c# - AvalonEdit 在其他格式上显示选择

Question

我目前将以下代码用作带有 AvalonEdit TextEditor 的 LineTransformer。我希望能够通过选择突出显示当前的单个搜索结果，但是该选择几乎不可见，因为 DocumentColorizingTransformer 的格式优先于显示突出显示的文本。如何让突出显示的选择显示而不是格式化或在格式化之前显示？

public class ColorizeSearchResults : DocumentColorizingTransformer {

    public ColorizeSearchResults() : base() {
        SearchTerm = "";
        MatchCase = false;
    }

    public string SearchTerm { get; set; }
    public bool MatchCase { get; set; }

    protected override void ColorizeLine(DocumentLine line) {
        if (SearchTerm.Length == 0)
            return;

        int lineStartOffset = line.Offset;
        string text = CurrentContext.Document.GetText(line);
        int count = 0;
        int start = 0;
        int index;
        while ((index = text.IndexOf(SearchTerm, start, MatchCase ? StringComparison.CurrentCulture : StringComparison.CurrentCultureIgnoreCase)) >= 0) {
            base.ChangeLinePart(
                lineStartOffset + index,
                lineStartOffset + index + SearchTerm.Length,
                (VisualLineElement element) => {
                    element.TextRunProperties.SetForegroundBrush(Brushes.White);
                    element.TextRunProperties.SetBackgroundBrush(Brushes.Magenta);
                });
            start = index + 1;
            count++;
        }
    }
}

Example of formatting showing over selection

Answer 1

参见 http://avalonedit.net/documentation/html/c06e9832-9ef0-4d65-ac2e-11f7ce9c7774.htm用于 AvalonEdit 渲染流程。

选择层在文本之前呈现。因此，如果文本有背景，它会覆盖选择背景。幸运的是，我们可以将背景设置为 Brush.Transparent(或 Selection.Brush 和您自己的颜色的混合)。

解决方案:我修改了 SelectionColorizer 代码以将选择背景重置为透明:

class SelectionColorizerWithBackground : ColorizingTransformer
{
    ICSharpCode.AvalonEdit.Editing.TextArea _textArea;

    public SelectionColorizerWithBackground(
        ICSharpCode.AvalonEdit.Editing.TextArea textArea)
    {
        if (textArea == null)
            throw new ArgumentNullException("textArea");
        this._textArea = textArea;
    }

    protected override void Colorize(ITextRunConstructionContext context)
    {
        int lineStartOffset = context.VisualLine.FirstDocumentLine.Offset;

        int lineEndOffset = context.VisualLine.LastDocumentLine.Offset +
            context.VisualLine.LastDocumentLine.TotalLength;

        foreach (var segment in _textArea.Selection.Segments)
        {
            int segmentStart = segment.StartOffset;
            if (segmentStart >= lineEndOffset)
                continue;

            int segmentEnd = segment.EndOffset;
            if (segmentEnd <= lineStartOffset)
                continue;

            int startColumn;
            if (segmentStart < lineStartOffset)
                startColumn = 0;
            else
                startColumn = context.VisualLine.ValidateVisualColumn(
                    segment.StartOffset, segment.StartVisualColumn,
                    _textArea.Selection.EnableVirtualSpace);

            int endColumn;
            if (segmentEnd > lineEndOffset)
                endColumn =
                    _textArea.Selection.EnableVirtualSpace
                        ? int.MaxValue
                        : context.VisualLine
                                 .VisualLengthWithEndOfLineMarker;
            else
                endColumn = context.VisualLine.ValidateVisualColumn(
                    segment.EndOffset, segment.EndVisualColumn,
                    _textArea.Selection.EnableVirtualSpace);

            ChangeVisualElements(
                startColumn, endColumn,
                element => {
                    element.TextRunProperties.SetBackgroundBrush(
                        System.Windows.Media.Brushes.Transparent);
                    if (_textArea.SelectionForeground != null)
                    {
                        element.TextRunProperties.SetForegroundBrush(
                            _textArea.SelectionForeground);
                    }
                });
        }
    }
}

要使用您应该执行以下操作的代码:

var lineTransformers = textEditor.TextArea.TextView.LineTransformers;

// Remove the original SelectionColorizer.
// Note: if you have syntax highlighting you need to do something else
// to avoid clearing other colorizers. If too complicated you can skip
// this step but to suffer a 2x performance penalty.
lineTransformers.Clear();

lineTransformers.Add(new ColorizeSearchResults());
lineTransformers.Add(
    new SelectionColorizerWithBackground(textEditor.TextArea));