[rygel] server, media-export: Add and use signals emitted after tracking child changes.

[Jens Georg <jensgeorg src gnome org>]

commit e99ef02d9318036f27a99a7f5db7977f192dafd7
Author: Krzesimir Nowak <krnowak openismus com>
Date:   Wed Feb 13 16:43:18 2013 +0100

    server,media-export: Add and use signals emitted after tracking child changes.
    
    child_added and child_removed are emitted when respectively
    add_child_tracked and remove_child_tracked are finished. We use those
    signals in media-export to store the container and, optionally, its
    new child in the database. That simplifies a code a bit in
    media-export and makes sure that update IDs are stored in database as
    well.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=693577

 src/librygel-server/rygel-trackable-container.vala |    4 ++
 .../media-export/rygel-media-export-harvester.vala |    6 +---
 .../rygel-media-export-harvesting-task.vala        |   13 +-------
 .../rygel-media-export-trackable-db-container.vala |   32 ++++++++++++++++++++
 4 files changed, 39 insertions(+), 16 deletions(-)
---
diff --git a/src/librygel-server/rygel-trackable-container.vala 
b/src/librygel-server/rygel-trackable-container.vala
index 5ccc141..5c1283e 100644
--- a/src/librygel-server/rygel-trackable-container.vala
+++ b/src/librygel-server/rygel-trackable-container.vala
@@ -51,6 +51,8 @@ public interface Rygel.TrackableContainer : Rygel.MediaContainer {
      * See the remove_child() virtual function.
      */
     protected abstract async void add_child (MediaObject object);
+    protected signal void child_added (MediaObject object);
+    protected signal void child_removed (MediaObject object);
 
     /**
      * Add a child object, emitting the #RygelContainer::container_updated signal
@@ -70,6 +72,7 @@ public interface Rygel.TrackableContainer : Rygel.MediaContainer {
             // Release the events that might have accumulated
             trackable.thaw_events ();
         }
+        this.child_added (object);
     }
 
     /**
@@ -101,6 +104,7 @@ public interface Rygel.TrackableContainer : Rygel.MediaContainer {
         // FIXME: Check if modification of child_count should lead to
         // LastChange event.
         this.updated ();
+        this.child_removed (object);
     }
 
     /**
diff --git a/src/plugins/media-export/rygel-media-export-harvester.vala 
b/src/plugins/media-export/rygel-media-export-harvester.vala
index 557113d..7732dc6 100644
--- a/src/plugins/media-export/rygel-media-export-harvester.vala
+++ b/src/plugins/media-export/rygel-media-export-harvester.vala
@@ -230,11 +230,7 @@ internal class Rygel.MediaExport.Harvester : GLib.Object {
                 parent = object.parent;
                 if (parent is TrackableContainer) {
                     var container = parent as TrackableContainer;
-                    container.remove_child_tracked.begin (object, () => {
-                        try {
-                            cache.save_container (container);
-                        } catch (Error error) { }
-                    });
+                    container.remove_child_tracked.begin (object);
                 }
                 if (parent == null) {
                     break;
diff --git a/src/plugins/media-export/rygel-media-export-harvesting-task.vala 
b/src/plugins/media-export/rygel-media-export-harvesting-task.vala
index a2e2e8f..f34a6c4 100644
--- a/src/plugins/media-export/rygel-media-export-harvesting-task.vala
+++ b/src/plugins/media-export/rygel-media-export-harvesting-task.vala
@@ -326,12 +326,7 @@ public class Rygel.MediaExport.HarvestingTask : Rygel.StateMachine,
                 (item as UpdatableObject).commit.begin ();
             } else {
                 var container = item.parent as TrackableContainer;
-                container.add_child_tracked.begin (item, () => {
-                    // save again to make sure we persist the update count
-                    try {
-                        cache.save_item (item);
-                    } catch (Error error) { }
-                }) ;
+                container.add_child_tracked.begin (item) ;
             }
         }
 
@@ -372,11 +367,7 @@ public class Rygel.MediaExport.HarvestingTask : Rygel.StateMachine,
             try {
                 if (cache.get_child_count (container.id) == 0) {
                     var parent = container.parent as TrackableContainer;
-                    parent.remove_child_tracked.begin (container, () => {
-                        try {
-                            cache.save_container (parent);
-                        } catch (Error error) { }
-                    });
+                    parent.remove_child_tracked.begin (container);
                 }
             } catch (Error error) { }
             this.containers.pop_head ();
diff --git a/src/plugins/media-export/rygel-media-export-trackable-db-container.vala 
b/src/plugins/media-export/rygel-media-export-trackable-db-container.vala
index aac9a35..7f9dd5a 100644
--- a/src/plugins/media-export/rygel-media-export-trackable-db-container.vala
+++ b/src/plugins/media-export/rygel-media-export-trackable-db-container.vala
@@ -33,6 +33,38 @@ public class Rygel.MediaExport.TrackableDbContainer : DBContainer,
                 child_count : 0);
     }
 
+    public override void constructed () {
+        base.constructed ();
+
+        this.child_added.connect (on_child_added);
+        this.child_removed.connect (on_child_removed);
+    }
+
+    private void on_child_added (MediaObject object) {
+        try {
+            var cache = this.media_db;
+
+            if (object is MediaItem) {
+                cache.save_item (object as MediaItem);
+            } else if (object is MediaContainer) {
+                 cache.save_container (object as MediaContainer);
+            } else {
+                assert_not_reached ();
+            }
+            cache.save_container (this);
+        } catch (Error error) {
+            warning ("Failed to save object: %s", error.message);
+        }
+    }
+
+    private void on_child_removed (MediaObject object) {
+        try {
+            this.media_db.save_container (this);
+        } catch (Error error) {
+            warning ("Failed to save object: %s", error.message);
+        }
+    }
+
     // TrackableContainer virtual function implementations:
     protected async void add_child (MediaObject object) {
         try {