Implementing Simultaneous Bold and Italic in MarkdownTextBlock

Microsoft.Toolkit.Uwp.UI.Controls/MarkdownTextBlock/Display/XamlRenderer.cs

@@ -781,6 +781,9 @@ private void RenderInline(InlineCollection inlineCollection, MarkdownInline elem
                 case MarkdownInlineType.Bold:
                     RenderBoldRun(inlineCollection, (BoldTextInline)element, context);
                     break;
+                case MarkdownInlineType.BoldItalic:
+                    RenderBoldItalicRun(inlineCollection, (BoldItalicTextInline)element, context);
+                    break;
                 case MarkdownInlineType.MarkdownLink:
                     RenderMarkdownLink(inlineCollection, (MarkdownLinkInline)element, parent, context);
                     break;
@@ -1027,6 +1030,28 @@ private void RenderItalicRun(InlineCollection inlineCollection, ItalicTextInline
             inlineCollection.Add(italicSpan);
         }
 
+        /// <summary>
+        /// Renders a text run element.
+        /// </summary>
+        /// <param name="inlineCollection"> The list to add to. </param>
+        /// <param name="element"> The parsed inline element to render. </param>
+        /// <param name="context"> Persistent state. </param>
+        private void RenderBoldItalicRun(InlineCollection inlineCollection, BoldItalicTextInline element, RenderContext context)
+        {
+            // Create the text run
+            Span bolditalicSpan = new Span
+            {
+                FontWeight = FontWeights.Bold,
+                FontStyle = FontStyle.Italic
+            };
+
+            // Render the children into the italic inline.
+            RenderInlineChildren(bolditalicSpan.Inlines, element.Inlines, bolditalicSpan, context);
+
+            // Add it to the current inlines
+            inlineCollection.Add(bolditalicSpan);
+        }
+
         /// <summary>
         /// Renders a strikethrough element.
         /// </summary>

Microsoft.Toolkit.Uwp.UI.Controls/MarkdownTextBlock/Helpers/Common.cs

@@ -35,6 +35,11 @@ internal enum InlineParseMethod
             /// </summary>
             Italic,
 
+            /// <summary>
+            /// An bold and italic block
+            /// </summary>
+            BoldItalic,
+
             /// <summary>
             /// A link block
             /// </summary>
@@ -106,6 +111,7 @@ internal class InlineTripCharHelper
 
         static Common()
         {
+            BoldItalicTextInline.AddTripChars(_triggerList);
             BoldTextInline.AddTripChars(_triggerList);
             ItalicTextInline.AddTripChars(_triggerList);
             MarkdownLinkInline.AddTripChars(_triggerList);
@@ -219,6 +225,9 @@ private static InlineParseResult FindNextInlineElement(string markdown, int star
                         InlineParseResult parseResult = null;
                         switch (currentTripChar.Method)
                         {
+                            case InlineParseMethod.BoldItalic:
+                                parseResult = BoldItalicTextInline.Parse(markdown, pos, end);
+                                break;
                             case InlineParseMethod.Bold:
                                 parseResult = BoldTextInline.Parse(markdown, pos, end);
                                 break;

Microsoft.Toolkit.Uwp.UI.Controls/MarkdownTextBlock/Parse/Inlines/BoldItalicTextInline.cs

@@ -0,0 +1,113 @@
+// ******************************************************************
+// Copyright (c) Microsoft. All rights reserved.
+// This code is licensed under the MIT License (MIT).
+// THE CODE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH
+// THE CODE OR THE USE OR OTHER DEALINGS IN THE CODE.
+// ******************************************************************
+
+using System.Collections.Generic;
+using Microsoft.Toolkit.Uwp.UI.Controls.Markdown.Helpers;
+
+namespace Microsoft.Toolkit.Uwp.UI.Controls.Markdown.Parse
+{
+    /// <summary>
+    /// Represents a span containing bold italic text.
+    /// </summary>
+    internal class BoldItalicTextInline : MarkdownInline, IInlineContainer
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="BoldItalicTextInline"/> class.
+        /// </summary>
+        public BoldItalicTextInline()
+            : base(MarkdownInlineType.BoldItalic)
+        {
+        }
+
+        /// <summary>
+        /// Gets or sets the contents of the inline.
+        /// </summary>
+        public IList<MarkdownInline> Inlines { get; set; }
+
+        /// <summary>
+        /// Returns the chars that if found means we might have a match.
+        /// </summary>
+        internal static void AddTripChars(List<Common.InlineTripCharHelper> tripCharHelpers)
+        {
+            tripCharHelpers.Add(new Common.InlineTripCharHelper() { FirstChar = '*', Method = Common.InlineParseMethod.BoldItalic });
+            tripCharHelpers.Add(new Common.InlineTripCharHelper() { FirstChar = '_', Method = Common.InlineParseMethod.BoldItalic });
+        }
+
+        /// <summary>
+        /// Attempts to parse a bold text span.
+        /// </summary>
+        /// <param name="markdown"> The markdown text. </param>
+        /// <param name="start"> The location to start parsing. </param>
+        /// <param name="maxEnd"> The location to stop parsing. </param>
+        /// <returns> A parsed bold text span, or <c>null</c> if this is not a bold text span. </returns>
+        internal static Common.InlineParseResult Parse(string markdown, int start, int maxEnd)
+        {
+            if (start >= maxEnd - 1)
+            {
+                return null;
+            }
+
+            // Check the start sequence.
+            string startSequence = markdown.Substring(start, 3);
+            if (startSequence != "***" && startSequence != "___")
+            {
+                return null;
+            }
+
+            // Find the end of the span.  The end sequence (either '***' or '___') must be the same
+            // as the start sequence.
+            var innerStart = start + 3;
+            int innerEnd = Common.IndexOf(markdown, startSequence, innerStart, maxEnd);
+            if (innerEnd == -1)
+            {
+                return null;
+            }
+
+            // The span must contain at least one character.
+            if (innerStart == innerEnd)
+            {
+                return null;
+            }
+
+            // The first character inside the span must NOT be a space.
+            if (Common.IsWhiteSpace(markdown[innerStart]))
+            {
+                return null;
+            }
+
+            // The last character inside the span must NOT be a space.
+            if (Common.IsWhiteSpace(markdown[innerEnd - 1]))
+            {
+                return null;
+            }
+
+            // We found something!
+            var result = new BoldItalicTextInline();
+            result.Inlines = Common.ParseInlineChildren(markdown, innerStart, innerEnd);
+            return new Common.InlineParseResult(result, start, innerEnd + 3);
+        }
+
+        /// <summary>
+        /// Converts the object into it's textual representation.
+        /// </summary>
+        /// <returns> The textual representation of this object. </returns>
+        public override string ToString()
+        {
+            if (Inlines == null)
+            {
+                return base.ToString();
+            }
+
+            return "***" + string.Join(string.Empty, Inlines) + "***";
+        }
+    }
+}

Microsoft.Toolkit.Uwp.UI.Controls/MarkdownTextBlock/Parse/MarkdownInline.cs

@@ -34,6 +34,11 @@ internal enum MarkdownInlineType
         /// </summary>
         MarkdownLink,
 
+        /// <summary>
+        /// An bold and italic block
+        /// </summary>
+        BoldItalic,
+
         /// <summary>
         /// A raw hyper link
         /// </summary>