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prefer full/UCS4 sub-tables over BMP/UCS2 ones #88

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prefer full/UCS4 sub-tables over BMP/UCS2 ones #88

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8861c84
prefer full/UCS4 sub-tables over BMP/UCS2 ones
leibnewton Oct 26, 2021
9bd971f
remove import directive for truetype package
leibnewton Nov 24, 2021
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21 changes: 12 additions & 9 deletions truetype/truetype.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@
//
// To measure a TrueType font in ideal FUnit space, use scale equal to
// font.FUnitsPerEm().
package truetype // import "github.com/golang/freetype/truetype"
package truetype

import (
"fmt"
Expand Down Expand Up @@ -133,7 +133,7 @@ func parseSubtables(table []byte, name string, offset, size int, pred func([]byt
if len(table) < size*nSubtables+offset {
return 0, 0, FormatError(name + " too short")
}
ok := false
bestScore := -1
for i := 0; i < nSubtables; i, offset = i+1, offset+size {
if pred != nil && !pred(table[offset:]) {
continue
Expand All @@ -143,19 +143,22 @@ func parseSubtables(table []byte, name string, offset, size int, pred func([]byt
pidPsid := u32(table, offset)
// We prefer the Unicode cmap encoding. Failing to find that, we fall
// back onto the Microsoft cmap encoding.
// And we prefer full/UCS4 encoding over BMP/UCS2. So the priority goes:
// unicodeEncodingFull > microsoftUCS4Encoding > unicodeEncodingBMPOnly > microsoftUCS2Encoding > microsoftSymbolEncoding
// It is in accord with the Psid part.
score := int(pidPsid & 0xFFFF)
if score <= bestScore {
continue
}
if pidPsid == unicodeEncodingBMPOnly || pidPsid == unicodeEncodingFull {
bestOffset, bestPID, ok = offset, pidPsid>>16, true
break

bestOffset, bestPID, bestScore = offset, pidPsid>>16, score
} else if pidPsid == microsoftSymbolEncoding ||
pidPsid == microsoftUCS2Encoding ||
pidPsid == microsoftUCS4Encoding {

bestOffset, bestPID, ok = offset, pidPsid>>16, true
// We don't break out of the for loop, so that Unicode can override Microsoft.
bestOffset, bestPID, bestScore = offset, pidPsid>>16, score
}
}
if !ok {
if bestScore < 0 {
return 0, 0, UnsupportedError(name + " encoding")
}
return bestOffset, bestPID, nil
Expand Down