Question

我正在尝试使用WPF RichTextEditor实现基本语法高亮。为此，我想以不同的颜色显示{} gropus。

这是应该将RichTextBox的内容分成不同组的代码：

    List<Tag> SplitIntoParts(TextRange textRange, int level)
    {
        if (textRange==null||textRange.IsEmpty)
        {
            return new List<Tag>();
        }
        string text = textRange.Text;
        if (text.Length==0)
        {
            return new List<Tag>();
        }
        int startPos=-1, counter = 0;
        List<Tag> result=new List<Tag>();
        for (int i = 0; i < text.Length; i++)
        {
            if (text[i]=='{')
            {
                if (counter==0)
                {
                    startPos = i;
                }
                counter++;
            }
            if (text[i]=='}')
            {
                if (counter==1)
                {
                    Tag t = new Tag()
                                {
                                    StartPosition = textRange.Start.GetPositionAtOffset(startPos), 
                                    EndPosition = textRange.Start.GetPositionAtOffset(i+1), 
                                    Level = level,
                                    Word = text.Substring(startPos,i+1-startPos)
                                };
                    result.Add(t);
                    var tr=new TextRange(textRange.Start.GetPositionAtOffset(startPos + 1), textRange.Start.GetPositionAtOffset(i));
                    result.AddRange(SplitIntoParts(tr, level + 1));
                }
                counter--;
            }
        }
        if (counter>0)//some open branches still left
        {
            var i = text.Length;
            Tag t = new Tag()
            {
                StartPosition = textRange.Start.GetPositionAtOffset(startPos),
                EndPosition = textRange.End,
                Level = level,
                Word = text.Substring(startPos, i - startPos)
            };
            result.Add(t);
            result.AddRange(SplitIntoParts(new TextRange(textRange.Start.GetPositionAtOffset(startPos + 1), textRange.Start.GetPositionAtOffset(i - 1)), level + 1));
        }

        return result;
    }

在这段代码中，我发现textRange.Start.GetPositionAtOffset（startPos + 1）表现得很奇怪：

让我们说，代码找到了以下组：

{test|try}

并使用以下代码选择它：

var t=new Tag()
                                {
                                    StartPosition = textRange.Start.GetPositionAtOffset(startPos), 
                                    EndPosition = textRange.Start.GetPositionAtOffset(i+1), 
                                    Level = level,
                                    Word = text.Substring(startPos,i+1-startPos)
                                };

（例如t.Word =='{test | try}'）

当我尝试通过传递

递归时

var tr=new TextRange(textRange.Start.GetPositionAtOffset(startPos + 1), textRange.Start.GetPositionAtOffset(i));
result.AddRange(SplitIntoParts(tr, level + 1));

而不是“test | try”，tr.Text ==“{test”

为什么我会遇到这种行为，我该如何处理？

Answer 1

GetPositionAtOffset并不只计算（可见）字符。幸运的是，我最近遇到了同样的问题，所以我创建了一个方法，使TextPointer获得指定的偏移量（仅计算可见字符的偏移量）。首先，它似乎有点复杂，但它确实不是： - ）。

作为一个参数，它需要内联（来自富文本框，如RichTextBox.Document.Blocks.FirstBlock.Inlines，它分别只获取rtb中第一段的内联，如果有的话......）;第二个参数是偏移本身。

建议给出第三个参数，TextPointer表示内容的开头。如果指定了内联，则从第一个内联确定起始位置，但是如果没有内联，则抛出异常，为避免这种情况，请将content start参数设置为RichTextBox.Document.ContentStart。方法如下：

    /// <summary>
    /// Returns the position of the specified offset in the text specified by the inlines.
    /// </summary>
    /// <param name="inlines">The inlines which specifies the text.</param>
    /// <param name="offset">The offset within the text to get the position of.</param>
    /// <param name="contentStartPosition">The position where the content starts. If null, the position before the start of the first inline will be used. If null and there are no inlines, an exception is thrown.</param>
    /// <returns>A <see cref="TextPointer"/> indicating the position of the specified offset.</returns>
    public static TextPointer GetPositionAtOffset(this InlineCollection inlines, int offset, TextPointer contentStartPosition = null)
    {
        if (inlines == null)
            throw new ArgumentNullException(nameof(inlines));
        if (!inlines.Any() && contentStartPosition == null)//if no inlines, can't determine start of content
            throw new ArgumentException("A content start position has to be specified if the inlines collection is empty.", nameof(contentStartPosition));

        if (contentStartPosition == null)
            contentStartPosition = inlines.First().ContentStart.DocumentStart;//if no content start specified, gets it
        int offsetWithInlineBorders = 0;//collects the value of offset (with inline borders)
        foreach (var inline in inlines)
        {
            int inlineLength = (inline as Run)?.Text.Length ?? (inline is LineBreak ? 1 : 0);//gets the length of the inline (length of a Run is the lengts of its text, length of a LineBreak is 1, other types are ignored)

            if (inlineLength < offset)//if position specified by the offset is beyond this inline...
                offsetWithInlineBorders += inlineLength + 2;//...then the whole length is added with the two borders
            else if (inlineLength == offset)//if position specified by the offset is at the end of this inline...
                offsetWithInlineBorders += inlineLength + 1;//...then the whole length is added with only the opening border
            else //inlineLength > value, if the position specified by the offset is within this inline
            {
                offsetWithInlineBorders += offset + 1;//...then adds the remaining length (the offset itself), plus the opening border
                break;//the inlines beyond are not needed
            }
            offset -= inlineLength;//substracts the added inline length
        }

        return contentStartPosition.GetPositionAtOffset(
            Math.Min(Math.Max(offsetWithInlineBorders, 0), contentStartPosition.GetOffsetToPosition(contentStartPosition.DocumentEnd)));//if the value is not within the boundaries of the text, returns the start or the end of the text
    }

祝你好运

Answer 2

GetPositionAtOffset计算符号，这可能不仅仅是文本插入位置。见MSDN：

将TextPointer返回到指定的位置符号中的偏移量，从当前TextPointer的开头开始。

TextRange GetPositionAtOffset的行为不符合预期

2 个答案: