C# StaticTextPointer.CreatePointer方法代码示例

        //-------------------------------------------------------------------
        //
        //  Private Methods
        //
        //-------------------------------------------------------------------

        #region Private Methods

        /// <summary>
        /// Fetch the next run at text position.
        /// </summary>
        private TextRun HandleText(StaticTextPointer position)
        {
            // Calculate the end of the run by finding either:
            //      a) the next intersection of highlight ranges, or
            //      b) the natural end of this textrun
            StaticTextPointer endOfRunPosition = _owner.Host.TextContainer.Highlights.GetNextPropertyChangePosition(position, LogicalDirection.Forward);

            // Clamp the text run at an arbitrary limit, so we don't make
            // an unbounded allocation.
            if (position.GetOffsetToPosition(endOfRunPosition) > 4096)
            {
                endOfRunPosition = position.CreatePointer(4096);
            }

            // Factor in any speller error squiggles on the run.
            TextDecorationCollection highlightDecorations = position.TextContainer.Highlights.GetHighlightValue(position, LogicalDirection.Forward, typeof(SpellerHighlightLayer)) as TextDecorationCollection;
            TextRunProperties properties;

            if (highlightDecorations == null)
            {
                properties = _lineProperties.DefaultTextRunProperties;
            }
            else
            {
                if (_spellerErrorProperties == null)
                {
                    _spellerErrorProperties = new TextProperties((TextProperties)_lineProperties.DefaultTextRunProperties, highlightDecorations);
                }
                properties = _spellerErrorProperties;
            }

            // Get character buffer for the text run.
            char[] textBuffer = new char[position.GetOffsetToPosition(endOfRunPosition)];

            // Copy characters from text run into buffer. Since we are dealing with plain text content, 
            // we expect to get all the characters from position to endOfRunPosition.
            int charactersCopied = position.GetTextInRun(LogicalDirection.Forward, textBuffer, 0, textBuffer.Length);
            Invariant.Assert(charactersCopied == textBuffer.Length);

            // Create text run, using characters copied as length
            return new TextCharacters(textBuffer, 0, charactersCopied, properties);
        }

        //-------------------------------------------------------------------
        //
        //  Protected Methods
        //
        //-------------------------------------------------------------------

        #region Protected Methods

        /// <summary>
        /// Fetch the next run at text position. 
        /// </summary>
        /// <param name="position">
        /// Current position in text array
        /// </param>
        /// <returns></returns>
        protected TextRun HandleText(StaticTextPointer position)
        {
            DependencyObject element;
            StaticTextPointer endOfRunPosition;

            Invariant.Assert(position.GetPointerContext(LogicalDirection.Forward) == TextPointerContext.Text, "TextPointer does not point to characters.");

            if (position.Parent != null)
            {
                element = position.Parent;
            }
            else
            {
                element = _paraClient.Paragraph.Element;
            }

            // Extract the aggregated properties into something that the textrun can use.
            // 


            TextProperties textProps = new TextProperties(element, position, false /* inline objects */, true /* get background */);

            // Calculate the end of the run by finding either:
            //      a) the next intersection of highlight ranges, or
            //      b) the natural end of this textrun
            endOfRunPosition = position.TextContainer.Highlights.GetNextPropertyChangePosition(position, LogicalDirection.Forward);

            // Clamp the text run at an arbitrary limit, so we don't make
            // an unbounded allocation.
            if (position.GetOffsetToPosition(endOfRunPosition) > 4096)
            {
                endOfRunPosition = position.CreatePointer(4096);
            }

            // Get character buffer for the text run.
            char[] textBuffer = new char[position.GetOffsetToPosition(endOfRunPosition)];

            // Copy characters from text run into buffer. Note the actual number of characters copied,
            // which may be different than the buffer's length. Buffer length only specifies the maximum
            // number of characters
            int charactersCopied = position.GetTextInRun(LogicalDirection.Forward, textBuffer, 0, textBuffer.Length);

            // Create text run using the actual number of characters copied
            return new TextCharacters(textBuffer, 0, charactersCopied, textProps);
        }

        /// <summary>
        /// Returns the closest neighboring TextPointer in an indicated
        /// direction where a property value calculated from an embedded
        /// object, scoping text element, or scoping highlight could
        /// change.
        /// </summary>
        /// <param name="textPosition">
        /// Position to query.
        /// </param>
        /// <param name="direction">
        /// Direction of content to query.
        /// </param>
        /// <returns>
        /// If the following symbol is TextPointerContext.EmbeddedElement,
        /// TextPointerContext.ElementBegin, or TextPointerContext.ElementEnd, returns
        /// a TextPointer exactly one symbol distant.
        ///
        /// If the following symbol is TextPointerContext.Text, the distance
        /// of the returned TextPointer is the minimum of the value returned
        /// by textPosition.GetTextLength and the distance to any highlight
        /// start or end edge.
        ///
        /// If the following symbol is TextPointerContext.None, returns null.
        /// </returns>
        internal virtual StaticTextPointer GetNextPropertyChangePosition(StaticTextPointer textPosition, LogicalDirection direction)
        {
            StaticTextPointer changePosition;
            StaticTextPointer characterRunEndPosition;

            switch (textPosition.GetPointerContext(direction))
            {
                case TextPointerContext.None:
                    changePosition = StaticTextPointer.Null;
                    break;

                case TextPointerContext.Text:
                    changePosition = GetNextHighlightChangePosition(textPosition, direction);
                    characterRunEndPosition = textPosition.GetNextContextPosition(LogicalDirection.Forward);

                    if (changePosition.IsNull ||
                        characterRunEndPosition.CompareTo(changePosition) < 0)
                    {
                        changePosition = characterRunEndPosition;
                    }

                    break;

                case TextPointerContext.EmbeddedElement:
                case TextPointerContext.ElementStart:
                case TextPointerContext.ElementEnd:
                default:
                    changePosition = textPosition.CreatePointer(+1);
                    break;
            }

            return changePosition;
        }