Wheels: link FreeType against the bundled HarfBuzz - #9913
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FreeType's autofitter can use HarfBuzz to work out which glyphs a script covers, so it can derive blue zones for scripts such as Arabic. Only the Windows wheels were built to allow that. macOS passed --with-harfbuzz=no, and Linux left it unconfigured, which meant FreeType defaulted to `dlopen`ing HarfBuzz at runtime with the name "libharfbuzz.so.0". `auditwheel`, part of the wheeling process, renames shared libraries to avoid conflicts, so the Linux wheels ended up with a FreeType that would only find HarfBuzz if the system had its own copy with the name "libharfbuzz.so.0"; the bundled copy was never used.
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| fi | ||
| # FreeType and HarfBuzz each want the other: | ||
| # HarfBuzz reads font data through FreeType, and FreeType's autofitter asks HarfBuzz which glyphs a script covers. | ||
| # Break the cycle by building FreeType twice, so that the FreeType we ship is linked against the HarfBuzz we ship. |
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It is unusual that this should be required, right? Have FreeType or Harfbuzz discussed this anywhere?
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Google search autocomplete (on a different device, on mobile right now) suggests https://www.google.com/search?q=freetype+harfbuzz+circular+dependency if you start typing "freetype harf", so that suggests it's a known thing.
Here's a recent-ish Debian bug about it https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1124239
Freetype notes the circular dependency in the release announcement for 2.14.0 on https://freetype.org/
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Follows up on #8497.
This came up as a side effect of #9909, where the last commit needed to increase the allowed comparison epsilon for the Arabic-language test, since different platforms in the CI stack would render it slightly differently... and it's a doozy! 😄
FreeType's autofitter can use HarfBuzz to work out which glyphs a script covers, so it can derive blue zones for scripts such as Arabic.
Only the Windows wheels were built that way. macOS passed
--with-harfbuzz=no(so no HarfBuzz interop, no way, no how), and Linux left it unconfigured, which meant FreeType defaulted todlopening HarfBuzz at runtime with the name "libharfbuzz.so.0".However,
auditwheelrenames shared libraries to avoid conflicts, so the Linux wheels ended up with a FreeType that would only find HarfBuzz if the system had its own copy with the name "libharfbuzz.so.0".In the current 12.3 wheel off PyPI, the interop symbols do not exist:
but in a wheel built by CI off this branch (see akx#18):