIRE_Deinitialize();
         return false;
     }