core: move source-outputs conditionally when update default_source

When the default source changes, the streams from the old default
source should be moved to the new default source, unless the
preferred_source string is set to the old default source and the
active port of the old default source is not unavailable

Signed-off-by: Hui Wang <hui.wang@canonical.com>

src/modules/module-switch-on-connect.c

@@ -116,9 +116,6 @@ static pa_hook_result_t sink_put_hook_callback(pa_core *c, pa_sink *sink, void*
 }
 
 static pa_hook_result_t source_put_hook_callback(pa_core *c, pa_source *source, void* userdata) {
-    pa_source_output *o;
-    uint32_t idx;
-    pa_source *old_default_source;
     const char *s;
     struct userdata *u = userdata;
 
@@ -172,29 +169,9 @@ static pa_hook_result_t source_put_hook_callback(pa_core *c, pa_source *source,
             return PA_HOOK_OK;
         }
 
-    old_default_source = c->default_source;
-
     /* Actually do the switch to the new source */
     pa_core_set_configured_default_source(c, source->name);
 
-    /* Now move all old outputs over */
-    if (pa_idxset_size(old_default_source->outputs) <= 0) {
-        pa_log_debug("No source outputs to move away.");
-        return PA_HOOK_OK;
-    }
-
-    PA_IDXSET_FOREACH(o, old_default_source->outputs, idx) {
-        if (pa_safe_streq(o->source->name, o->preferred_source) || !PA_SOURCE_OUTPUT_IS_LINKED(o->state))
-            continue;
-
-        if (pa_source_output_move_to(o, source, false) < 0)
-            pa_log_info("Failed to move source output %u \"%s\" to %s.", o->index,
-                        pa_strnull(pa_proplist_gets(o->proplist, PA_PROP_APPLICATION_NAME)), source->name);
-        else
-            pa_log_info("Successfully moved source output %u \"%s\" to %s.", o->index,
-                        pa_strnull(pa_proplist_gets(o->proplist, PA_PROP_APPLICATION_NAME)), source->name);
-    }
-
     return PA_HOOK_OK;
 }
 

src/pulsecore/core.c

@@ -435,6 +435,10 @@ void pa_core_update_default_source(pa_core *core) {
                 old_default_source ? old_default_source->name : "(unset)", best ? best->name : "(unset)");
     pa_subscription_post(core, PA_SUBSCRIPTION_EVENT_SERVER | PA_SUBSCRIPTION_EVENT_CHANGE, PA_INVALID_INDEX);
     pa_hook_fire(&core->hooks[PA_CORE_HOOK_DEFAULT_SOURCE_CHANGED], core->default_source);
+
+    /* try to move the streams from old_default_source to the new default_source conditionally */
+    if (old_default_source)
+	pa_source_move_streams_to_default_source(core, old_default_source);
 }
 
 void pa_core_set_exit_idle_time(pa_core *core, int time) {

src/pulsecore/source.c

@@ -666,8 +666,10 @@ void pa_source_put(pa_source *s) {
     pa_subscription_post(s->core, PA_SUBSCRIPTION_EVENT_SOURCE | PA_SUBSCRIPTION_EVENT_NEW, s->index);
     pa_hook_fire(&s->core->hooks[PA_CORE_HOOK_SOURCE_PUT], s);
 
-    /* This function must be called after the PA_CORE_HOOK_SOURCE_PUT hook,
-     * because module-switch-on-connect needs to know the old default source */
+    /* It's good to fire the SOURCE_PUT hook before updating the default source,
+     * because module-switch-on-connect will set the new source as the default
+     * source, and if we were to call pa_core_update_default_source() before that,
+     * the default source might change twice, causing unnecessary stream moving. */
     pa_core_update_default_source(s->core);
 }
 
@@ -2988,3 +2990,36 @@ void pa_source_set_reference_volume_direct(pa_source *s, const pa_cvolume *volum
     pa_subscription_post(s->core, PA_SUBSCRIPTION_EVENT_SOURCE|PA_SUBSCRIPTION_EVENT_CHANGE, s->index);
     pa_hook_fire(&s->core->hooks[PA_CORE_HOOK_SOURCE_VOLUME_CHANGED], s);
 }
+
+void pa_source_move_streams_to_default_source(pa_core *core, pa_source *old_source) {
+    pa_source_output *o;
+    uint32_t idx;
+    bool old_source_is_unavailable = false;
+
+    pa_assert(core);
+    pa_assert(old_source);
+
+    if (core->default_source == NULL || core->default_source->unlink_requested)
+        return;
+
+    if (old_source == core->default_source)
+        return;
+
+    if (old_source->active_port && old_source->active_port->available == PA_AVAILABLE_NO)
+        old_source_is_unavailable = true;
+
+    PA_IDXSET_FOREACH(o, old_source->outputs, idx) {
+        if (!PA_SOURCE_OUTPUT_IS_LINKED(o->state))
+            continue;
+
+        if (!o->source)
+            continue;
+
+        if (pa_safe_streq(old_source->name, o->preferred_source) && !old_source_is_unavailable)
+            continue;
+
+        pa_log_info("The source output %u \"%s\" is moving to %s due to change of the default source.",
+                    o->index, pa_strnull(pa_proplist_gets(o->proplist, PA_PROP_APPLICATION_NAME)), core->default_source->name);
+        pa_source_output_move_to(o, core->default_source, false);
+    }
+}

src/pulsecore/source.h

@@ -479,6 +479,12 @@ int64_t pa_source_get_latency_within_thread(pa_source *s, bool allow_negative);
  * sets s->reference_volume and fires change notifications. */
 void pa_source_set_reference_volume_direct(pa_source *s, const pa_cvolume *volume);
 
+/* When the default_source is changed or the active_port of a source is changed to
+ * PA_AVAILABLE_NO, this function is called to move the streams of the old
+ * default_source or the source with active_port equals PA_AVAILABLE_NO to the
+ * current default_source conditionally*/
+void pa_source_move_streams_to_default_source(pa_core *core, pa_source *old_source);
+
 #define pa_source_assert_io_context(s) \
     pa_assert(pa_thread_mq_get() || !PA_SOURCE_IS_LINKED((s)->state))