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LibPDF: Postpone CFF encoding processing after Top DICT has been read

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The encoding offset defaults to 0, i.e. the Standard Encoding.
That means reading the encoding only if the tag is present causes
us to not read it if a font uses the Standard Encoding.

Now, we always read an encoding, even if it's the (implicit) default
one.
This commit is contained in:
Nico Weber 2023-10-16 16:28:13 -04:00 • committed by Andreas Kling
parent 1cfe639b6c
commit eeada4678c
1 changed files with 17 additions and 16 deletions
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33
Userland/Libraries/LibPDF/Fonts/CFF.cpp
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@ -72,8 +72,7 @@ PDFErrorOr<NonnullRefPtr<CFF>> CFF::create(ReadonlyBytes const& cff_bytes, RefPt
// CFF spec, "8 Top DICT INDEX"
int charset_offset = 0;
Vector<u8> encoding_codes; // Maps GID to its codepoint.
HashMap<Card8, SID> encoding_supplemental; // Maps codepoint to SID.
int encoding_offset = 0;
auto charstrings_offset = 0;
Vector<ByteBuffer> subroutines;
float defaultWidthX = 0;
@ -113,22 +112,8 @@ PDFErrorOr<NonnullRefPtr<CFF>> CFF::create(ReadonlyBytes const& cff_bytes, RefPt
dbgln("CFF: has unimplemented SyntheticBase, might not look right");
break;
case TopDictOperator::Encoding: {
auto encoding_offset = 0;
if (!operands.is_empty())
encoding_offset = operands[0].get<int>();
// CFF spec, "Table 16 Encoding ID"
switch (encoding_offset) {
case 0:
dbgln("CFF: Built-in Standard Encoding not yet implemented");
break;
case 1:
dbgln("CFF: Built-in Expert Encoding not yet implemented");
break;
default:
encoding_codes = TRY(parse_encoding(Reader(cff_bytes.slice(encoding_offset)), encoding_supplemental));
break;
}
break;
}
case TopDictOperator::Charset: {
@ -186,6 +171,22 @@ PDFErrorOr<NonnullRefPtr<CFF>> CFF::create(ReadonlyBytes const& cff_bytes, RefPt
// Create glyphs (now that we have the subroutines) and associate missing information to store them and their encoding
auto glyphs = TRY(parse_charstrings(Reader(cff_bytes.slice(charstrings_offset)), subroutines));
// CFF spec, "Table 16 Encoding ID"
// FIXME: Only read this if the built-in encoding is actually needed? (ie. `if (!encoding)`)
Vector<u8> encoding_codes; // Maps GID to its codepoint.
HashMap<Card8, SID> encoding_supplemental; // Maps codepoint to SID.
switch (encoding_offset) {
case 0:
dbgln("CFF: Built-in Standard Encoding not yet implemented");
break;
case 1:
dbgln("CFF: Built-in Expert Encoding not yet implemented");
break;
default:
encoding_codes = TRY(parse_encoding(Reader(cff_bytes.slice(encoding_offset)), encoding_supplemental));
break;
}
// CFF spec, "Table 22 Charset ID"
Vector<DeprecatedFlyString> charset;
switch (charset_offset) {