Fixed detecting infinite layout exception in specific cases

QuestPDF.Examples/ContinousPage.cs

@@ -0,0 +1,46 @@
+using System.Diagnostics;
+using System.Linq;
+using NUnit.Framework;
+using QuestPDF.Drawing;
+using QuestPDF.Examples.Engine;
+using QuestPDF.Fluent;
+using QuestPDF.Helpers;
+using QuestPDF.Infrastructure;
+
+namespace QuestPDF.Examples
+{
+    public class ContinuousPageDocument : IDocument
+    {
+        public DocumentMetadata GetMetadata() => DocumentMetadata.Default;
+
+        public void Compose(IDocumentContainer container)
+        {
+            container.Page(page =>
+            {
+                page.Margin(20);
+                page.ContinuousSize(150);
+                
+                page.Header().Text("Header");
+                
+                page.Content().PaddingVertical(10).Border(1).Padding(10).Stack(stack =>
+                {
+                    foreach (var index in Enumerable.Range(1, 100))
+                        stack.Item().Text($"Line {index}", TextStyle.Default.Color(Placeholders.Color()));
+                });
+                
+                page.Footer().Text("Footer");
+            });
+        }
+    }
+    
+    public class ContinuousPageExamples
+    {
+        [Test]
+        public void ContinuousPage()
+        {
+            var path = "example.pdf";
+            new ContinuousPageDocument().GeneratePdf(path);
+            Process.Start("explorer", path);
+        }
+    }
+}

QuestPDF/Drawing/DocumentGenerator.cs

@@ -60,7 +60,10 @@ namespace QuestPDF.Drawing
                 var spacePlan = content.Measure(Size.Max) as Size;
 
                 if (spacePlan == null)
-                    break;
+                {
+                    canvas.EndDocument();
+                    ThrowLayoutException();
+                }
 
                 try
                 {
@@ -78,7 +81,7 @@ namespace QuestPDF.Drawing
                 if (currentPage >= documentMetadata.DocumentLayoutExceptionThreshold)
                 {
                     canvas.EndDocument();
-                    throw new DocumentLayoutException("Composed layout generates infinite document.");
+                    ThrowLayoutException();
                 }
                 
                 if (spacePlan is FullRender)
@@ -88,6 +91,11 @@ namespace QuestPDF.Drawing
             }
             
             canvas.EndDocument();
+            
+            void ThrowLayoutException()
+            {
+                throw new DocumentLayoutException("Composed layout generates infinite document.");
+            }
         }
     }
 }

QuestPDF/Elements/Page.cs

@@ -1,3 +1,4 @@
+using System;
 using QuestPDF.Fluent;
 using QuestPDF.Helpers;
 using QuestPDF.Infrastructure;
@@ -36,9 +37,20 @@ namespace QuestPDF.Elements
                 .Decoration(decoration =>
                 {
                     decoration.Header().Element(Header);
-                    decoration.Content().Extend().Element(Content);
+                    
+                    decoration
+                        .Content()
+                        .Element(x => IsClose(MinSize.Width, MaxSize.Width) ? x.ExtendHorizontal() : x)
+                        .Element(x => IsClose(MinSize.Height, MaxSize.Height) ? x.ExtendVertical() : x)
+                        .Element(Content);
+                    
                     decoration.Footer().Element(Footer);
                 });
+
+            bool IsClose(float x, float y)
+            {
+                return Math.Abs(x - y) < Size.Epsilon;
+            }
         }
     }
 }

QuestPDF/Elements/Row.cs

@@ -7,29 +7,31 @@ using QuestPDF.Infrastructure;
 
 namespace QuestPDF.Elements
 {
-    internal abstract class RowElement : ContainerElement
+    internal abstract class RowElement : Constrained
     {
-        public float Width { get; set; } = 1;
+        public float Size { get; protected set;  }
         
-        internal override void Draw(Size availableSpace)
+        public void SetWidth(float width)
         {
-            Child?.Draw(availableSpace);
+            MinWidth = width;
+            MaxWidth = width;
         }
     }
     
     internal class ConstantRowElement : RowElement
     {
-        public ConstantRowElement(float width)
+        public ConstantRowElement(float size)
         {
-            Width = width;
+            Size = size;
+            SetWidth(size);
         }
     }
     
     internal class RelativeRowElement : RowElement
     {
-        public RelativeRowElement(float width)
+        public RelativeRowElement(float size)
         {
-            Width = width;
+            Size = size;
         }
     }
     
@@ -84,70 +86,61 @@ namespace QuestPDF.Elements
     
     internal class Row : Element
     {
-        public ICollection<RowElement> Children { get; internal set; } = new List<RowElement>();
         public float Spacing { get; set; } = 0;
-
+        
+        public ICollection<RowElement> Children { get; internal set; } = new List<RowElement>();
+        private Element? RootElement { get; set; }
+        
         internal override void HandleVisitor(Action<Element?> visit)
         {
-            Children.ToList().ForEach(x => x.HandleVisitor(visit));
+            if (RootElement == null)
+                ComposeTree();
+            
+            RootElement.HandleVisitor(visit);
             base.HandleVisitor(visit);
         }
 
         internal override ISpacePlan Measure(Size availableSpace)
         {
-            return Compose(availableSpace.Width).Measure(availableSpace);
+            UpdateElementsWidth(availableSpace.Width);
+            return RootElement.Measure(availableSpace);
         }
 
         internal override void Draw(Size availableSpace)
         {
-            Compose(availableSpace.Width).Draw(availableSpace);
+            UpdateElementsWidth(availableSpace.Width);
+            RootElement.Draw(availableSpace);
         }
         
         #region structure
         
-        private Element Compose(float availableWidth)
+        private void ComposeTree()
         {
-            var elements = AddSpacing(Children, Spacing);
-            var rowElements = ReduceRows(elements, availableWidth);
-            var tree = BuildTree(rowElements.ToArray());
-            tree.HandleVisitor(x => x.Initialize(PageContext, Canvas));
+            Children = AddSpacing(Children, Spacing);
             
-            return tree;
+            var elements = Children.Cast<Element>().ToArray();
+            RootElement = BuildTree(elements);
         }
-        
-        private static ICollection<Element> ReduceRows(ICollection<RowElement> elements, float availableWidth)
+
+        private void UpdateElementsWidth(float availableWidth)
         {
-            var constantWidth = elements
+            var constantWidth = Children
                 .Where(x => x is ConstantRowElement)
                 .Cast<ConstantRowElement>()
-                .Sum(x => x.Width);
+                .Sum(x => x.Size);
         
-            var relativeWidth = elements
+            var relativeWidth = Children
                 .Where(x => x is RelativeRowElement)
                 .Cast<RelativeRowElement>()
-                .Sum(x => x.Width);
+                .Sum(x => x.Size);
 
             var widthPerRelativeUnit = (availableWidth - constantWidth) / relativeWidth;
             
-            return elements
-                .Select(x =>
-                {
-                    if (x is RelativeRowElement r)
-                        return new ConstantRowElement(r.Width * widthPerRelativeUnit)
-                        {
-                            Child = x.Child
-                        };
-                    
-                    return x;
-                })
-                .Select(x => new Constrained
-                {
-                    MinWidth = x.Width,
-                    MaxWidth = x.Width,
-                    Child = x.Child
-                })
-                .Cast<Element>()
-                .ToList();
+            Children
+                .Where(x => x is RelativeRowElement)
+                .Cast<RelativeRowElement>()
+                .ToList()
+                .ForEach(x => x.SetWidth(x.Size * widthPerRelativeUnit));
         }
         
         private static ICollection<RowElement> AddSpacing(ICollection<RowElement> elements, float spacing)

QuestPDF/Fluent/ElementExtensions.cs

@@ -18,10 +18,10 @@ namespace QuestPDF.Fluent
         {
             if (element?.Child != null && element.Child is Empty == false)
             {
-                var message = $"Container {element.GetType().Name} already contains an {element.Child.GetType().Name} child. " +
-                              $"Tried to assign {child?.GetType()?.Name}." +
-                              $"You should not assign multiple elements to single-child containers.";
-                
+                var message = "You should not assign multiple child elements to a single-child container. " +
+                              "This may happen when a container variable is used outside of its scope/closure OR the container is used in multiple fluent API chains OR the container is used incorrectly in a loop. " +
+                              "This exception is thrown to help you detect that some part of the code is overriding fragments of the document layout with a new content - essentially destroying existing content.";
+
                 throw new DocumentComposeException(message);
             }
 

QuestPDF/Fluent/PageExtensions.cs

@@ -12,14 +12,24 @@ namespace QuestPDF.Fluent
 
         public void Size(PageSize pageSize)
         {
-            Page.MinSize = pageSize;
-            Page.MaxSize = pageSize;
+            MinSize(pageSize);
+            MaxSize(pageSize);
         }
-
+        
         public void ContinuousSize(float width)
         {
-            Page.MinSize = new PageSize(width, 0);
-            Page.MaxSize = new PageSize(width, Infrastructure.Size.Max.Height);
+            MinSize(new PageSize(width, 0));
+            MaxSize(new PageSize(width, Infrastructure.Size.Max.Height));
+        }
+
+        public void MinSize(PageSize pageSize)
+        {
+            Page.MinSize = pageSize;
+        }
+        
+        public void MaxSize(PageSize pageSize)
+        {
+            Page.MaxSize = pageSize;
         }
 
         public void MarginLeft(float value)

QuestPDF/QuestPDF.csproj

@@ -4,9 +4,9 @@
         <Authors>MarcinZiabek</Authors>
         <Company>CodeFlint</Company>
         <PackageId>QuestPDF</PackageId>
-        <Version>2021.9.0</Version>
+        <Version>2021.9.3</Version>
         <PackageDescription>QuestPDF is an open-source, modern and battle-tested library that can help you with generating PDF documents by offering friendly, discoverable and predictable C# fluent API.</PackageDescription>
-        <PackageReleaseNotes>Added support for registering custom fonts from a stream.</PackageReleaseNotes>
+        <PackageReleaseNotes>Added support for registering custom fonts from a stream. Fixed continuous page setting. Improved exception messages.</PackageReleaseNotes>
         <LangVersion>8</LangVersion>
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
         <PackageIcon>Logo.png</PackageIcon>