Add general purpose AST node for creating new Avalonia lists. Implement xaml compile time parsing of row/column definitions.

src/Avalonia.Base/Collections/AvaloniaList.cs

@@ -63,6 +63,15 @@ namespace Avalonia.Collections
             _inner = new List<T>();
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AvaloniaList{T}"/>.
+        /// </summary>
+        /// <param name="capacity">Initial list capacity.</param>
+        public AvaloniaList(int capacity)
+        {
+            _inner = new List<T>(capacity);
+        }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="AvaloniaList{T}"/> class.
         /// </summary>
@@ -175,6 +184,15 @@ namespace Avalonia.Collections
             set { this[index] = (T)value; }
         }
 
+        /// <summary>
+        /// Gets or sets the total number of elements the internal data structure can hold without resizing.
+        /// </summary>
+        public int Capacity
+        {
+            get => _inner.Capacity;
+            set => _inner.Capacity = value;
+        }
+
         /// <summary>
         /// Adds an item to the collection.
         /// </summary>

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/AstNodes/AvaloniaXamlIlAvaloniaListConstantAstNode.cs

@@ -0,0 +1,54 @@
+using System.Collections.Generic;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers;
+using XamlX.Ast;
+using XamlX.Emit;
+using XamlX.IL;
+using XamlX.TypeSystem;
+
+namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.AstNodes
+{
+    class AvaloniaXamlIlAvaloniaListConstantAstNode : XamlAstNode, IXamlAstValueNode, IXamlAstILEmitableNode
+    {
+        private readonly IXamlType _elementType;
+        private readonly IReadOnlyList<IXamlAstValueNode> _values;
+        private readonly IXamlConstructor _constructor;
+        private readonly IXamlMethod _listAddMethod;
+        private readonly IXamlMethod _listSetCapacityMethod;
+
+        public AvaloniaXamlIlAvaloniaListConstantAstNode(IXamlLineInfo lineInfo, AvaloniaXamlIlWellKnownTypes types, IXamlType listType, IXamlType elementType, IReadOnlyList<IXamlAstValueNode> values) : base(lineInfo)
+        {
+            _constructor = listType.GetConstructor();
+            _listAddMethod = listType.GetMethod(new FindMethodMethodSignature("Add", types.XamlIlTypes.Void, elementType));
+            _listSetCapacityMethod = listType.GetMethod(new FindMethodMethodSignature("set_Capacity", types.XamlIlTypes.Void, types.Int));
+
+            _elementType = elementType;
+            _values = values;
+
+            Type = new XamlAstClrTypeReference(lineInfo, listType, false);
+        }
+
+        public IXamlAstTypeReference Type { get; }
+        
+        public XamlILNodeEmitResult Emit(XamlEmitContext<IXamlILEmitter, XamlILNodeEmitResult> context, IXamlILEmitter codeGen)
+        {
+            codeGen.Newobj(_constructor);
+
+            codeGen
+                .Dup()
+                .Ldc_I4(_values.Count)
+                .EmitCall(_listSetCapacityMethod);
+            
+            foreach (var value in _values)
+            {
+                codeGen.Dup();
+                
+                context.Emit(value, codeGen, _elementType);
+            
+                codeGen.EmitCall(_listAddMethod);
+            }
+            
+            return XamlILNodeEmitResult.Type(0, Type.GetClrType());
+        }
+    }
+}

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/AvaloniaXamlIlLanguage.cs

@@ -353,6 +353,16 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
                 }
             }
 
+            if (type.Equals(types.ColumnDefinitions))
+            {
+                return ConvertDefinitionList(node, text, types, types.ColumnDefinitions, types.ColumnDefinition, "column definitions", out result);
+            }
+
+            if (type.Equals(types.RowDefinitions))
+            {
+                return ConvertDefinitionList(node, text, types, types.RowDefinitions, types.RowDefinition, "row definitions", out result);
+            }
+
             if (type.FullName == "Avalonia.AvaloniaProperty")
             {
                 var scope = context.ParentNodes().OfType<AvaloniaXamlIlTargetTypeMetadataNode>().FirstOrDefault();
@@ -366,5 +376,43 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
             result = null;
             return false;
         }
+
+        private static bool ConvertDefinitionList(
+            IXamlAstValueNode node, 
+            string text,
+            AvaloniaXamlIlWellKnownTypes types,
+            IXamlType listType,
+            IXamlType elementType,
+            string errorDisplayName,
+            out IXamlAstValueNode result)
+        {
+            try
+            {
+                var lengths = GridLength.ParseLengths(text);
+
+                var definitionTypeRef = new XamlAstClrTypeReference(node, elementType, false);
+
+                var definitionConstructorGridLength = elementType.GetConstructor(new List<IXamlType> {types.GridLength});
+
+                IXamlAstValueNode CreateDefinitionNode(GridLength length)
+                {
+                    var lengthNode = new AvaloniaXamlIlGridLengthAstNode(node, types, length);
+
+                    return new XamlAstNewClrObjectNode(node, definitionTypeRef,
+                        definitionConstructorGridLength, new List<IXamlAstValueNode> {lengthNode});
+                }
+
+                var definitionNodes =
+                    new List<IXamlAstValueNode>(lengths.Select(CreateDefinitionNode));
+
+                result = new AvaloniaXamlIlAvaloniaListConstantAstNode(node, types, listType, elementType, definitionNodes);
+
+                return true;
+            }
+            catch
+            {
+                throw new XamlX.XamlLoadException($"Unable to parse \"{text}\" as a {errorDisplayName}", node);
+            }
+        }
     }
 }

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs

@@ -50,6 +50,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
 
         public IXamlType RelativeSource { get; }
         public IXamlType UInt { get; }
+        public IXamlType Int { get; }
         public IXamlType Long { get; }
         public IXamlType Uri { get; }
         public IXamlType FontFamily { get; }
@@ -72,6 +73,10 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
         public IXamlType StandardCursorType { get; }
         public IXamlType Cursor { get; }
         public IXamlConstructor CursorTypeConstructor { get; }
+        public IXamlType RowDefinition { get; }
+        public IXamlType RowDefinitions { get; }
+        public IXamlType ColumnDefinition { get; }
+        public IXamlType ColumnDefinitions { get; }
 
         public AvaloniaXamlIlWellKnownTypes(TransformerConfiguration cfg)
         {
@@ -130,6 +135,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             ReflectionBindingExtension = cfg.TypeSystem.GetType("Avalonia.Markup.Xaml.MarkupExtensions.ReflectionBindingExtension");
             RelativeSource = cfg.TypeSystem.GetType("Avalonia.Data.RelativeSource");
             UInt = cfg.TypeSystem.GetType("System.UInt32");
+            Int = cfg.TypeSystem.GetType("System.Int32");
             Long = cfg.TypeSystem.GetType("System.Int64");
             Uri = cfg.TypeSystem.GetType("System.Uri");
             FontFamily = cfg.TypeSystem.GetType("Avalonia.Media.FontFamily");
@@ -156,6 +162,10 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             StandardCursorType = cfg.TypeSystem.GetType("Avalonia.Input.StandardCursorType");
             Cursor = cfg.TypeSystem.GetType("Avalonia.Input.Cursor");
             CursorTypeConstructor = Cursor.GetConstructor(new List<IXamlType> { StandardCursorType });
+            ColumnDefinition = cfg.TypeSystem.GetType("Avalonia.Controls.ColumnDefinition");
+            ColumnDefinitions = cfg.TypeSystem.GetType("Avalonia.Controls.ColumnDefinitions");
+            RowDefinition = cfg.TypeSystem.GetType("Avalonia.Controls.RowDefinition");
+            RowDefinitions = cfg.TypeSystem.GetType("Avalonia.Controls.RowDefinitions");
         }
     }