private static void ChildrenPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// The first change to the default value of a mutable collection property (e.g. GeometryGroup.Children)
// will promote the property value from a default value to a local value. This is technically a sub-property
// change because the collection was changed and not a new collection set (GeometryGroup.Children.
// Add versus GeometryGroup.Children = myNewChildrenCollection). However, we never marshalled
// the default value to the compositor. If the property changes from a default value, the new local value
// needs to be marshalled to the compositor. We detect this scenario with the second condition
// e.OldValueSource != e.NewValueSource. Specifically in this scenario the OldValueSource will be
// Default and the NewValueSource will be Local.
if (e.IsASubPropertyChange &&
(e.OldValueSource == e.NewValueSource))
{
return;
}
GeometryGroup target = ((GeometryGroup)d);
// If this is both non-null and mutable, we need to unhook the Changed event.
GeometryCollection oldCollection = null;
GeometryCollection newCollection = null;
if ((e.OldValueSource != BaseValueSourceInternal.Default) || e.IsOldValueModified)
{
oldCollection = (GeometryCollection)e.OldValue;
if ((oldCollection != null) && !oldCollection.IsFrozen)
{
oldCollection.ItemRemoved -= target.ChildrenItemRemoved;
oldCollection.ItemInserted -= target.ChildrenItemInserted;
}
}
// If this is both non-null and mutable, we need to hook the Changed event.
if ((e.NewValueSource != BaseValueSourceInternal.Default) || e.IsNewValueModified)
{
newCollection = (GeometryCollection)e.NewValue;
if ((newCollection != null) && !newCollection.IsFrozen)
{
newCollection.ItemInserted += target.ChildrenItemInserted;
newCollection.ItemRemoved += target.ChildrenItemRemoved;
}
}
if (oldCollection != newCollection && target.Dispatcher != null)
{
using (CompositionEngineLock.Acquire())
{
DUCE.IResource targetResource = (DUCE.IResource)target;
int channelCount = targetResource.GetChannelCount();
for (int channelIndex = 0; channelIndex < channelCount; channelIndex++)
{
DUCE.Channel channel = targetResource.GetChannel(channelIndex);
Debug.Assert(!channel.IsOutOfBandChannel);
Debug.Assert(!targetResource.GetHandle(channel).IsNull);
// resource shouldn't be null because
// 1) If the field is one of our collections, we don't allow null elements
// 2) Codegen already made sure the collection contains DUCE.IResources
// ... so we'll Assert it
if (newCollection != null)
{
int count = newCollection.Count;
for (int i = 0; i < count; i++)
{
DUCE.IResource resource = newCollection.Internal_GetItem(i) as DUCE.IResource;
Debug.Assert(resource != null);
resource.AddRefOnChannel(channel);
}
}
if (oldCollection != null)
{
int count = oldCollection.Count;
for (int i = 0; i < count; i++)
{
DUCE.IResource resource = oldCollection.Internal_GetItem(i) as DUCE.IResource;
Debug.Assert(resource != null);
resource.ReleaseOnChannel(channel);
}
}
}
}
}
target.PropertyChanged(ChildrenProperty);
}
internal override bool IsObviouslyEmpty()
{
GeometryCollection children = Children;
return((children == null) || (children.Count == 0));
}
