Create only DISPLAY alarms in reminders, not AUDIO

Creating "AUDIO" VALARM notification actions causes endless problems:
users may only hear a sound notification (with no visuals), if at all,
and most other apps don't honor nor support editing audio-only alarms.
Other systems typically play a sound automatically on "DISPLAY" alarms.

https://datatracker.ietf.org/doc/html/rfc5545#section-3.6.6 says:

> Multiple mutually independent "VALARM" calendar components
> can be specified for a single "VEVENT" or "VTODO" calendar component.

However, each component states:

> 'action' and 'trigger' are both REQUIRED,
> but MUST NOT occur more than once.

To keep the UI simple, we should pick one or the other; "DISPLAY" it is.
Remove "AUDIO" alarm code and add a warning to never add it again.

Fixes: https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1280
Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/680>

src/gui/event-editor/gcal-alarm-row.blp

@@ -2,18 +2,6 @@ using Gtk 4.0;
 using Adw 1;
 
 template $GcalAlarmRow: Adw.ActionRow {
-  ToggleButton volume_button {
-    valign: center;
-    icon-name: "audio-volume-high-symbolic";
-    tooltip-text: _("Toggle Alarm Sound");
-    notify::active => $on_sound_toggle_changed_cb(template) not-swapped;
-    active: true;
-
-    styles [
-      "flat",
-    ]
-  }
-
   Button remove_button {
     valign: center;
     icon-name: "edit-delete-symbolic";

src/gui/event-editor/gcal-alarm-row.c

@@ -207,7 +207,6 @@ setup_alarm (GcalAlarmRow *self)
 {
   g_autofree gchar *formatted_duration = NULL;
   ECalComponentAlarmTrigger *trigger;
-  ECalComponentAlarmAction action;
   ICalDuration *duration;
 
   trigger = e_cal_component_alarm_get_trigger (self->alarm);
@@ -215,9 +214,6 @@ setup_alarm (GcalAlarmRow *self)
   formatted_duration = format_alarm_duration (duration);
 
   adw_preferences_row_set_title (ADW_PREFERENCES_ROW (self), formatted_duration);
-
-  action = e_cal_component_alarm_get_action (self->alarm);
-  gtk_toggle_button_set_active (self->volume_button, action == E_CAL_COMPONENT_ALARM_AUDIO);
 }
 
 
@@ -232,28 +228,6 @@ on_remove_button_clicked_cb (GtkButton    *button,
   g_signal_emit (self, signals[REMOVE_ALARM], 0);
 }
 
-static void
-on_sound_toggle_changed_cb (GtkToggleButton *button,
-                            GParamSpec      *pspec,
-                            GcalAlarmRow    *self)
-{
-  ECalComponentAlarmAction action;
-  gboolean has_sound;
-
-  has_sound = gtk_toggle_button_get_active (button);
-
-  /* Setup the alarm action */
-  action = has_sound ? E_CAL_COMPONENT_ALARM_AUDIO : E_CAL_COMPONENT_ALARM_DISPLAY;
-
-  e_cal_component_alarm_set_action (self->alarm, action);
-
-  /* Update the volume icon */
-  gtk_button_set_icon_name (GTK_BUTTON (self->volume_button),
-                            has_sound ? "audio-volume-high-symbolic" : "audio-volume-muted-symbolic");
-
-  g_signal_emit (self, signals[UPDATE_ALARM], 0);
-}
-
 
 /*
  * GObject overrides
@@ -348,7 +322,6 @@ gcal_alarm_row_class_init (GcalAlarmRowClass *klass)
   gtk_widget_class_bind_template_child (widget_class, GcalAlarmRow, volume_button);
 
   gtk_widget_class_bind_template_callback (widget_class, on_remove_button_clicked_cb);
-  gtk_widget_class_bind_template_callback (widget_class, on_sound_toggle_changed_cb);
 }
 
 static void

src/gui/event-editor/gcal-reminders-section.c

@@ -128,7 +128,12 @@ create_alarm (guint minutes)
 
   alarm = e_cal_component_alarm_new ();
   e_cal_component_alarm_take_trigger (alarm, trigger);
-  e_cal_component_alarm_set_action (alarm, E_CAL_COMPONENT_ALARM_AUDIO);
+
+  /* ONLY create "DISPLAY" alarm types. Don't expose "AUDIO" as an alarm type possibility for users to create;
+   * they're mutually independent from "DISPLAY" in RFC5545, and audio-only alarms are useless for users in practice.
+   * Furthermore, some other applications don't even allow creating/viewing/editing audio-only alarms on events!
+   * We should instead expect alarm notification systems to automatically play sounds when displaying notifications. */
+  e_cal_component_alarm_set_action (alarm, E_CAL_COMPONENT_ALARM_DISPLAY);
 
   return alarm;
 }