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)); }