event-editor/summary-section: Override grab_focus()

This will allow for a cleaner and more predictable focus behavior,
as this will give the capability to the dialog to grab focus
on either the "Done" button or summary section depending on the
writability, as opposed to the current approach, where the
summary section assumes that it is already writable and grabs focus,
which then the dialog sets focus on the "Done" button.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/782>

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

@@ -123,6 +123,19 @@ gcal_event_editor_section_iface_init (GcalEventEditorSectionInterface *iface)
 }
 
 
+/*
+ * GtkWidget overrides
+ */
+
+static gboolean
+gcal_summary_section_grab_focus (GtkWidget *widget)
+{
+  GcalSummarySection *self = GCAL_SUMMARY_SECTION (widget);
+
+  return gtk_widget_grab_focus (GTK_WIDGET (self->summary_entry));
+}
+
+
 /*
  * GObject overrides
  */
@@ -145,6 +158,8 @@ gcal_summary_section_class_init (GcalSummarySectionClass *klass)
 
   object_class->finalize = gcal_summary_section_finalize;
 
+  widget_class->grab_focus = gcal_summary_section_grab_focus;
+
   gtk_widget_class_set_template_from_resource (widget_class, "/org/gnome/calendar/ui/event-editor/gcal-summary-section.ui");
 
   gtk_widget_class_bind_template_child (widget_class, GcalSummarySection, location_entry);