Fixed applying text style for fallback styles

Source/QuestPDF.Examples/TextExamples.cs

@@ -1004,5 +1004,39 @@ namespace QuestPDF.Examples
                         });
                 });
         }
+        
+        [Test]
+         public void FontFallback_Nested()
+        {
+            RenderingTest
+                .Create()
+                .ProduceImages()
+                .ShowResults()
+                .RenderDocument(container =>
+                {
+                    container.Page(page =>
+                    {
+                        page.Margin(50);
+                        page.PageColor(Colors.White);
+                        page.Size(PageSizes.A6.Landscape());
+                        
+                        page.DefaultTextStyle(x => x
+                            .FontSize(24)
+                            .Bold()
+                            .Fallback(y => y
+                                .FontFamily("Microsoft YaHei")
+                                .Underline()
+                                .BackgroundColor(Colors.Red.Lighten2)));
+
+                        page.Content().Text(text =>
+                        {
+                            text.Line("Normal 中文文本 text.");
+                            text.Line("Background 中文文本 text.").NormalWeight().BackgroundColor(Colors.Green.Lighten2);
+                            text.Line("Background 中文文本 text.").Strikethrough().Underline(false);
+                            text.Line("Background 中文文本 text.").Italic();
+                        });
+                    });
+                });
+        }
     }
 }

Source/QuestPDF.UnitTests/QuestPDF.UnitTests.csproj

@@ -3,6 +3,7 @@
     <PropertyGroup>
         <TargetFramework>netcoreapp3.1</TargetFramework>
         <IsPackable>false</IsPackable>
+        <LangVersion>9</LangVersion>
     </PropertyGroup>
 
     <ItemGroup>

Source/QuestPDF.UnitTests/TextStyleTests.cs

@@ -0,0 +1,58 @@
+using FluentAssertions;
+using NUnit.Framework;
+using QuestPDF.Fluent;
+using QuestPDF.Helpers;
+using QuestPDF.Infrastructure;
+
+namespace QuestPDF.UnitTests
+{
+    [TestFixture]
+    public class TextStyleTests
+    {
+        [Test]
+        public void Font()
+        {
+            // arrange
+            var defaultTextStyle = TextStyle
+                .Default
+                .FontSize(20)
+                .FontFamily("Arial")
+                .BackgroundColor(Colors.Green.Lighten2)
+                .Fallback(y => y
+                    .FontFamily("Microsoft YaHei")
+                    .Underline()
+                    .NormalWeight()
+                    .BackgroundColor(Colors.Blue.Lighten2));
+
+            var spanTextStyle = TextStyle
+                .Default
+                .Bold()
+                .Strikethrough()
+                .BackgroundColor(Colors.Red.Lighten2);
+            
+            // act
+            var targetStyle = spanTextStyle.ApplyGlobalStyle(defaultTextStyle, true).ApplyGlobalStyle(TextStyle.LibraryDefault, false);
+            
+            // assert
+            var expectedStyle = TextStyle.LibraryDefault with
+            {
+                Size = 20, 
+                FontFamily = "Arial",
+                FontWeight = FontWeight.Bold,
+                BackgroundColor = Colors.Red.Lighten2,
+                HasStrikethrough = true,
+                Fallback = TextStyle.LibraryDefault with
+                {
+                    Size = 20,
+                    FontFamily = "Microsoft YaHei",
+                    FontWeight = FontWeight.Bold,
+                    BackgroundColor = Colors.Red.Lighten2,
+                    HasUnderline = true,
+                    HasStrikethrough = true
+                }
+            };
+
+            targetStyle.Should().BeEquivalentTo(expectedStyle);
+        }
+    }
+}

Source/QuestPDF/Drawing/DocumentGenerator.cs

@@ -64,7 +64,7 @@ namespace QuestPDF.Drawing
             var container = new DocumentContainer();
             document.Compose(container);
             var content = container.Compose();
-            ApplyDefaultTextStyle(content, TextStyle.LibraryDefault);
+            ApplyDefaultTextStyle(content, TextStyle.Default);
             ApplyContentDirection(content, ContentDirection.LeftToRight);
             
             var debuggingState = Settings.EnableDebugging ? ApplyDebugging(content) : null;
@@ -203,7 +203,8 @@ namespace QuestPDF.Drawing
                 {
                     if (textBlockItem is TextBlockSpan textSpan)
                     {
-                        textSpan.Style = textSpan.Style.ApplyGlobalStyle(documentDefaultTextStyle);
+                        textSpan.Style = textSpan.Style.ApplyGlobalStyle(documentDefaultTextStyle, true);
+                        textSpan.Style = textSpan.Style.ApplyGlobalStyle(TextStyle.LibraryDefault, false);
                     }
                     else if (textBlockItem is TextBlockElement textElement)
                     {
@@ -215,10 +216,10 @@ namespace QuestPDF.Drawing
             }
 
             if (content is DynamicHost dynamicHost)
-                dynamicHost.TextStyle = dynamicHost.TextStyle.ApplyGlobalStyle(documentDefaultTextStyle);
+                dynamicHost.TextStyle = dynamicHost.TextStyle.ApplyGlobalStyle(documentDefaultTextStyle, true);
             
             if (content is DefaultTextStyle defaultTextStyleElement)
-               documentDefaultTextStyle = defaultTextStyleElement.TextStyle.ApplyGlobalStyle(documentDefaultTextStyle);
+               documentDefaultTextStyle = defaultTextStyleElement.TextStyle.ApplyGlobalStyle(documentDefaultTextStyle, true);
 
             foreach (var child in content.GetChildren())
                 ApplyDefaultTextStyle(child, documentDefaultTextStyle);

Source/QuestPDF/Infrastructure/TextStyleManager.cs

@@ -224,18 +224,18 @@ namespace QuestPDF.Infrastructure
             throw new ArgumentOutOfRangeException(nameof(property), property, "Expected to mutate the TextStyle object. Provided property type is not supported.");
         }
         
-        internal static TextStyle ApplyGlobalStyle(this TextStyle style, TextStyle parent)
+        internal static TextStyle ApplyGlobalStyle(this TextStyle style, TextStyle parent, bool overrideStyle)
         {
             var cacheKey = (style, parent);
-            return TextStyleApplyGlobalCache.GetOrAdd(cacheKey, key => ApplyStyle(key.origin, key.parent, overrideStyle: false).ApplyFontFallback());
+            return TextStyleApplyGlobalCache.GetOrAdd(cacheKey, key => ApplyStyle(key.origin, key.parent, overrideStyle: false).ApplyFontFallback(overrideStyle));
         }
         
-        private static TextStyle ApplyFontFallback(this TextStyle style)
+        private static TextStyle ApplyFontFallback(this TextStyle style, bool overrideStyle)
         {
             var targetFallbackStyle = style
                 ?.Fallback
-                ?.ApplyStyle(style, overrideStyle: false, applyFallback: false)
-                ?.ApplyFontFallback();
+                ?.ApplyStyle(style, overrideStyle: overrideStyle, overrideFontFamily: false, applyFallback: false)
+                ?.ApplyFontFallback(overrideStyle);
             
             return MutateStyle(style, TextStyleProperty.Fallback, targetFallbackStyle);
         }
@@ -251,13 +251,16 @@ namespace QuestPDF.Infrastructure
             });
         }
         
-        private static TextStyle ApplyStyle(this TextStyle style, TextStyle parent, bool overrideStyle = true, bool applyFallback = true)
+        private static TextStyle ApplyStyle(this TextStyle style, TextStyle parent, bool overrideStyle = true, bool overrideFontFamily = true, bool applyFallback = true)
         {
             var result = style;
 
             result = MutateStyle(result, TextStyleProperty.Color, parent.Color, overrideStyle);
             result = MutateStyle(result, TextStyleProperty.BackgroundColor, parent.BackgroundColor, overrideStyle);
-            result = MutateStyle(result, TextStyleProperty.FontFamily, parent.FontFamily, overrideStyle);
+            
+            if (style.FontFamily == null)
+                result = MutateStyle(result, TextStyleProperty.FontFamily, parent.FontFamily, overrideFontFamily);
+            
             result = MutateStyle(result, TextStyleProperty.Size, parent.Size, overrideStyle);
             result = MutateStyle(result, TextStyleProperty.LineHeight, parent.LineHeight, overrideStyle);
             result = MutateStyle(result, TextStyleProperty.LetterSpacing, parent.LetterSpacing, overrideStyle);