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local hb = require("harf-base")
local hbfonts = hb.fonts
local hbfonts = hbfonts or {}
local cfftag = hb.Tag.new("CFF ")
local cff2tag = hb.Tag.new("CFF2")
local os2tag = hb.Tag.new("OS/2")
local posttag = hb.Tag.new("post")
local glyftag = hb.Tag.new("glyf")
local function trim(str)
return str:gsub("^%s*(.-)%s*$", "%1")
end
local function split(str, sep)
if str then
local result = string.explode(str, sep.."+")
for i, s in next, result do
result[i] = trim(result[i])
end
return result
end
end
local function parse(str, size)
local name, options = str:match("%s*(.*)%s*:%s*(.*)%s*")
local spec = {
specification = str,
size = size,
variants = {}, features = {}, options = {},
}
name = trim(name or str)
local filename = name:match("%[(.*)%]")
if filename then
-- [file]
-- [file:index]
filename = string.explode(filename, ":+")
spec.file = filename[1]
spec.index = tonumber(filename[2]) or 0
else
-- name
-- name/variants
local fontname, variants = name:match("(.-)%s*/%s*(.*)")
spec.name = fontname or name
spec.variants = split(variants, "/")
end
if options then
options = split(options, ";+")
for _, opt in next, options do
if opt:find("[+-]") == 1 then
local feature = hb.Feature.new(opt)
spec.features[#spec.features + 1] = feature
elseif opt ~= "" then
local key, val = opt:match("(.*)%s*=%s*(.*)")
if key == "language" then val = hb.Language.new(val) end
spec.options[key or opt] = val or true
end
end
end
return spec
end
local function loadfont(spec)
local path, index = spec.path, spec.index
if not path then
return nil
end
local key = string.format("%s:%d", path, index)
local data = hbfonts[key]
if data then
return data
end
local hbface = hb.Face.new(path, index)
local tags = hbface and hbface:get_table_tags()
-- If the face has no table tags then it isn’t a valid SFNT font that
-- HarfBuzz can handle.
if tags then
local hbfont = hb.Font.new(hbface)
local upem = hbface:get_upem()
-- The engine seems to use the font type to tell whether there is a CFF
-- table or not, so we check for that here.
local fonttype = nil
local hasos2 = false
local haspost = false
for i = 1, #tags do
local tag = tags[i]
if tag == cfftag or tag == cff2tag then
fonttype = "opentype"
elseif tag == glyftag then
fonttype = "truetype"
elseif tag == os2tag then
hasos2 = true
elseif tag == posttag then
haspost = true
end
end
local fontextents = hbfont:get_h_extents()
local ascender = fontextents and fontextents.ascender or upem * .8
local descender = fontextents and fontextents.descender or upem * .2
local gid = hbfont:get_nominal_glyph(0x0020)
local space = gid and hbfont:get_glyph_h_advance(gid) or upem / 2
local slant = 0
if haspost then
local post = hbface:get_table(posttag)
local length = post:get_length()
local data = post:get_data()
if length >= 32 and string.unpack(">i4", data) <= 0x00030000 then
local italicangle = string.unpack(">i4", data, 5) / 2^16
if italicangle ~= 0 then
slant = -math.tan(italicangle * math.pi / 180) * 65536.0
end
end
end
-- Load glyph metrics for all glyphs in the font. We used to do this on
-- demand to make loading fonts faster, but hit many limitations inside
-- the engine (mainly with shared backend fonts, where the engine would
-- assume all fonts it decides to share load the same set of glyphs).
--
-- Getting glyph advances is fast enough, but glyph extents are slower
-- especially in CFF fonts. We might want to have an option to ignore exact
-- glyph extents and use font ascender and descender if this proved to be
-- too slow.
local glyphcount = hbface:get_glyph_count()
local glyphs = {}
for gid = 0, glyphcount - 1 do
local width = hbfont:get_glyph_h_advance(gid)
local height, depth, italic = nil, nil, nil
local extents = hbfont:get_glyph_extents(gid)
if extents then
height = extents.y_bearing
depth = extents.y_bearing + extents.height
if extents.x_bearing < 0 then
italic = -extents.x_bearing
end
end
glyphs[gid] = {
width = width,
height = height or ascender,
depth = -(depth or descender),
italic = italic or 0,
}
end
local unicodes = hbface:collect_unicodes()
local characters = {}
for _, uni in next, unicodes do
characters[uni] = hbfont:get_nominal_glyph(uni)
end
local xheight, capheight = 0, 0
if hasos2 then
local os2 = hbface:get_table(os2tag)
local length = os2:get_length()
local data = os2:get_data()
if length >= 96 and string.unpack(">H", data) > 1 then
-- We don’t need much of the table, so we read from hard-coded offsets.
xheight = string.unpack(">H", data, 87)
capheight = string.unpack(">H", data, 89)
end
end
if xheight == 0 then
local gid = characters[120] -- x
if gid then
xheight = glyphs[gid].height
else
xheight = ascender / 2
end
end
if capheight == 0 then
local gid = characters[88] -- X
if gid then
capheight = glyphs[gid].height
else
capheight = ascender
end
end
data = {
face = hbface,
font = hbfont,
upem = upem,
fonttype = fonttype,
space = space,
xheight = xheight,
capheight = capheight,
slant = slant,
glyphs = glyphs,
unicodes = characters,
psname = hbface:get_name(hb.ot.NAME_ID_POSTSCRIPT_NAME),
fullname = hbface:get_name(hb.ot.NAME_ID_FULL_NAME),
haspng = hbface:ot_color_has_png(),
loaded = {}, -- Cached loaded glyph data.
}
hbfonts[key] = data
return data
end
end
-- Drop illegal characters from PS Name, per the spec
-- https://docs.microsoft.com/en-us/typography/opentype/spec/name#nid6
local function sanitize(psname)
local new = psname:gsub(".", function(c)
local b = c:byte()
if (b < 33 or b > 126)
or c == "["
or c == "]"
or c == "("
or c == ")"
or c == "{"
or c == "}"
or c == "<"
or c == ">"
or c == "/"
or c == "%"
then
return "-"
end
return c
end)
return new
end
local tlig = hb.texlig
local function scalefont(data, spec)
local size = spec.size
local options = spec.options
local hbface = data.face
local hbfont = data.font
local upem = data.upem
local space = data.space
if size < 0 then
size = -655.36 * size
end
-- We shape in font units (at UPEM) and then scale output with the desired
-- sfont size.
local scale = size / upem
hbfont:set_scale(upem, upem)
-- Populate font’s characters table.
local glyphs = data.glyphs
local characters = {}
for gid, glyph in next, glyphs do
characters[hb.CH_GID_PREFIX + gid] = {
index = gid,
width = glyph.width * scale,
height = glyph.height * scale,
depth = glyph.depth * scale,
italic = glyph.italic * scale,
}
end
local unicodes = data.unicodes
for uni, gid in next, unicodes do
characters[uni] = characters[hb.CH_GID_PREFIX + gid]
end
-- Select font palette, we support `palette=index` option, and load the first
-- one otherwise.
local paletteidx = tonumber(options.palette) or 1
-- Load CPAL palette from the font.
local palette = nil
if hbface:ot_color_has_palettes() and hbface:ot_color_has_layers() then
local count = hbface:ot_color_palette_get_count()
if paletteidx <= count then
palette = hbface:ot_color_palette_get_colors(paletteidx)
end
end
local letterspace = 0
if options.letterspace then
letterspace = tonumber(options.letterspace) / 100 * upem
elseif options.kernfactor then
letterspace = tonumber(options.kernfactor) * upem
end
space = space + letterspace
local slantfactor = nil
if options.slant then
slantfactor = tonumber(options.slant) * 1000
end
local mode = nil
local width = nil
if options.embolden then
mode = 2
-- The multiplication by 7200.0/7227 is to undo the opposite conversion
-- the engine is doing and make the final number written in the PDF file
-- match XeTeX’s.
width = (size * tonumber(options.embolden) / 6553.6) * (7200.0/7227)
end
local hscale = upem
local extendfactor = nil
if options.extend then
extendfactor = tonumber(options.extend) * 1000
hscale = hscale * tonumber(options.extend)
end
local vscale = upem
local squeezefactor = nil
if options.squeeze then
squeezefactor = tonumber(options.squeeze) * 1000
vscale = vscale * tonumber(options.squeeze)
end
if options.texlig then
for char in next, characters do
local ligatures = tlig[char]
if ligatures then
characters[char].ligatures = ligatures
end
end
end
return {
name = spec.specification,
filename = spec.path,
designsize = size,
psname = sanitize(data.psname),
fullname = data.fullname,
index = spec.index,
size = size,
units_per_em = upem,
type = "real",
embedding = "subset",
tounicode = 1,
nomath = true,
format = data.fonttype,
slant = slantfactor,
mode = mode,
width = width,
extend = extendfactor,
squeeze = squeezefactor,
characters = characters,
parameters = {
slant = data.slant,
space = space * scale,
space_stretch = space * scale / 2,
space_shrink = space * scale / 3,
x_height = data.xheight * scale,
quad = size,
extra_space = space * scale / 3,
[8] = data.capheight * scale, -- for XeTeX compatibility.
},
hb = {
scale = scale,
spec = spec,
palette = palette,
shared = data,
letterspace = letterspace,
hscale = hscale,
vscale = vscale,
},
}
end
local function define_font(name, size)
local spec = type(name) == "string" and parse(name, size) or name
if spec.file then
spec.path = kpse.find_file(spec.file, "truetype fonts") or
kpse.find_file(spec.file, "opentype fonts")
else
-- XXX support font names
end
if spec.specification == "" then return nil end
local tfmdata = nil
local hbdata = loadfont(spec)
if hbdata then
tfmdata = scalefont(hbdata, spec)
else
tfmdata = font.read_tfm(spec.specification, spec.size)
end
return tfmdata
end
return define_font
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