Fixes #418

src/Myra/Attributes/SkipSaveAttribute.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace Myra.Attributes
+{
+	/// <summary>
+	/// Determines that property shouldn't be saved during MML serialization
+	/// </summary>
+	[AttributeUsage(AttributeTargets.Property)]
+	public class SkipSaveAttribute: Attribute
+	{
+	}
+}

src/Myra/Graphics2D/UI/Containers/Grid.cs

@@ -28,10 +28,14 @@ public enum GridSelectionMode
 
 	public class Grid : MultipleItemsContainerBase
 	{
-		public static AttachedPropertyInfo<int> ColumnProperty = AttachedPropertiesRegistry.Create(typeof(Grid), "Column", 0);
-		public static AttachedPropertyInfo<int> RowProperty = AttachedPropertiesRegistry.Create(typeof(Grid), "Row", 0);
-		public static AttachedPropertyInfo<int> ColumnSpanProperty = AttachedPropertiesRegistry.Create(typeof(Grid), "ColumnSpan", 1);
-		public static AttachedPropertyInfo<int> RowSpanProperty = AttachedPropertiesRegistry.Create(typeof(Grid), "RowSpan", 1);
+		public static readonly AttachedPropertyInfo<int> ColumnProperty = 
+			AttachedPropertiesRegistry.Create(typeof(Grid), "Column", 0, AttachedPropertyOption.AffectsArrange);
+		public static readonly AttachedPropertyInfo<int> RowProperty = 
+			AttachedPropertiesRegistry.Create(typeof(Grid), "Row", 0, AttachedPropertyOption.AffectsArrange);
+		public static readonly AttachedPropertyInfo<int> ColumnSpanProperty = 
+			AttachedPropertiesRegistry.Create(typeof(Grid), "ColumnSpan", 1, AttachedPropertyOption.AffectsArrange);
+		public static readonly AttachedPropertyInfo<int> RowSpanProperty = 
+			AttachedPropertiesRegistry.Create(typeof(Grid), "RowSpan", 1, AttachedPropertyOption.AffectsArrange);
 
 		private readonly GridLayout _layout = new GridLayout();
 

src/Myra/Graphics2D/UI/Containers/StackPanel.cs

@@ -1,9 +1,14 @@
-using System.Collections.ObjectModel;
+using System;
+using System.Collections.ObjectModel;
 using System.ComponentModel;
+using System.ComponentModel.DataAnnotations;
 using System.Xml.Serialization;
 
 #if MONOGAME || FNA
 using Microsoft.Xna.Framework;
+using Myra.Attributes;
+using Myra.MML;
+
 #elif STRIDE
 using Stride.Core.Mathematics;
 #else
@@ -12,9 +17,17 @@
 
 namespace Myra.Graphics2D.UI
 {
-	public abstract class StackPanel: MultipleItemsContainerBase
+	public abstract class StackPanel : MultipleItemsContainerBase
 	{
+		public static readonly AttachedPropertyInfo<ProportionType> ProportionTypeProperty =
+			AttachedPropertiesRegistry.Create(typeof(StackPanel), "ProportionType", ProportionType.Auto, AttachedPropertyOption.AffectsMeasure);
+		public static readonly AttachedPropertyInfo<float> ProportionValueProperty =
+			AttachedPropertiesRegistry.Create(typeof(StackPanel), "ProportionValue", 1.0f, AttachedPropertyOption.AffectsMeasure);
+
+
+		private readonly ObservableCollection<Proportion> _proportions = new ObservableCollection<Proportion>();
 		private readonly GridLayout _layout = new GridLayout();
+		private bool _childrenDirty = true;
 		private int _spacing;
 
 		[Browsable(false)]
@@ -65,21 +78,38 @@ public Proportion DefaultProportion
 			}
 		}
 
-		[Browsable(false)]
-		public ObservableCollection<Proportion> Proportions
+		private ObservableCollection<Proportion> InternalProportions
 		{
 			get => Orientation == Orientation.Horizontal ? _layout.ColumnsProportions : _layout.RowsProportions;
 		}
 
+
+		[Browsable(false)]
+		[Obsolete("Use StackPanel.GetProportion/StackPanel.SetProportion")]
+		[SkipSave]
+		public ObservableCollection<Proportion> Proportions => _proportions;
+
 		protected StackPanel()
 		{
 			GridLinesColor = Color.White;
 			DefaultProportion = Proportion.StackPanelDefault;
+
+			_proportions.CollectionChanged += (s, e) => InvalidateChildren();
+		}
+
+		private void InvalidateChildren()
+		{
+			_childrenDirty = true;
 		}
 
-		protected override void InternalUpdateChildren()
+		protected void UpdateChildren()
 		{
-			base.InternalUpdateChildren();
+			if (!_childrenDirty)
+			{
+				return;
+			}
+
+			InternalProportions.Clear();
 
 			var index = 0;
 			foreach (var widget in Widgets)
@@ -93,18 +123,49 @@ protected override void InternalUpdateChildren()
 					Grid.SetRow(widget, index);
 				}
 
+				if (index < _proportions.Count)
+				{
+					var prop = _proportions[index];
+					SetProportionType(widget, prop.Type);
+					SetProportionValue(widget, prop.Value);
+				}
+
+				InternalProportions.Add(new Proportion(GetProportionType(widget), GetProportionValue(widget)));
+
 				++index;
 			}
+
+			_childrenDirty = false;
 		}
 
 		protected override Point InternalMeasure(Point availableSize)
 		{
+			UpdateChildren();
+
 			return _layout.Measure(Widgets, availableSize);
 		}
 
 		protected override void InternalArrange()
 		{
+			UpdateChildren();
+
 			_layout.Arrange(Widgets, ActualBounds);
 		}
+
+		public override void OnAttachedPropertyChanged(BaseAttachedPropertyInfo propertyInfo)
+		{
+			base.OnAttachedPropertyChanged(propertyInfo);
+
+			if (propertyInfo.Id == ProportionTypeProperty.Id ||
+				propertyInfo.Id == ProportionValueProperty.Id)
+			{
+				InvalidateChildren();
+			}
+		}
+
+		public static ProportionType GetProportionType(Widget widget) => ProportionTypeProperty.GetValue(widget);
+		public static void SetProportionType(Widget widget, ProportionType value) => ProportionTypeProperty.SetValue(widget, value);
+		public static float GetProportionValue(Widget widget) => ProportionValueProperty.GetValue(widget);
+		public static void SetProportionValue(Widget widget, float value) => ProportionValueProperty.SetValue(widget, value);
 	}
 }

src/Myra/Graphics2D/UI/Properties/PropertyGrid.cs

@@ -1338,7 +1338,6 @@ public void Rebuild()
 					hasSetter = false;
 				}
 
-
 				var record = new FieldRecord(field)
 				{
 					HasSetter = hasSetter,
@@ -1357,8 +1356,9 @@ public void Rebuild()
 				{
 					var record = new AttachedPropertyRecord(attachedProperty)
 					{
-						Category = ParentType.Name
+						Category = attachedProperty.OwnerType.Name
 					};
+
 					records.Add(record);
 				}
 			}

src/Myra/Graphics2D/UI/Widget.Children.cs

@@ -84,21 +84,15 @@ private void UpdateChildren()
 
 			_childrenCopy.SortWidgetsByZIndex();
 
-			InternalUpdateChildren();
-
 			_childrenDirty = false;
 		}
 
-		protected void InvalidateChildren()
+		private void InvalidateChildren()
 		{
 			InvalidateMeasure();
 			_childrenDirty = true;
 		}
 
-		protected virtual void InternalUpdateChildren()
-		{
-		}
-
 		public int CalculateTotalChildCount(bool visibleOnly)
 		{
 			var result = ChildrenCopy.Count;

src/Myra/MML/AttachedPropertiesRegistry.cs

@@ -5,15 +5,28 @@
 
 namespace Myra.MML
 {
+	public interface INotifyAttachedPropertyChanged
+	{
+		void OnAttachedPropertyChanged(BaseAttachedPropertyInfo propertyInfo);
+	}
+
+	public enum AttachedPropertyOption
+	{
+		None,
+		AffectsArrange,
+		AffectsMeasure,
+	}
+
 	public abstract class BaseAttachedPropertyInfo
 	{
 		public Type OwnerType { get; private set; }
 		public int Id { get; private set; }
 		public string Name { get; private set; }
+		public AttachedPropertyOption Option { get; private set; }
 		public abstract Type PropertyType { get; }
 		public abstract object DefaultValueObject { get; }
 
-		protected BaseAttachedPropertyInfo(int id, string name, Type ownerType)
+		protected BaseAttachedPropertyInfo(int id, string name, Type ownerType, AttachedPropertyOption option)
 		{
 			if (string.IsNullOrEmpty(name))
 			{
@@ -23,19 +36,21 @@ protected BaseAttachedPropertyInfo(int id, string name, Type ownerType)
 			OwnerType = ownerType ?? throw new ArgumentNullException(nameof(ownerType));
 			Name = name;
 			Id = id;
+			Option = option;
 		}
 
 		public abstract object GetValueObject(BaseObject obj);
 		public abstract void SetValueObject(BaseObject obj, object value);
 	}
 
-	public class AttachedPropertyInfo<T>: BaseAttachedPropertyInfo
+	public class AttachedPropertyInfo<T> : BaseAttachedPropertyInfo
 	{
 		public T DefaultValue { get; private set; }
 		public override Type PropertyType => typeof(T);
 		public override object DefaultValueObject => DefaultValue;
 
-		public AttachedPropertyInfo(int id, string name, Type ownerType, T defaultValue): base(id, name, ownerType)
+		public AttachedPropertyInfo(int id, string name, Type ownerType, T defaultValue, AttachedPropertyOption option) :
+			base(id, name, ownerType, option)
 		{
 			DefaultValue = defaultValue;
 		}
@@ -62,8 +77,20 @@ public void SetValue(BaseObject obj, T value)
 			var asWidget = obj as Widget;
 			if (asWidget != null)
 			{
-				asWidget.InvalidateMeasure();
+				switch (Option)
+				{
+					case AttachedPropertyOption.None:
+						break;
+					case AttachedPropertyOption.AffectsArrange:
+						asWidget.InvalidateArrange();
+						break;
+					case AttachedPropertyOption.AffectsMeasure:
+						asWidget.InvalidateMeasure();
+						break;
+				}
 			}
+
+			obj.OnAttachedPropertyChanged(this);
 		}
 
 		public override object GetValueObject(BaseObject widget) => GetValue(widget);
@@ -76,9 +103,9 @@ public static class AttachedPropertiesRegistry
 		private static readonly Dictionary<int, BaseAttachedPropertyInfo> _properties = new Dictionary<int, BaseAttachedPropertyInfo>();
 		private static readonly Dictionary<Type, BaseAttachedPropertyInfo[]> _propertiesByType = new Dictionary<Type, BaseAttachedPropertyInfo[]>();
 
-		public static AttachedPropertyInfo<T> Create<T>(Type type, string name, T defaultValue)
+		public static AttachedPropertyInfo<T> Create<T>(Type type, string name, T defaultValue, AttachedPropertyOption option)
 		{
-			var result = new AttachedPropertyInfo<T>(_properties.Count, name, type, defaultValue);
+			var result = new AttachedPropertyInfo<T>(_properties.Count, name, type, defaultValue, option);
 			_properties[result.Id] = result;
 
 			return result;
@@ -92,15 +119,23 @@ public static BaseAttachedPropertyInfo[] GetPropertiesOfType(Type type)
 				return result;
 			}
 
-			// Make sure all static fields of type are initialized
-			RuntimeHelpers.RunClassConstructor(type.TypeHandle);
 			var propertiesList = new List<BaseAttachedPropertyInfo>();
-			foreach(var pair in _properties)
+
+			// Build list of all attached properties
+			var currentType = type;
+			while (currentType != null && currentType != typeof(object))
 			{
-				if (pair.Value.OwnerType == type)
+				// Make sure all static fields of type are initialized
+				RuntimeHelpers.RunClassConstructor(currentType.TypeHandle);
+				foreach (var pair in _properties)
 				{
-					propertiesList.Add(pair.Value);
+					if (pair.Value.OwnerType == currentType)
+					{
+						propertiesList.Add(pair.Value);
+					}
 				}
+
+				currentType = currentType.BaseType;
 			}
 
 			result = propertiesList.ToArray();

src/Myra/MML/BaseContext.cs

@@ -5,6 +5,7 @@
 using System.Xml.Serialization;
 using FontStashSharp;
 using Myra.Utility;
+using Myra.Attributes;
 
 #if MONOGAME || FNA
 using Microsoft.Xna.Framework;
@@ -37,7 +38,7 @@ public static ITypeSerializer FindSerializer(Type type)
 			return null;
 		}
 
-		protected static void ParseProperties(Type type, 
+		protected static void ParseProperties(Type type, bool checkSkipSave,
 			out List<PropertyInfo> complexProperties, 
 			out List<PropertyInfo> simpleProperties)
 		{
@@ -54,12 +55,21 @@ protected static void ParseProperties(Type type,
 					continue;
 				}
 
-				var attr = property.FindAttribute<XmlIgnoreAttribute>();
+				Attribute attr = property.FindAttribute<XmlIgnoreAttribute>();
 				if (attr != null)
 				{
 					continue;
 				}
 
+				if (checkSkipSave)
+				{
+					attr = property.FindAttribute<SkipSaveAttribute>();
+					if (attr != null)
+					{
+						continue;
+					}
+				}
+
 				var propertyType = property.PropertyType;
 				if (propertyType.IsPrimitive || 
 					propertyType.IsNullablePrimitive() ||

src/Myra/MML/BaseObject.cs

@@ -6,7 +6,7 @@
 
 namespace Myra.MML
 {
-	public class BaseObject: IItemWithId
+	public class BaseObject: IItemWithId, INotifyAttachedPropertyChanged
 	{
 		private string _id = null;
 
@@ -54,5 +54,9 @@ protected internal virtual void OnIdChanged()
 		{
 			IdChanged.Invoke(this);
 		}
+
+		public virtual void OnAttachedPropertyChanged(BaseAttachedPropertyInfo propertyInfo)
+		{
+		}
 	}
 }

src/Myra/MML/LoadContext.cs

@@ -80,7 +80,7 @@ public void Load<T>(object obj, XElement el, T handler) where T : class
 			var baseObject = obj as BaseObject;
 
 			List<PropertyInfo> complexProperties, simpleProperties;
-			ParseProperties(type, out complexProperties, out simpleProperties);
+			ParseProperties(type, false, out complexProperties, out simpleProperties);
 
 			string newName;
 			foreach (var attr in el.Attributes())