Allow Grid column/row definitions to be supplied as a string.

Closes #48.

Perspex.Controls/ColumnDefinitions.cs

@@ -6,9 +6,19 @@
 
 namespace Perspex.Controls
 {
+    using System.Linq;
     using Perspex.Collections;
+    using Perspex.Controls.Parsers;
 
     public class ColumnDefinitions : PerspexList<ColumnDefinition>
     {
+        public ColumnDefinitions()
+        {
+        }
+
+        public ColumnDefinitions(string s)
+        {
+            this.AddRange(GridLengthsParser.Parse(s).Select(x => new ColumnDefinition(x)));
+        }
     }
 }

Perspex.Controls/Parsers/GridLengthsParser.cs

@@ -0,0 +1,53 @@
+// -----------------------------------------------------------------------
+// <copyright file="GridLengthsParser.cs" company="Steven Kirk">
+// Copyright 2014 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls.Parsers
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+
+
+    /// <summary>
+    /// Parses a string of <see cref="GridLength"/>s for <see cref="ColumnDefinitions"/> and
+    /// <see cref="RowDefinitions"/>.
+    /// </summary>
+    public static class GridLengthsParser
+    {
+        /// <summary>
+        /// Parses a string of <see cref="GridLength"/>s.
+        /// </summary>
+        /// <param name="s">The string.</param>
+        /// <returns>A collection of <see cref="GridLength"/>s.</returns>
+        public static IEnumerable<GridLength> Parse(string s)
+        {
+            var parts = s.Split(',').Select(x => x.ToUpperInvariant().Trim());
+
+            foreach (var part in parts)
+            {
+                if (part == "AUTO")
+                {
+                    yield return GridLength.Auto;
+                }
+                else if (part.EndsWith("*"))
+                {
+                    var valueString = part.Substring(0, part.Length - 1).Trim();
+                    var value = valueString.Length > 0 ? double.Parse(valueString) : 1;
+                    yield return new GridLength(value, GridUnitType.Star);
+                }
+                else if (part.EndsWith("PX"))
+                {
+                    var value = double.Parse(part.Substring(0, part.Length - 2));
+                    yield return new GridLength(value, GridUnitType.Pixel);
+                }
+                else
+                {
+                    throw new FormatException("Invalid grid length: " + part);
+                }
+            }
+        }
+    }
+}

Perspex.Controls/Perspex.Controls.csproj

@@ -37,6 +37,7 @@
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="MenuItemAccessKeyHandler.cs" />
+    <Compile Include="Parsers\GridLengthsParser.cs" />
     <Compile Include="Primitives\AccessText.cs" />
     <Compile Include="Border.cs" />
     <Compile Include="GlobalSuppressions.cs" />

Perspex.Controls/RowDefinitions.cs

@@ -6,9 +6,19 @@
 
 namespace Perspex.Controls
 {
+    using System.Linq;
     using Perspex.Collections;
+    using Perspex.Controls.Parsers;
 
     public class RowDefinitions : PerspexList<RowDefinition>
     {
+        public RowDefinitions()
+        {
+        }
+
+        public RowDefinitions(string s)
+        {
+            this.AddRange(GridLengthsParser.Parse(s).Select(x => new RowDefinition(x)));
+        }
     }
 }

Perspex.Diagnostics/DevTools.cs

@@ -66,11 +66,7 @@ namespace Perspex.Diagnostics
 
             this.Content = new Grid
             {
-                RowDefinitions = new RowDefinitions
-                {
-                    new RowDefinition(new GridLength(1, GridUnitType.Star)),
-                    new RowDefinition(GridLength.Auto),
-                },
+                RowDefinitions = new RowDefinitions("*,Auto"),
                 Children = new Controls
                 {
                     new TabControl

Tests/Perspex.Controls.UnitTests/Parsers/GridLengthsParserTests.cs

@@ -0,0 +1,54 @@
+// -----------------------------------------------------------------------
+// <copyright file="GridLengthsParserTests.cs" company="Steven Kirk">
+// Copyright 2015 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls.UnitTests.Parsers
+{
+    using System;
+    using System.Linq;
+    using Perspex.Controls.Parsers;
+    using Xunit;
+
+    public class GridLengthsParserTests
+    {
+        [Fact]
+        public void Parser_Should_Correctly_Parse_Grid_Lengths()
+        {
+            var s = "*,Auto,2*,4px";
+            var result = GridLengthsParser.Parse(s);
+
+            Assert.Equal(
+                new[]
+                {
+                    new GridLength(1, GridUnitType.Star),
+                    GridLength.Auto,
+                    new GridLength(2, GridUnitType.Star),
+                    new GridLength(4, GridUnitType.Pixel),
+                },
+                result);
+        }
+
+        [Fact]
+        public void Parser_Should_Throw_For_Invalid_Star_Value()
+        {
+            var s = "*,Auto,x*,4px";
+            Assert.Throws<FormatException>(() => GridLengthsParser.Parse(s).ToList());
+        }
+
+        [Fact]
+        public void Parser_Should_Throw_For_Invalid_Unit_Value()
+        {
+            var s = "*,Auto,4ab,4px";
+            Assert.Throws<FormatException>(() => GridLengthsParser.Parse(s).ToList());
+        }
+
+        [Fact]
+        public void Parser_Should_Throw_For_Empty_Entry()
+        {
+            var s = "*,Auto,,4px";
+            Assert.Throws<FormatException>(() => GridLengthsParser.Parse(s).ToList());
+        }
+    }
+}

Tests/Perspex.Controls.UnitTests/Perspex.Controls.UnitTests.csproj

@@ -91,6 +91,7 @@
     <Compile Include="ContentPresenterTests.cs" />
     <Compile Include="BorderTests.cs" />
     <Compile Include="GlobalSuppressions.cs" />
+    <Compile Include="Parsers\GridLengthsParserTests.cs" />
     <Compile Include="PopupTests.cs" />
     <Compile Include="DropDownTests.cs" />
     <Compile Include="Presenters\ItemsPresenterTests.cs" />