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Allow multiple kern subtables.

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We still only use the first subtable, but we no longer fail if there's
more than one subtable.

Updates fogleman/gg#7
This commit is contained in:
Nigel Tao 2017-04-29 10:42:25 +10:00
parent b12e981082
commit bcfeb16b74
1 changed files with 12 additions and 3 deletions
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15
truetype/truetype.go
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@ -324,11 +324,20 @@ func (f *Font) parseKern() error {
if version != 0 {
return UnsupportedError(fmt.Sprintf("kern version: %d", version))
}
n, offset := u16(f.kern, offset), offset+2
if n != 1 {
return UnsupportedError(fmt.Sprintf("kern nTables: %d", n))
if n == 0 {
return UnsupportedError("kern nTables: 0")
}
offset += 2
// TODO: support multiple subtables. In practice, almost all .ttf files
// have only one subtable, if they have a kern table at all. But it's not
// impossible. Xolonium Regular (https://fontlibrary.org/en/font/xolonium)
// has 3 subtables. Those subtables appear to be disjoint, rather than
// being the same kerning pairs encoded in three different ways.
//
// For now, we'll use only the first subtable.
offset += 2 // Skip the version.
length, offset := int(u16(f.kern, offset)), offset+2
coverage, offset := u16(f.kern, offset), offset+2
if coverage != 0x0001 {