Add display of sample rate

src/alsa-scarlett-gui.css

@@ -228,6 +228,31 @@ button.toggle {
   text-shadow: 0 0 5px #00c000, 0 0 15px #00c000;
 }
 
+/* Sample Rates */
+.window-frame button.sample-rate.sample-rate-44100 {
+  text-shadow: 0 0 5px #00c000, 0 0 15px #00c000;
+}
+
+.window-frame button.sample-rate.sample-rate-48000 {
+  text-shadow: 0 0 5px #00c000, 0 0 15px #00c000;
+}
+
+.window-frame button.sample-rate.sample-rate-88200 {
+  text-shadow: 0 0 5px #ff8000, 0 0 15px #ff8000;
+}
+
+.window-frame button.sample-rate.sample-rate-96000 {
+  text-shadow: 0 0 5px #ff8000, 0 0 15px #ff8000;
+}
+
+.window-frame button.sample-rate.sample-rate-176400 {
+  text-shadow: 0 0 5px #ff0000, 0 0 15px #c00000;
+}
+
+.window-frame button.sample-rate.sample-rate-192000 {
+  text-shadow: 0 0 5px #ff0000, 0 0 15px #c00000;
+}
+
 /* Button controls where checked is dimmer */
 
 /* Mute button */

src/iface-mixer.c

@@ -11,6 +11,7 @@
 #include "widget-gain.h"
 #include "widget-input-select.h"
 #include "widget-label.h"
+#include "widget-sample-rate.h"
 #include "window-helper.h"
 #include "window-levels.h"
 #include "window-mixer.h"
@@ -114,6 +115,30 @@ static void add_power_status_control(
   gtk_box_append(GTK_BOX(b), w);
 }
 
+static void add_sample_rate_control(
+  struct alsa_card *card,
+  GtkWidget        *global_controls
+) {
+  GtkWidget *b = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);
+  gtk_widget_set_tooltip_text(
+    b,
+    "The Sample Rate cannot be changed here because it is set by the "
+    "application which is using the interface, usually a sound "
+    "server like PulseAudio, JACK, or PipeWire. If this shows N/A, "
+    "no application is currently using the interface.\n\n"
+    "Note that not all features are available on all interfaces at "
+    "sample rates above 48kHz. Please refer to the user guide for "
+    "your interface for more information."
+  );
+  gtk_box_append(GTK_BOX(global_controls), b);
+
+  GtkWidget *l = gtk_label_new("Sample Rate");
+  gtk_box_append(GTK_BOX(b), l);
+  GtkWidget *w = make_sample_rate_widget(card);
+  gtk_widget_add_css_class(w, "sample-rate");
+  gtk_box_append(GTK_BOX(b), w);
+}
+
 static void add_speaker_switching_controls(
   struct alsa_card *card,
   GtkWidget        *global_controls
@@ -690,21 +715,24 @@ static void create_global_controls(
     ? GTK_ORIENTATION_HORIZONTAL
     : GTK_ORIENTATION_VERTICAL;
   GtkWidget *global_controls = create_global_box(top, x, orient);
-  GtkWidget *left = global_controls;
-  GtkWidget *right = global_controls;
+  GtkWidget *column[3];
+
+  for (int i = 0; i < 3; i++)
+    column[i] = global_controls;
 
   if (card->has_speaker_switching) {
-    left = gtk_box_new(GTK_ORIENTATION_VERTICAL, 15);
-    right = gtk_box_new(GTK_ORIENTATION_VERTICAL, 15);
-    gtk_box_append(GTK_BOX(global_controls), left);
-    gtk_box_append(GTK_BOX(global_controls), right);
+    for (int i = 0; i < 3; i++) {
+      column[i] = gtk_box_new(GTK_ORIENTATION_VERTICAL, 15);
+      gtk_box_append(GTK_BOX(global_controls), column[i]);
+    }
   }
 
-  add_clock_source_control(card, left);
-  add_sync_status_control(card, right);
-  add_power_status_control(card, right);
-  add_speaker_switching_controls(card, left);
-  add_talkback_controls(card, right);
+  add_clock_source_control(card, column[0]);
+  add_sync_status_control(card, column[1]);
+  add_power_status_control(card, column[1]);
+  add_sample_rate_control(card, column[2]);
+  add_speaker_switching_controls(card, column[0]);
+  add_talkback_controls(card, column[1]);
 }
 
 static GtkWidget *create_main_window_controls(struct alsa_card *card) {

src/widget-sample-rate.c

@@ -0,0 +1,123 @@
+// SPDX-FileCopyrightText: 2024 Geoffrey D. Bennett <g@b4.vu>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "gtkhelper.h"
+#include "widget-boolean.h"
+
+struct sample_rate {
+  struct alsa_card *card;
+  GtkWidget        *button;
+  guint             source;
+  char             *path;
+  int               sample_rate;
+};
+
+static void button_set_text(GtkWidget *button, int value) {
+  gtk_widget_remove_css_classes_by_prefix(button, "sample-rate-");
+
+  if (!value) {
+    gtk_button_set_label(GTK_BUTTON(button), "N/A");
+    return;
+  }
+
+  char *text;
+  if (value % 1000 == 0)
+    text = g_strdup_printf("%dkHz", value / 1000);
+  else
+    text = g_strdup_printf("%.1fkHz", value / 1000.0);
+  gtk_button_set_label(GTK_BUTTON(button), text);
+  g_free(text);
+
+  char *css_class = g_strdup_printf(
+    "sample-rate-%d", value
+  );
+  gtk_widget_add_css_class(button, css_class);
+  g_free(css_class);
+}
+
+// Read the sample rate from /proc/asound/cardN/stream0
+// and return it as an integer
+//
+// Looking for a line containing:
+//   Momentary freq = 48000 Hz (0x6.0000)
+static int get_sample_rate(struct sample_rate *data) {
+  if (!data->path)
+    return 0;
+
+  FILE *file = fopen(data->path, "r");
+  if (!file) {
+    perror("fopen");
+    return 0;
+  }
+
+  char *line = NULL;
+  size_t len = 0;
+  ssize_t read;
+
+  int sample_rate = 0;
+
+  while ((read = getline(&line, &len, file)) != -1) {
+    if (strstr(line, "Momentary freq = ")) {
+      char *start = strstr(line, "Momentary freq = ") + 17;
+      char *end = strstr(start, " Hz");
+
+      if (!start || !end)
+        continue;
+
+      *end = '\0';
+      sample_rate = atoi(start);
+
+      break;
+    }
+  }
+
+  free(line);
+  fclose(file);
+
+  return sample_rate;
+}
+
+static gboolean update_sample_rate(struct sample_rate *data) {
+  int sample_rate = get_sample_rate(data);
+
+  if (sample_rate != data->sample_rate) {
+    data->sample_rate = sample_rate;
+    button_set_text(data->button, sample_rate);
+  }
+
+  return G_SOURCE_CONTINUE;
+}
+
+static void on_destroy(struct sample_rate *data, GObject *widget) {
+  if (data->source)
+    g_source_remove(data->source);
+  g_free(data->path);
+  g_free(data);
+}
+
+GtkWidget *make_sample_rate_widget(
+  struct alsa_card *card
+) {
+  struct sample_rate *data = g_malloc0(sizeof(struct sample_rate));
+  data->card = card;
+  data->button = gtk_toggle_button_new();
+  data->sample_rate = -1;
+
+  gtk_widget_add_css_class(data->button, "fixed");
+  gtk_widget_add_css_class(data->button, "sample-rate");
+
+  // can only update if it's a real card
+  if (card->num != SIMULATED_CARD_NUM) {
+    data->path = g_strdup_printf("/proc/asound/card%d/stream0", card->num);
+    data->source =
+      g_timeout_add_seconds(1, (GSourceFunc)update_sample_rate, data);
+  }
+
+  // initial update (will show "N/A" for simulated card)
+  update_sample_rate(data);
+
+  // cleanup when the button is destroyed
+  g_object_weak_ref(G_OBJECT(data->button), (GWeakNotify)on_destroy, data);
+
+  return data->button;
+}

src/widget-sample-rate.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: 2024 Geoffrey D. Bennett <g@b4.vu>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <gtk/gtk.h>
+
+#include "alsa.h"
+
+GtkWidget *make_sample_rate_widget(
+  struct alsa_card *alsa_card
+);