/// <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>
/// 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>
/// Fetch text run and character string associated with it
/// </summary>
internal CharacterBufferRange FetchTextRun(
int cpFetch,
int cpFirst,
out TextRun textRun,
out int runLength
)
{
int offsetToFirstCp;
textRun = _runCache.FetchTextRun(this, cpFetch, cpFirst, out offsetToFirstCp, out runLength);
CharacterBufferRange charString;
switch (TextRunInfo.GetRunType(textRun))
{
case Plsrun.Text:
{
CharacterBufferReference charBufferRef = textRun.CharacterBufferReference;
charString = new CharacterBufferRange(
charBufferRef.CharacterBuffer,
charBufferRef.OffsetToFirstChar + offsetToFirstCp,
runLength
);
break;
}
case Plsrun.InlineObject:
Debug.Assert(offsetToFirstCp == 0);
unsafe
{
charString = new CharacterBufferRange(TextStore.StrObjectReplacement, 0, 1);
}
break;
case Plsrun.LineBreak:
Debug.Assert(offsetToFirstCp == 0);
unsafe
{
//
// Line break is to be represented as "Line Separator" such that
// it doesn't terminate the optimal paragraph formatting session, but still breaks the line
// unambiguously.
//
charString = new CharacterBufferRange(TextStore.StrLineSeparator, 0, 1);
}
break;
case Plsrun.ParaBreak:
Debug.Assert(offsetToFirstCp == 0);
unsafe
{
//
// Paragraph break is special as it also terminates the paragraph.
// It should be represented as "Paragraph Separator" such that it will be correctly handled
// in Bidi and Optimal paragraph formatting.
//
charString = new CharacterBufferRange(TextStore.StrParaSeparator, 0, 1);
}
break;
case Plsrun.Hidden:
unsafe
{
charString = new CharacterBufferRange(TextStore.StrHidden, 0, 1);
}
break;
default:
charString = CharacterBufferRange.Empty;
break;
}
return(charString);
}
