Specificaly, when a range or sorted array has unexpected order, we take that as
font data being garbage and bail out. This fixes significant slowdown on a bad
version of Chandas font which has a 600KB GPOS with garbage inside.
Later on, I like to add a maximum-work counter for collect_glyphs to protect
against malicious fonts as well.
Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=794896
Not optimized to use sortedness yet. Also start putting in place infra
to faster reject bad data.
A version of Chandas.ttf found on some Chrome bots has 660kb of GPOS,
mostly junk. That is causing 48 million of set->add() calls in
collect_glyphs(), which is insane.
In the upcoming commits, I'll be speeding that up by optimizing
add_sorted_array(), while also reducing work by rejecting out-of-sort
arrays quickly and propagate the rejection.
Part of https://bugs.chromium.org/p/chromium/issues/detail?id=794896
The font Garamond Premier Pro Caption (and possibly many other
Adobe fonts), have many FeatureParamsSize tables with the old
wrong offset. We handle fixing those up, but they were still
contributing to edit_count, and when I reduced HB_SANITIZE_MAX_EDIT
from 100 to 8 in 14c2de3218, these
fonts were now getting GPOS dropped and hence kerning disabled.
Fix, by not counting edits made towareds offset fix-up. I'll
also increase edit count again, in the next commit.
Use the DEFINE_ENUM_FLAG_OPERATORS macro in winnt.h on Visual Studio,
which defines the bitwise operators for the enumerations that we want to
mark as hb_mark_as_flags_t, which will take care of the situation on newer
Visual Studio (>= 2012), where the build breaks with C2057 errors as the
underlying types of the enumerations is not clear to the compiler when we
do a bitwise op within the declaration of the enumerations themselves.
Also disable the C4200 (nonstandard extension used : zero-sized array in
struct/union) and C4800 ('type' : forcing value to bool 'true' or 'false'
(performance warning)) warnings as the C4200 is the intended scenario and
C4800 is harmless but is so far an unavoidable side effect of using
DEFINE_ENUM_FLAG_OPERATORS.
Behdad Esfahbod
Chun-wei Fan