Merge pull request #6953 from Gillibald/feature/textBlockInlines

Add TextBlock inlines support

samples/ControlCatalog/Pages/TextBlockPage.xaml

@@ -117,6 +117,17 @@
           <TextBlock Text="👪 👨‍👩‍👧 👨‍👩‍👧‍👦" />
         </StackPanel>
       </Border>
+      <Border>
+        <TextBlock Margin="10" TextWrapping="Wrap">
+          This <Span FontWeight="Bold">is</Span> a
+          <Span Background="Silver" Foreground="Maroon">TextBlock</Span>
+          with <Span TextDecorations="Underline">several</Span>
+          <Span FontStyle="Italic">Span</Span> elements,
+          <Span Foreground="Blue">
+            using a <Bold>variety</Bold> of <Italic>styles</Italic>
+          </Span>.
+        </TextBlock>
+      </Border>
     </WrapPanel>
   </StackPanel>
 </UserControl>

src/Avalonia.Base/Metadata/TrimSurroundingWhitespaceAttribute.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace Avalonia.Metadata
+{
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
+    public class TrimSurroundingWhitespaceAttribute : Attribute
+    {
+
+    }
+}

src/Avalonia.Base/Metadata/WhitespaceSignificantCollectionAttribute.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace Avalonia.Metadata
+{
+    /// <summary>
+    /// Indicates that a collection type should be processed as being whitespace significant by a XAML processor.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
+    public class WhitespaceSignificantCollectionAttribute : Attribute
+    {
+    }
+}

src/Avalonia.Controls/Documents/Bold.cs

@@ -0,0 +1,17 @@
+using Avalonia.Media;
+
+namespace Avalonia.Controls.Documents
+{
+    /// <summary>
+    /// Bold element - markup helper for indicating bolded content.
+    /// Equivalent to a Span with FontWeight property set to FontWeights.Bold.
+    /// Can contain other inline elements.
+    /// </summary>
+    public sealed class Bold : Span
+    {
+        static Bold()
+        {
+            FontWeightProperty.OverrideDefaultValue<Bold>(FontWeight.Bold);
+        }
+    }
+}

src/Avalonia.Controls/Documents/Inline.cs

@@ -0,0 +1,71 @@
+using System.Collections.Generic;
+using System.Text;
+using Avalonia.Media;
+using Avalonia.Media.TextFormatting;
+using Avalonia.Utilities;
+
+namespace Avalonia.Controls.Documents 
+{
+    /// <summary>
+    /// Inline element.
+    /// </summary>
+    public abstract class Inline : TextElement
+    {
+        /// <summary>
+        /// AvaloniaProperty for <see cref="TextDecorations" /> property.
+        /// </summary>
+        public static readonly StyledProperty<TextDecorationCollection> TextDecorationsProperty =
+            AvaloniaProperty.Register<Inline, TextDecorationCollection>(
+                nameof(TextDecorations));
+
+        /// <summary>
+        /// AvaloniaProperty for <see cref="BaselineAlignment" /> property.
+        /// </summary>
+        public static readonly StyledProperty<BaselineAlignment> BaselineAlignmentProperty =
+            AvaloniaProperty.Register<Inline, BaselineAlignment>(
+                nameof(BaselineAlignment),
+                BaselineAlignment.Baseline);
+
+        /// <summary>
+        /// The TextDecorations property specifies decorations that are added to the text of an element.
+        /// </summary>
+        public TextDecorationCollection TextDecorations
+        {
+            get { return GetValue(TextDecorationsProperty); }
+            set { SetValue(TextDecorationsProperty, value); }
+        }
+
+        /// <summary>
+        /// Describes how the baseline for a text-based element is positioned on the vertical axis,
+        /// relative to the established baseline for text.
+        /// </summary>
+        public BaselineAlignment BaselineAlignment
+        {
+            get { return GetValue(BaselineAlignmentProperty); }
+            set { SetValue(BaselineAlignmentProperty, value); }
+        }
+
+        internal abstract int BuildRun(StringBuilder stringBuilder, IList<ValueSpan<TextRunProperties>> textStyleOverrides, int firstCharacterIndex);
+
+        internal abstract int AppendText(StringBuilder stringBuilder);
+
+        protected TextRunProperties CreateTextRunProperties()
+        {
+            return new GenericTextRunProperties(new Typeface(FontFamily, FontStyle, FontWeight), FontSize,
+                TextDecorations, Foreground, Background, BaselineAlignment);
+        }
+
+        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
+        {
+            base.OnPropertyChanged(change);
+
+            switch (change.Property.Name)
+            {
+                case nameof(TextDecorations):
+                case nameof(BaselineAlignment):
+                    Invalidate();
+                    break;
+            }
+        }
+    }
+}

src/Avalonia.Controls/Documents/InlineCollection.cs

@@ -0,0 +1,123 @@
+using System;
+using System.Text;
+using Avalonia.Collections;
+using Avalonia.LogicalTree;
+using Avalonia.Metadata;
+
+namespace Avalonia.Controls.Documents
+{
+    /// <summary>
+    /// A collection of <see cref="Inline"/>s.
+    /// </summary>
+    [WhitespaceSignificantCollection]
+    public class InlineCollection : AvaloniaList<Inline>
+    {
+        private string? _text = string.Empty;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="InlineCollection"/> class.
+        /// </summary>
+        public InlineCollection(ILogical parent) : base(0)
+        {
+            ResetBehavior = ResetBehavior.Remove;
+
+            this.ForEachItem(
+                x =>
+                {
+                    ((ISetLogicalParent)x).SetParent(parent);
+                    x.Invalidated += Invalidate;
+                    Invalidate();
+                },
+                x =>
+                {
+                    ((ISetLogicalParent)x).SetParent(null);
+                    x.Invalidated -= Invalidate;
+                    Invalidate();
+                },
+                () => throw new NotSupportedException());
+        }
+
+        public bool HasComplexContent => Count > 0;
+
+        /// <summary>
+        /// Gets or adds the text held by the inlines collection.
+        /// <remarks>
+        /// Can be null for complex content.
+        /// </remarks>
+        /// </summary>
+        public string? Text
+        {
+            get
+            {
+                if (!HasComplexContent)
+                {
+                    return _text;
+                }
+
+                var builder = new StringBuilder();
+
+                foreach(var inline in this)
+                {
+                    inline.AppendText(builder);
+                }
+
+                return builder.ToString();
+            }
+            set
+            {
+                if (HasComplexContent)
+                {
+                    Add(new Run(value));
+                }
+                else
+                {
+                    _text = value;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Add a text segment to the collection.
+        /// <remarks>
+        /// For non complex content this appends the text to the end of currently held text.
+        /// For complex content this adds a <see cref="Run"/> to the collection.
+        /// </remarks>
+        /// </summary>
+        /// <param name="text"></param>
+        public void Add(string text)
+        {
+            if (HasComplexContent)
+            {
+                Add(new Run(text));
+            }
+            else
+            {
+                _text += text;
+            }
+        }
+
+        public override void Add(Inline item)
+        {
+            if (!HasComplexContent)
+            {
+                base.Add(new Run(_text));
+
+                _text = string.Empty;
+            }
+
+            base.Add(item);
+        }
+
+        /// <summary>
+        /// Raised when an inline in the collection changes.
+        /// </summary>
+        public event EventHandler? Invalidated;
+
+        /// <summary>
+        /// Raises the <see cref="Invalidated"/> event.
+        /// </summary>
+        protected void Invalidate() => Invalidated?.Invoke(this, EventArgs.Empty);
+
+        private void Invalidate(object? sender, EventArgs e) => Invalidate();
+    }
+}

src/Avalonia.Controls/Documents/Italic.cs

@@ -0,0 +1,17 @@
+using Avalonia.Media;
+
+namespace Avalonia.Controls.Documents
+{
+    /// <summary>
+    /// Italic element - markup helper for indicating italicized content.
+    /// Equivalent to a Span with FontStyle property set to FontStyles.Italic.
+    /// Can contain other inline elements.
+    /// </summary>
+    public sealed class Italic : Span
+    {
+        static Italic()
+        {
+            FontStyleProperty.OverrideDefaultValue<Italic>(FontStyle.Italic);
+        }
+    }
+}

src/Avalonia.Controls/Documents/LineBreak.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Avalonia.Media.TextFormatting;
+using Avalonia.Metadata;
+using Avalonia.Utilities;
+
+namespace Avalonia.Controls.Documents 
+{
+    /// <summary>
+    /// LineBreak element that forces a line breaking. 
+    /// </summary>
+    [TrimSurroundingWhitespace]
+    public class LineBreak : Inline
+    {
+        /// <summary>
+        /// Creates a new LineBreak instance.
+        /// </summary>
+        public LineBreak()
+        {
+        }
+
+        internal override int BuildRun(StringBuilder stringBuilder,
+            IList<ValueSpan<TextRunProperties>> textStyleOverrides, int firstCharacterIndex)
+        {
+            var length = AppendText(stringBuilder);
+
+            textStyleOverrides.Add(new ValueSpan<TextRunProperties>(firstCharacterIndex, length,
+                CreateTextRunProperties()));
+
+            return length;
+        }
+
+        internal override int AppendText(StringBuilder stringBuilder)
+        {
+            var text = Environment.NewLine;
+
+            stringBuilder.Append(text);
+
+            return text.Length;
+        }
+    }
+}
+