[libgee] Improve the read-only view property by using weak pointers

[Didier 'Ptitjes' Villevalois <dvillevalois src gnome org>]

commit 75b5e11db8559694869bb97e0042f5342282d692
Author: Julien Peeters <contact julienpeeters fr>
Date:   Thu Sep 10 18:15:13 2009 +0200

    Improve the read-only view property by using weak pointers
    
    Fixes bug 594758.
    
    By using weak pointers the read-only view is destroyed when there is no
    references to it anymore.

 gee/abstractcollection.vala       |   11 +++++++----
 gee/abstractlist.vala             |   11 ++++++++---
 gee/abstractmap.vala              |   11 +++++++----
 gee/abstractset.vala              |   11 ++++++++---
 gee/collection.vala               |    2 +-
 gee/list.vala                     |    2 +-
 gee/map.vala                      |    2 +-
 gee/readonlycollection.vala       |    2 +-
 gee/readonlylist.vala             |    2 +-
 gee/readonlymap.vala              |    2 +-
 gee/readonlyset.vala              |    2 +-
 gee/set.vala                      |    2 +-
 tests/testreadonlycollection.vala |   10 ++++++++++
 13 files changed, 48 insertions(+), 22 deletions(-)
---
diff --git a/gee/abstractcollection.vala b/gee/abstractcollection.vala
index 2acf92c..2ff78f1 100644
--- a/gee/abstractcollection.vala
+++ b/gee/abstractcollection.vala
@@ -143,17 +143,20 @@ public abstract class Gee.AbstractCollection<G> : Object, Iterable<G>, Collectio
 	 */
 	public abstract Iterator<G> iterator ();
 
-	protected Collection<G> _read_only_view;
+	private weak Collection<G> _read_only_view;
 
 	/**
 	 * @inheritDoc
 	 */
 	public virtual Collection<G> read_only_view {
-		get {
+		owned get {
+			Collection<G> instance = _read_only_view;
 			if (_read_only_view == null) {
-				_read_only_view = new ReadOnlyCollection<G> (this);
+				instance = new ReadOnlyCollection<G> (this);
+				_read_only_view = instance;
+				instance.add_weak_pointer (&_read_only_view);
 			}
-			return _read_only_view;
+			return instance;
 		}
 	}
 }
diff --git a/gee/abstractlist.vala b/gee/abstractlist.vala
index dc57958..da70499 100644
--- a/gee/abstractlist.vala
+++ b/gee/abstractlist.vala
@@ -95,15 +95,20 @@ public abstract class Gee.AbstractList<G> : Gee.AbstractCollection<G>, List<G> {
 		TimSort<G>.sort (this, compare);
 	}
 
+	private weak List<G> _read_only_view;
+
 	/**
 	 * @inheritDoc
 	 */
 	public virtual new List<G> read_only_view {
-		get {
+		owned get {
+			List<G> instance = _read_only_view;
 			if (_read_only_view == null) {
-				_read_only_view = new ReadOnlyList<G> (this);
+				instance = new ReadOnlyList<G> (this);
+				_read_only_view = instance;
+				instance.add_weak_pointer (&_read_only_view);
 			}
-			return _read_only_view as List<G>;
+			return instance;
 		}
 	}
 }
diff --git a/gee/abstractmap.vala b/gee/abstractmap.vala
index 0666fbe..25f702c 100644
--- a/gee/abstractmap.vala
+++ b/gee/abstractmap.vala
@@ -111,17 +111,20 @@ public abstract class Gee.AbstractMap<K,V> : Object, Map<K,V> {
 		return true;
 	}
 
-	protected Map<K,V> _read_only_view;
+	private weak Map<K,V> _read_only_view;
 
 	/**
 	 * @inheritDoc
 	 */
 	public virtual Map<K,V> read_only_view {
-		get {
+		owned get {
+			Map<K,V> instance = _read_only_view;
 			if (_read_only_view == null) {
-				_read_only_view = new ReadOnlyMap<K,V> (this);
+				instance = new ReadOnlyMap<K,V> (this);
+				_read_only_view = instance;
+				instance.add_weak_pointer (&_read_only_view);
 			}
-			return _read_only_view;
+			return instance;
 		}
 	}
 
diff --git a/gee/abstractset.vala b/gee/abstractset.vala
index a9177ec..850257e 100644
--- a/gee/abstractset.vala
+++ b/gee/abstractset.vala
@@ -31,15 +31,20 @@
  */
 public abstract class Gee.AbstractSet<G> : Gee.AbstractCollection<G>, Set<G> {
 
+	private weak Set<G> _read_only_view;
+
 	/**
 	 * @inheritDoc
 	 */
 	public virtual new Set<G> read_only_view {
-		get {
+		owned get {
+			Set<G> instance = _read_only_view;
 			if (_read_only_view == null) {
-				_read_only_view = new ReadOnlySet<G> (this);
+				instance = new ReadOnlySet<G> (this);
+				_read_only_view = instance;
+				instance.add_weak_pointer (&_read_only_view);
 			}
-			return _read_only_view as Set<G>;
+			return instance;
 		}
 	}
 }
diff --git a/gee/collection.vala b/gee/collection.vala
index b506e6a..d70da7a 100644
--- a/gee/collection.vala
+++ b/gee/collection.vala
@@ -125,6 +125,6 @@ public interface Gee.Collection<G> : Iterable<G> {
 	/**
 	 * Property giving access to the read-only view of this collection.
 	 */
-	public abstract Collection<G> read_only_view { get; }
+	public abstract Collection<G> read_only_view { owned get; }
 }
 
diff --git a/gee/list.vala b/gee/list.vala
index 4c00223..29f1734 100644
--- a/gee/list.vala
+++ b/gee/list.vala
@@ -109,6 +109,6 @@ public interface Gee.List<G> : Collection<G> {
 	/**
 	 * Property giving access to the read-only view of this list.
 	 */
-	public abstract new List<G> read_only_view { get; }
+	public abstract new List<G> read_only_view { owned get; }
 }
 
diff --git a/gee/map.vala b/gee/map.vala
index 1e53198..40d25f3 100644
--- a/gee/map.vala
+++ b/gee/map.vala
@@ -116,6 +116,6 @@ public interface Gee.Map<K,V> : GLib.Object {
 	/**
 	 * Property giving access to the read-only view this map.
 	 */
-	public abstract Map<K,V> read_only_view { get; }
+	public abstract Map<K,V> read_only_view { owned get; }
 }
 
diff --git a/gee/readonlycollection.vala b/gee/readonlycollection.vala
index 11c3bb1..b29f914 100644
--- a/gee/readonlycollection.vala
+++ b/gee/readonlycollection.vala
@@ -147,7 +147,7 @@ internal class Gee.ReadOnlyCollection<G> : Object, Iterable<G>, Collection<G> {
 	}
 
 	public virtual Collection<G> read_only_view {
-		get { return this; }
+		owned get { return this; }
 	}
 
 }
diff --git a/gee/readonlylist.vala b/gee/readonlylist.vala
index 46ac354..f29a790 100644
--- a/gee/readonlylist.vala
+++ b/gee/readonlylist.vala
@@ -117,7 +117,7 @@ internal class Gee.ReadOnlyList<G> : Gee.ReadOnlyCollection<G>, List<G> {
 	 * @inheritDoc
 	 */
 	public virtual new List<G> read_only_view {
-		get { return this; }
+		owned get { return this; }
 	}
 }
 
diff --git a/gee/readonlymap.vala b/gee/readonlymap.vala
index 1034cd5..180b941 100644
--- a/gee/readonlymap.vala
+++ b/gee/readonlymap.vala
@@ -129,7 +129,7 @@ internal class Gee.ReadOnlyMap<K,V> : Object, Map<K,V> {
 	}
 
 	public virtual Map<K,V> read_only_view {
-		get { return this; }
+		owned get { return this; }
 	}
 
 }
diff --git a/gee/readonlyset.vala b/gee/readonlyset.vala
index 0430d79..8b51503 100644
--- a/gee/readonlyset.vala
+++ b/gee/readonlyset.vala
@@ -43,7 +43,7 @@ internal class Gee.ReadOnlySet<G> : Gee.ReadOnlyCollection<G>, Set<G> {
 	}
 
 	public virtual new Set<G> read_only_view {
-		get { return this; }
+		owned get { return this; }
 	}
 
 }
diff --git a/gee/set.vala b/gee/set.vala
index 35a83d9..15e8ff6 100644
--- a/gee/set.vala
+++ b/gee/set.vala
@@ -28,7 +28,7 @@ public interface Gee.Set<G> : Collection<G> {
 	/**
 	 * Property giving access to the read-only view of this set.
 	 */
-	public abstract new Set<G> read_only_view { get; }
+	public abstract new Set<G> read_only_view { owned get; }
 
 }
 
diff --git a/tests/testreadonlycollection.vala b/tests/testreadonlycollection.vala
index eaa4af7..f18ee31 100644
--- a/tests/testreadonlycollection.vala
+++ b/tests/testreadonlycollection.vala
@@ -43,6 +43,16 @@ public abstract class ReadOnlyCollectionTests : Gee.TestCase {
 	public void test_unique_read_only_view_instance () {
 		var another_ro_collection = test_collection.read_only_view;
 		assert (ro_collection == another_ro_collection);
+
+		weak Collection<string> saved_instance = ro_collection;
+		long instance_address = (long) saved_instance;
+		assert (instance_address == (long) another_ro_collection);
+
+		another_ro_collection = null;
+		ro_collection = null;
+
+		another_ro_collection = test_collection.read_only_view;
+		assert (instance_address != (long) another_ro_collection);
 	}
 
 	public void test_add () {