path: root/luaotfload.lua

module("luaotfload", package.seeall)

luaotfload.module = {
    name          = "luaotfload",
    version       = 2.2,
    date          = "2013/04/15",
    description   = "OpenType layout system.",
    author        = "Elie Roux & Hans Hagen",
    copyright     = "Elie Roux",
    license       = "CC0"
}

local luatexbase = luatexbase

local type, next, dofile = type, next, dofile
local stringfind = string.find
local find_file  = kpse.find_file

local add_to_callback, create_callback =
      luatexbase.add_to_callback, luatexbase.create_callback
local reset_callback, call_callback =
      luatexbase.reset_callback, luatexbase.call_callback

local dummy_function = function () end

--[[doc--
No final decision has been made on how to handle font definition.  At
the moment, there are three candidates: The \identifier{generic}
callback as hard-coded in the font loader, the \identifier{old}
wrapper, and a simplified version of the latter (\identifier{patch})
that does nothing besides applying font patches.
--doc]]--
luaotfload.font_definer = "patch" --- | “generic” | “old”

local error, warning, info, log =
    luatexbase.provides_module(luaotfload.module)

--[[doc--
This is a necessary initalization in order not to rebuild an existing
font.
Maybe 600 should be replaced by \texmacro{pdfpkresolution} %% (why?)
or \luafunction{texconfig.pk_dpi} (and it should be replaced
dynamically), but we don't have access (yet) to the
\identifier{texconfig} table, so we let it be 600.
Anyway, it does still work fine even if \texmacro{pdfpkresolution} is
changed.
--doc]]--

kpse.init_prog("", 600, "/")

--[[doc--
We set the minimum version requirement for \LUATEX to v0.74, as it was
the first version to include version 5.2 of the \LUA interpreter.
--doc]]--

local luatex_version = 74

if tex.luatexversion < luatex_version then
    warning("LuaTeX v%.2f is old, v%.2f is recommended.",
             tex.luatexversion/100,
             luatex_version   /100)
end

--[[doc--
\subsection{Module loading}

We load the files imported from \CONTEXT with this function.
It automatically prepends the prefix \fileent{otfl-} to its argument,
so we can refer to the files with their actual \CONTEXT name.
--doc]]--

local fl_prefix = "otfl" -- “luatex” for luatex-plain
local loadmodule = function (name)
    local tofind = fl_prefix .."-"..name
    local found = find_file(tofind,"tex")
    if found then
        log("loading file %s.", found)
        dofile(found)
    else
        error("file %s not found.", tofind)
    end
end

--[[doc--
Virtual fonts are resolved via a callback.
\luafunction{find_vf_file} derives the name of the virtual font file
from the filename.
(NB: \CONTEXT handles this likewise in \fileent{font-vf.lua}.)
--doc]]--
local Cs, P, lpegmatch = lpeg.Cs, lpeg.P, lpeg.match

local p_dot, p_slash = P".",  P"/"
local p_suffix       = (p_dot * (1 - p_dot - p_slash)^1 * P(-1)) / ""
local p_removesuffix = Cs((p_suffix + 1)^1)

local find_vf_file = function (name)
    local fullname = find_file(name, "ovf")
    if not fullname then
        --fullname = find_file(file.removesuffix(name), "ovf")
        fullname = find_file(lpegmatch(p_removesuffix, name), "ovf")
    end
    if fullname then
        log("loading virtual font file %s.", fullname)
    end
    return fullname
end

--[[-- keep --]]
--- from Hans (all merged):

---   file name              modified  include name
--- × basics-gen.lua         t         luat-basics-gen
--- × font-def -> fonts-def  t         luatex-font-def (there’s also the normal font-def!)
--- × fonts-enc              f         luatex-font-enc
--- × fonts-ext              t         luatex-fonts-ext
--- × fonts-lua              f         luatex-fonts-lua
---   fonts-tfm              f         luatex-fonts-tfm
--- × fonts-cbk              f         luatex-fonts-lua

--- from Hans (unmerged):
---   font-otc.lua -> otfl-font-otc.lua

--- from luaotfload:
---   otfl-luat-ovr.lua    -- override some luat-dum functions
---   otfl-font-clr.lua
---   otfl-font-ltx.lua
---   otfl-font-nms.lua
---   otfl-font-pfb.lua    -- ?

--[[-- new --]]
--- basics-nod          (merged as fonts-nod !)
--- fonts-demo-vf-1.lua
--- fonts-syn           (merged)

--[[-- merged, to be dropped --]]
--- otfl-data-con.lua
--- otfl-font-cid.lua
--- otfl-font-con.lua
--- otfl-font-ini.lua
--- otfl-font-ota.lua
--- otfl-font-otb.lua
--- otfl-font-otf.lua
--- otfl-font-oti.lua
--- otfl-font-otn.lua

--[[doc--

\subsection{Preparing the Font Loader}
We treat the fontloader as a black box so behavior is consistent
between formats.
The wrapper file is \fileent{otfl-fonts.lua} which we imported from
\href{http://standalone.contextgarden.net/current/context/experimental/tex/generic/context/luatex/}{\LUATEX-Plain}.
It has roughly two purposes:

\begin{enumerate}

   \item insert the functionality required for fontloader; and

   \item put it in place via the respective callbacks.

\end{enumerate}

How the first step is executed depends on the presence on the
\emph{merged font loader code}.
In \identifier{luaotfload} this is contained in the file
\fileent{otfl-fonts-merged.lua}.
If this file cannot be found,  the original libraries from \CONTEXT of
which the merged code was composed are loaded instead.

Hans provides two global tables to control the font loader:

  \begin{itemize}
    \item  \luafunction{generic_context}:
           encapsulation mechanism, callback functions
    \item  \luafunction{non generic_context}:
           customized code insertion
  \end{itemize}


With \luafunction{non_generic_context} we can tailor the font loader
insertion to our file naming habits (key \luafunction{load_before}).
Additionally, \luafunction{skip_loading} can be unset to force loading
of the original libraries as though the merged code was absent.
Another key, \luafunction{load_after} is called at the time when the
font loader is actually inserted.
In combination with the option \luafunction{no_callbacks_yet} in
\luafunction{generic_context}, we can insert our own,
\identifier{luatexbase}-style callback handling here.
--doc]]--
if not _G.    generic_context then _G.    generic_context = { } end
if not _G.non_generic_context then _G.non_generic_context = { } end

local     generic_context =    generic_context
local non_generic_context =non_generic_context

generic_context.no_callbacks_yet = true

_G.non_generic_context = { luatex_fonts = {
        load_before     = "otfl-fonts-merged.lua",
        -- load_after      = nil, --- TODO, this is meant for callbacks
        skip_loading    = true,
}}

--[[doc--
The imported font loader will call \luafunction{callback.register} once
while reading \fileent{font-def.lua}.
This is unavoidable unless we modify the imported files, but harmless
if we make it call a dummy instead.
--doc]]--

local trapped_register = callback.register
callback.register      = dummy_function

--[[doc--
Now that things are sorted out we can finally load the fontloader.
--doc]]--

loadmodule"fonts.lua"

--[[doc--
By default, the fontloader requires a number of \emphasis{private
attributes} for internal use.
These must be kept consistent with the attribute handling methods as
provided by \identifier{luatexbase}.
Our strategy is to override the function that allocates new attributes
before we initialize the font loader, making it a wrapper around
\luafunction{luatexbase.new_attribute}.\footnote{%
    Many thanks, again, to Hans Hagen for making this part
    configurable!
}
The attribute identifiers are prefixed “\fileent{otfl@}” to
avoid name clashes.
--doc]]--

do
    local new_attribute = luatexbase.new_attribute
    local the_attributes = luatexbase.attributes

    _G.attributes = _G.attributes or { }

    _G.attributes.private = function (name)
        local attr   = "otfl@" .. name
        local number = the_attributes[attr]
        if not number then
            number = new_attribute(attr)
        end
        return number
    end
end

--[[doc--

\subsection{Callbacks}

After the fontloader is ready we can restore the callback trap from
\identifier{luatexbase}.
--doc]]--

callback.register = trapped_register

--[[doc--
We do our own callback handling with the means provided by luatexbase.

Note: \luafunction{pre_linebreak_filter} and \luafunction{hpack_filter}
are coupled in \CONTEXT in the concept of \emph{node processor}.
--doc]]--

add_to_callback("pre_linebreak_filter",
                generic_context.callback_pre_linebreak_filter,
                "luaotfload.node_processor",
                1)
add_to_callback("hpack_filter",
                generic_context.callback_hpack_filter,
                "luaotfload.node_processor",
                1)
add_to_callback("find_vf_file",
                find_vf_file, "luaotfload.find_vf_file")

loadmodule"font-otc.lua"   -- TODO check what we can drop from otfl-features

loadmodule"lib-dir.lua"    -- required by font-nms
loadmodule"luat-ovr.lua"

if fonts and fonts.readers.tfm then
  --------------------------------------------------------------------
  --- OFM; read this first
  --------------------------------------------------------------------
  --- I can’t quite make out whether this is still relevant
  --- as those ofm fonts always fail, even in the 2011 version
  --- (mktexpk:  don't know how to create bitmap font for omarabb.ofm)
  --- the font loader appears to read ofm like tfm so if this
  --- hack was supposed achieve that, we should excise it anyways
  fonts.readers.ofm  = fonts.readers.tfm
  fonts.handlers.ofm = fonts.handlers.tfm --- empty anyways
  fonts.formats.ofm  = fonts.formats.tfm  --- “type1”
  --- fonts.readers.sequence[#fonts.readers.sequence+1] = "ofm"
  --------------------------------------------------------------------
end

--[[doc--

Now we load the modules written for \identifier{luaotfload}.

--doc]]--
loadmodule"font-pfb.lua"    --- new in 2.0, added 2011
loadmodule"font-nms.lua"
loadmodule"font-clr.lua"
loadmodule"font-ltx.lua"    --- new in 2.0, added 2011

--[[doc--

We create a callback for patching fonts on the fly, to be used by other
packages.
It initially contains the empty function that we are going to override
below.

--doc]]--

create_callback("luaotfload.patch_font", "simple", dummy_function)

--[[doc--

This is a wrapper for the imported font loader.
As of 2013, everything it does appear to be redundand, so we won’t use
it unless somebody points out a cogent reason.
Nevertheless, it has been adapted to work with the current structure of
font data objects and will stay here for reference / until breakage is
reported.

\emphasis{TODO}
This one also enables patching fonts.
The current fontloader apparently comes with a dedicated mechanism for
that already: enhancers.
How those work remains to be figured out.

--doc]]--
local define_font_wrapper = function (...)
    --- we use “tfmdata” (not “fontdata”) for consistency with the
    --- font loader
    local tfmdata = fonts.definers.read(...)
    if type(tfmdata) == "table" and tfmdata.shared then
        local metadata = tfmdata.shared.rawdata.metadata
        local mathdata = metadata.math --- do all fonts have this field?
        if mathdata then
            local mathconstants = { } --- why new hash, not modify in place?
            local units_per_em  = metadata.units_per_em
            local size          = tfmdata.size
            for k,v in next, mathdata do
                --- afaics this is alread taken care of by
                --- definers.read
                if stringfind(k, "Percent") then
                    -- keep percent values as is
                    print(k,v)
                    mathconstants[k] = v
                else
                    mathconstants[k] = v / units_per_em * size
                end
            end
            --- for \overwithdelims
            --- done by definers.read as well
            mathconstants.FractionDelimiterSize             = 1.01 * size
            --- fontloader has 2.4 × size
            mathconstants.FractionDelimiterDisplayStyleSize = 2.39 * size
            tfmdata.MathConstants = mathconstants
        end
        call_callback("luaotfload.patch_font", tfmdata)
    end
    return tfmdata
end

--[[doc--

\subsection{\CONTEXT override}

We provide a simplified version of the original font definition
callback.

--doc]]--

local read_font_file = fonts.definers.read
local patch_defined_font = function (...)
    local tfmdata = read_font_file(...)-- spec -> size -> id -> tmfdata
    if type(tfmdata) == "table" then
        call_callback("luaotfload.patch_font", tfmdata)
    end
    return tfmdata
end

caches.compilemethod = "both"

reset_callback("define_font")

--[[doc--
Finally we register the callbacks
--doc]]--

if luaotfload.font_definer == "old"  then
  add_to_callback("define_font",
                  define_font_wrapper,
                  "luaotfload.define_font",
                  1)
elseif luaotfload.font_definer == "generic"  then
  add_to_callback("define_font",
                  generic_context.callback_define_font,
                  "luaotfload.define_font",
                  1)
elseif luaotfload.font_definer == "patch"  then
  add_to_callback("define_font",
                  patch_defined_font,
                  "luaotfload.define_font",
                  1)
end

loadmodule"features.lua"

-- vim:tw=71:sw=4:ts=4:expandtab