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LibPDF: Improve Type2 hint counting

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There were two issues with how we counted hints with Type2 CharString
commands: the first was that we assumed a single hint per command, even
though there are commands that accept multiple hints thanks to taking a
variable number of operands; and secondly, the hintmask/ctrlmask
commands can also take operands (i.e., hints) themselves in certain
situations.

This commit fixes these two issues by correctly counting hints in both
cases. This in turn fixes cases when there were more than 8 hints in
total, therefore a hintmask/ctrlmask command needed to read more than
one byte past the operator itself.
This commit is contained in:
Rodrigo Tobar 2023-02-26 14:38:10 +08:00 • committed by Andreas Kling
parent bf61f94413
commit de5e7b487c
1 changed files with 4 additions and 2 deletions
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6
Userland/Libraries/LibPDF/Fonts/Type1FontProgram.cpp
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@ -271,7 +271,7 @@ PDFErrorOr<Type1FontProgram::Glyph> Type1FontProgram::parse_glyph(ReadonlyBytes
// hints operators // hints operators
case HStemHM: case HStemHM:
state.n_hints++; state.n_hints += state.sp / 2;
[[fallthrough]]; [[fallthrough]];
case HStem: case HStem:
maybe_read_width(Odd); maybe_read_width(Odd);
@ -279,7 +279,7 @@ PDFErrorOr<Type1FontProgram::Glyph> Type1FontProgram::parse_glyph(ReadonlyBytes
break; break;
case VStemHM: case VStemHM:
state.n_hints++; state.n_hints += state.sp / 2;
[[fallthrough]]; [[fallthrough]];
case VStem: case VStem:
maybe_read_width(Odd); maybe_read_width(Odd);
@ -289,9 +289,11 @@ PDFErrorOr<Type1FontProgram::Glyph> Type1FontProgram::parse_glyph(ReadonlyBytes
case Hintmask: case Hintmask:
case Cntrmask: { case Cntrmask: {
maybe_read_width(Odd); maybe_read_width(Odd);
state.n_hints += state.sp / 2;
auto hint_bytes = (state.n_hints + 8 - 1) / 8; auto hint_bytes = (state.n_hints + 8 - 1) / 8;
TRY(require(hint_bytes)); TRY(require(hint_bytes));
i += hint_bytes; i += hint_bytes;
state.sp = 0;
break; break;
} }