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Check script of combining marks during font fallback #6857

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Merged
merged 1 commit into from
Oct 26, 2022
Merged

Check script of combining marks during font fallback #6857

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12 changes: 12 additions & 0 deletions src/Microsoft.DotNet.Wpf/src/PresentationCore/MS/internal/Classification.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -261,6 +261,18 @@ static public short GetUnicodeClass(int unicodeScalar)
}


/// <summary>
/// Lookup script ID for a Unicode scalar value
/// </summary>
static public ScriptID GetScript(int unicodeScalar)
{
unsafe
{
return (ScriptID)Classification.CharAttributeTable[GetUnicodeClass(unicodeScalar)].Script;
}
}


/// <summary>
/// Compute Unicode scalar value from unicode codepoint stream
/// </summary>
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17 changes: 11 additions & 6 deletions src/Microsoft.DotNet.Wpf/src/PresentationCore/MS/internal/FontFace/PhysicalFontFamily.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -291,7 +291,8 @@ ref int nextValid
// 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;
const int NOBASE = -1; // null char is a valid base
int baseChar = NOBASE;

// Determine how many characters we can advance, i.e., find the first invalid character.
for (; advance < unicodeString.Length; advance += sizeofChar)
Expand All @@ -307,12 +308,16 @@ out sizeofChar

if (!Classification.IsCombining(originalChar))
{
hasBaseChar = true;
baseChar = originalChar;
}
else if (hasBaseChar)
else if (baseChar != NOBASE)
{
// continue to advance for combining mark with base char
continue;
// continue to advance for combining mark with base char (can be precomposed by shaping engine)
// except if it is a different script (#6801)
if (Classification.GetScript(baseChar) == Classification.GetScript(originalChar))
{
continue;
}
}

int ch = digitMap[originalChar];
Expand Down Expand Up @@ -365,7 +370,7 @@ out sizeofChar
// 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))
|| (baseChar != NOBASE && Classification.IsCombining(ch) && Classification.GetScript(ch) == Classification.GetScript(baseChar))
)
continue;

Expand Down