Added color serialization #96

Author: FlorianRappl

CHANGELOG.md

@@ -3,6 +3,7 @@
 Released on Wednesday, January 5 2022.
 
 - Fixed issue with `text-shadow` missing the color part (#97)
+- Added `Color.UseHex` to change color output format (#96)
 
 # 0.16.2
 

docs/tutorials/03-Questions.md

@@ -4,6 +4,22 @@ section: "AngleSharp.Css"
 ---
 # Frequently Asked Questions
 
-## What to ask?
+## How to change the color output?
 
-(tbd)
+By default, AngleSharp.Css uses `rgba()` for the serialization of `Color`. To change this you can set
+
+```cs
+Color.UseHex = true;
+```
+
+which will automatically use hex for all non-transparent colors. All other colors would still be represented via the `rgba()` function.
+
+So you'd get:
+
+```cs
+Color.UseHex = true;
+var color1 = new Color(65, 12, 48);
+// color1.CssText = #410C30
+var color2 = new Color(65, 12, 48, 10);
+// color2.CssText = rgba(65, 12, 48, 0.04)
+```

src/AngleSharp.Css.Tests/Library/StringRepresentation.cs

@@ -1,6 +1,7 @@
 namespace AngleSharp.Css.Tests.Library
 {
     using AngleSharp.Css.Parser;
+    using AngleSharp.Css.Values;
     using NUnit.Framework;
     using System.IO;
 
@@ -20,5 +21,25 @@ public void PrettyStyleFormatterStringifyShouldWork_Issue41()
                 Assert.AreEqual("@media (min-width: 800px) { \n\t.ad_column {\n\t\twidth: 728px;\n\t\theight: 90px;\n\t}\n}", stringWriter.ToString());
             }
         }
+
+        [Test]
+        public void SimpleColorWorksWithHexOutput_Issue96()
+        {
+            var color = new Color(65, 12, 48);
+            Color.UseHex = true;
+            var text = color.CssText;
+            Color.UseHex = false;
+            Assert.AreEqual("#410C30", text);
+        }
+
+        [Test]
+        public void TransparentColorDoesNotWorkWithHexOutput_Issue96()
+        {
+            var color = new Color(65, 12, 48, 10);
+            Color.UseHex = true;
+            var text = color.CssText;
+            Color.UseHex = false;
+            Assert.AreEqual("rgba(65, 12, 48, 0.04)", text);
+        }
     }
 }

src/AngleSharp.Css/Values/Primitives/Color.cs

@@ -373,6 +373,13 @@ public static Color FromHwba(Double h, Double w, Double b, Double alpha)
 
         #region Properties
 
+        /// <summary>
+        /// Gets or sets if hex codes should be used for serialization.
+        /// This will not be applied in case of transparent colors, i.e.,
+        /// when alpha is not 1.
+        /// </summary>
+        public static Boolean UseHex { get; set; }
+
         /// <summary>
         /// Gets the CSS text representation.
         /// </summary>
@@ -388,6 +395,10 @@ public String CssText
                 {
                     return CssKeywords.Invert;
                 }
+                else if (_alpha == 255 && UseHex)
+                {
+                    return $"#{_red.ToString("X2", CultureInfo.InvariantCulture)}{_green.ToString("X2", CultureInfo.InvariantCulture)}{_blue.ToString("X2", CultureInfo.InvariantCulture)}";
+                }
                 else
                 {
                     var fn = FunctionNames.Rgba;