From 9138da7d4a53d65bc15f3a5dc73fd373db40bdf7 Mon Sep 17 00:00:00 2001
From: Philipp Gesang <phg42.2a@gmail.com>
Date: Wed, 12 Feb 2014 07:50:06 +0100
Subject: [*] move source files to ./src

---
 src/luaotfload-letterspace.lua | 544 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 544 insertions(+)
 create mode 100644 src/luaotfload-letterspace.lua

(limited to 'src/luaotfload-letterspace.lua')

diff --git a/src/luaotfload-letterspace.lua b/src/luaotfload-letterspace.lua
new file mode 100644
index 0000000..20f29f5
--- /dev/null
+++ b/src/luaotfload-letterspace.lua
@@ -0,0 +1,544 @@
+if not modules then modules = { } end modules ['letterspace'] = {
+    version   = "2.5",
+    comment   = "companion to luaotfload-main.lua",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL; adapted by Philipp Gesang",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+local log                = luaotfload.log
+local report             = log.report
+
+local getmetatable       = getmetatable
+local require            = require
+local setmetatable       = setmetatable
+local tonumber           = tonumber
+
+local next               = next
+local nodes, node, fonts = nodes, node, fonts
+
+local find_node_tail     = node.tail or node.slide
+local free_node          = node.free
+local copy_node          = node.copy
+local new_node           = node.new
+local insert_node_before = node.insert_before
+
+local nodepool           = nodes.pool
+
+local new_kern           = nodepool.kern
+local new_glue           = nodepool.glue
+
+local nodecodes          = nodes.nodecodes
+
+local glyph_code         = nodecodes.glyph
+local kern_code          = nodecodes.kern
+local disc_code          = nodecodes.disc
+local math_code          = nodecodes.math
+
+local fonthashes         = fonts.hashes
+local chardata           = fonthashes.characters
+local quaddata           = fonthashes.quads
+local otffeatures        = fonts.constructors.newfeatures "otf"
+
+--[[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
+
+letterspace.keepligature = false
+letterspace.keeptogether = false
+
+---=================================================================---
+---                     preliminary definitions
+---=================================================================---
+-- We set up a layer emulating some Context internals that are needed
+-- for the letterspacing callback.
+-----------------------------------------------------------------------
+--- node-ini
+-----------------------------------------------------------------------
+
+local bothways  = function (t) return table.swapped (t, t) end
+local kerncodes = bothways { [0] = "fontkern"
+                           , [1] = "userkern"
+                           , [2] = "accentkern"
+                           }
+
+kerncodes.kerning    = kerncodes.fontkern --- idiosyncrasy
+local kerning_code   = kerncodes.kerning
+local userkern_code  = kerncodes.userkern
+
+
+-----------------------------------------------------------------------
+--- node-res
+-----------------------------------------------------------------------
+
+nodes.pool        = nodes.pool or { }
+local pool        = nodes.pool
+
+local kern        = new_node ("kern", kerncodes.userkern)
+local glue_spec   = new_node "glue_spec"
+
+pool.kern = function (k)
+  local n = copy_node (kern)
+  n.kern = k
+  return n
+end
+
+pool.glue = function (width, stretch, shrink,
+                      stretch_order, shrink_order)
+  local n = new_node"glue"
+  if not width then
+    -- no spec
+  elseif width == false or tonumber(width) then
+    local s = copy_node(glue_spec)
+    if width         then s.width         = width         end
+    if stretch       then s.stretch       = stretch       end
+    if shrink        then s.shrink        = shrink        end
+    if stretch_order then s.stretch_order = stretch_order end
+    if shrink_order  then s.shrink_order  = shrink_order  end
+    n.spec = s
+  else
+    -- shared
+    n.spec = copy_node(width)
+  end
+  return n
+end
+
+-----------------------------------------------------------------------
+--- font-hsh
+-----------------------------------------------------------------------
+--- some initialization resembling font-hsh
+local fonthashes         = fonts.hashes
+local identifiers        = fonthashes.identifiers --- was: fontdata
+local chardata           = fonthashes.characters
+local quaddata           = fonthashes.quads
+local parameters         = fonthashes.parameters
+
+--- ('a, 'a) hash -> (('a, 'a) hash -> 'a -> 'a) -> ('a, 'a) hash
+local setmetatableindex = function (t, f)
+  local mt = getmetatable(t)
+  if mt then
+    mt.__index = f
+  else
+    setmetatable(t, { __index = f })
+  end
+  return t
+end
+
+if not parameters then
+  parameters = { }
+  setmetatableindex(parameters, function(t, k)
+    if k == true then
+      return parameters[currentfont()]
+    else
+      local parameters = identifiers[k].parameters
+      t[k] = parameters
+      return parameters
+    end
+  end)
+  --fonthashes.parameters = parameters
+end
+
+if not chardata then
+  chardata = { }
+  setmetatableindex(chardata, function(t, k)
+    if k == true then
+      return chardata[currentfont()]
+    else
+      local tfmdata = identifiers[k]
+      if not tfmdata then --- unsafe
+        tfmdata = font.fonts[k]
+      end
+      if tfmdata then
+        local characters = tfmdata.characters
+        t[k] = characters
+        return characters
+      end
+    end
+  end)
+  fonthashes.characters = chardata
+end
+
+if not quaddata then
+  quaddata = { }
+  setmetatableindex(quaddata, function(t, k)
+    if k == true then
+      return quads[currentfont()]
+    else
+      local parameters = parameters[k]
+      local quad = parameters and parameters.quad or 0
+      t[k] = quad
+      return quad
+    end
+  end)
+  --fonthashes.quads = quaddata
+end
+
+---=================================================================---
+---                 character kerning functionality
+---=================================================================---
+
+local kern_injector = function (fillup, kern)
+  if fillup then
+    local g = new_glue(kern)
+    local s = g.spec
+    s.stretch = kern
+    s.stretch_order = 1
+    return g
+  else
+    return new_kern(kern)
+  end
+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 kernfactors = { } --- fontid -> factor
+
+local kerncharacters
+kerncharacters = function (head)
+  local start, done   = head, false
+  local lastfont      = nil
+  local keepligature  = letterspace.keepligature --- function
+  local keeptogether  = letterspace.keeptogether --- function
+  local fillup        = false
+
+  local identifiers   = fonthashes.identifiers
+  local kernfactors   = kernfactors
+
+  local firstkern     = true
+
+  while start do
+    local id = start.id
+    if id == glyph_code then
+
+      --- 1) look up kern factor (slow, but cached rudimentarily)
+      local krn
+      local fontid = start.font
+      do
+        krn = kernfactors[fontid]
+        if not krn then
+          local tfmdata = identifiers[fontid]
+          if not tfmdata then -- unsafe
+            tfmdata = font.fonts[fontid]
+          end
+          if tfmdata then
+            fontproperties = tfmdata.properties
+            if fontproperties then
+              krn = fontproperties.kerncharacters
+            end
+          end
+          kernfactors[fontid] = krn
+        end
+        if not krn or krn == 0 then
+          firstkern = true
+          goto nextnode
+        elseif firstkern then
+          firstkern = false
+          if (id ~= disc_code) and (not start.components) then
+            --- not a ligature, skip node
+            goto nextnode
+          end
+        end
+      end
+
+      if krn == "max" then
+        krn = .25
+        fillup = true
+      else
+        fillup = false
+      end
+
+      lastfont = fontid
+
+      --- 2) resolve ligatures
+      local c = start.components
+
+      if c then
+        if keepligature and keepligature(start) then
+          -- keep 'm
+        else
+          --- c = kerncharacters (c) --> taken care of after replacing
+          local s = start
+          local p, n = s.prev, s.next
+          local tail = find_node_tail(c)
+          if p then
+            p.next = c
+            c.prev = p
+          else
+            head = c
+          end
+          if n then
+            n.prev = tail
+          end
+          tail.next = n
+          start = c
+          s.components = nil
+          -- we now leak nodes !
+          --  free_node(s)
+          done = true
+        end
+      end -- kern ligature
+
+      --- 3) apply the extra kerning
+      local prev = start.prev
+      if prev then
+        local pid = prev.id
+
+        if not pid then
+          -- nothing
+
+        elseif pid == kern_code then
+          if prev.subtype == kerning_code   --- context does this by means of an
+          or prev.subtype == userkern_code  --- attribute; we may need a test
+          then
+            if keeptogether and prev.prev.id == glyph_code and keeptogether(prev.prev,start) then
+              -- keep
+            else
+              prev.subtype = userkern_code
+              prev.kern = prev.kern + quaddata[lastfont]*krn -- here
+              done = true
+            end
+          end
+
+        elseif pid == glyph_code then
+          if prev.font == lastfont then
+            local prevchar, lastchar = prev.char, start.char
+            if keeptogether and keeptogether(prev,start) then
+              -- keep 'm
+            elseif identifiers[lastfont] then
+              local kerns = chardata[lastfont][prevchar].kerns
+              local kern = kerns and kerns[lastchar] or 0
+              krn = kern + quaddata[lastfont]*krn -- here
+              insert_node_before(head,start,kern_injector(fillup,krn))
+              done = true
+            end
+          else
+            krn = quaddata[lastfont]*krn -- here
+            insert_node_before(head,start,kern_injector(fillup,krn))
+            done = true
+          end
+
+        elseif pid == disc_code then
+          -- a bit too complicated, we can best not copy and just calculate
+          -- but we could have multiple glyphs involved so ...
+          local disc = prev -- disc
+          local pre, post, replace = disc.pre, disc.post, disc.replace
+          local prv, nxt = disc.prev, disc.next
+
+          if pre and prv then -- must pair with start.prev
+            -- this one happens in most cases
+            local before = copy_node(prv)
+            pre.prev = before
+            before.next = pre
+            before.prev = nil
+            pre = kerncharacters (before)
+            pre = pre.next
+            pre.prev = nil
+            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)
+            tail.next = after
+            after.prev = tail
+            after.next = nil
+            post = kerncharacters (post)
+            tail.next = nil
+            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)
+            replace.prev = before
+            before.next = replace
+            before.prev = nil
+            tail.next = after
+            after.prev = tail
+            after.next = nil
+            replace = kerncharacters (before)
+            replace = replace.next
+            replace.prev = nil
+            after.prev.next = nil
+            disc.replace = replace
+            free_node(after)
+            free_node(before)
+          elseif identifiers[lastfont] then
+            if prv and prv.id == glyph_code and prv.font == lastfont then
+              local prevchar, lastchar = prv.char, start.char
+              local kerns = chardata[lastfont][prevchar].kerns
+              local kern = kerns and kerns[lastchar] or 0
+              krn = kern + quaddata[lastfont]*krn -- here
+            else
+              krn = quaddata[lastfont]*krn -- here
+            end
+            disc.replace = kern_injector(false,krn) -- only kerns permitted, no glue
+          end
+
+        end
+      end
+    end
+
+    ::nextnode::
+    if start then
+      start = start.next
+    end
+  end
+  return head, done
+end
+
+---=================================================================---
+---                         integration
+---=================================================================---
+
+--- · callback:     kerncharacters
+--- · enabler:      enablefontkerning
+--- · disabler:     disablefontkerning
+
+--- callback wrappers
+
+--- (node_t -> node_t) -> string -> string list -> bool
+local registered_as = { } --- procname -> callbacks
+local add_processor = function (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
+
+--- string -> bool
+local remove_processor = function (name)
+  local callbacks = registered_as[name]
+  if callbacks then
+    for i=1, #callbacks do
+      luatexbase.remove_from_callback(callbacks[i], name)
+    end
+    return true
+  end
+  return false --> unregistered
+end
+
+--- now for the simplistic variant
+--- unit -> bool
+local enablefontkerning = function ( )
+  return add_processor( kerncharacters
+                      , "luaotfload.letterspace"
+                      , "pre_linebreak_filter"
+                      , "hpack_filter")
+end
+
+--- unit -> bool
+local disablefontkerning = function ( )
+  return remove_processor "luaotfload.letterspace"
+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 initializefontkerning = function (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,
+  }
+}
+
+--[[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 initializecompatfontkerning = function (tfmdata, percentage)
+  local factor = tonumber (percentage)
+  if not factor then
+    report ("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,
+  }
+}
+
+--[[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
+
-- 
cgit v1.2.3