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"""Compiles/decompiles SVG table.
https://docs.microsoft.com/en-us/typography/opentype/spec/svg
The XML format is:
.. code-block:: xml
<SVG>
<svgDoc endGlyphID="1" startGlyphID="1">
<![CDATA[ <complete SVG doc> ]]
</svgDoc>
...
<svgDoc endGlyphID="n" startGlyphID="m">
<![CDATA[ <complete SVG doc> ]]
</svgDoc>
</SVG>
"""
from fontTools.misc.textTools import bytesjoin, safeEval, strjoin, tobytes, tostr
from fontTools.misc import sstruct
from . import DefaultTable
from collections.abc import Sequence
from dataclasses import dataclass, astuple
from io import BytesIO
import struct
import logging
log = logging.getLogger(__name__)
SVG_format_0 = """
> # big endian
version: H
offsetToSVGDocIndex: L
reserved: L
"""
SVG_format_0Size = sstruct.calcsize(SVG_format_0)
doc_index_entry_format_0 = """
> # big endian
startGlyphID: H
endGlyphID: H
svgDocOffset: L
svgDocLength: L
"""
doc_index_entry_format_0Size = sstruct.calcsize(doc_index_entry_format_0)
class table_S_V_G_(DefaultTable.DefaultTable):
def decompile(self, data, ttFont):
self.docList = []
# Version 0 is the standardized version of the table; and current.
# https://www.microsoft.com/typography/otspec/svg.htm
sstruct.unpack(SVG_format_0, data[:SVG_format_0Size], self)
if self.version != 0:
log.warning(
"Unknown SVG table version '%s'. Decompiling as version 0.", self.version)
# read in SVG Documents Index
# data starts with the first entry of the entry list.
pos = subTableStart = self.offsetToSVGDocIndex
self.numEntries = struct.unpack(">H", data[pos:pos+2])[0]
pos += 2
if self.numEntries > 0:
data2 = data[pos:]
entries = []
for i in range(self.numEntries):
docIndexEntry, data2 = sstruct.unpack2(doc_index_entry_format_0, data2, DocumentIndexEntry())
entries.append(docIndexEntry)
for entry in entries:
start = entry.svgDocOffset + subTableStart
end = start + entry.svgDocLength
doc = data[start:end]
compressed = False
if doc.startswith(b"\x1f\x8b"):
import gzip
bytesIO = BytesIO(doc)
with gzip.GzipFile(None, "r", fileobj=bytesIO) as gunzipper:
doc = gunzipper.read()
del bytesIO
compressed = True
doc = tostr(doc, "utf_8")
self.docList.append(
SVGDocument(doc, entry.startGlyphID, entry.endGlyphID, compressed)
)
def compile(self, ttFont):
version = 0
offsetToSVGDocIndex = SVG_format_0Size # I start the SVGDocIndex right after the header.
# get SGVDoc info.
docList = []
entryList = []
numEntries = len(self.docList)
datum = struct.pack(">H",numEntries)
entryList.append(datum)
curOffset = len(datum) + doc_index_entry_format_0Size*numEntries
seenDocs = {}
allCompressed = getattr(self, "compressed", False)
for i, doc in enumerate(self.docList):
if isinstance(doc, (list, tuple)):
doc = SVGDocument(*doc)
self.docList[i] = doc
docBytes = tobytes(doc.data, encoding="utf_8")
if (allCompressed or doc.compressed) and not docBytes.startswith(b"\x1f\x8b"):
import gzip
bytesIO = BytesIO()
# mtime=0 strips the useless timestamp and makes gzip output reproducible;
# equivalent to `gzip -n`
with gzip.GzipFile(None, "w", fileobj=bytesIO, mtime=0) as gzipper:
gzipper.write(docBytes)
gzipped = bytesIO.getvalue()
if len(gzipped) < len(docBytes):
docBytes = gzipped
del gzipped, bytesIO
docLength = len(docBytes)
if docBytes in seenDocs:
docOffset = seenDocs[docBytes]
else:
docOffset = curOffset
curOffset += docLength
seenDocs[docBytes] = docOffset
docList.append(docBytes)
entry = struct.pack(">HHLL", doc.startGlyphID, doc.endGlyphID, docOffset, docLength)
entryList.append(entry)
entryList.extend(docList)
svgDocData = bytesjoin(entryList)
reserved = 0
header = struct.pack(">HLL", version, offsetToSVGDocIndex, reserved)
data = [header, svgDocData]
data = bytesjoin(data)
return data
def toXML(self, writer, ttFont):
for i, doc in enumerate(self.docList):
if isinstance(doc, (list, tuple)):
doc = SVGDocument(*doc)
self.docList[i] = doc
attrs = {"startGlyphID": doc.startGlyphID, "endGlyphID": doc.endGlyphID}
if doc.compressed:
attrs["compressed"] = 1
writer.begintag("svgDoc", **attrs)
writer.newline()
writer.writecdata(doc.data)
writer.newline()
writer.endtag("svgDoc")
writer.newline()
def fromXML(self, name, attrs, content, ttFont):
if name == "svgDoc":
if not hasattr(self, "docList"):
self.docList = []
doc = strjoin(content)
doc = doc.strip()
startGID = int(attrs["startGlyphID"])
endGID = int(attrs["endGlyphID"])
compressed = bool(safeEval(attrs.get("compressed", "0")))
self.docList.append(SVGDocument(doc, startGID, endGID, compressed))
else:
log.warning("Unknown %s %s", name, content)
class DocumentIndexEntry(object):
def __init__(self):
self.startGlyphID = None # USHORT
self.endGlyphID = None # USHORT
self.svgDocOffset = None # ULONG
self.svgDocLength = None # ULONG
def __repr__(self):
return "startGlyphID: %s, endGlyphID: %s, svgDocOffset: %s, svgDocLength: %s" % (self.startGlyphID, self.endGlyphID, self.svgDocOffset, self.svgDocLength)
@dataclass
class SVGDocument(Sequence):
data: str
startGlyphID: int
endGlyphID: int
compressed: bool = False
# Previously, the SVG table's docList attribute contained a lists of 3 items:
# [doc, startGlyphID, endGlyphID]; later, we added a `compressed` attribute.
# For backward compatibility with code that depends of them being sequences of
# fixed length=3, we subclass the Sequence abstract base class and pretend only
# the first three items are present. 'compressed' is only accessible via named
# attribute lookup like regular dataclasses: i.e. `doc.compressed`, not `doc[3]`
def __getitem__(self, index):
return astuple(self)[:3][index]
def __len__(self):
return 3
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