TextRunCacheImp.cs source code in C# .NET

                        Code:
                         / DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / MS / Internal / TextFormatting / TextRunCacheImp.cs / 1 / TextRunCacheImp.cs
                        
                        
                            //------------------------------------------------------------------------ 
//
//  Microsoft Windows Client Platform
//  Copyright (C) Microsoft Corporation, 2001
// 
//  File:      TextRunCacheImp.cs
// 
//  Contents:  Cache of text and text properties of run 
//
//  Created:   2-25-2003 [....] ([....]) 
//
//-----------------------------------------------------------------------

 
using System;
using System.Collections.Generic; 
using System.Globalization; 
using System.Windows;
using System.Diagnostics; 
using System.Windows.Media.TextFormatting;

using SR=MS.Internal.PresentationCore.SR;
using SRID=MS.Internal.PresentationCore.SRID; 

namespace MS.Internal.TextFormatting 
{ 
    /// 
    /// TextFormatter caches runs it receives from GetTextRun callback. This cache 
    /// object is managed by text layout client.
    ///
    /// This method is used to improve performance in application whose fetching the
    /// run has significant performance implication. Application using this caching 
    /// mechanism is responsible for invalidating the content in the cache when
    /// its changed. 
    ///  
    internal sealed class TextRunCacheImp
    { 
        private SpanVector      _textRunVector;         // text run vector indexed by cp
        private SpanPosition    _latestPosition;

 
        /// 
        /// Default constructor used internally 
        ///  
        /// 
        /// Text layout client never create their own run cache as its implementation 
        /// should be opaque to them.
        /// 
        internal TextRunCacheImp()
        { 
            _textRunVector = new SpanVector(null);
            _latestPosition = new SpanPosition(); 
        } 

 
        /// 
        /// Client to notify change in part of the cache when text or
        /// properties of the run is being added, removed or replaced.
        ///  
        /// 
        /// The client's expectation of this notification is that TextFormatter 
        /// retains valid state for run cache in response to this change. It's 
        /// expected that at least TextFormatter will refetch the runs affected
        /// by the change. Subsequent runs may or may not be refected depending 
        /// on the state of the cache after the change.
        /// 
        public void Change(
            int     textSourceCharacterIndex, 
            int     addition,
            int     removal 
            ) 
        {
            if (textSourceCharacterIndex < 0) 
                return;

            int cchActive = 0;
            for (int i = 0; i < _textRunVector.Count; i++) 
                cchActive += _textRunVector[i].length;
 
            if (textSourceCharacterIndex >= cchActive) 
                return;
 
            SpanRider textRunSpanRider = new SpanRider(_textRunVector, _latestPosition, textSourceCharacterIndex);
            _latestPosition = textRunSpanRider.SpanPosition;

            // we remove runs from the cache starting from the one containing the change 
            // to the end of the active range. We do not try to interpret the scope of
            // the change and try to minimize the range in which the cache is invalidated, 
            // because that would require an in-depth understanding of how our client 
            // implement their formatting change mechanism and how they respond to future
            // refetch after the change which could vary among different clients. That 
            // kind of work is beyond the purpose of this notification.

            _latestPosition = _textRunVector.SetValue(
                textRunSpanRider.CurrentSpanStart, 
                cchActive - textRunSpanRider.CurrentSpanStart,
                _textRunVector.Default, 
                _latestPosition 
                );
        } 


        /// 
        /// Fetch cached textrun 
        /// 
        internal TextRun FetchTextRun( 
            FormatSettings          settings, 
            int                     cpFetch,
            int                     cpFirst, 
            out int                 offsetToFirstCp,
            out int                 runLength
            )
        { 
            SpanRider textRunSpanRider = new SpanRider(_textRunVector, _latestPosition, cpFetch);
            _latestPosition = textRunSpanRider.SpanPosition; 
            TextRun textRun = (TextRun)textRunSpanRider.CurrentElement; 

            if(textRun == null) 
            {
                // run not already cached, fetch new run and cache it

                textRun = settings.TextSource.GetTextRun(cpFetch); 

                if (textRun.Length < 1) 
                { 
                    throw new ArgumentOutOfRangeException("textRun.Length", SR.Get(SRID.ParameterMustBeGreaterThanZero));
                } 

                Plsrun plsrun = TextRunInfo.GetRunType(textRun);

                if (plsrun == Plsrun.Text || plsrun == Plsrun.InlineObject) 
                {
                    TextRunProperties properties = textRun.Properties; 
 
                    if (properties == null)
                        throw new ArgumentException(SR.Get(SRID.TextRunPropertiesCannotBeNull)); 

                    if (properties.FontRenderingEmSize <= 0)
                        throw new ArgumentException(SR.Get(SRID.PropertyOfClassMustBeGreaterThanZero, "FontRenderingEmSize", "TextRunProperties"));
 
                    double realMaxFontRenderingEmSize = settings.Formatter.IdealToReal(Constants.InfiniteWidth) / Constants.GreatestMutiplierOfEm;
 
                    if (properties.FontRenderingEmSize > realMaxFontRenderingEmSize) 
                        throw new ArgumentException(SR.Get(SRID.PropertyOfClassCannotBeGreaterThan, "FontRenderingEmSize", "TextRunProperties", realMaxFontRenderingEmSize));
 
                    CultureInfo culture = CultureMapper.GetSpecificCulture(properties.CultureInfo);

                    if (culture == null)
                        throw new ArgumentException(SR.Get(SRID.PropertyOfClassCannotBeNull, "CultureInfo", "TextRunProperties")); 

                    if (properties.Typeface == null) 
                        throw new ArgumentException(SR.Get(SRID.PropertyOfClassCannotBeNull, "Typeface", "TextRunProperties")); 
                }
 

                //
                // TextRun is specifial to SpanVector because TextRun also encodes position which needs to be
                // consistent with the positions encoded by SpanVector. In run cache, the begining of a span 
                // should always correspond to the begining of a cached text run. If the end of the currently fetched
                // run overlaps with the begining of an already cached run, the begining of the cached run needs to be 
                // adjusted as well as its span. Because we can't gurantee the correctness of the overlapped range 
                // so we'll simply remove the overlapped runs here.
                // 

                // Move the rider to the end of the current run
                textRunSpanRider.At(cpFetch + textRun.Length - 1);
                _latestPosition = textRunSpanRider.SpanPosition; 

                if (textRunSpanRider.CurrentElement != _textRunVector.Default) 
                { 
                    // The end overlaps with one or more cached runs, clear the range from the
                    // begining of the current fetched run to the end of the last overlapped cached run. 
                    _latestPosition = _textRunVector.SetReference(
                        cpFetch,
                        textRunSpanRider.CurrentPosition + textRunSpanRider.Length - cpFetch,
                        _textRunVector.Default, 
                        _latestPosition
                        ); 
                } 

                _latestPosition = _textRunVector.SetReference(cpFetch, textRun.Length, textRun, _latestPosition); 

                // Refresh the rider's SpanPosition following previous SpanVector.SetReference calls
                textRunSpanRider.At(_latestPosition, cpFetch);
            } 

            offsetToFirstCp = textRunSpanRider.CurrentPosition - textRunSpanRider.CurrentSpanStart; 
            runLength = textRunSpanRider.Length; 
            Debug.Assert(textRun != null && runLength > 0, "Invalid run!");
 
            bool isText = textRun is ITextSymbols;

            if (isText)
            { 
                // Chop text run to optimal length so we dont spend forever analysing
                // them all at once. 
 
                int looseCharLength = TextStore.TypicalCharactersPerLine - cpFetch + cpFirst;
 
                if(looseCharLength <= 0)
                {
                    // this line already exceeds typical line length, incremental fetch goes
                    // about a quarter of the typical length. 

                    looseCharLength = (int)Math.Round(TextStore.TypicalCharactersPerLine * 0.25); 
                } 

                if(runLength > looseCharLength) 
                {
                    if (TextRunInfo.GetRunType(textRun) == Plsrun.Text)
                    {
                        // 
                        // When chopping the run at the typical line length,
                        // - don't chop in between of higher & lower surrogate 
                        // - don't chop combining mark away from its base character 
                        // - don't chop joiner from surrounding characters
                        // 
                        // Starting from the initial chopping point, we look ahead to find a safe position. We stop at
                        // a limit in case the run consists of many combining mark & joiner. That is rare and doesn't make
                        // much sense in shaping already.
                        // 

                        CharacterBufferReference charBufferRef = textRun.CharacterBufferReference; 
 
                        // We look ahead by one more line at most. It is not normal to have
                        // so many combining mark or joiner characters in a row. It doesn't make sense to 
                        // look further if so.
                        int lookAheadLimit = Math.Min(runLength, looseCharLength + TextStore.TypicalCharactersPerLine);

                        int sizeOfChar = 0; 
                        int endOffset  = 0;
                        bool canBreakAfterPrecedingChar = false; 
 
                        for (endOffset = looseCharLength - 1; endOffset < lookAheadLimit; endOffset += sizeOfChar)
                        { 
                            CharacterBufferRange charString = new CharacterBufferRange(
                                charBufferRef.CharacterBuffer,
                                charBufferRef.OffsetToFirstChar + offsetToFirstCp + endOffset,
                                runLength - endOffset 
                                );
 
                            int ch = Classification.UnicodeScalar(charString, out sizeOfChar); 

                            // We can only safely break if the preceding char is not a joiner character (i.e. can-break-after), 
                            // and the current char is not combining or joiner (i.e. can-break-before).
                            if (canBreakAfterPrecedingChar && !Classification.IsCombining(ch) && !Classification.IsJoiner(ch) )
                            {
                                break; 
                            }
 
                            canBreakAfterPrecedingChar = !Classification.IsJoiner(ch); 
                        }
 
                        looseCharLength = Math.Min(runLength, endOffset);
                    }

                    runLength = looseCharLength; 
                }
            } 
 

            Debug.Assert( 

                // valid run found
                runLength > 0
 
                // non-text run always fetched at run start
                &&  (   isText 
                    || textRunSpanRider.CurrentSpanStart - textRunSpanRider.CurrentPosition == 0) 

                // span rider of both text and format point to valid position 
                &&  (textRunSpanRider.Length > 0 && textRunSpanRider.CurrentElement != null),

                "Text run fetching error!"
                ); 

            return textRun; 
        } 

 
        /// 
        /// Get text immediately preceding cpLimit.
        /// 
        internal TextSpan GetPrecedingText(TextSource textSource, int cpLimit) 
        {
            if (cpLimit > 0) 
            { 
                SpanRider textRunSpanRider = new SpanRider(_textRunVector, _latestPosition);
                if (textRunSpanRider.At(cpLimit - 1)) 
                {
                    CharacterBufferRange charString = CharacterBufferRange.Empty;
                    CultureInfo culture = null;
 
                    TextRun run = textRunSpanRider.CurrentElement as TextRun;
 
                    if (run != null) 
                    {
                        // Only TextRun containing text would have non-empty Character buffer range. 
                        if ( TextRunInfo.GetRunType(run) == Plsrun.Text
                          && run.CharacterBufferReference.CharacterBuffer != null)
                        {
                            charString = new CharacterBufferRange( 
                                run.CharacterBufferReference,
                                cpLimit - textRunSpanRider.CurrentSpanStart); 
 
                            culture = CultureMapper.GetSpecificCulture(run.Properties.CultureInfo);
                        } 

                        return new TextSpan(
                            cpLimit - textRunSpanRider.CurrentSpanStart, // cp length
                            new CultureSpecificCharacterBufferRange(culture, charString) 
                         );
                    } 
                } 
            }
 
            // not in cache so call back to client
            return textSource.GetPrecedingText(cpLimit);
        }
 
        /// 
        /// Return all TextRuns cached. If for a particular range there is no TextRun cached, the TextSpan would 
        /// contain null TextRun object. 
        /// 
        internal IList> GetTextRunSpans() 
        {
            IList> textRunList = new List>(_textRunVector.Count);

            for (int i = 0; i < _textRunVector.Count; i++) 
            {
                Span currentSpan = _textRunVector[i]; 
                textRunList.Add(new TextSpan(currentSpan.length, currentSpan.element as TextRun)); 
            }
 
            return textRunList;
        }
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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TextRunCacheImp.cs source code in C# .NET

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