Fixed: memory leak in CPComboBox

Previously, when assigning a listDelegate to a CPComboBox, we never deleted the observers added by this method. Now we add and delete these observers in the method addObservers and removeObservers.

This PR fix another issue. Previously, the behavior of the panel of the comboBox wasn't the same as the one in Cocoa. Now, when closing the panel, the hit view won't be the first responder as it was. Cocoa works like this as well.

AppKit/CPComboBox.j

@@ -160,7 +160,7 @@ var CPComboBoxTextSubview = @"text",
 
 - (void)setIntercellSpacing:(CGSize)aSize
 {
-    if (_intercellSpacing && CGSizeEqualToSize(aSize, _intercellSpacing))
+    if (!aSize || (_intercellSpacing && CGSizeEqualToSize(aSize, _intercellSpacing)))
         return;
 
     _intercellSpacing = aSize;
@@ -396,49 +396,53 @@ var CPComboBoxTextSubview = @"text",
     if (_listDelegate === aDelegate)
         return;
 
-    var defaultCenter = [CPNotificationCenter defaultCenter];
-
-    if (_listDelegate)
-    {
-        [defaultCenter removeObserver:self name:_CPPopUpListWillPopUpNotification object:_listDelegate];
-        [defaultCenter removeObserver:self name:_CPPopUpListWillDismissNotification object:_listDelegate];
-        [defaultCenter removeObserver:self name:_CPPopUpListDidDismissNotification object:_listDelegate];
-        [defaultCenter removeObserver:self name:_CPPopUpListItemWasClickedNotification object:_listDelegate];
-
-        var oldTableView = [_listDelegate tableView];
-
-        if (oldTableView)
-        {
-            [defaultCenter removeObserver:self name:CPTableViewSelectionIsChangingNotification object:oldTableView];
-            [defaultCenter removeObserver:self name:CPTableViewSelectionDidChangeNotification object:oldTableView];
-        }
-    }
+    [self _removeObserversForListDelegate:_listDelegate];
 
     _listDelegate = aDelegate;
 
+    // We only add the observers if the CPComboBox is displayed
+    if ([self window])
+        [self _addObserversForListDelegate:_listDelegate]
+
+    // Apply our text style to the list
+    [_listDelegate setFont:[self font]];
+    [_listDelegate setAlignment:[self alignment]];
+
+    [self setHasVerticalScroller:_hasVerticalScroller];
+    [self setIntercellSpacing:_intercellSpacing];
+    [self setItemHeight:_itemHeight];
+}
+
+- (void)_addObserversForListDelegate:(_CPPopUpList)aDelegate
+{
+    if (!aDelegate)
+        return;
+
+    var defaultCenter = [CPNotificationCenter defaultCenter];
+
     [defaultCenter addObserver:self
                       selector:@selector(comboBoxWillPopUp:)
                           name:_CPPopUpListWillPopUpNotification
-                        object:_listDelegate];
+                        object:aDelegate];
 
     [defaultCenter addObserver:self
                       selector:@selector(comboBoxWillDismiss:)
                           name:_CPPopUpListWillDismissNotification
-                        object:_listDelegate];
+                        object:aDelegate];
 
     [defaultCenter addObserver:self
                       selector:@selector(listDidDismiss:)
                           name:_CPPopUpListDidDismissNotification
-                        object:_listDelegate];
+                        object:aDelegate];
 
     [defaultCenter addObserver:self
                       selector:@selector(itemWasClicked:)
                           name:_CPPopUpListItemWasClickedNotification
-                        object:_listDelegate];
+                        object:aDelegate];
 
-    [[_listDelegate scrollView] setHasVerticalScroller:_hasVerticalScroller];
+    [[aDelegate scrollView] setHasVerticalScroller:_hasVerticalScroller];
 
-    var tableView = [_listDelegate tableView];
+    var tableView = [aDelegate tableView];
 
     [defaultCenter addObserver:self
                       selector:@selector(comboBoxSelectionIsChanging:)
@@ -449,13 +453,27 @@ var CPComboBoxTextSubview = @"text",
                       selector:@selector(comboBoxSelectionDidChange:)
                           name:CPTableViewSelectionDidChangeNotification
                         object:tableView];
+}
 
-    // Apply our text style to the list
-    [_listDelegate setFont:[self font]];
-    [_listDelegate setAlignment:[self alignment]];
-    [[_listDelegate scrollView] setHasVerticalScroller:_hasVerticalScroller];
-    [[_listDelegate tableView] setIntercellSpacing:_intercellSpacing];
-    [[_listDelegate tableView] setRowHeight:_itemHeight];
+- (void)_removeObserversForListDelegate:(_CPPopUpList)aDelegate
+{
+    if (!aDelegate)
+        return;
+
+    var defaultCenter = [CPNotificationCenter defaultCenter];
+
+    [defaultCenter removeObserver:self name:_CPPopUpListWillPopUpNotification object:aDelegate];
+    [defaultCenter removeObserver:self name:_CPPopUpListWillDismissNotification object:aDelegate];
+    [defaultCenter removeObserver:self name:_CPPopUpListDidDismissNotification object:aDelegate];
+    [defaultCenter removeObserver:self name:_CPPopUpListItemWasClickedNotification object:aDelegate];
+
+    var oldTableView = [aDelegate tableView];
+
+    if (oldTableView)
+    {
+        [defaultCenter removeObserver:self name:CPTableViewSelectionIsChangingNotification object:oldTableView];
+        [defaultCenter removeObserver:self name:CPTableViewSelectionDidChangeNotification object:oldTableView];
+    }
 }
 
 - (int)indexOfItemWithObjectValue:(id)anObject
@@ -982,6 +1000,28 @@ var CPComboBoxTextSubview = @"text",
     }
 }
 
+
+#pragma mark -
+#pragma mark Observers method
+
+- (void)_addObservers
+{
+    if (_isObserving)
+        return;
+
+    [super _addObservers];
+    [self _addObserversForListDelegate:_listDelegate];
+}
+
+- (void)_removeObservers
+{
+    if (!_isObserving)
+        return;
+
+    [super _removeObservers];
+    [self _removeObserversForListDelegate:_listDelegate];
+}
+
 @end
 
 @implementation CPComboBox (CPComboBoxDelegate)