RichTextBox 用表情符号/图像替换字符串

Question

在 RichtTextBox 中，我想用表情符号图像自动替换表情符号字符串（例如 :D）。到目前为止我已经开始工作了，除了当我在现有的单词/字符串之间写表情符号字符串时，图像被插入到行尾。

例如： hello (inserting :D here) this is a message
结果是： hello this is a message ☺ << 图片

另一个（小）问题是，插入后插入符号位置设置在图像之前。

这是我已经得到的：

public class Emoticon
{
    public Emoticon(string key, Bitmap bitmap)
    {
        Key = key;
        Bitmap = bitmap;
        BitmapImage = bitmap.ToBitmapImage();
    }

    public string Key { get; }
    public Bitmap Bitmap { get; }
    public BitmapImage BitmapImage { get; }
}

public class EmoticonRichTextBox : RichTextBox
{
    private readonly List<Emoticon> _emoticons;

    public EmoticonRichTextBox()
    {
        _emoticons = new List<Emoticon>
        {
            new Emoticon(":D", Properties.Resources.grinning_face)
        };
    }

    protected override void OnTextChanged(TextChangedEventArgs e)
    {
        base.OnTextChanged(e);
        Dispatcher.InvokeAsync(Look);
    }

    private void Look()
    {
        const string keyword = ":D";

        var text = new TextRange(Document.ContentStart, Document.ContentEnd);
        var current = text.Start.GetInsertionPosition(LogicalDirection.Forward);

        while (current != null)
        {
            var textInRun = current.GetTextInRun(LogicalDirection.Forward);
            if (!string.IsNullOrWhiteSpace(textInRun))
            {
                var index = textInRun.IndexOf(keyword, StringComparison.Ordinal);
                if (index != -1)
                {
                    var selectionStart = current.GetPositionAtOffset(index, LogicalDirection.Forward);
                    if (selectionStart == null)
                        continue;

                    var selectionEnd = selectionStart.GetPositionAtOffset(keyword.Length, LogicalDirection.Forward);
                    var selection = new TextRange(selectionStart, selectionEnd) { Text = string.Empty };

                    var emoticon = _emoticons.FirstOrDefault(x => x.Key.Equals(keyword));
                    if (emoticon == null)
                        continue;

                    var image = new System.Windows.Controls.Image
                    {
                        Source = emoticon.BitmapImage,
                        Height = 18,
                        Width = 18,
                        Margin = new Thickness(0, 3, 0, 0)
                    };

                    // inserts at the end of the line
                    selection.Start?.Paragraph?.Inlines.Add(image);

                    // doesn't work
                    CaretPosition = CaretPosition.GetPositionAtOffset(1, LogicalDirection.Forward);
                }
            }

            current = current.GetNextContextPosition(LogicalDirection.Forward);
        }
    }
}

public static class BitmapExtensions
{
    public static BitmapImage ToBitmapImage(this Bitmap bitmap)
    {
        using (var stream = new MemoryStream())
        {
            bitmap.Save(stream, ImageFormat.Png);
            stream.Position = 0;

            var image = new BitmapImage();
            image.BeginInit();
            image.CacheOption = BitmapCacheOption.OnLoad;
            image.DecodePixelHeight = 18;
            image.DecodePixelWidth = 18;
            image.StreamSource = stream;
            image.EndInit();
            image.Freeze();

            return image;
        }
    }
}

Answer 1

故障线路为selection.Start?.Paragraph?.Inlines.Add(image);。您将图像附加到段落的末尾。您应该使用 InsertBefore 或 InsertAfter 方法之一。

但是要使用这些方法，您应该遍历内联并找到合适的内联插入之前或之后。这并不难。您可以通过比较 selectionStart 和 selectionEnd 与内联的 ElementStart 和 ElementEnd 属性来确定内联。

另一个棘手的可能性是您要插入的位置可能位于行内。然后你应该拆分那个内联并创建另外三个：

一个包含插入位置之前的元素
一个包含图像
一个包含插入位置之后的元素。

然后，您可以删除内联并在适当的位置插入新的三个内联。

Wpf的RichTextBox没有最漂亮的API。有时很难与之合作。还有另一个控件叫做 AvalonEdit。它比 RichTextBox 更容易使用。你可以考虑一下。

Answer 2

作为 @Yusuf Tarık Günaydın suggested, I looked for the AvalonEdit 控制，相当容易做到这一点。

在这个 example 的帮助下，我只需要创建一个 VisualLineElementGenerator 来查找表情匹配并插入图像。

public static class BitmapExtensions
{
    public static BitmapImage ToBitmapImage(this Bitmap bitmap)
    {
        using (var stream = new MemoryStream())
        {
            bitmap.Save(stream, ImageFormat.Png);
            stream.Position = 0;

            var image = new BitmapImage();
            image.BeginInit();
            image.CacheOption = BitmapCacheOption.OnLoad;
            image.DecodePixelHeight = 18;
            image.DecodePixelWidth = 18;
            image.StreamSource = stream;
            image.EndInit();
            image.Freeze();

            return image;
        }
    }
}

public class Emoticon
{
    public Emoticon(string key, Bitmap bitmap)
    {
        Key = key;
        Bitmap = bitmap;
        BitmapImage = bitmap.ToBitmapImage();
    }

    public string Key { get; }
    public Bitmap Bitmap { get; }
    public BitmapImage BitmapImage { get; }
}

public class EmoticonTextBox : TextEditor
{
    public EmoticonTextBox()
    {
        HorizontalScrollBarVisibility = ScrollBarVisibility.Auto;
        VerticalScrollBarVisibility = ScrollBarVisibility.Disabled;

        TextArea.TextView.ElementGenerators.Add(new ImageElementGenerator());
    }
}

public class ImageElementGenerator : VisualLineElementGenerator
{
    // To use this class:
    // textEditor.TextArea.TextView.ElementGenerators.Add(new ImageElementGenerator());

    private static readonly Regex ImageRegex = new Regex(@":D", RegexOptions.IgnoreCase);

    private readonly List<Emoticon> _emoticons;

    public ImageElementGenerator()
    {
        _emoticons = new List<Emoticon>
        {
            new Emoticon(":D", Properties.Resources.grinning_face)
        };
    }

    private Match FindMatch(int startOffset)
    {
        var endOffset = CurrentContext.VisualLine.LastDocumentLine.EndOffset;
        var relevantText = CurrentContext.Document.GetText(startOffset, endOffset - startOffset);

        return ImageRegex.Match(relevantText);
    }

    public override int GetFirstInterestedOffset(int startOffset)
    {
        var match = FindMatch(startOffset);
        return match.Success ? startOffset + match.Index : -1;
    }

    public override VisualLineElement ConstructElement(int offset)
    {
        var match = FindMatch(offset);
        if (!match.Success || match.Index != 0)
            return null;

        var key = match.Groups[0].Value;
        var emoticon = _emoticons.FirstOrDefault(x => x.Key.Equals(key));

        var bitmap = emoticon?.BitmapImage;
        if (bitmap == null)
            return null;

        var image = new System.Windows.Controls.Image
        {
            Source = bitmap,
            Width = bitmap.PixelWidth,
            Height = bitmap.PixelHeight
        };

        return new InlineObjectElement(match.Length, image);
    }
}

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