Rewire shorthand resolution

Author: FlorianRappl

src/AngleSharp.Css/BrowsingContextExtensions.cs

@@ -59,6 +59,22 @@ internal static DeclarationInfo GetDeclarationInfo(this IBrowsingContext context
             return factory.Create(propertyName);
         }
 
+        internal static ICssProperty CreateShorthand(this IBrowsingContext context, String name, ICssValue[] longhands, Boolean important)
+        {
+            var factory = context.GetFactory<IDeclarationFactory>();
+            var info = factory.Create(name);
+            var value = info.Combine(longhands);
+            return new CssProperty(name, info.Converter, info.Flags, value, important);
+        }
+
+        internal static ICssProperty[] CreateLonghands(this IBrowsingContext context, ICssProperty shorthand)
+        {
+            var factory = context.GetFactory<IDeclarationFactory>();
+            var info = factory.Create(shorthand.Name);
+            var values = info.Seperate(factory, shorthand.RawValue);
+            return factory.CreateProperties(info.Longhands, values, shorthand.IsImportant);
+        }
+
         internal static CssProperty CreateProperty(this IBrowsingContext context, String propertyName)
         {
             var info = context.GetDeclarationInfo(propertyName);
@@ -75,7 +91,25 @@ internal static CssProperty CreateProperty(this IBrowsingContext context, String
         private static Boolean IsAllowingUnknownDeclarations(this IBrowsingContext context)
         {
             var parser = context.GetProvider<CssParser>();
-            return parser != null ? parser.Options.IsIncludingUnknownDeclarations : true;
+            return parser?.Options.IsIncludingUnknownDeclarations ?? true;
+        }
+
+        private static ICssProperty[] CreateProperties(this IDeclarationFactory factory, String[] names, ICssValue[] values, Boolean important)
+        {
+            if (values != null && values.Length == names.Length)
+            {
+                var properties = new ICssProperty[names.Length];
+
+                for (var i = 0; i < names.Length; i++)
+                {
+                    var info = factory.Create(names[i]);
+                    properties[i] = new CssProperty(names[i], info.Converter, info.Flags, values[i], important);
+                }
+
+                return properties;
+            }
+
+            return null;
         }
     }
 }

src/AngleSharp.Css/DeclarationInfo.cs

@@ -21,7 +21,8 @@ public class DeclarationInfo
         public DeclarationInfo(String name, IValueConverter converter, PropertyFlags flags = PropertyFlags.None, ICssValue initialValue = null, String[] shorthands = null, String[] longhands = null)
         {
             Name = name;
-            Converter = Or(converter, AssignInitial(initialValue));
+            Converter = initialValue != null ? Or(converter, AssignInitial(initialValue)) : converter;
+            Aggregator = converter as IValueAggregator;
             Flags = flags;
             InitialValue = initialValue;
             Shorthands = shorthands ?? Array.Empty<String>();
@@ -43,6 +44,11 @@ public DeclarationInfo(String name, IValueConverter converter, PropertyFlags fla
         /// </summary>
         public IValueConverter Converter { get; }
 
+        /// <summary>
+        /// Gets the value aggregator, if any.
+        /// </summary>
+        public IValueAggregator Aggregator { get; }
+
         /// <summary>
         /// Gets the flags of the declaration.
         /// </summary>

src/AngleSharp.Css/Declarations/AnimationDeclaration.cs

@@ -30,7 +30,7 @@ static class AnimationDeclaration
             PropertyNames.AnimationName,
         };
 
-        sealed class AnimationConverter : IValueConverter
+        sealed class AnimationAggregator : IValueAggregator, IValueConverter
         {
             private static readonly IValueConverter ListConverter = WithAny(
                 TimeConverter.Option(),
@@ -43,13 +43,6 @@ sealed class AnimationConverter : IValueConverter
                 IdentifierConverter.Option()).FromList();
 
             public ICssValue Convert(StringSource source) => ListConverter.Convert(source);
-        }
-
-        sealed class AnimationAggregator : IValueAggregator, IValueConverter
-        {
-            private static readonly IValueConverter converter = new AnimationConverter();
-
-            public ICssValue Convert(StringSource source) => converter.Convert(source);
 
             public ICssValue Merge(ICssValue[] values)
             {
@@ -72,9 +65,7 @@ public ICssValue Merge(ICssValue[] values)
 
             public ICssValue[] Split(ICssValue value)
             {
-                var list = value as CssListValue;
-
-                if (list != null)
+                if (value is CssListValue list)
                 {
                     return new[]
                     {

src/AngleSharp.Css/Declarations/BackgroundDeclaration.cs

@@ -221,7 +221,7 @@ private static Int32 GetCount(params CssListValue[] lists)
 
                 foreach (var list in lists)
                 {
-                    count = Math.Max(count, list.Count);
+                    count = Math.Max(count, list?.Count ?? 0);
                 }
 
                 return count;

src/AngleSharp.Css/Declarations/BorderColorDeclaration.cs

@@ -39,7 +39,7 @@ sealed class BorderColorAggregator : IValueAggregator, IValueConverter
 
             public ICssValue Merge(ICssValue[] values)
             {
-                if (values.Length > 0)
+                if (values[0] != null)
                 {
                     return new CssPeriodicValue(values);
                 }

src/AngleSharp.Css/Declarations/BorderWidthDeclaration.cs

@@ -39,7 +39,7 @@ sealed class BorderWidthAggregator : IValueAggregator, IValueConverter
 
             public ICssValue Merge(ICssValue[] values)
             {
-                if (values.Length > 0)
+                if (values[0] != null)
                 {
                     return new CssPeriodicValue(values);
                 }