Before, the IntType::cmp functions providing this and was truncating
the hb_codepoint_t to 16bits before comparison. I have no idea how
this was never discovered, and I'm too lazy to try to reproduce this
with Pango (which uses non-16bit codepoint numbers for missing glyphs).
This makes a lot of code safer. We only try modifying the object in one
place, after making sure it's safe to do so. So, do a const_cast<> in
that one place...
Currently:
- Initializing skippy is very expensive,
- Our lookup accelerator (using set-digests) can be very ineffecite,
As such, we end up many times initializing skippy but then failing
coverage check. Reordering fixes that.
When, later, we fix our accelerator to have truly small false-positive
rate (for example by using the frozen-sets), then we might want to
reorder these checks such that we wouldn't calculate coverage number
if skippy is going to fail.
This shows a 5% speedup with Roboto already.
I experimented with replacing use of hb_set_digest_t with this new
hb_frozen_set_t, hoping to get a huge speedup for busy lookups
(like kern lookup in Roboto), but I only got 6% speendup in Roboto
and 4% in NotoNastaliqUrduDraft :(.
This code is C++ only. There isn't a single C++ compiler that fails to
understand the "inline" keyword, since it's required by C++98. Any
compiler older than C++98 is likely to choke on the template usage
further down, so this isn't necessary.
Moreover, the C++ standard says you cannot define macros.
[lib.macro.names] says "Nor shall such a translation unit define macros
for names lexically identical to keywords." -- technically, it's a
promise that the Standard Library headers won't do it, the wording means
that the entire translation unit won't do it, which implies no source
can do it.
MSVC complains about it:
fatal error C1189: #error : The C++ Standard Library forbids macroizing
keywords. Enable warning C4005 to find the forbidden macro.
Author: Thiago Macieira <thiago.macieira@intel.com>
Behdad Esfahbod
Collin Fair
Konstantin Ritt