feat(control): add the highlight-text-block control.

src/Shared/HandyControl_Shared/Controls/Text/HighlightTextBlock.cs

@@ -0,0 +1,199 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Documents;
+using System.Windows.Media;
+
+namespace HandyControl.Controls
+{
+    public class HighlightTextBlock : TextBlock
+    {
+        public static readonly DependencyProperty SourceTextProperty =
+            DependencyProperty.Register("SourceText", typeof(string), typeof(HighlightTextBlock), new PropertyMetadata(null, OnSourceTextChanged));
+        public static readonly DependencyProperty QueriesTextProperty =
+            DependencyProperty.Register("QueriesText", typeof(string), typeof(HighlightTextBlock), new PropertyMetadata(null, OnQueriesTextChanged));
+        public static readonly DependencyProperty HighlightBrushProperty =
+            DependencyProperty.Register("HighlightBrush", typeof(Brush), typeof(HighlightTextBlock), new PropertyMetadata(Brushes.Yellow));
+
+        private static void OnSourceTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) =>
+            ((HighlightTextBlock) d).RefreshInlines();
+
+        private static void OnQueriesTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) =>
+            ((HighlightTextBlock) d).RefreshInlines();
+
+        /// <summary>
+        /// Replace the original property Text for binding text.
+        /// </summary>
+        /// <remarks>
+        /// Don't use the <see cref="TextBlock.Text"/> property!
+        /// Because the <see cref="TextBlock.Text"/> has some unique behaviors
+        /// that is not needed at <see cref="HighlightTextBlock"/> at <see cref="TextBlock"/>,
+        /// which will cause some unexpected issue. 
+        /// </remarks>
+        public string SourceText
+        {
+            get => (string) GetValue(SourceTextProperty);
+            set => SetValue(SourceTextProperty, value);
+        }
+
+        /// <summary>
+        /// Gets or sets the text that need to be highlighted.
+        /// It can be an array of text separated by spaces.
+        /// </summary>
+        public string QueriesText
+        {
+            get => (string) GetValue(QueriesTextProperty);
+            set => SetValue(QueriesTextProperty, value);
+        }
+
+        /// <summary>
+        /// Gets or sets the <see cref="Brush"/> of the background of the highlight text.
+        /// </summary>
+        public Brush HighlightBrush
+        {
+            get => (Brush) GetValue(HighlightBrushProperty);
+            set => SetValue(HighlightBrushProperty, value);
+        }
+
+        private void RefreshInlines()
+        {
+            Inlines.Clear();
+
+            if (string.IsNullOrEmpty(SourceText)) return;
+            if (string.IsNullOrEmpty(QueriesText))
+            {
+                Inlines.Add(SourceText);
+                return;
+            }
+
+            var sourceText = SourceText;
+            var queries = QueriesText.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
+            var intervals = from query in queries.Distinct()
+                            from interval in GetQueryIntervals(sourceText, query)
+                            select interval;
+            var mergedIntervals = MergeIntervals(intervals.ToList());
+            var fragments = SplitTextByOrderedDisjointIntervals(sourceText, mergedIntervals);
+
+            Inlines.AddRange(GenerateRunElement(fragments));
+        }
+
+        private IEnumerable GenerateRunElement(IEnumerable<Fragment> fragments)
+        {
+            return from item in fragments
+                   select item.IsQuery
+                   ? GetHighlightRun(item.Text)
+                   : new Run(item.Text);
+        }
+
+        private Run GetHighlightRun(string highlightText)
+        {
+            var run = new Run(highlightText);
+            run.SetBinding(TextElement.BackgroundProperty, new Binding
+            {
+                Source = this,
+                Path = new PropertyPath(nameof(HighlightBrush)),
+                Mode = BindingMode.OneWay
+            });
+            return run;
+        }
+
+        private static IEnumerable<Fragment> SplitTextByOrderedDisjointIntervals(string sourceText, List<Range> mergedIntervals)
+        {
+            if (string.IsNullOrEmpty(sourceText)) yield break;
+
+            if (!mergedIntervals?.Any() ?? true)
+            {
+                yield return new Fragment { Text = sourceText, IsQuery = false };
+                yield break;
+            }
+
+            var range0 = mergedIntervals.First();
+            int start0 = range0.Start;
+            int end0 = range0.End;
+
+            if (start0 > 0) yield return new Fragment { Text = sourceText.Substring(0, start0), IsQuery = false };
+            yield return new Fragment { Text = sourceText.Substring(start0, end0 - start0), IsQuery = true };
+
+            int previousEnd = end0;
+            foreach (var range in mergedIntervals.Skip(1))
+            {
+                int start = range.Start;
+                int end = range.End;
+                yield return new Fragment { Text = sourceText.Substring(previousEnd, start - previousEnd), IsQuery = false };
+                yield return new Fragment { Text = sourceText.Substring(start, end - start), IsQuery = true };
+                previousEnd = end;
+            }
+
+            if (previousEnd < sourceText.Length)
+                yield return new Fragment { Text = sourceText.Substring(previousEnd), IsQuery = false };
+        }
+
+        private static List<Range> MergeIntervals(List<Range> intervals)
+        {
+            if (!intervals?.Any() ?? true) return new List<Range>();
+
+            intervals.Sort((x, y) => x.Start != y.Start ? x.Start - y.Start : x.End - y.End);
+
+            var pointer = intervals[0];
+            int startPointer = pointer.Start;
+            int endPointer = pointer.End;
+
+            var result = new List<Range>();
+            foreach (var range in intervals.Skip(1))
+            {
+                int start = range.Start;
+                int end = range.End;
+
+                if (start <= endPointer)
+                {
+                    if (endPointer < end)
+                    {
+                        endPointer = end;
+                    }
+                }
+                else
+                {
+                    result.Add(new Range { Start = startPointer, End = endPointer });
+                    startPointer = start;
+                    endPointer = end;
+                }
+            }
+            result.Add(new Range { Start = startPointer, End = endPointer });
+            return result;
+        }
+
+        private static IEnumerable<Range> GetQueryIntervals(string sourceText, string query)
+        {
+            if (string.IsNullOrEmpty(sourceText) || string.IsNullOrEmpty(query)) yield break;
+
+            int nextStartIndex = 0;
+            while (nextStartIndex < sourceText.Length)
+            {
+                int index = sourceText.IndexOf(query, nextStartIndex, StringComparison.CurrentCultureIgnoreCase);
+
+                if (index == -1) yield break;
+
+                nextStartIndex = index + query.Length;
+                yield return new Range { Start = index, End = nextStartIndex };
+            }
+        }
+
+        private struct Fragment
+        {
+            public string Text { get; set; }
+
+            public bool IsQuery { get; set; }
+        }
+
+        private struct Range
+        {
+            public int Start { get; set; }
+
+            public int End { get; set; }
+        }
+    }
+}