window: block automatic creation of nameless events

We shouldn't let nameless events be created.
This commit blocks all ways to create them
when the name is not set.

The user can still edit events' data.

data/ui/window.ui

@@ -367,6 +367,7 @@
                 <property name="visible">True</property>
                 <property name="can_focus">True</property>
                 <property name="receives_default">True</property>
+                <property name="sensitive">False</property>
                 <signal name="clicked" handler="create_event" object="GcalWindow" swapped="yes"/>
                 <style>
                   <class name="suggested-action"/>
@@ -396,6 +397,7 @@
                 <property name="can_focus">True</property>
                 <property name="hexpand">True</property>
                 <signal name="activate" handler="create_event" object="GcalWindow" swapped="yes"/>
+                <signal name="notify::text" handler="new_event_entry_text_changed" object="GcalWindow" swapped="yes"/>
               </object>
               <packing>
                 <property name="left_attach">0</property>

src/gcal-window.c

@@ -168,6 +168,10 @@ static void           place_new_event_widget             (GcalWindow          *w
 static void           close_new_event_widget             (GtkButton           *button,
                                                           gpointer             user_data);
 
+static void           new_event_entry_text_changed       (GObject             *object,
+                                                          GParamSpec          *pspec,
+                                                          gpointer             user_data);
+
 static void           create_notification                (GcalWindow          *window,
                                                           gchar               *message,
                                                           gchar               *button_label);
@@ -673,6 +677,34 @@ close_new_event_widget (GtkButton *button,
   set_new_event_mode (GCAL_WINDOW (user_data), FALSE);
 }
 
+static void
+new_event_entry_text_changed (GObject    *object,
+                              GParamSpec *pspec,
+                              gpointer    user_data)
+{
+  GcalWindowPrivate *priv;
+  static gboolean blocked = TRUE;
+  gint length;
+
+  g_return_if_fail (user_data);
+  priv = gcal_window_get_instance_private (GCAL_WINDOW (object));
+
+  length = g_utf8_strlen (gtk_entry_get_text (GTK_ENTRY (user_data)), -1);
+
+  gtk_widget_set_sensitive (priv->new_event_create_button, length > 0);
+
+  if (length > 0 && blocked)
+    {
+      g_signal_handlers_unblock_by_func (user_data, create_event, object);
+      blocked = FALSE;
+    }
+  else if (length < 1 && !blocked)
+    {
+      g_signal_handlers_block_by_func (user_data, create_event, object);
+      blocked = TRUE;
+    }
+}
+
 /**
  * create_notification: Internal method for creating a notification
  * @window:
@@ -1292,6 +1324,7 @@ gcal_window_class_init(GcalWindowClass *klass)
   gtk_widget_class_bind_template_callback (widget_class, create_event_detailed_cb);
   gtk_widget_class_bind_template_callback (widget_class, show_new_event_widget);
   gtk_widget_class_bind_template_callback (widget_class, close_new_event_widget);
+  gtk_widget_class_bind_template_callback (widget_class, new_event_entry_text_changed);
   gtk_widget_class_bind_template_callback (widget_class, event_activated);
 
   /* Syncronization related */
@@ -1335,6 +1368,8 @@ gcal_window_constructed (GObject *object)
   g_free (clock_format);
   g_object_unref (helper_settings);
 
+  // Prevents nameless events' creation
+  g_signal_handlers_block_by_func (priv->new_event_what_entry, create_event, object);
 
   /* header_bar: menu */
   builder = gtk_builder_new ();