/// <summary>
/// Map character supported by the typeface
/// </summary>
/// <remarks>
/// Combining mark is considered part of the character that may be supported
/// thru precomposed form or OpenType glyph substitution table.
/// </remarks>
private int MapCharacters(
MS.Internal.Text.TextInterface.Font font,
CharacterBufferRange unicodeString,
CultureInfo digitCulture,
ref int nextValid
)
{
DigitMap digitMap = new DigitMap(digitCulture);
int sizeofChar = 0;
int advance;
// skip all the leading joiner characters. They need to be shaped with the
// surrounding strong characters.
advance = Classification.AdvanceWhile(unicodeString, ItemClass.JoinerClass);
if (advance >= unicodeString.Length)
{
// It is rare that the run only contains joiner characters.
// If it really happens, just return.
return(advance);
}
//
// If the run starts with combining marks, we will not be able to find base characters for them
// within the run. These combining marks will be mapped to their best fonts as normal characters.
//
bool hasBaseChar = false;
// Determine how many characters we can advance, i.e., find the first invalid character.
for (; advance < unicodeString.Length; advance += sizeofChar)
{
// Get the character and apply digit substitution, if any.
int originalChar = Classification.UnicodeScalar(
new CharacterBufferRange(unicodeString, advance, unicodeString.Length - advance),
out sizeofChar
);
if (Classification.IsJoiner(originalChar))
{
continue;
}
if (!Classification.IsCombining(originalChar))
{
hasBaseChar = true;
}
else if (hasBaseChar)
{
// continue to advance for combining mark with base char
continue;
}
int ch = digitMap[originalChar];
if (font.HasCharacter(checked ((uint)ch)))
{
continue;
}
// If ch is a substituted character, can we substitute a different character instead?
if (ch != originalChar)
{
ch = DigitMap.GetFallbackCharacter(ch);
if (ch != 0 && font.HasCharacter(checked ((uint)ch)))
{
continue;
}
}
// If we fall through to here it's invalid.
break;
}
// UnicodeScalar won't return a sizeofChar that exceeds the string length.
Debug.Assert(advance <= unicodeString.Length);
// Find the next valid character.
if (advance < unicodeString.Length)
{
// UnicodeScalar won't return a sizeofChar that exceeds the string length.
Debug.Assert(advance + sizeofChar <= unicodeString.Length);
for (nextValid = advance + sizeofChar; nextValid < unicodeString.Length; nextValid += sizeofChar)
{
// Get the character.
int originalChar = Classification.UnicodeScalar(
new CharacterBufferRange(unicodeString, nextValid, unicodeString.Length - nextValid),
out sizeofChar
);
// Apply digit substitution, if any.
int ch = digitMap[originalChar];
//
// Combining mark should always be shaped by the same font as the base char.
// If the physical font is invalid for the base char, it should also be invalid for the
// following combining mark so that both characters will go onto the same fallback font.
// - When the fallback font is physical font, the font will be valid for both characters
// if and only if it is valid for the base char. Otherwise, it will be invalid for both.
// - When the fallback font is composite font, it maps the combining mark to the same font
// as the base char such that they will eventually be resolved to the same physical font.
// That means FamilyMap for the combining mark is not used when it follows a base char.
//
// The same goes for joiner. Note that "hasBaseChar" here indicates if there is an invalid base
// char in front.
if (Classification.IsJoiner(ch) ||
(hasBaseChar && Classification.IsCombining(ch))
)
{
continue;
}
// If we have a glyph it's valid.
if (font.HasCharacter(checked ((uint)ch)))
{
break;
}
// If ch is a substituted character, can we substitute a different character instead?
if (ch != originalChar)
{
ch = DigitMap.GetFallbackCharacter(ch);
if (ch != 0 && font.HasCharacter(checked ((uint)ch)))
{
break;
}
}
}
}
return(advance);
}
internal GlyphTypeface MapGlyphTypeface(
FontStyle style,
FontWeight weight,
FontStretch stretch,
CharacterBufferRange charString,
CultureInfo digitCulture,
ref int advance,
ref int nextValid
)
{
int smallestInvalid = charString.Length;
// Add all the cached font faces to a priority queue.
MatchingStyle targetStyle = new MatchingStyle(style, weight, stretch);
PriorityQueue <MatchingFace> queue = new PriorityQueue <MatchingFace>(
checked ((int)_family.Count),
new MatchingFaceComparer(targetStyle));
foreach (Text.TextInterface.Font face in _family)
{
queue.Push(new MatchingFace(face));
}
// Remember the best style match.
MS.Internal.Text.TextInterface.Font bestStyleTypeface = null;
// Iterate in priority order.
for (; queue.Count != 0; queue.Pop())
{
int invalid = 0;
MS.Internal.Text.TextInterface.Font font = queue.Top.FontFace;
int valid = MapCharacters(font, charString, digitCulture, ref invalid);
if (valid > 0)
{
if (smallestInvalid > 0 && smallestInvalid < valid)
{
// advance only to smallestInvalid because there's a better match after that
advance = smallestInvalid;
nextValid = 0;
}
else
{
advance = valid;
nextValid = invalid;
}
return(new GlyphTypeface(font));
}
else
{
if (invalid < smallestInvalid)
{
// keep track of the current shortest length of invalid characters,
smallestInvalid = invalid;
}
if (bestStyleTypeface == null)
{
bestStyleTypeface = font;
}
}
}
// no face can map the specified character string,
// fall back to the closest style match
advance = 0;
nextValid = smallestInvalid;
Debug.Assert(bestStyleTypeface != null);
return(new GlyphTypeface(bestStyleTypeface));
}
