event-popover: Set better default focus widget

When mapped, move focus to either the first meeting row - if any - or
to the edit button.

Closes https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/980

src/gui/gcal-event-popover.c

@@ -558,6 +558,28 @@ on_time_format_changed_cb (GcalEventPopover *self)
 }
 
 
+/*
+ * GtkWidget overrides
+ */
+
+static void
+gcal_event_popover_map (GtkWidget *widget)
+{
+  GcalEventPopover *self = (GcalEventPopover *) widget;
+  GtkListBoxRow *first_meeting_row;
+
+  GTK_WIDGET_CLASS (gcal_event_popover_parent_class)->map (widget);
+
+  first_meeting_row = gtk_list_box_get_row_at_index (self->meetings_listbox, 0);
+  g_message ("Meeting row: %p (%s)", first_meeting_row, first_meeting_row ? G_OBJECT_TYPE_NAME (first_meeting_row) : "none");
+
+  if (first_meeting_row)
+    gtk_widget_grab_focus (GTK_WIDGET (first_meeting_row));
+  else
+    gtk_widget_grab_focus (self->edit_button);
+}
+
+
 /*
  * GObject overrides
  */
@@ -636,6 +658,8 @@ gcal_event_popover_class_init (GcalEventPopoverClass *klass)
   object_class->get_property = gcal_event_popover_get_property;
   object_class->set_property = gcal_event_popover_set_property;
 
+  widget_class->map = gcal_event_popover_map;
+
   /**
    * GcalEventPopover::context:
    *