Handle interfaces with fixed mixer inputs

src/alsa.c

@@ -598,6 +598,10 @@ static void get_routing_snks(struct alsa_card *card) {
     if (strncmp(elem->name, "Mixer Input", 11) == 0 ||
         strncmp(elem->name, "Matrix", 6) == 0) {
       elem->port_category = PC_MIX;
+
+      if (!alsa_get_elem_writable(elem))
+        card->has_fixed_mixer_inputs = 1;
+
     } else if (strncmp(elem->name, "DSP Input", 9) == 0) {
       elem->port_category = PC_DSP;
     } else if (strncmp(elem->name, "PCM", 3) == 0 ||

src/alsa.h

@@ -186,6 +186,7 @@ struct alsa_card {
   GtkWidget          *routing_mixer_out_grid;
   int                 has_speaker_switching;
   int                 has_talkback;
+  int                 has_fixed_mixer_inputs;
   int                 routing_out_count[PC_COUNT];
   int                 routing_in_count[PC_COUNT];
   GMenu              *routing_src_menu;

src/routing-lines.c

@@ -261,6 +261,12 @@ void draw_routing_lines(
     struct routing_snk *r_snk = &g_array_index(
       card->routing_snks, struct routing_snk, i
     );
+    struct alsa_elem *elem = r_snk->elem;
+
+    // don't draw lines to read-only mixer sinks
+    if (elem->port_category == PC_MIX &&
+        card->has_fixed_mixer_inputs)
+      continue;
 
     // if dragging and a routing sink is being reconnected then draw
     // it with dots
@@ -271,7 +277,7 @@ void draw_routing_lines(
       cairo_set_dash(cr, NULL, 0, 0);
 
     // get the sink and skip if it's "Off"
-    int r_src_idx = alsa_get_elem_value(r_snk->elem);
+    int r_src_idx = alsa_get_elem_value(elem);
     if (!r_src_idx)
       continue;
 
@@ -300,7 +306,7 @@ void draw_routing_lines(
     draw_connection(
       cr,
       x1, y1, r_src->port_category,
-      x2, y2, r_snk->elem->port_category,
+      x2, y2, elem->port_category,
       r, g, b, 2
     );
   }

src/window-routing.c

@@ -241,11 +241,12 @@ static void create_routing_grid(struct alsa_card *card) {
       GTK_ORIENTATION_HORIZONTAL, GTK_ALIGN_CENTER
     );
   }
-  card->routing_mixer_in_grid = create_routing_group_grid(
-    card, "routing_mixer_in_grid", "Mixer\nInputs",
-    "Mixer Inputs are used to mix multiple audio channels together",
-    GTK_ORIENTATION_HORIZONTAL, GTK_ALIGN_CENTER
-  );
+  if (!card->has_fixed_mixer_inputs)
+    card->routing_mixer_in_grid = create_routing_group_grid(
+      card, "routing_mixer_in_grid", "Mixer\nInputs",
+      "Mixer Inputs are used to mix multiple audio channels together",
+      GTK_ORIENTATION_HORIZONTAL, GTK_ALIGN_CENTER
+    );
   card->routing_mixer_out_grid = create_routing_group_grid(
     card, "routing_mixer_out_grid",
     card->has_talkback ? "Mixer Outputs" : "Mixer\nOutputs",
@@ -290,7 +291,9 @@ static void create_routing_grid(struct alsa_card *card) {
   gtk_label_set_justify(GTK_LABEL(src_label), GTK_JUSTIFY_CENTER);
   gtk_grid_attach(routing_grid, src_label, left_col_num, 3, 1, 1);
 
-  GtkWidget *snk_label = gtk_label_new("← Sinks\n↓");
+  GtkWidget *snk_label = gtk_label_new(
+    card->has_fixed_mixer_inputs ? "Sinks\n↓" : "← Sinks\n↓"
+  );
   gtk_label_set_justify(GTK_LABEL(snk_label), GTK_JUSTIFY_CENTER);
   gtk_grid_attach(routing_grid, snk_label, right_col_num, 0, 1, 1);
 }
@@ -720,6 +723,9 @@ static void make_routing_alsa_elem(struct routing_snk *r_snk) {
   // the top, in card->routing_mixer_in_grid after the DSP Inputs
   } else if (elem->port_category == PC_MIX) {
 
+    if (card->has_fixed_mixer_inputs)
+      return;
+
     char name[10];
 
     snprintf(name, 10, "%d", elem->lr_num);