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[VARC] Encode indices as 1,2,3,4 bytes long

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Previously it was 2 or 4.
This commit is contained in:
Behdad Esfahbod 2023-12-20 05:06:19 -07:00
parent 263d4d9a68
commit d37b3942ee
1 changed files with 38 additions and 25 deletions
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63
Lib/fontTools/ttLib/tables/otTables.py
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@ -220,12 +220,12 @@ class VarTransform:
class VarComponentFlags(IntFlag):
GID_IS_24BIT = 0x01
INDICES_ARE_LONG = 0x02
HAVE_LOCATION = 0x04
HAVE_TRANSFORM = 0x08
RESET_UNSPECIFIED_AXES = 0x10
USE_MY_METRICS = 0x20
INDICES_SIZE = 0x03 # Currently has to be the first two bits; search for indicesSize
GID_IS_24BIT = 0x04
USE_MY_METRICS = 0x8
HAVE_LOCATION = 0x10
HAVE_TRANSFORM = 0x20
RESET_UNSPECIFIED_AXES = 0x40
RETAIN_FLAGS = RESET_UNSPECIFIED_AXES | USE_MY_METRICS
RESERVED = 0x40 | 0x80
@ -252,18 +252,23 @@ class VarComponent:
i += 2
self.glyphName = font.glyphOrder[glyphID]
fmt = "L" if flags & VarComponentFlags.INDICES_ARE_LONG else "H"
indicesSize = (flags & VarComponentFlags.INDICES_SIZE) + 1
unpacker = {
1: lambda v: struct.unpack(">B", v)[0],
2: lambda v: struct.unpack(">H", v)[0],
3: lambda v: struct.unpack(">L", b"\0" + v)[0],
4: lambda v: struct.unpack(">L", v)[0],
}[indicesSize]
self.AxisIndicesIndex = self.AxisValuesIndex = self.TransformIndex = None
if flags & VarComponentFlags.HAVE_LOCATION:
l = 8 if flags & VarComponentFlags.INDICES_ARE_LONG else 4
self.AxisIndicesIndex, self.AxisValuesIndex = struct.unpack(
">" + fmt * 2, data[i : i + l]
)
i += l
self.AxisIndicesIndex = unpacker(data[i : i + indicesSize])
i += indicesSize
self.AxisValuesIndex = unpacker(data[i : i + indicesSize])
i += indicesSize
if flags & VarComponentFlags.HAVE_TRANSFORM:
l = 4 if flags & VarComponentFlags.INDICES_ARE_LONG else 2
self.TransformIndex = struct.unpack(">" + fmt, data[i : i + l])[0]
i += l
self.TransformIndex = unpacker(data[i : i + indicesSize])
i += indicesSize
return data[i:]
@ -279,25 +284,33 @@ class VarComponent:
else:
data.append(struct.pack(">H", glyphID))
indicesSize = 1
for attr in ("AxisIndicesIndex", "AxisValuesIndex", "TransformIndex"):
value = getattr(self, attr)
if value is not None and value > 65535:
flags |= VarComponentFlags.INDICES_ARE_LONG
break
if value is not None:
if value > 0xFFFFFF:
indicesSize = max(indicesSize, 4)
elif value > 0xFFFF:
indicesSize = max(indicesSize, 3)
elif value > 0xFF:
indicesSize = max(indicesSize, 2)
flags |= indicesSize - 1
fmt = "L" if flags & VarComponentFlags.INDICES_ARE_LONG else "H"
packer = {
1: lambda v: struct.pack(">B", v),
2: lambda v: struct.pack(">H", v),
3: lambda v: struct.pack(">L", v)[1:],
4: lambda v: struct.pack(">L", v),
}[indicesSize]
assert (self.AxisIndicesIndex is None) == (self.AxisValuesIndex is None)
if self.AxisIndicesIndex is not None:
flags |= VarComponentFlags.HAVE_LOCATION
data.append(
struct.pack(
">" + (fmt * 2), self.AxisIndicesIndex, self.AxisValuesIndex
)
)
data.append(packer(self.AxisIndicesIndex))
data.append(packer(self.AxisValuesIndex))
if self.TransformIndex is not None:
flags |= VarComponentFlags.HAVE_TRANSFORM
data.append(struct.pack(">" + fmt, self.TransformIndex))
data.append(packer(self.TransformIndex))
return struct.pack("B", flags) + bytesjoin(data)