feat(shapers): Support named instances with FontConfig

FontConfig will use the upper bits of the face index for named instance index, and hb_font_create() handles this, but we were stripping these bits prematurely. Strip them before sending the index to libtextpdf instead. With named instances supported, saying \font[name=Foo, weight=700] of a variable font will set the correct variation coordinates for the named instance, instead of always using the default instance.
sile-typesetter · Jan 25, 2023 · 29119b9 · 29119b9
1 parent 8279a4e
commit 29119b9
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diff --git a/shapers/harfbuzz.lua b/shapers/harfbuzz.lua
@@ -81,10  81,6 @@ function shaper.getFace (opts)
   SU.debug("fonts", "Resolved font family", opts.family, "->", face and face.filename)
   if not face or not face.filename then SU.error("Couldn't find face '"..opts.family.."'") end
   if SILE.makeDeps then SILE.makeDeps:add(face.filename) end
-  if bitshim.rshift(face.index, 16) ~= 0 then
-    SU.warn("GX feature in '"..opts.family.."' is not supported, fallback to regular font face.")
-    face.index = bitshim.band(face.index, 0xff)
-  end
   face.variations = opts.variations or ""
   face.pointsize = ("%g"):format(SILE.measurement(opts.size):tonumber())
 

diff --git a/src/justenoughlibtexpdf.c b/src/justenoughlibtexpdf.c
@@ -105,6  105,10 @@ int pdf_loadfont(lua_State *L) {
   if (lua_isnumber(L, -1)) { index = lua_tointeger(L, -1); }
   lua_pop(L,1);
 
   /* FontConfig uses the upper bits of the face index for named instance index,
    * but libtexpdf knows nothing about this. */
   index &= 0xFFFFu;
 
   lua_pushstring(L, "pointsize");
   lua_gettable(L, -2);
   if (lua_isnumber(L, -1)) { ptsize = lua_tonumber(L, -1); }