sound: update the volume-slider after getting a valid stream

In the ubuntu 20.04, we met an issue about the output volume-slider
on the machine with the legacy HDA audio driver, the output device
is the Speaker first (analog-stereo pa sink), then we connect a hdmi
monitor, the HDMI audio is in the output combo-box, we select the
hdmi audio (hdmi-stereo pa sink) from the combo-box, the hdmi audio
becomes the active output device now, we adjust the output volume from
the volume-slider, the slider UI is changed, but the output sound
is not changed with the UI.

The root cause is when the speaker is active, the pulseaudio only
keeps the analog-stereo sink, the sink hdmi-stereo is unlinked, when
users select the hdmi audio from UI, the pulseaudio will unlink
analo-stereo sink and create hdmi-stereo sink, but before hdmi-stereo
is created, the output_device_changed_cb() is called and
gvc_mixer_control_get_stream_from_device() returns a NULL since the
hdmi-stereo sink is not created yet in the pulseaudio. Because stream
is NULL, the output_volume_slider->stream is NULL, users can't change
the output volume via the volume-slider.

To fix it, we add a output_volume_slider->stream check in the
device_update_cb(), if it is NULL, get the stream and set it to
volume-slider. In this function, the sink hdmi-stereo is created
already, so the stream is not NULL. And this change also applies to
input as well.

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

panels/sound/cc-sound-panel.c

@@ -91,18 +91,12 @@ allow_amplified_changed_cb (CcSoundPanel *self)
 }
 
 static void
-output_device_changed_cb (CcSoundPanel *self)
+set_output_stream (CcSoundPanel   *self,
+                   GvcMixerStream *stream)
 {
-  GvcMixerUIDevice *device;
-  GvcMixerStream *stream = NULL;
   GvcChannelMap *map = NULL;
   gboolean can_fade = FALSE, has_lfe = FALSE;
 
-  device = cc_device_combo_box_get_device (self->output_device_combo_box);
-
-  if (device != NULL)
-    stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
-
   cc_volume_slider_set_stream (self->output_volume_slider, stream, CC_STREAM_TYPE_OUTPUT);
   cc_level_bar_set_stream (self->output_level_bar, stream, CC_STREAM_TYPE_OUTPUT);
 
@@ -118,11 +112,33 @@ output_device_changed_cb (CcSoundPanel *self)
 
   gtk_widget_set_visible (GTK_WIDGET (self->fade_row), can_fade);
   gtk_widget_set_visible (GTK_WIDGET (self->subwoofer_row), has_lfe);
+}
+
+static void
+output_device_changed_cb (CcSoundPanel *self)
+{
+  GvcMixerUIDevice *device;
+  GvcMixerStream *stream = NULL;
+
+  device = cc_device_combo_box_get_device (self->output_device_combo_box);
+
+  if (device != NULL)
+    stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
+
+  set_output_stream (self, stream);
 
   if (device != NULL)
     gvc_mixer_control_change_output (self->mixer_control, device);
 }
 
+static void
+set_input_stream (CcSoundPanel   *self,
+                  GvcMixerStream *stream)
+{
+  cc_volume_slider_set_stream (self->input_volume_slider, stream, CC_STREAM_TYPE_INPUT);
+  cc_level_bar_set_stream (self->input_level_bar, stream, CC_STREAM_TYPE_INPUT);
+}
+
 static void
 input_device_changed_cb (CcSoundPanel *self)
 {
@@ -134,8 +150,7 @@ input_device_changed_cb (CcSoundPanel *self)
   if (device != NULL)
     stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
 
-  cc_volume_slider_set_stream (self->input_volume_slider, stream, CC_STREAM_TYPE_INPUT);
+  set_input_stream (self, stream);
-  cc_level_bar_set_stream (self->input_level_bar, stream, CC_STREAM_TYPE_INPUT);
 
   if (device != NULL)
     gvc_mixer_control_change_input (self->mixer_control, device);
@@ -147,12 +162,18 @@ output_device_update_cb (CcSoundPanel *self,
 {
   GvcMixerUIDevice *device;
   gboolean has_multi_profiles;
+  GvcMixerStream *stream = NULL;
 
   device = cc_device_combo_box_get_device (self->output_device_combo_box);
   cc_profile_combo_box_set_device (self->output_profile_combo_box, self->mixer_control, device);
   has_multi_profiles = (cc_profile_combo_box_get_profile_count (self->output_profile_combo_box) > 1);
   gtk_widget_set_visible (GTK_WIDGET (self->output_profile_row),
                           has_multi_profiles);
+
+  if (cc_volume_slider_get_stream (self->output_volume_slider) == NULL)
+    stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
+  if (stream != NULL)
+    set_output_stream (self, stream);
 }
 
 static void
@@ -161,12 +182,18 @@ input_device_update_cb (CcSoundPanel *self,
 {
   GvcMixerUIDevice *device;
   gboolean has_multi_profiles;
+  GvcMixerStream *stream = NULL;
 
   device = cc_device_combo_box_get_device (self->input_device_combo_box);
   cc_profile_combo_box_set_device (self->input_profile_combo_box, self->mixer_control, device);
   has_multi_profiles = (cc_profile_combo_box_get_profile_count (self->input_profile_combo_box) > 1);
   gtk_widget_set_visible (GTK_WIDGET (self->input_profile_row),
                           has_multi_profiles);
+
+  if (cc_volume_slider_get_stream (self->input_volume_slider) == NULL)
+    stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
+  if (stream != NULL)
+    set_input_stream (self, stream);
 }
 
 static void

panels/sound/cc-volume-slider.c

@@ -247,6 +247,14 @@ cc_volume_slider_set_stream (CcVolumeSlider *self,
     }
 }
 
+GvcMixerStream *
+cc_volume_slider_get_stream (CcVolumeSlider *self)
+{
+  g_return_val_if_fail (CC_IS_VOLUME_SLIDER (self), NULL);
+
+  return self->stream;
+}
+
 void
 cc_volume_slider_set_is_amplified (CcVolumeSlider *self,
                                    gboolean        is_amplified)

panels/sound/cc-volume-slider.h

@@ -40,4 +40,6 @@ void cc_volume_slider_set_stream        (CcVolumeSlider  *slider,
 void cc_volume_slider_set_is_amplified  (CcVolumeSlider  *slider,
                                          gboolean         is_amplified);
 
+GvcMixerStream *cc_volume_slider_get_stream (CcVolumeSlider *slider);
+
 G_END_DECLS