POC

src/modules/mixer/e_mod_main.c

@@ -487,7 +487,7 @@ _slider_drag_stop_cb(void *data EINA_UNUSED, Evas_Object *obj,
 {
    EINA_SAFETY_ON_NULL_RETURN(mixer_context->sink_default);
    Emix_Sink *s = (Emix_Sink *)mixer_context->sink_default;
-   int val = s->volume.volumes[0];
+   int val = s->set_volume.volumes[0];
    elm_slider_value_set(obj, val);
 }
 

src/modules/mixer/emixer.c

@@ -55,7 +55,7 @@ _cb_sink_volume_drag_stop(void *data,
 {
    Evas_Object *bxv = data;
    Emix_Sink *sink = evas_object_data_get(bxv, "sink");
-   int vol = sink->volume.volumes[0];
+   int vol = sink->set_volume.volumes[0];
    elm_slider_value_set(obj, vol);
 }
 

src/modules/mixer/lib/emix.c

@@ -280,6 +280,13 @@ emix_sink_volume_set(Emix_Sink *sink, Emix_Volume volume)
                                 ctx->loaded->ebackend_sink_volume_set &&
                                 sink));
 
+   sink->set_volume.channel_count = volume.channel_count;
+   sink->set_volume.volumes = calloc(volume.channel_count, sizeof(int));
+   for (unsigned int i = 0; i < volume.channel_count; i++)
+     {
+        sink->set_volume.volumes[i] = volume.volumes[i];
+     }
+
    ctx->loaded->ebackend_sink_volume_set(sink, volume);
 }
 

src/modules/mixer/lib/emix.h

@@ -55,6 +55,7 @@ typedef struct _Emix_Port {
 typedef struct _Emix_Sink {
    const char *name;
    Emix_Volume volume;
+   Emix_Volume set_volume;
    Eina_Bool mute;
    Eina_List *ports;
 } Emix_Sink;