diff --git a/src/alsa.c b/src/alsa.c
index 6b55dfb..9fc12d6 100644
--- a/src/alsa.c
+++ b/src/alsa.c
@@ -116,6 +116,20 @@ int is_elem_routing_snk(struct alsa_elem *elem) {
   return 0;
 }
 
+// add a callback to the list of callbacks for this element
+void alsa_elem_add_callback(
+  struct alsa_elem *elem,
+  AlsaElemCallback *callback,
+  void             *data
+) {
+  struct alsa_elem_callback *cb = calloc(1, sizeof(struct alsa_elem_callback));
+
+  cb->callback = callback;
+  cb->data = data;
+
+  elem->callbacks = g_list_append(elem->callbacks, cb);
+}
+
 //
 // alsa snd_ctl_elem_*() mediation functions
 // for simulated elements, fake the ALSA element
@@ -401,11 +415,17 @@ static void alsa_get_elem_list(struct alsa_card *card) {
 }
 
 static void alsa_elem_change(struct alsa_elem *elem) {
-  if (!elem->widget)
+  if (!elem || !elem->callbacks)
     return;
-  if (!elem->widget_callback)
-    return;
-  elem->widget_callback(elem);
+
+  for (GList *l = elem->callbacks; l; l = l->next) {
+    struct alsa_elem_callback *cb = (struct alsa_elem_callback *)l->data;
+
+    if (!cb || !cb->callback)
+      continue;
+
+    cb->callback(elem, cb->data);
+  }
 }
 
 static gboolean alsa_card_callback(
diff --git a/src/alsa.h b/src/alsa.h
index 2013d29..f04b44b 100644
--- a/src/alsa.h
+++ b/src/alsa.h
@@ -17,7 +17,7 @@ struct alsa_card;
 
 // typedef for callbacks to update widgets when the alsa element
 // notifies of a change
-typedef void (AlsaElemCallback)(struct alsa_elem *);
+typedef void (AlsaElemCallback)(struct alsa_elem *, void *);
 
 // port categories for routing_src and routing_snk entries
 // must match the level meter ordering from the driver
@@ -92,6 +92,12 @@ struct routing_snk {
   // pointer back to the element this entry is associated with
   struct alsa_elem *elem;
 
+  // box widget on the routing page
+  GtkWidget *box_widget;
+
+  // socket widget on the routing page
+  GtkWidget *socket_widget;
+
   // PC_DSP, PC_MIX, PC_PCM, or PC_HW
   int port_category;
 
@@ -103,6 +109,12 @@ struct routing_snk {
   GtkWidget *mixer_label_bottom;
 };
 
+// hold one callback & its data
+struct alsa_elem_callback {
+  AlsaElemCallback *callback;
+  void             *data;
+};
+
 // entry in alsa_card elems (ALSA control elements) array
 struct alsa_elem {
 
@@ -125,15 +137,8 @@ struct alsa_elem {
   // TODO: move this to struct routing_snk?
   int lr_num;
 
-  // the primary GTK widget and callback function for this ALSA
-  // control element
-  GtkWidget        *widget;
-  AlsaElemCallback *widget_callback;
-
-  // text label for volume controls
-  // handle for routing controls
-  // second button for dual controls
-  GtkWidget *widget2;
+  // the callback functions for this ALSA control element
+  GList *callbacks;
 
   // for boolean buttons, the two possible texts
   // for dual buttons, the four possible texts
@@ -203,6 +208,13 @@ struct alsa_elem *get_elem_by_prefix(GArray *elems, char *prefix);
 int get_max_elem_by_name(GArray *elems, char *prefix, char *needle);
 int is_elem_routing_snk(struct alsa_elem *elem);
 
+// add callback to alsa_elem callback list
+void alsa_elem_add_callback(
+  struct alsa_elem *elem,
+  AlsaElemCallback *callback,
+  void             *data
+);
+
 // alsa snd_ctl_elem_*() functions
 int alsa_get_elem_type(struct alsa_elem *elem);
 char *alsa_get_elem_name(struct alsa_elem *elem);
diff --git a/src/iface-mixer.c b/src/iface-mixer.c
index 2dada67..ded58b8 100644
--- a/src/iface-mixer.c
+++ b/src/iface-mixer.c
@@ -92,18 +92,19 @@ static void add_speaker_switching_controls(
   if (!speaker_switching)
     return;
 
-  make_dual_boolean_alsa_elems(speaker_switching, "Off", "On", "Main", "Alt");
-  GtkWidget *b = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);
+  GtkWidget *w = make_dual_boolean_alsa_elems(
+    speaker_switching,
+    "Speaker Switching",
+    "Off", "On", "Main", "Alt"
+  );
+
   gtk_widget_set_tooltip_text(
-    b,
+    w,
     "Speaker Switching lets you swap between two pairs of "
     "monitoring speakers very easily."
   );
-  GtkWidget *l = gtk_label_new("Speaker Switching");
-  gtk_box_append(GTK_BOX(global_controls), b);
-  gtk_box_append(GTK_BOX(b), l);
-  gtk_box_append(GTK_BOX(b), speaker_switching->widget);
-  gtk_box_append(GTK_BOX(b), speaker_switching->widget2);
+
+  gtk_box_append(GTK_BOX(global_controls), w);
 }
 
 static void add_talkback_controls(
@@ -119,19 +120,20 @@ static void add_talkback_controls(
   if (!talkback)
     return;
 
-  make_dual_boolean_alsa_elems(talkback, "Disabled", "Enabled", "Off", "On");
-  GtkWidget *b = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);
+  GtkWidget *w = make_dual_boolean_alsa_elems(
+    talkback,
+    "Talkback",
+    "Disabled", "Enabled", "Off", "On"
+  );
+
   gtk_widget_set_tooltip_text(
-    b,
+    w,
     "Talkback lets you add another channel (usually the talkback "
     "mic) to a mix with a button push, usually to talk to "
     "musicians, and without using an additional mic channel."
   );
-  GtkWidget *l = gtk_label_new("Talkback");
-  gtk_box_append(GTK_BOX(global_controls), b);
-  gtk_box_append(GTK_BOX(b), l);
-  gtk_box_append(GTK_BOX(b), talkback->widget);
-  gtk_box_append(GTK_BOX(b), talkback->widget2);
+
+  gtk_box_append(GTK_BOX(global_controls), w);
 }
 
 static GtkWidget *create_global_box(GtkWidget *grid, int *x, int orient) {
@@ -502,7 +504,7 @@ static void create_output_controls(
         elem, "*audio-volume-high", "*audio-volume-muted"
       );
       gtk_widget_set_tooltip_text(w, "Mute HW controlled outputs");
-      gtk_grid_attach(GTK_GRID(output_grid), elem->widget, 0, 2, 1, 1);
+      gtk_grid_attach(GTK_GRID(output_grid), w, 0, 2, 1, 1);
     } else if (strcmp(elem->name, "Dim Playback Switch") == 0) {
       w = make_boolean_alsa_elem(
         elem, "*audio-volume-medium", "*audio-volume-low"
diff --git a/src/routing-lines.c b/src/routing-lines.c
index 502d94e..77c6d90 100644
--- a/src/routing-lines.c
+++ b/src/routing-lines.c
@@ -258,7 +258,7 @@ static void get_snk_center(
   double             *x,
   double             *y
 ) {
-  get_widget_center(r_snk->elem->widget2, parent, x, y);
+  get_widget_center(r_snk->socket_widget, parent, x, y);
   if (IS_MIXER(r_snk->port_category))
     (*y)++;
 }
diff --git a/src/widget-boolean.c b/src/widget-boolean.c
index bfcd804..c9c78e8 100644
--- a/src/widget-boolean.c
+++ b/src/widget-boolean.c
@@ -3,32 +3,42 @@
 
 #include "widget-boolean.h"
 
+struct boolean {
+  struct alsa_elem *elem;
+  GtkWidget        *button;
+};
+
 static void button_clicked(GtkWidget *widget, struct alsa_elem *elem) {
   int value = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(widget));
 
   alsa_set_elem_value(elem, value);
 }
 
-static void toggle_button_set_text(struct alsa_elem *elem, const char *text) {
+static void toggle_button_set_text(GtkWidget *button, const char *text) {
   if (!text)
     return;
 
   if (*text == '*') {
     GtkWidget *icon = gtk_image_new_from_icon_name(text + 1);
-    gtk_button_set_child(GTK_BUTTON(elem->widget), icon);
+    gtk_button_set_child(GTK_BUTTON(button), icon);
   } else {
-    gtk_button_set_label(GTK_BUTTON(elem->widget), text);
+    gtk_button_set_label(GTK_BUTTON(button), text);
   }
 }
 
-static void toggle_button_updated(struct alsa_elem *elem) {
+static void toggle_button_updated(
+  struct alsa_elem *elem,
+  void             *private
+) {
+  struct boolean *data = private;
+
   int is_writable = alsa_get_elem_writable(elem);
-  gtk_widget_set_sensitive(elem->widget, is_writable);
+  gtk_widget_set_sensitive(data->button, is_writable);
 
   int value = !!alsa_get_elem_value(elem);
-  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(elem->widget), value);
+  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(data->button), value);
 
-  toggle_button_set_text(elem, elem->bool_text[value]);
+  toggle_button_set_text(data->button, elem->bool_text[value]);
 }
 
 GtkWidget *make_boolean_alsa_elem(
@@ -36,23 +46,24 @@ GtkWidget *make_boolean_alsa_elem(
   const char       *disabled_text,
   const char       *enabled_text
 ) {
-  GtkWidget *button = gtk_toggle_button_new();
+  struct boolean *data = g_malloc(sizeof(struct boolean));
+  data->elem = elem;
+  data->button = gtk_toggle_button_new();
 
   g_signal_connect(
-    button, "clicked", G_CALLBACK(button_clicked), elem
+    data->button, "clicked", G_CALLBACK(button_clicked), elem
   );
-  elem->widget = button;
-  elem->widget_callback = toggle_button_updated;
+  alsa_elem_add_callback(elem, toggle_button_updated, data);
   elem->bool_text[0] = disabled_text;
   elem->bool_text[1] = enabled_text;
 
   // find the maximum width and height of both possible labels
   int max_width = 0, max_height = 0;
   for (int i = 0; i < 2; i++) {
-    toggle_button_set_text(elem, elem->bool_text[i]);
+    toggle_button_set_text(data->button, elem->bool_text[i]);
 
     GtkRequisition *size = gtk_requisition_new();
-    gtk_widget_get_preferred_size(button, size, NULL);
+    gtk_widget_get_preferred_size(data->button, size, NULL);
 
     if (size->width > max_width)
       max_width = size->width;
@@ -62,9 +73,9 @@ GtkWidget *make_boolean_alsa_elem(
 
   // set the widget minimum size to the maximum label size so that the
   // widget doesn't change size when the label changes
-  gtk_widget_set_size_request(button, max_width, max_height);
+  gtk_widget_set_size_request(data->button, max_width, max_height);
 
-  toggle_button_updated(elem);
+  toggle_button_updated(elem, data);
 
-  return button;
+  return data->button;
 }
diff --git a/src/widget-combo.c b/src/widget-combo.c
index 127709a..ccce1f7 100644
--- a/src/widget-combo.c
+++ b/src/widget-combo.c
@@ -3,15 +3,25 @@
 
 #include "widget-combo.h"
 
-static void combo_box_changed(GtkWidget *widget, struct alsa_elem *elem) {
-  int value = gtk_combo_box_get_active(GTK_COMBO_BOX(widget));
+struct combo {
+  struct alsa_elem *elem;
+  GtkWidget        *combo_box;
+};
 
-  alsa_set_elem_value(elem, value);
+static void combo_box_changed(GtkWidget *widget, struct combo *data) {
+  int value = gtk_combo_box_get_active(GTK_COMBO_BOX(data->combo_box));
+
+  alsa_set_elem_value(data->elem, value);
 }
 
-static void combo_box_updated(struct alsa_elem *elem) {
+static void combo_box_updated(
+  struct alsa_elem *elem,
+  void             *private
+) {
+  struct combo *data = private;
+
   int value = alsa_get_elem_value(elem);
-  gtk_combo_box_set_active(GTK_COMBO_BOX(elem->widget), value);
+  gtk_combo_box_set_active(GTK_COMBO_BOX(data->combo_box), value);
 }
 
 // Center-align text in the combo box
@@ -29,23 +39,26 @@ static void combo_box_center_text(GtkComboBoxText *widget) {
 }
 
 GtkWidget *make_combo_box_alsa_elem(struct alsa_elem *elem) {
-  GtkWidget *combo_box = gtk_combo_box_text_new();
-  combo_box_center_text(GTK_COMBO_BOX_TEXT(combo_box));
+  struct combo *data = g_malloc(sizeof(struct combo));
+  data->elem = elem;
+  data->combo_box = gtk_combo_box_text_new();
+
+  combo_box_center_text(GTK_COMBO_BOX_TEXT(data->combo_box));
 
   int count = alsa_get_item_count(elem);
 
   for (int i = 0; i < count; i++) {
     const char *text = alsa_get_item_name(elem, i);
-    gtk_combo_box_text_append(GTK_COMBO_BOX_TEXT(combo_box), NULL, text);
+    gtk_combo_box_text_append(GTK_COMBO_BOX_TEXT(data->combo_box), NULL, text);
   }
 
   g_signal_connect(
-    combo_box, "changed", G_CALLBACK(combo_box_changed), elem
+    data->combo_box, "changed", G_CALLBACK(combo_box_changed), data
   );
-  elem->widget = combo_box;
-  elem->widget_callback = combo_box_updated;
 
-  combo_box_updated(elem);
+  alsa_elem_add_callback(elem, combo_box_updated, data);
 
-  return combo_box;
+  combo_box_updated(elem, data);
+
+  return data->combo_box;
 }
diff --git a/src/widget-dual.c b/src/widget-dual.c
index 95f1bb4..51f09a2 100644
--- a/src/widget-dual.c
+++ b/src/widget-dual.c
@@ -3,18 +3,28 @@
 
 #include "widget-dual.h"
 
-static void dual_button_clicked(GtkWidget *widget, struct alsa_elem *elem) {
-  int value1 = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(elem->widget));
-  int value2 = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(elem->widget2));
+struct dual_button {
+  struct alsa_elem *elem;
+  GtkWidget        *button1;
+  GtkWidget        *button2;
+};
+
+static void dual_button_clicked(GtkWidget *widget, struct dual_button *data) {
+  int value1 = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(data->button1));
+  int value2 = gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(data->button2));
 
   int value = value1 ? value2 + 1 : 0;
 
-  alsa_set_elem_value(elem, value);
+  alsa_set_elem_value(data->elem, value);
 
-  gtk_widget_set_sensitive(elem->widget2, value1);
+  gtk_widget_set_sensitive(data->button2, value1);
 }
 
-static void dual_button_updated(struct alsa_elem *elem) {
+static void dual_button_updated(
+  struct alsa_elem   *elem,
+  void               *private
+) {
+  struct dual_button *data = private;
 
   // value (from ALSA control) is 0/1/2
   // value1 (first button) is 0/1/1
@@ -22,14 +32,14 @@ static void dual_button_updated(struct alsa_elem *elem) {
   int value = alsa_get_elem_value(elem);
   int value1 = !!value;
 
-  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(elem->widget), value1);
-  gtk_button_set_label(GTK_BUTTON(elem->widget), elem->bool_text[value1]);
-  gtk_widget_set_sensitive(elem->widget2, value1);
+  gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(data->button1), value1);
+  gtk_button_set_label(GTK_BUTTON(data->button1), elem->bool_text[value1]);
+  gtk_widget_set_sensitive(data->button2, value1);
   if (value1) {
     int value2 = value - 1;
-    gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(elem->widget2), value2);
+    gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(data->button2), value2);
     gtk_button_set_label(
-      GTK_BUTTON(elem->widget2), elem->bool_text[value2 + 2]
+      GTK_BUTTON(data->button2), elem->bool_text[value2 + 2]
     );
   }
 }
@@ -38,31 +48,40 @@ static void dual_button_updated(struct alsa_elem *elem) {
 // buttons:
 // first button disables/enables the feature
 // second button switches between the two enabled states
-void make_dual_boolean_alsa_elems(
+GtkWidget *make_dual_boolean_alsa_elems(
   struct alsa_elem *elem,
+  const char       *label_text,
   const char       *disabled_text_1,
   const char       *enabled_text_1,
   const char       *disabled_text_2,
   const char       *enabled_text_2
 ) {
-  GtkWidget *button1 = gtk_toggle_button_new();
-  GtkWidget *button2 = gtk_toggle_button_new();
+  struct dual_button *data = g_malloc(sizeof(struct dual_button));
+  data->elem = elem;
+  data->button1 = gtk_toggle_button_new();
+  data->button2 = gtk_toggle_button_new();
 
   g_signal_connect(
-    button1, "clicked", G_CALLBACK(dual_button_clicked), elem
+    data->button1, "clicked", G_CALLBACK(dual_button_clicked), data
   );
   g_signal_connect(
-    button2, "clicked", G_CALLBACK(dual_button_clicked), elem
+    data->button2, "clicked", G_CALLBACK(dual_button_clicked), data
   );
-  elem->widget = button1;
-  elem->widget2 = button2;
-  elem->widget_callback = dual_button_updated;
+  alsa_elem_add_callback(elem, dual_button_updated, data);
   elem->bool_text[0] = disabled_text_1;
   elem->bool_text[1] = enabled_text_1;
   elem->bool_text[2] = disabled_text_2;
   elem->bool_text[3] = enabled_text_2;
 
-  gtk_button_set_label(GTK_BUTTON(elem->widget2), disabled_text_2);
+  gtk_button_set_label(GTK_BUTTON(data->button2), disabled_text_2);
 
-  dual_button_updated(elem);
+  dual_button_updated(elem, data);
+
+  GtkWidget *box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);
+  GtkWidget *label = gtk_label_new(label_text);
+  gtk_box_append(GTK_BOX(box), label);
+  gtk_box_append(GTK_BOX(box), GTK_WIDGET(data->button1));
+  gtk_box_append(GTK_BOX(box), GTK_WIDGET(data->button2));
+
+  return box;
 }
diff --git a/src/widget-dual.h b/src/widget-dual.h
index 2add820..ab8e2b1 100644
--- a/src/widget-dual.h
+++ b/src/widget-dual.h
@@ -9,8 +9,9 @@
 // buttons:
 // first button disables/enables the feature
 // second button switches between the two features states
-void make_dual_boolean_alsa_elems(
+GtkWidget *make_dual_boolean_alsa_elems(
   struct alsa_elem *alsa_elem,
+  const char       *label_text,
   const char       *disabled_text_1,
   const char       *enabled_text_1,
   const char       *disabled_text_2,
diff --git a/src/widget-gain.c b/src/widget-gain.c
index 6b75a08..afcab48 100644
--- a/src/widget-gain.c
+++ b/src/widget-gain.c
@@ -4,18 +4,30 @@
 #include "gtkdial.h"
 #include "widget-gain.h"
 
-static void gain_changed(GtkWidget *widget, struct alsa_elem *elem) {
-  int value = gtk_dial_get_value(GTK_DIAL(widget));
+struct gain {
+  struct alsa_elem *elem;
+  GtkWidget        *vbox;
+  GtkWidget        *dial;
+  GtkWidget        *label;
+};
 
-  alsa_set_elem_value(elem, value);
+static void gain_changed(GtkWidget *widget, struct gain *data) {
+  int value = gtk_dial_get_value(GTK_DIAL(data->dial));
+
+  alsa_set_elem_value(data->elem, value);
 }
 
-static void gain_updated(struct alsa_elem *elem) {
+static void gain_updated(
+  struct alsa_elem *elem,
+  void             *private
+) {
+  struct gain *data = private;
+
   int is_writable = alsa_get_elem_writable(elem);
-  gtk_widget_set_sensitive(elem->widget, is_writable);
+  gtk_widget_set_sensitive(data->dial, is_writable);
 
   int alsa_value = alsa_get_elem_value(elem);
-  gtk_dial_set_value(GTK_DIAL(elem->widget), alsa_value);
+  gtk_dial_set_value(GTK_DIAL(data->dial), alsa_value);
 
   char s[20];
   float scale = (float)(elem->max_dB - elem->min_dB) /
@@ -28,39 +40,38 @@ static void gain_updated(struct alsa_elem *elem) {
   else
     snprintf(s, 20, "%.0fdB", value);
 
-  gtk_label_set_text(GTK_LABEL(elem->widget2), s);
+  gtk_label_set_text(GTK_LABEL(data->label), s);
 }
 
+//GList *make_gain_alsa_elem(struct alsa_elem *elem) {
 GtkWidget *make_gain_alsa_elem(struct alsa_elem *elem) {
-  GtkWidget *vbox = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
-  gtk_widget_set_hexpand(vbox, TRUE);
+  struct gain *data = g_malloc(sizeof(struct gain));
+  data->elem = elem;
+  data->vbox = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
+  gtk_widget_set_hexpand(data->vbox, TRUE);
 
-  GtkWidget *dial = gtk_dial_new_with_range(
-    elem->min_val, elem->max_val, 1
-  );
+  data->dial = gtk_dial_new_with_range(elem->min_val, elem->max_val, 1);
 
   // calculate 0dB value from min/max dB and min/max value
   float scale = (float)(elem->max_dB - elem->min_dB) /
                        (elem->max_val - elem->min_val);
   int zero_db_value = (int)((0 - elem->min_dB) / scale + elem->min_val);
 
-  gtk_dial_set_zero_db(GTK_DIAL(dial), zero_db_value);
+  gtk_dial_set_zero_db(GTK_DIAL(data->dial), zero_db_value);
 
-  gtk_widget_set_vexpand(dial, TRUE);
+  data->label = gtk_label_new(NULL);
+  gtk_widget_set_vexpand(data->dial, TRUE);
 
   g_signal_connect(
-    dial, "value-changed", G_CALLBACK(gain_changed), elem
+    data->dial, "value-changed", G_CALLBACK(gain_changed), data
   );
-  elem->widget = dial;
-  elem->widget_callback = gain_updated;
 
-  GtkWidget *label = gtk_label_new(NULL);
-  elem->widget2 = label;
+  alsa_elem_add_callback(elem, gain_updated, data);
 
-  gain_updated(elem);
+  gain_updated(elem, data);
 
-  gtk_box_append(GTK_BOX(vbox), dial);
-  gtk_box_append(GTK_BOX(vbox), label);
+  gtk_box_append(GTK_BOX(data->vbox), data->dial);
+  gtk_box_append(GTK_BOX(data->vbox), data->label);
 
-  return vbox;
+  return data->vbox;
 }
diff --git a/src/widget-label.c b/src/widget-label.c
index 9af9fb2..814e1c5 100644
--- a/src/widget-label.c
+++ b/src/widget-label.c
@@ -3,21 +3,29 @@
 
 #include "widget-label.h"
 
-static void label_updated(struct alsa_elem *elem) {
+struct label {
+  struct alsa_elem *elem;
+  GtkWidget        *label;
+};
+
+static void label_updated(struct alsa_elem *elem, void *private) {
+  struct label *data = private;
+
   const char *text = alsa_get_item_name(elem, alsa_get_elem_value(elem));
 
-  gtk_label_set_text(GTK_LABEL(elem->widget), text);
+  gtk_label_set_text(GTK_LABEL(data->label), text);
 }
 
 GtkWidget *make_label_alsa_elem(struct alsa_elem *elem) {
-  GtkWidget *label = gtk_label_new(NULL);
-  gtk_widget_set_halign(label, GTK_ALIGN_CENTER);
-  gtk_widget_set_valign(label, GTK_ALIGN_CENTER);
+  struct label *data = g_malloc(sizeof(struct label));
+  data->label = gtk_label_new(NULL);
 
-  elem->widget = label;
-  elem->widget_callback = label_updated;
+  gtk_widget_set_halign(data->label, GTK_ALIGN_CENTER);
+  gtk_widget_set_valign(data->label, GTK_ALIGN_CENTER);
 
-  label_updated(elem);
+  alsa_elem_add_callback(elem, label_updated, data);
 
-  return label;
+  label_updated(elem, data);
+
+  return data->label;
 }
diff --git a/src/window-routing.c b/src/window-routing.c
index fdf5b82..12d1a50 100644
--- a/src/window-routing.c
+++ b/src/window-routing.c
@@ -642,8 +642,7 @@ static void setup_src_drag(struct routing_src *r_src) {
 }
 
 static void setup_snk_drag(struct routing_snk *r_snk) {
-  struct alsa_elem *elem = r_snk->elem;
-  GtkWidget *box = elem->widget;
+  GtkWidget *box = r_snk->box_widget;
 
   // handle drags on the box
   GtkDragSource *source = gtk_drag_source_new();
@@ -670,7 +669,7 @@ static void setup_snk_drag(struct routing_snk *r_snk) {
   // set the box as a drop target
   GtkDropTarget *dest = gtk_drop_target_new(G_TYPE_INT, GDK_ACTION_COPY);
   gtk_widget_add_controller(box, GTK_EVENT_CONTROLLER(dest));
-  g_signal_connect(dest, "drop", G_CALLBACK(dropped_on_snk), elem);
+  g_signal_connect(dest, "drop", G_CALLBACK(dropped_on_snk), r_snk->elem);
   g_signal_connect(dest, "accept", G_CALLBACK(snk_drop_accept), r_snk);
   g_signal_connect(dest, "enter", G_CALLBACK(snk_drop_enter), r_snk);
   g_signal_connect(dest, "leave", G_CALLBACK(snk_drop_leave), r_snk);
@@ -747,11 +746,11 @@ static void make_snk_routing_widget(
   struct alsa_elem *elem = r_snk->elem;
 
   // create a box, a "socket", and a label
-  GtkWidget *box = elem->widget = gtk_box_new(orientation, 5);
+  GtkWidget *box = r_snk->box_widget = gtk_box_new(orientation, 5);
   gtk_widget_add_css_class(box, "route-label");
   GtkWidget *label = gtk_label_new(name);
   gtk_box_append(GTK_BOX(box), label);
-  GtkWidget *socket = elem->widget2 = make_socket_widget();
+  GtkWidget *socket = r_snk->socket_widget = make_socket_widget();
   if (orientation == GTK_ORIENTATION_VERTICAL) {
     gtk_box_append(GTK_BOX(box), socket);
     gtk_widget_set_margin_start(box, 5);
@@ -777,7 +776,7 @@ static void make_snk_routing_widget(
   setup_snk_drag(r_snk);
 }
 
-static void routing_updated(struct alsa_elem *elem) {
+static void routing_updated(struct alsa_elem *elem, void *data) {
   struct alsa_card *card = elem->card;
 
   update_mixer_labels(card);
@@ -797,7 +796,7 @@ static void make_routing_alsa_elem(struct routing_snk *r_snk) {
     snprintf(name, 10, "%d", elem->lr_num);
     make_snk_routing_widget(r_snk, name, GTK_ORIENTATION_VERTICAL);
     gtk_grid_attach(
-      GTK_GRID(card->routing_dsp_in_grid), elem->widget,
+      GTK_GRID(card->routing_dsp_in_grid), r_snk->box_widget,
       r_snk->port_num + 1, 0, 1, 1
     );
 
@@ -810,7 +809,7 @@ static void make_routing_alsa_elem(struct routing_snk *r_snk) {
     snprintf(name, 10, "%d", elem->lr_num);
     make_snk_routing_widget(r_snk, name, GTK_ORIENTATION_VERTICAL);
     gtk_grid_attach(
-      GTK_GRID(card->routing_mixer_in_grid), elem->widget,
+      GTK_GRID(card->routing_mixer_in_grid), r_snk->box_widget,
       r_snk->port_num + 1, 0, 1, 1
     );
 
@@ -828,7 +827,7 @@ static void make_routing_alsa_elem(struct routing_snk *r_snk) {
     free(name);
 
     gtk_grid_attach(
-      GTK_GRID(card->routing_pcm_out_grid), elem->widget,
+      GTK_GRID(card->routing_pcm_out_grid), r_snk->box_widget,
       0, r_snk->port_num + 1, 1, 1
     );
 
@@ -848,14 +847,14 @@ static void make_routing_alsa_elem(struct routing_snk *r_snk) {
     free(name);
 
     gtk_grid_attach(
-      GTK_GRID(card->routing_hw_out_grid), elem->widget,
+      GTK_GRID(card->routing_hw_out_grid), r_snk->box_widget,
       0, r_snk->port_num + 1, 1, 1
     );
   } else {
     printf("invalid port category %d\n", r_snk->port_category);
   }
 
-  elem->widget_callback = routing_updated;
+  alsa_elem_add_callback(elem, routing_updated, NULL);
 }
 
 static void add_routing_widgets(