Allow configuring HPF cutoff frequency from audio setup dialog

Add a control to the setup dialog for the HPF cutoff frequency.  Also
save it to the config file.

Slider has ticks for Off and also for the default 3kHz frequency.  The
fill level of the slider is set to limit the cutoff to the Nyquist
frequency of the selected sampling rate.

To do that, I needed to get a callback on rate combobox change, and the
manual entry of the combobox made that a challenge.

Author: xyzzy42

src/interface.c

@@ -612,6 +612,21 @@ static int get_rate(GtkComboBox *rate_list)
 	return rate;
 }
 
+static void rate_entered(GtkWidget *rate_entry, struct main_window *w)
+{
+	UNUSED(rate_entry);
+	gtk_range_set_fill_level(w->hpf_range, get_rate(w->rate_list) / 2);
+}
+
+static void rate_changed(GtkWidget *rate_list, struct main_window *w)
+{
+	/* Only act on combo list selections, not on every keystroke of manual
+	 * entry.  rate_entered() will handle manual entry finished.  */
+	if (gtk_combo_box_get_active(GTK_COMBO_BOX(rate_list)) == -1)
+		return;
+	gtk_range_set_fill_level(w->hpf_range, get_rate(w->rate_list) / 2);
+}
+
 static void populate_rate_list(GtkComboBox *rate_list, unsigned int current_rate, unsigned int rates)
 {
 	unsigned int i;
@@ -620,6 +635,7 @@ static void populate_rate_list(GtkComboBox *rate_list, unsigned int current_rate
 	static const char * const labels[] = AUDIO_RATE_LABELS;
 
 	int active = -1; // -1 will set no active entry
+	g_signal_handlers_block_matched(G_OBJECT(rate_list), G_SIGNAL_MATCH_FUNC, 0,0,NULL, rate_changed, NULL);
 	GtkListStore *list = GTK_LIST_STORE(gtk_combo_box_get_model(rate_list));
 	gtk_tree_model_get_iter_first(GTK_TREE_MODEL(list), &iter);
 	for(i=0; i < ARRAY_SIZE(freqs); i++, gtk_tree_model_iter_next(GTK_TREE_MODEL(list), &iter)) {
@@ -633,6 +649,7 @@ static void populate_rate_list(GtkComboBox *rate_list, unsigned int current_rate
 		if (supported && current_rate == freqs[i])
 			active = i;
 	}
+	g_signal_handlers_unblock_matched(G_OBJECT(rate_list), G_SIGNAL_MATCH_FUNC, 0,0,NULL, rate_changed, NULL);
 	gtk_combo_box_set_active(rate_list, active);
 	if (active == -1) {
 		GtkWidget *entry = gtk_bin_get_child(GTK_BIN(rate_list));
@@ -695,18 +712,21 @@ static void audio_setup(GtkMenuItem *m, struct main_window *w)
 	if (new_rate == -1)
 		new_rate = w->nominal_sr; /* clear entry too? */
 
-	i = set_audio_device(selected, &new_rate, NULL, FILTER_CUTOFF, w->is_light);
+	int hpf_freq = gtk_range_get_value(w->hpf_range);
+
+	i = set_audio_device(selected, &new_rate, NULL, hpf_freq, w->is_light);
 	if (i == 0) {
 		w->nominal_sr = new_rate;
 		// Only save settings to config if it worked
 		w->audio_rate = new_rate;
+		w->hpf_freq = hpf_freq;
 		// If selected dev is the default, save -1 "default" to config
 		w->audio_device = devices[selected].isdefault ? -1 : selected;
 		recompute(w);
 	} else if (i < 0) {
 		/* Try to restore old settings */
 		new_rate = w->nominal_sr;
-		i = set_audio_device(current_dev, &new_rate, NULL, FILTER_CUTOFF, w->is_light);
+		i = set_audio_device(current_dev, &new_rate, NULL, w->hpf_freq, w->is_light);
 		if (i < 0)
 			error("Unable to restore previous audio settings.  Audio not working.");
 	}
@@ -913,9 +933,23 @@ static void init_audio_dialog(struct main_window *w)
 	gtk_cell_layout_set_attributes(GTK_CELL_LAYOUT(rates), renderer, "text", 0, "sensitive", 1, NULL);
 	gtk_grid_attach(grid, rates, 1, 1, 1, 1);
 
+	gtk_grid_attach(grid, label = gtk_label_new("High Pass Cutoff"), 0, 2, 1, 1);
+	g_object_set(G_OBJECT(label), "halign", GTK_ALIGN_END, NULL);
+
+	GtkWidget *hpf = gtk_scale_new_with_range(GTK_ORIENTATION_HORIZONTAL, 0, 24000, 100);
+	w->hpf_range = GTK_RANGE(hpf);
+	gtk_scale_add_mark(GTK_SCALE(w->hpf_range), 0, GTK_POS_BOTTOM, "Off");
+	gtk_scale_add_mark(GTK_SCALE(w->hpf_range), FILTER_CUTOFF, GTK_POS_BOTTOM, "Default");
+	gtk_range_set_restrict_to_fill_level(w->hpf_range, true);
+	gtk_range_set_show_fill_level(w->hpf_range, true);
+	gtk_range_set_value(w->hpf_range, FILTER_CUTOFF);
+	gtk_grid_attach(grid, hpf, 1, 2, 1, 1);
+
 	gtk_widget_show_all(content);
 
 	g_signal_connect(G_OBJECT(w->device_list), "changed", G_CALLBACK(device_changed), w);
+	g_signal_connect(G_OBJECT(gtk_bin_get_child(GTK_BIN(w->rate_list))), "activate", G_CALLBACK(rate_entered), w);
+	g_signal_connect(G_OBJECT(w->rate_list), "changed", G_CALLBACK(rate_changed), w);
 }
 
 /* Set up the main window and populate with widgets */
@@ -1143,11 +1177,12 @@ static void start_interface(GApplication* app, void *p)
 	w->nominal_sr = 0; // Use default rate, e.g. PA_SAMPLE_RATE
 	w->audio_device = -1;
 	w->audio_rate = 0;
+	w->hpf_freq = FILTER_CUTOFF;
 
 	load_config(w);
 
 	w->nominal_sr = w->audio_rate;
-	if(start_portaudio(w->audio_device, &w->nominal_sr, &real_sr, FILTER_CUTOFF, w->is_light)) {
+	if(start_portaudio(w->audio_device, &w->nominal_sr, &real_sr, w->hpf_freq, w->is_light)) {
 		g_application_quit(app);
 		return;
 	}

src/tg.h

@@ -293,6 +293,7 @@ struct main_window {
 	GtkWidget *audio_setup;
 	GtkComboBox *device_list;
 	GtkComboBox *rate_list;
+	GtkRange *hpf_range;
 
 	struct output_panel *active_panel;
 
@@ -310,6 +311,7 @@ struct main_window {
 	int nominal_sr;	// requested audio device rate
 	int audio_device;// Selected device
 	int audio_rate;  // Selected rate
+	int hpf_freq;    // Low-pass filter cutoff frequency
 
 	bool vertical_layout;
 
@@ -338,7 +340,8 @@ void error(char *format,...);
 	OP(light_algorithm, is_light, int) \
 	OP(vertical_paperstrip, vertical_layout, bool) \
 	OP(audio_device, audio_device, int) \
-	OP(audio_rate, audio_rate, int)
+	OP(audio_rate, audio_rate, int) \
+	OP(highpass_cutoff_freq, hpf_freq, int)
 
 struct conf_data {
 #define DEF(NAME,PLACE,TYPE) TYPE PLACE;