[gnome-photos] application: Add API to prevent the main window from getting destroyed

[Debarshi Ray <debarshir src gnome org>]

commit 45cca03a9d3ab08973d0062b2166d4db8414935c
Author: Debarshi Ray <debarshir gnome org>
Date:   Fri Apr 22 20:00:21 2016 +0200

    application: Add API to prevent the main window from getting destroyed
    
    We don't want the application to shut down while certain critical
    asynchronous operations are in flight. eg., saving the pipeline or
    deleting an item.
    
    The problem with g_application_hold is that it doesn't prevent the
    main window from getting destroyed, and some of the callbacks of
    these operations expect the widget hierarchy to be in place. While we
    can try to make things more robust on a case by case basis, it will be
    hard to ensure that all corner cases have been covered.
    
    It is much safer to temporarily override the default
    GtkWidget::delete-event handler to only hide the PhotosMainWindow
    instead of destroying it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=764076

 src/photos-application.c |   43 +++++++++++++++++++++++++++++++++++++++++++
 src/photos-application.h |    4 ++++
 2 files changed, 47 insertions(+), 0 deletions(-)
---
diff --git a/src/photos-application.c b/src/photos-application.c
index 68d3eae..4b1368c 100644
--- a/src/photos-application.c
+++ b/src/photos-application.c
@@ -104,7 +104,9 @@ struct _PhotosApplication
   PhotosSearchProvider *search_provider;
   PhotosSelectionController *sel_cntrlr;
   TrackerExtractPriority *extract_priority;
+  gboolean main_window_deleted;
   guint create_miners_count;
+  guint use_count;
   guint32 activation_timestamp;
   gulong source_added_id;
   gulong source_removed_id;
@@ -420,6 +422,20 @@ photos_application_tracker_clear_rdf_types (GObject *source_object, GAsyncResult
 }
 
 
+static gboolean
+photos_application_delete_event (PhotosApplication *self)
+{
+  gboolean ret_val = GDK_EVENT_PROPAGATE;
+
+  self->main_window_deleted = TRUE;
+
+  if (self->use_count > 0)
+    ret_val = gtk_widget_hide_on_delete (self->main_window);
+
+  return ret_val;
+}
+
+
 static void
 photos_application_destroy (PhotosApplication *self)
 {
@@ -615,8 +631,15 @@ photos_application_create_window (PhotosApplication *self)
   g_return_val_if_fail (photos_application_sanity_check_gegl (self), FALSE);
 
   self->main_window = photos_main_window_new (GTK_APPLICATION (self));
+  g_signal_connect_object (self->main_window,
+                           "delete-event",
+                           G_CALLBACK (photos_application_delete_event),
+                           self,
+                           G_CONNECT_AFTER | G_CONNECT_SWAPPED);
   g_signal_connect_swapped (self->main_window, "destroy", G_CALLBACK (photos_application_destroy), self);
 
+  self->main_window_deleted = FALSE;
+
   g_application_hold (G_APPLICATION (self));
   tracker_extract_priority_proxy_new_for_bus (G_BUS_TYPE_SESSION,
                                               G_DBUS_PROXY_FLAGS_NONE,
@@ -1767,3 +1790,23 @@ photos_application_get_scale_factor (PhotosApplication *self)
  out:
   return ret_val;
 }
+
+
+void
+photos_application_hold (PhotosApplication *self)
+{
+  g_return_if_fail (PHOTOS_IS_APPLICATION (self));
+  self->use_count++;
+}
+
+
+void
+photos_application_release (PhotosApplication *self)
+{
+  g_return_if_fail (PHOTOS_IS_APPLICATION (self));
+  g_return_if_fail (self->use_count > 0);
+
+  self->use_count--;
+  if (self->main_window_deleted && self->use_count == 0)
+    gtk_widget_destroy (self->main_window);
+}
diff --git a/src/photos-application.h b/src/photos-application.h
index caaa28e..f77a147 100644
--- a/src/photos-application.h
+++ b/src/photos-application.h
@@ -50,6 +50,10 @@ GList                 *photos_application_get_miners_running     (PhotosApplicat
 
 gint                   photos_application_get_scale_factor       (PhotosApplication *self);
 
+void                   photos_application_hold                   (PhotosApplication *self);
+
+void                   photos_application_release                (PhotosApplication *self);
+
 G_END_DECLS
 
 #endif /* PHOTOS_APPLICATION_H */