Display -inf when volume/gain controls are at zero/off

src/iface-mixer.c

@@ -174,7 +174,7 @@ static void create_input_gain_control(
   int               current_row,
   int               line_num
 ) {
-  GtkWidget *w = make_gain_alsa_elem(elem);
+  GtkWidget *w = make_gain_alsa_elem(elem, 0);
 
   gtk_grid_attach(GTK_GRID(grid), w, line_num, current_row, 1, 1);
 }
@@ -466,7 +466,7 @@ static void create_output_controls(
     // output controls
     if (strncmp(elem->name, "Line", 4) == 0) {
       if (strstr(elem->name, "Playback Volume")) {
-        w = make_gain_alsa_elem(elem);
+        w = make_gain_alsa_elem(elem, 1);
         gtk_grid_attach(
           GTK_GRID(output_grid), w, line_num - 1 + line_1_col, 1, 1, 1
         );
@@ -503,7 +503,7 @@ static void create_output_controls(
 
       GtkWidget *l = gtk_label_new(gen4 ? "Line 1–2" : "HW");
       gtk_grid_attach(GTK_GRID(output_grid), l, 0, 0, 1, 1);
-      w = make_gain_alsa_elem(elem);
+      w = make_gain_alsa_elem(elem, 1);
       gtk_widget_set_tooltip_text(
         w,
         gen4
@@ -522,7 +522,7 @@ static void create_output_controls(
         "This control shows the setting of the headphone volume knob."
       );
       gtk_grid_attach(GTK_GRID(output_grid), l, 1, 0, 1, 1);
-      w = make_gain_alsa_elem(elem);
+      w = make_gain_alsa_elem(elem, 1);
       gtk_grid_attach(GTK_GRID(output_grid), w, 1, 1, 1, 1);
     } else if (strcmp(elem->name, "Mute Playback Switch") == 0) {
       w = make_boolean_alsa_elem(

src/widget-gain.c

@@ -9,6 +9,7 @@ struct gain {
   GtkWidget        *vbox;
   GtkWidget        *dial;
   GtkWidget        *label;
+  int               zero_is_off;
 };
 
 static void gain_changed(GtkWidget *widget, struct gain *data) {
@@ -30,21 +31,35 @@ static void gain_updated(
   gtk_dial_set_value(GTK_DIAL(data->dial), alsa_value);
 
   char s[20];
+  char *p = s;
   float scale = (float)(elem->max_dB - elem->min_dB) /
                        (elem->max_val - elem->min_val);
 
   float value = (float)alsa_value * scale + elem->min_dB;
 
-  if (scale < 1)
-    snprintf(s, 20, "%.1f", value);
-  else
-    snprintf(s, 20, "%.0fdB", value);
+  if (value > elem->max_dB)
+    value = elem->max_dB;
+  else if (value < elem->min_dB)
+    value = elem->min_dB;
+
+  if (data->zero_is_off && alsa_value == 0) {
+    p += sprintf(p, "−∞");
+  } else {
+    if (value < 0)
+      p += sprintf(p, "−");
+    if (scale < 1)
+      p += sprintf(p, "%.1f", fabs(value));
+    else
+      p += sprintf(p, "%.0f", fabs(value));
+  }
+  if (scale >= 1)
+    p += sprintf(p, "dB");
 
   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 *make_gain_alsa_elem(struct alsa_elem *elem, int zero_is_off) {
   struct gain *data = g_malloc(sizeof(struct gain));
   data->elem = elem;
   data->vbox = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
@@ -62,6 +77,8 @@ GtkWidget *make_gain_alsa_elem(struct alsa_elem *elem) {
   data->label = gtk_label_new(NULL);
   gtk_widget_set_vexpand(data->dial, TRUE);
 
+  data->zero_is_off = zero_is_off;
+
   g_signal_connect(
     data->dial, "value-changed", G_CALLBACK(gain_changed), data
   );

src/widget-gain.h

@@ -7,4 +7,4 @@
 
 #include "alsa.h"
 
-GtkWidget *make_gain_alsa_elem(struct alsa_elem *alsa_elem);
+GtkWidget *make_gain_alsa_elem(struct alsa_elem *alsa_elem, int zero_is_off);

src/window-mixer.c

@@ -76,7 +76,7 @@ GtkWidget *create_mixer_controls(struct alsa_card *card) {
     }
 
     // create the gain control and attach to the grid
-    GtkWidget *w = make_gain_alsa_elem(elem);
+    GtkWidget *w = make_gain_alsa_elem(elem, 1);
     gtk_grid_attach(GTK_GRID(mixer_top), w, input_num + 1, mix_num + 2, 1, 1);
 
     // look up the r_snk entry for the mixer input number