freetype/harfbuzz: APIs to query font metadata (#1215)

This is necessary for proper language support in mupdf with arbitrary
fonts in html/pdf - mupdf expects a real font server for its callbacks,
we're told abstract typeface, script and language that must be
accounted for whenever offering close-kin substitutes of a typeface.

There are marginal uses for this elsewhere, eg. localized font
names in UI - koreader/koreader#6763

ffi-cdecl/freetype2_decl.c

@@ -5,7 +5,19 @@
 #include <freetype/freetype.h>
 #include <freetype/ftsynth.h>
 #include <freetype/ftoutln.h>
-
+#include <freetype/ftsnames.h>
+#include <freetype/tttables.h>
+#include <freetype/tttags.h>
+#include <freetype/ttnameid.h>
+
+cdecl_type(FT_String)
+cdecl_type(FT_Byte)
+cdecl_type(FT_UShort)
+cdecl_type(FT_Short)
+cdecl_type(FT_Int)
+cdecl_type(FT_UInt)
+cdecl_type(FT_Long)
+cdecl_type(FT_ULong)
 cdecl_type(FT_Error)
 cdecl_type(FT_Pos)
 
@@ -105,11 +117,89 @@ cdecl_func(FT_Outline_Embolden)
 cdecl_func(FT_Outline_Translate)
 cdecl_func(FT_MulFix)
 
-cdecl_const(FT_LOAD_RENDER)
+cdecl_func(FT_Get_First_Char)
+cdecl_func(FT_Get_Next_Char)
+
 cdecl_const(FT_LOAD_DEFAULT)
-cdecl_const(FT_LOAD_TARGET_LIGHT)
-cdecl_const(FT_LOAD_NO_AUTOHINT)
+cdecl_const(FT_LOAD_NO_SCALE)
 cdecl_const(FT_LOAD_NO_HINTING)
+cdecl_const(FT_LOAD_RENDER)
+cdecl_const(FT_LOAD_NO_BITMAP)
+cdecl_const(FT_LOAD_VERTICAL_LAYOUT)
 cdecl_const(FT_LOAD_FORCE_AUTOHINT)
+cdecl_const(FT_LOAD_CROP_BITMAP)
+cdecl_const(FT_LOAD_PEDANTIC)
+cdecl_const(FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH)
+cdecl_const(FT_LOAD_NO_RECURSE)
+cdecl_const(FT_LOAD_IGNORE_TRANSFORM)
+cdecl_const(FT_LOAD_MONOCHROME)
+cdecl_const(FT_LOAD_LINEAR_DESIGN)
+
+cdecl_const(FT_LOAD_SBITS_ONLY)
+cdecl_const(FT_LOAD_NO_AUTOHINT)
+
+cdecl_const(FT_LOAD_TARGET_NORMAL)
+cdecl_const(FT_LOAD_TARGET_LIGHT)
+cdecl_const(FT_LOAD_TARGET_MONO)
+cdecl_const(FT_LOAD_TARGET_LCD)
+cdecl_const(FT_LOAD_TARGET_LCD_V)
+
+cdecl_const(FT_FACE_FLAG_SCALABLE)
+cdecl_const(FT_FACE_FLAG_FIXED_SIZES)
+cdecl_const(FT_FACE_FLAG_FIXED_WIDTH)
+cdecl_const(FT_FACE_FLAG_HORIZONTAL)
+cdecl_const(FT_FACE_FLAG_VERTICAL)
+cdecl_const(FT_FACE_FLAG_SFNT)
 cdecl_const(FT_FACE_FLAG_KERNING)
+cdecl_const(FT_FACE_FLAG_MULTIPLE_MASTERS)
+cdecl_const(FT_FACE_FLAG_GLYPH_NAMES)
+cdecl_const(FT_FACE_FLAG_EXTERNAL_STREAM)
+cdecl_const(FT_FACE_FLAG_FAST_GLYPHS)
+cdecl_const(FT_FACE_FLAG_HINTER)
+
+
+cdecl_const(FT_STYLE_FLAG_BOLD)
+cdecl_const(FT_STYLE_FLAG_ITALIC)
+
+
 cdecl_const(FT_KERNING_DEFAULT)
+cdecl_const(FT_KERNING_UNFITTED)
+cdecl_const(FT_KERNING_UNSCALED)
+
+cdecl_struct(TT_OS2_)
+cdecl_type(TT_OS2)
+
+cdecl_enum(FT_Sfnt_Tag_)
+cdecl_type(FT_Sfnt_Tag)
+cdecl_func(FT_Get_Sfnt_Table)
+
+cdecl_struct(FT_SfntName_)
+cdecl_type(FT_SfntName)
+
+
+
+cdecl_const(TT_NAME_ID_COPYRIGHT)
+cdecl_const(TT_NAME_ID_FONT_FAMILY)
+cdecl_const(TT_NAME_ID_FONT_SUBFAMILY)
+cdecl_const(TT_NAME_ID_UNIQUE_ID)
+cdecl_const(TT_NAME_ID_FULL_NAME)
+cdecl_const(TT_NAME_ID_VERSION_STRING)
+cdecl_const(TT_NAME_ID_PS_NAME)
+cdecl_const(TT_NAME_ID_TRADEMARK)
+cdecl_const(TT_NAME_ID_MANUFACTURER)
+cdecl_const(TT_NAME_ID_DESIGNER)
+cdecl_const(TT_NAME_ID_DESCRIPTION)
+cdecl_const(TT_NAME_ID_VENDOR_URL)
+cdecl_const(TT_NAME_ID_DESIGNER_URL)
+cdecl_const(TT_NAME_ID_LICENSE)
+cdecl_const(TT_NAME_ID_LICENSE_URL)
+cdecl_const(TT_NAME_ID_PREFERRED_FAMILY)
+cdecl_const(TT_NAME_ID_PREFERRED_SUBFAMILY)
+cdecl_const(TT_NAME_ID_MAC_FULL_NAME)
+cdecl_const(TT_NAME_ID_SAMPLE_TEXT)
+cdecl_const(TT_NAME_ID_CID_FINDFONT_NAME)
+cdecl_const(TT_NAME_ID_WWS_FAMILY)
+cdecl_const(TT_NAME_ID_WWS_SUBFAMILY)
+
+cdecl_func(FT_Get_Sfnt_Name_Count)
+cdecl_func(FT_Get_Sfnt_Name)

ffi-cdecl/harfbuzz_cdecl.c

@@ -394,6 +394,7 @@ cdecl_func(hb_ft_font_set_funcs)
 
 cdecl_type(hb_ot_math_glyph_part_flags_t)
 cdecl_type(hb_ot_var_axis_flags_t)
+cdecl_type(hb_ot_name_id_t)
 
 cdecl_struct(hb_ot_name_entry_t)
 cdecl_struct(hb_ot_color_layer_t)
@@ -508,3 +509,30 @@ cdecl_func(hb_ot_var_named_instance_get_design_coords)
 cdecl_func(hb_ot_var_normalize_variations)
 cdecl_func(hb_ot_var_normalize_coords)
 
+// Annoyingly, this one isn't an enum for some reason...
+cdecl_const(HB_OT_NAME_ID_COPYRIGHT)
+cdecl_const(HB_OT_NAME_ID_FONT_FAMILY)
+cdecl_const(HB_OT_NAME_ID_FONT_SUBFAMILY)
+cdecl_const(HB_OT_NAME_ID_UNIQUE_ID)
+cdecl_const(HB_OT_NAME_ID_FULL_NAME)
+cdecl_const(HB_OT_NAME_ID_VERSION_STRING)
+cdecl_const(HB_OT_NAME_ID_POSTSCRIPT_NAME)
+cdecl_const(HB_OT_NAME_ID_TRADEMARK)
+cdecl_const(HB_OT_NAME_ID_MANUFACTURER)
+cdecl_const(HB_OT_NAME_ID_DESIGNER)
+cdecl_const(HB_OT_NAME_ID_DESCRIPTION)
+cdecl_const(HB_OT_NAME_ID_VENDOR_URL)
+cdecl_const(HB_OT_NAME_ID_DESIGNER_URL)
+cdecl_const(HB_OT_NAME_ID_LICENSE)
+cdecl_const(HB_OT_NAME_ID_LICENSE_URL)
+cdecl_const(HB_OT_NAME_ID_TYPOGRAPHIC_FAMILY)
+cdecl_const(HB_OT_NAME_ID_TYPOGRAPHIC_SUBFAMILY)
+cdecl_const(HB_OT_NAME_ID_MAC_FULL_NAME)
+cdecl_const(HB_OT_NAME_ID_SAMPLE_TEXT)
+cdecl_const(HB_OT_NAME_ID_CID_FINDFONT_NAME)
+cdecl_const(HB_OT_NAME_ID_WWS_FAMILY)
+cdecl_const(HB_OT_NAME_ID_WWS_SUBFAMILY)
+cdecl_const(HB_OT_NAME_ID_LIGHT_BACKGROUND)
+cdecl_const(HB_OT_NAME_ID_DARK_BACKGROUND)
+cdecl_const(HB_OT_NAME_ID_VARIATIONS_PS_PREFIX)
+

ffi/freetype.lua

@@ -125,10 +125,46 @@ function FTFace_mt.__index:getHeightAndAscender()
 end
 
 function FTFace_mt.__index:done()
+    -- Note that past this point, accessing self is illegal, FT2 frees the pointer
     assert(ft2.FT_Done_Face(self) == 0, "freetype error when freeing face")
 end
 
-FTFace_mt.__gc = FTFace_mt.__index.done;
+function FTFace_mt.__index:getInfo()
+    local finfo = {
+        name = ffi.string(self.family_name),
+        -- Style
+        mono = bit.band(tonumber(self.face_flags), ft2.FT_FACE_FLAG_FIXED_WIDTH) ~= 0,
+        hint = bit.band(tonumber(self.face_flags), ft2.FT_FACE_FLAG_HINTER) ~= 0,
+        bold = bit.band(tonumber(self.style_flags), ft2.FT_STYLE_FLAG_BOLD) ~= 0,
+        italic = bit.band(tonumber(self.style_flags), ft2.FT_STYLE_FLAG_ITALIC) ~= 0,
+        serif = nil,
+        ui = false,
+        names = nil,
+    }
+
+    -- In practice, just going by latin name can tell us more than the depressingly absent tags
+    finfo.ui = finfo.name:match("UI$") ~= nil
+    local lname = finfo.name:lower()
+    if lname:match("serif") then
+        finfo.serif = true
+    elseif lname:match("sans") then
+        finfo.serif = false
+    elseif bit.band(tonumber(self.face_flags), ft2.FT_FACE_FLAG_SFNT) ~= 0 then
+        local os2 = ft2.FT_Get_Sfnt_Table(self, ft2.FT_SFNT_OS2)
+        if os2 ~= nil then
+            local kls = tonumber(ffi.cast("TT_OS2*", os2).sFamilyClass)
+            if kls ~= 0 then -- 0 is usually bogus
+                -- class 8 = sans, otherwise serif
+                finfo.serif = bit.band(kls, 0x0800) == 0
+            end
+        end
+        if finfo.serif == nil then
+            --TODO: Maybe it's worth to consult panose tables too?
+            finfo.serif = true
+        end
+    end
+    return finfo
+end
 
 local FTFaceType = ffi.metatype("struct FT_FaceRec_", FTFace_mt) -- luacheck: ignore 211
 
@@ -157,4 +193,14 @@ function FT.newFace(filename, pxsize, faceindex)
     return face
 end
 
+function FT.getFaceCount(filename, info)
+    -- Probes number of faces available within the font file
+    local ftface = ffi.new("FT_Face[1]")
+    if ft2.FT_New_Face(freetypelib, filename, -1, ftface) ~= 0 then return nil end
+    local fp = ftface[0]
+    local nfaces = tonumber(ftface[0].num_faces)
+    fp:done()
+    return nfaces
+end
+
 return FT