[banshee] SmartPlaylists: Let child sources decide if the parent can add them

[Bertrand Lorentz <blorentz src gnome org>]

commit 91a596b691473cbf752403898e39a360bcdbd522
Author: AndrÃs G. Aragoneses <knocte gmail com>
Date:   Sat Aug 27 13:40:05 2011 +0100

    SmartPlaylists: Let child sources decide if the parent can add them
    
    SmartPlaylists, when loaded from the database, are added to their
    parent source after they have been initialized, refreshed and
    reloaded. The consequence of this is that it was completely up
    to their parent if it was OK to add them as children of not.
    However SmartPlaylistSources can have an setting enabled called
    HiddenWhenEmpty, which is what the default/predefined smart
    playlists have activated to prevent polluting the UI (especially
    for new users that haven't imported anything yet), so this was
    not taken in account and causing BGO#657479.
    
    The alternative fix to this would be to just call Reload() on the
    playlist after it has been added to the parent, but that could cause
    extra overhead and this is a more elegant solution: returning bool for
    SetParentSource so children can veto their addition to the parent.
    
    We also get the side-benefit of having the "virtual" keyword on
    this method be actually useful, because before this commit,
    SmartPlaylistSource was the only derived class that was overriding
    it, but calling just the base method, so indeed not overriding it
    but having redundant and unnecessary code.
    
    Signed-off-by: Bertrand Lorentz <bertrand lorentz gmail com>

 .../Banshee.SmartPlaylist/SmartPlaylistSource.cs   |    6 +++++-
 .../Banshee.Services/Banshee.Sources/Source.cs     |   10 ++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)
---
diff --git a/src/Core/Banshee.Services/Banshee.SmartPlaylist/SmartPlaylistSource.cs b/src/Core/Banshee.Services/Banshee.SmartPlaylist/SmartPlaylistSource.cs
index 686974a..4200d46 100644
--- a/src/Core/Banshee.Services/Banshee.SmartPlaylist/SmartPlaylistSource.cs
+++ b/src/Core/Banshee.Services/Banshee.SmartPlaylist/SmartPlaylistSource.cs
@@ -512,9 +512,13 @@ namespace Banshee.SmartPlaylist
             }
         }
 
-        public override void SetParentSource (Source parent)
+        public override bool SetParentSource (Source parent)
         {
             base.SetParentSource (parent);
+            if (IsHiddenWhenEmpty && Count == 0) {
+                return false;
+            }
+            return true;
         }
 
 #endregion
diff --git a/src/Core/Banshee.Services/Banshee.Sources/Source.cs b/src/Core/Banshee.Services/Banshee.Sources/Source.cs
index 867748f..20645b0 100644
--- a/src/Core/Banshee.Services/Banshee.Sources/Source.cs
+++ b/src/Core/Banshee.Services/Banshee.Sources/Source.cs
@@ -190,9 +190,10 @@ namespace Banshee.Sources
             get { return SourceMergeType.None; }
         }
 
-        public virtual void SetParentSource (Source parent)
+        public virtual bool SetParentSource (Source parent)
         {
             this.parent = parent;
+            return true;
         }
 
         public virtual bool ContainsChildSource (Source child)
@@ -206,9 +207,10 @@ namespace Banshee.Sources
         {
             lock (Children) {
                 if (!child_sources.Contains (child)) {
-                    child.SetParentSource (this);
-                    child_sources.Add (child);
-                    OnChildSourceAdded (child);
+                    if (child.SetParentSource (this)) {
+                        child_sources.Add (child);
+                        OnChildSourceAdded (child);
+                    }
                 }
             }
         }