diff options
Diffstat (limited to 'luaotfload-letterspace.lua')
| -rw-r--r-- | luaotfload-letterspace.lua | 316 |
1 files changed, 288 insertions, 28 deletions
diff --git a/luaotfload-letterspace.lua b/luaotfload-letterspace.lua index b8bd36d..7c5a967 100644 --- a/luaotfload-letterspace.lua +++ b/luaotfload-letterspace.lua @@ -6,52 +6,182 @@ if not modules then modules = { } end modules ['letterspace'] = { license = "see context related readme files" } +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 free_nodelist = node.flush_list local copy_node = node.copy -local copy_nodelist = node.copy_list +local new_node = node.new local insert_node_before = node.insert_before -local insert_node_after = node.insert_after local nodepool = nodes.pool -local tasks = nodes.tasks local new_kern = nodepool.kern local new_glue = nodepool.glue local nodecodes = nodes.nodecodes -local kerncodes = nodes.kerncodes -local skipcodes = nodes.skipcodes local glyph_code = nodecodes.glyph local kern_code = nodecodes.kern local disc_code = nodecodes.disc -local glue_code = nodecodes.glue -local hlist_code = nodecodes.hlist -local vlist_code = nodecodes.vlist local math_code = nodecodes.math -local kerning_code = kerncodes.kerning -local userkern_code = kerncodes.userkern +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 -typesetters = typesetters or { } -local typesetters = typesetters +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 -typesetters.kernfont = typesetters.kernfont or { } -local kernfont = typesetters.kernfont +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 -kernfont.keepligature = false -kernfont.keeptogether = false +---=================================================================--- +--- character kerning functionality +---=================================================================--- -local kern_injector = function (fillup,kern) +local kern_injector = function (fillup, kern) if fillup then local g = new_glue(kern) local s = g.spec @@ -66,13 +196,11 @@ end --[[doc-- Caveat lector. - This is a preliminary, makeshift 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. It should not be relied upon to be present in future - versions. + 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]]-- @@ -82,8 +210,8 @@ local kerncharacters kerncharacters = function (head) local start, done = head, false local lastfont = nil - local keepligature = kernfont.keepligature --- function - local keeptogether = kernfont.keeptogether --- function + local keepligature = letterspace.keepligature --- function + local keeptogether = letterspace.keeptogether --- function local fillup = false local identifiers = fonthashes.identifiers @@ -275,7 +403,139 @@ kerncharacters = function (head) return head, done end -kernfont.handler = kerncharacters +---=================================================================--- +--- 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 + logs.names_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 |