add content visibility property - fixes #90

Author: jogibear9988

src/AngleSharp.Css.Tests/Declarations/CssContentVisibilityProperty.cs

@@ -0,0 +1,25 @@
+namespace AngleSharp.Css.Tests.Declarations
+{
+    using NUnit.Framework;
+    using static CssConstructionFunctions;
+
+    [TestFixture]
+    public class CssContentVisibilityPropertyTests
+    {
+        [Test]
+        public void CssContentVisibilityIsHidden()
+        {
+            var source = "a{content-visibility:hidden}";
+            var parsed = ParseStyle(source);
+            Assert.AreEqual("content-visibility: hidden", parsed.Style.CssText);
+        }
+
+        [Test]
+        public void CssContentVisibilityIsUnkown()
+        {
+            var source = "a{content-visibility:aa}";
+            var parsed = ParseStyle(source);
+            Assert.AreEqual("", parsed.Style.CssText);
+        }
+    }
+}

src/AngleSharp.Css/Constants/InitialValues.cs

@@ -165,6 +165,7 @@ static class InitialValues
         public static readonly ICssValue QuotesDecl = new Quote("«", "»");
         public static readonly ICssValue PointerEventsDecl = new Constant<PointerEvent>(CssKeywords.Auto, PointerEvent.Auto);
         public static readonly ICssValue ContentDecl = new Constant<Object>(CssKeywords.Normal, null);
+        public static readonly ICssValue ContentVisibilityDecl = new Constant<Visibility>(CssKeywords.Visible, Visibility.Visible);
         public static readonly ICssValue CounterIncrementDecl = new Constant<Object>(CssKeywords.None, null);
         public static readonly ICssValue CounterResetDecl = new Constant<Object>(CssKeywords.None, null);
         public static readonly ICssValue DisplayDecl = new Constant<DisplayMode>(CssKeywords.Inline, DisplayMode.Inline);

src/AngleSharp.Css/Constants/Map.cs

@@ -894,5 +894,15 @@ static class Map
             { CssKeywords.MinContent, Sizing.MinContent},
             { CssKeywords.MaxContent, Sizing.MaxContent },
         };
+
+        /// <summary>
+        /// Contains the string-ContentVisibility mapping.
+        /// </summary>
+        public static readonly Dictionary<String, Visibility> ContentVisibilities = new Dictionary<String, Visibility>(StringComparer.OrdinalIgnoreCase)
+        {
+            { CssKeywords.Visible, Visibility.Visible },
+            { CssKeywords.Hidden, Visibility.Hidden },
+            { CssKeywords.Collapse, Visibility.Collapse },
+        };
     }
 }

src/AngleSharp.Css/Constants/PropertyNames.cs

@@ -477,6 +477,11 @@ public static class PropertyNames
         /// </summary>
         public static readonly String Content = "content";
 
+        /// <summary>
+        /// The content-visibility declaration.
+        /// </summary>
+        public static readonly String ContentVisibility = "content-visibility";
+
         /// <summary>
         /// The counter-increment declaration.
         /// </summary>

src/AngleSharp.Css/Declarations/ContentVisibilityDeclaration.cs

@@ -0,0 +1,17 @@
+namespace AngleSharp.Css.Declarations
+{
+    using AngleSharp.Css.Dom;
+    using System;
+    using static ValueConverters;
+
+    static class ContentVisibilityDeclaration
+    {
+        public static String Name = PropertyNames.ContentVisibility;
+
+        public static IValueConverter Converter = VisibilityConverter;
+
+        public static ICssValue InitialValue = InitialValues.ContentVisibilityDecl;
+
+        public static PropertyFlags Flags = PropertyFlags.None;
+    }
+}

src/AngleSharp.Css/Factories/DefaultDeclarationFactory.cs

@@ -123,6 +123,13 @@ public class DefaultDeclarationFactory : IDeclarationFactory
                     initialValue: ContentDeclaration.InitialValue,
                     flags: ContentDeclaration.Flags)
             },
+            {
+                ContentVisibilityDeclaration.Name, new DeclarationInfo(
+                    name: ContentVisibilityDeclaration.Name,
+                    converter: ContentVisibilityDeclaration.Converter,
+                    initialValue: ContentVisibilityDeclaration.InitialValue,
+                    flags: ContentVisibilityDeclaration.Flags)
+            },
             {
                 BoxDecorationBreakDeclaration.Name, new DeclarationInfo(
                     name: BoxDecorationBreakDeclaration.Name,

src/AngleSharp.Css/ValueConverters.cs

@@ -560,6 +560,11 @@ static class ValueConverters
         /// </summary>
         public static readonly IValueConverter FootnotePolicyConverter = Map.FootnotePolicies.ToConverter();
 
+        /// <summary>
+        /// Represents a converter for the Visibility enumeration.
+        /// </summary>
+        public static readonly IValueConverter ContentVisibilityConverter = Map.Visibilities.ToConverter();
+
         #endregion
 
         #region Specific