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|
-----------------------------------------------------------------------
-- FILE: luaotfload-letterspace.lua
-- DESCRIPTION: part of luaotfload / letterspacing
-----------------------------------------------------------------------
assert(luaotfload_module, "This is a part of luaotfload and should not be loaded independently") {
name = "luaotfload-letterspace",
version = "3.23", --TAGVERSION
date = "2022-10-03", --TAGDATE
description = "luaotfload submodule / letterspacing",
license = "GPL v2.0",
copyright = "PRAGMA ADE / ConTeXt Development Team",
author = "Hans Hagen, PRAGMA-ADE, Hasselt NL; adapted by Philipp Gesang, Ulrike Fischer, Marcel Krüger"
}
--- This code diverged quite a bit from its origin in Context. Please
--- do *not* report bugs on the Context list.
local logreport = luaotfload.log.report
local getmetatable = getmetatable
local setmetatable = setmetatable
local tonumber = tonumber
local unpack = table.unpack
local next = next
local node, fonts = node, fonts
local nodedirect = node.direct
local getfield = nodedirect.getfield
local setfield = nodedirect.setfield
local getfont = nodedirect.getfont
local getid = nodedirect.getid
local getnext = nodedirect.getnext
local setnext = nodedirect.setnext
local getprev = nodedirect.getprev
local setprev = nodedirect.setprev
local getboth = nodedirect.getboth
local setlink = nodedirect.setlink
local getdisc = nodedirect.getdisc
local setdisc = nodedirect.setdisc
local getsubtype = nodedirect.getsubtype
local setsubtype = nodedirect.setsubtype
local getchar = nodedirect.getchar
local setchar = nodedirect.setchar
local getkern = nodedirect.getkern
local setkern = nodedirect.setkern
local getglue = nodedirect.getglue
local setglue = nodedirect.setglue
local hasattribute = nodedirect.has_attribute
local setattribute = nodedirect.set_attribute
local getattributelist = nodedirect.getattributelist
local setattributelist = nodedirect.setattributelist
local find_node_tail = nodedirect.tail
local todirect = nodedirect.todirect
local tonode = nodedirect.tonode
local insert_node_before = nodedirect.insert_before
local real_free_node = nodedirect.free
local copy_node = nodedirect.copy
local new_node = nodedirect.new
local glyph_code = node.id"glyph"
local kern_code = node.id"kern"
local disc_code = node.id"disc"
local glue_code = node.id"glue"
local whatsit_code = node.id"whatsit"
local fonthashes = fonts.hashes
local identifiers = fonthashes.identifiers
local chardata = fonthashes.characters
local otffeatures = fonts.constructors.newfeatures "otf"
local markdata
-- For every attribute list cached in attribute_table, we have to make
-- sure that it doesn't get deleted. Therefore attribute_cleanup maps
-- from a node which has the attribute_list referenced in
-- attribute_table to the key from attribute_table.
-- Whenever a node which has an entry in attribute_cleanup is deleted,
-- we delete the corresponding entry from attribute_table since we can
-- no longer guarantee that it's references somewhere.
local attribute_table = {}
local attribute_cleanup = {}
local attr = luatexbase.new_attribute("luaotfload.letterspace_done")
local function free_node(n)
local k = attribute_cleanup[n]
if k then
attribute_cleanup[n], attribute_table[k] = nil
end
return real_free_node(n)
end
local function getprevreal(n)
repeat
n = getprev(n)
until not n or getid(n) ~= whatsit_code
return n
end
local function getnextreal(n)
repeat
n = getnext(n)
until not n or getid(n) ~= whatsit_code
return n
end
--[[doc--
Since the letterspacing method was derived initially from Context’s
typo-krn.lua we keep the sub-namespace “letterspace” inside the
“luaotfload” table.
--doc]]--
luaotfload.letterspace = luaotfload.letterspace or { }
local letterspace = luaotfload.letterspace
local lectured = false
letterspace.keepligature = true
letterspace.keeptogether = false
letterspace.keepwordspacing = false
---=================================================================---
--- preliminary definitions
---=================================================================---
-- We set up a layer emulating some Context internals that are needed
-- for the letterspacing callback.
-----------------------------------------------------------------------
--- node-ini
-----------------------------------------------------------------------
local kerning_code = 0
local userkern_code = 1
local userskip_code = 0
local spaceskip_code = 13
local xspaceskip_code = 14
if not chardata then
chardata = { }
table.setmetatableindex(chardata, function(t, k)
if k == true then
return chardata[currentfont()]
else
local tfmdata = font.getfont(k) or font.fonts[k]
if tfmdata then
local characters = tfmdata.characters
t[k] = characters
return characters
end
end
end)
fonthashes.characters = chardata
end
if not markdata then
markdata = setmetatable({}, {__index = function(t, k)
if k == true then
return t[currentfont()]
else
local tfmdata = font.getfont(k) or font.fonts[k]
if tfmdata then
local marks = tfmdata.resources.marks or {}
t[k] = marks
return marks
end
end
end})
end
---=================================================================---
--- character kerning functionality
---=================================================================---
-- UF changed 2017-07-14
local function kern_injector (fillup, kern)
if fillup then
local g = new_node(glue_code)
setglue(g, 0, kern, 0, 1, 0)
return g
end
local g = new_node(kern_code)
setkern(g,kern)
return g
end
-- /UF
local function kernable_skip (n)
local st = getsubtype (n)
return st == userskip_code
or st == spaceskip_code
or st == xspaceskip_code
end
--[[doc--
Caveat lector.
This is an adaptation of the Context character kerning mechanism
that emulates XeTeX-style fontwise letterspacing. Note that in its
present state it is far inferior to the original, which is
attribute-based and ignores font-boundaries. Nevertheless, due to
popular demand the following callback has been added.
--doc]]--
local kernamounts = table.setmetatableindex(function (t, f) --- fontid -> {kern, fill}
local tfmdata = font.getfont(f) or font.fonts[f]
if tfmdata then
local fontproperties = tfmdata.properties
local fontparameters = tfmdata.parameters
if fontproperties and fontparameters then
local r
if fontproperties.kerncharacters == "max" then
r = {fontparameters.quad/4, true}
elseif fontproperties.kerncharacters then
r = {fontproperties.kerncharacters * fontparameters.quad, false}
else
r = {}
end
t[f] = r
return r
end
end
return {}
end)
local kerncharacters
kerncharacters = function (head)
local start = head
local lastfont = nil
local keeptogether = letterspace.keeptogether --- function
local keepligature = letterspace.keepligature
-- if not lectured and keepligature ~= true then
-- logreport ("both", 0, "letterspace",
-- "Breaking ligatures through letterspacing is deprecated and "
-- .. "will be removed soon. Please disable unwanted ligatures through "
-- .. "font features instead and reset luaotfload.letterspace.keepligature "
-- .. "to true to maintain compatibility with future versions of luaotfload.")
-- lectured = true
-- end
if type(keepligature) ~= "function" then
local savedligature = keepligature
keepligature = function() return savedligature end
end
local keepwordspacing = letterspace.keepwordspacing
if type(keepwordspacing) ~= "function" then
local savedwordspacing = keepwordspacing
keepwordspacing = function() return savedwordspacing end
end
local kernamounts = kernamounts
local firstkern = true
while start do
local id = getid(start)
if id == glyph_code then
--- 1) look up kern factor (slow, but cached rudimentarily)
if hasattribute(start, attr, 1) then -- We already kerned this node
firstkern = false -- TODO: I'm not sure about this one yet
goto nextnode
end
local fontid = getfont(start)
local krn, fillup = unpack(kernamounts[fontid])
if not krn or krn == 0 then
firstkern = true
goto nextnode
elseif firstkern then
firstkern = false
if (id ~= disc_code) and (not getfield(start, "components")) then
--- not a ligature, skip node
goto nextnode
end
end
lastfont = fontid
--- 2) resolve ligatures
local c = getfield(start, "components")
if c then
if keepligature(start) then
-- keep 'm
c = nil
else
while c do
local s = start
local p, n = getboth (s)
if p then
setlink (p, c)
else
head = c
end
if n then
local tail = find_node_tail(c)
setlink (tail, n)
end
start = c
setfield(s, "components", nil)
free_node(s) --> double free with multipart components
c = getfield (start, "components")
end
end
end -- kern ligature
--- 3) apply the extra kerning
local prev = getprevreal(start)
if prev then
local pid = getid(prev)
if not pid then
-- nothing
elseif pid == glue_code and kernable_skip(prev)
and not keepwordspacing(prev, lastfont) then
local wd, stretch, shrink = getglue(prev)
if wd > 0 then
local newwd = wd + krn
local stretched = (stretch * newwd) / wd
local shrunk = (shrink * newwd) / wd
if fillup then
setglue(prev, newwd, 2 * stretched, 2 * shrunk, 1, 0)
else
setglue(prev, newwd, stretched, shrunk, 0, 0)
end
end
elseif pid == kern_code then
local prev_subtype = getsubtype(prev)
if prev_subtype == kerning_code --- context does this by means of an
or prev_subtype == userkern_code --- attribute; we may need a test
then
local pprev = getprevreal(prev)
local pprev_id = getid(pprev)
if keeptogether
and pprev_id == glyph_code
and keeptogether(pprev, start)
then
-- keep
else
setsubtype (prev, userkern_code)
local prev_kern = getkern(prev)
prev_kern = prev_kern + krn
setkern (prev, prev_kern)
end
end
elseif pid == glyph_code then
if getfont(prev) == lastfont then
local prevchar = getchar(prev)
local lastchar = getchar(start)
if keeptogether and keeptogether(prev, start) then
-- keep 'm
elseif identifiers[lastfont] then
local lastfontchars = chardata[lastfont]
if lastfontchars then
local prevchardata = lastfontchars[prevchar]
if not prevchardata then
--- font doesn’t contain the glyph
else
local kern = 0
local kerns = prevchardata.kerns
if kerns then kern = kerns[lastchar] or kern end
krn = kern + (markdata[lastfont][lastchar] and 0 or krn) -- here
insert_node_before(head,start,kern_injector(fillup,krn))
end
end
end
else
insert_node_before(head,start,kern_injector(fillup,krn))
end
elseif pid == disc_code then
local disc = prev -- disc
local pre, post, replace = getdisc (disc)
local prv = getprevreal(disc)
local nxt = getnextreal(disc)
if pre and prv then -- must pair with start.prev
-- this one happens in most cases
local before = copy_node(prv)
setprev(pre, before)
setnext(before, pre)
setprev(before, nil)
pre = kerncharacters (before)
pre = getnext(pre)
setprev(pre, nil)
setfield(disc, "pre", pre)
free_node(before)
end
if post and nxt then -- must pair with start
local after = copy_node(nxt)
local tail = find_node_tail(post)
setnext(tail, after)
setprev(after, tail)
post = kerncharacters (post)
setnext(getprev(after), nil)
setfield(disc, "post", post)
free_node(after)
end
if replace and prv and nxt then -- must pair with start and start.prev
local before = copy_node(prv)
local after = copy_node(nxt)
local tail = find_node_tail(replace)
setprev(replace, before)
setnext(before, replace)
setprev(before, nil)
setnext(tail, after)
setprev(after, tail)
setnext(after, nil)
replace = kerncharacters (before)
replace = getnext(replace)
setprev(replace, nil)
setnext(getprev(after), nil)
setfield(disc, "replace", replace)
free_node(after)
free_node(before)
elseif identifiers[lastfont] then
if prv
and getid(prv) == glyph_code
and getfont(prv) == lastfont
then
local kern = 0
local prevchar = getchar(prv)
local lastchar = getchar(start)
local lastfontchars = chardata[lastfont]
if lastfontchars then
local prevchardata = lastfontchars[prevchar]
if not prevchardata then
--- font doesn’t contain the glyph
else
local kerns = prevchardata.kerns
if kerns then kern = kerns[lastchar] or kern end
end
end
krn = kern + (markdata[lastfont][lastchar] and 0 or krn) -- here
end
setfield(disc, "replace", kern_injector(false, krn))
end --[[if replace and prv and nxt]]
end --[[if not pid]]
local attr_list = getattributelist(start)
local new_attr_list = attribute_table[attr_list]
if new_attr_list then
setattributelist(start, new_attr_list)
else
setattribute(start, attr, 1)
attribute_cleanup[start] = attr_list
attribute_table[attr_list] = getattributelist(start)
end
end --[[if prev]]
end --[[if id == glyph_code]]
::nextnode::
if start then
start = getnext(start)
end
end
return head
end
---=================================================================---
--- integration
---=================================================================---
--- · callback: kerncharacters
--- · enabler: enablefontkerning
--- callback wrappers
--- (node_t -> node_t) -> string -> string list -> bool
local registered_as = { } --- procname -> callbacks
local function add_processor (processor, name, ...)
local callbacks = { ... }
for i=1, #callbacks do
luatexbase.add_to_callback(callbacks[i], processor, name)
end
registered_as[name] = callbacks --- for removal
return true
end
--- When font kerning is requested, usually by defining a font with the
--- ``letterspace`` parameter, we inject a wrapper for the
--- ``kerncharacters()`` node processor in the relevant callbacks. This
--- wrapper initially converts the received head node into its “direct”
--- counterpart. Likewise, the callback result is converted back to an
--- ordinary node prior to returning. Internally, ``kerncharacters()``
--- performs all node operations on direct nodes.
--- unit -> bool
local function enablefontkerning ( )
local function handler (hd)
local direct_hd = todirect (hd)
logreport ("term", 5, "letterspace",
"kerncharacters() invoked with node.direct interface \z
(``%s`` -> ``%s``)", tostring (hd), tostring (direct_hd))
local direct_hd = kerncharacters (direct_hd)
if not direct_hd then --- bad
logreport ("both", 0, "letterspace",
"kerncharacters() failed to return a valid new head")
end
for k, v in next, attribute_cleanup do attribute_cleanup[k], attribute_table[v] = nil end
assert(not next(attribute_table))
return tonode (direct_hd)
end
return add_processor( handler
, "luaotfload.letterspace"
, "pre_linebreak_filter"
, "hpack_filter")
end
--[[doc--
Fontwise kerning is enabled via the “kernfactor” option at font
definition time. Unlike the Context implementation which relies on
Luatex attributes, it uses a font property for passing along the
letterspacing factor of a node.
The callback is activated the first time a letterspaced font is
requested and stays active until the end of the run. Since the font
is a property of individual glyphs, every glyph in the entire
document must be checked for the kern property. This is quite
inefficient compared to Context’s attribute based approach, but Xetex
compatibility reduces our options significantly.
--doc]]--
local fontkerning_enabled = false --- callback state
--- fontobj -> float -> unit
local function initializefontkerning (tfmdata, factor)
if factor ~= "max" then
factor = tonumber (factor) or 0
end
if factor == "max" or factor ~= 0 then
local fontproperties = tfmdata.properties
if fontproperties then
--- hopefully this field stays unused otherwise
fontproperties.kerncharacters = factor
end
if not fontkerning_enabled then
fontkerning_enabled = enablefontkerning ()
end
end
end
--- like the font colorization, fontwise kerning is hooked into the
--- feature mechanism
otffeatures.register {
name = "kernfactor",
description = "kernfactor",
initializers = {
base = initializefontkerning,
node = initializefontkerning,
plug = initializefontkerning,
}
}
--[[doc--
The “letterspace” feature is essentially identical with the above
“kernfactor” method, but scales the factor to percentages to match
Xetex’s behavior. (See the Xetex reference, page 5, section 1.2.2.)
Since Xetex doesn’t appear to have a (documented) “max” keyword, we
assume all input values are numeric.
--doc]]--
local function initializecompatfontkerning (tfmdata, percentage)
local factor = tonumber (percentage)
if not factor then
logreport ("both", 0, "letterspace",
"Invalid argument to letterspace: %s (type %q), " ..
"was expecting percentage as Lua number instead.",
percentage, type (percentage))
return
end
return initializefontkerning (tfmdata, factor * 0.01)
end
otffeatures.register {
name = "letterspace",
description = "letterspace",
initializers = {
base = initializecompatfontkerning,
node = initializecompatfontkerning,
plug = initializecompatfontkerning,
}
}
--[[example--
See https://bitbucket.org/phg/lua-la-tex-tests/src/tip/pln-letterspace-8-compare.tex
for an example.
--example]]--
--- vim:sw=2:ts=2:expandtab:tw=71
|