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//-----------------------------------------------------------------------
//
// 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 Worachai Chaoweeraprasit (wchao)
//
//------------------------------------------------------------------------
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
{
/// <summary>
/// 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.
/// </summary>
internal sealed class TextRunCacheImp
{
private SpanVector _textRunVector; // text run vector indexed by cp
private SpanPosition _latestPosition;
/// <summary>
/// Default constructor used internally
/// </summary>
/// <remarks>
/// Text layout client never create their own run cache as its implementation
/// should be opaque to them.
/// </remarks>
internal TextRunCacheImp()
{
_textRunVector = new SpanVector(null);
_latestPosition = new SpanPosition();
}
/// <summary>
/// Client to notify change in part of the cache when text or
/// properties of the run is being added, removed or replaced.
/// </summary>
/// <remarks>
/// 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.
/// </remarks>
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
);
}
/// <summary>
/// Fetch cached textrun
/// </summary>
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 = Constants.RealInfiniteWidth / 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);
}
// If the TextRun was obtained from the cache, make sure it has the right PixelsPerDip set on its properties.
if (textRun.Properties != null)
{
textRun.Properties.PixelsPerDip = settings.TextSource.PixelsPerDip;
}
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;
}
/// <summary>
/// Get text immediately preceding cpLimit.
/// </summary>
internal TextSpan<CultureSpecificCharacterBufferRange> 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<CultureSpecificCharacterBufferRange>(
cpLimit - textRunSpanRider.CurrentSpanStart, // cp length
new CultureSpecificCharacterBufferRange(culture, charString)
);
}
}
}
// not in cache so call back to client
return textSource.GetPrecedingText(cpLimit);
}
/// <summary>
/// Return all TextRuns cached. If for a particular range there is no TextRun cached, the TextSpan would
/// contain null TextRun object.
/// </summary>
internal IList<TextSpan<TextRun>> GetTextRunSpans()
{
IList<TextSpan<TextRun>> textRunList = new List<TextSpan<TextRun>>(_textRunVector.Count);
for (int i = 0; i < _textRunVector.Count; i++)
{
Span currentSpan = _textRunVector[i];
textRunList.Add(new TextSpan<TextRun>(currentSpan.length, currentSpan.element as TextRun));
}
return textRunList;
}
}
}
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