[lib] add font-afm.lua

1 files changed, 971 insertions, 0 deletions

diff --git a/luaotfload-font-afm.lua b/luaotfload-font-afm.lua
new file mode 100644
index 0000000..cb0c243
--- /dev/null
+++ b/luaotfload-font-afm.lua
@@ -0,0 +1,971 @@
+if not modules then modules = { } end modules ['font-afm'] = {
+    version   = 1.001,
+    comment   = "companion to font-ini.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+--[[ldx--
+<p>Some code may look a bit obscure but this has to do with the
+fact that we also use this code for testing and much code evolved
+in the transition from <l n='tfm'/> to <l n='afm'/> to <l
+n='otf'/>.</p>
+
+<p>The following code still has traces of intermediate font support
+where we handles font encodings. Eventually font encoding goes
+away.</p>
+--ldx]]--
+
+local fonts, logs, trackers, containers, resolvers = fonts, logs, trackers, containers, resolvers
+
+local next, type, tonumber = next, type, tonumber
+local format, match, gmatch, lower, gsub, strip = string.format, string.match, string.gmatch, string.lower, string.gsub, string.strip
+local abs = math.abs
+local P, S, C, R, lpegmatch, patterns = lpeg.P, lpeg.S, lpeg.C, lpeg.R, lpeg.match, lpeg.patterns
+local derivetable = table.derive
+
+local trace_features     = false  trackers.register("afm.features",   function(v) trace_features = v end)
+local trace_indexing     = false  trackers.register("afm.indexing",   function(v) trace_indexing = v end)
+local trace_loading      = false  trackers.register("afm.loading",    function(v) trace_loading  = v end)
+local trace_defining     = false  trackers.register("fonts.defining", function(v) trace_defining = v end)
+
+local report_afm         = logs.reporter("fonts","afm loading")
+
+local findbinfile        = resolvers.findbinfile
+
+local definers           = fonts.definers
+local readers            = fonts.readers
+local constructors       = fonts.constructors
+
+local afm                = constructors.newhandler("afm")
+local pfb                = constructors.newhandler("pfb")
+
+local afmfeatures        = constructors.newfeatures("afm")
+local registerafmfeature = afmfeatures.register
+
+afm.version              = 1.410 -- incrementing this number one up will force a re-cache
+afm.cache                = containers.define("fonts", "afm", afm.version, true)
+afm.autoprefixed         = true -- this will become false some day (catches texnansi-blabla.*)
+
+afm.helpdata             = { }  -- set later on so no local for this
+afm.syncspace            = true -- when true, nicer stretch values
+afm.addligatures         = true -- best leave this set to true
+afm.addtexligatures      = true -- best leave this set to true
+afm.addkerns             = true -- best leave this set to true
+
+local function setmode(tfmdata,value)
+    if value then
+        tfmdata.properties.mode = lower(value)
+    end
+end
+
+registerafmfeature {
+    name         = "mode",
+    description  = "mode",
+    initializers = {
+        base = setmode,
+        node = setmode,
+    }
+}
+
+--[[ldx--
+<p>We start with the basic reader which we give a name similar to the
+built in <l n='tfm'/> and <l n='otf'/> reader.</p>
+--ldx]]--
+
+--~ Comment FONTIDENTIFIER LMMATHSYMBOLS10
+--~ Comment CODINGSCHEME TEX MATH SYMBOLS
+--~ Comment DESIGNSIZE 10.0 pt
+--~ Comment CHECKSUM O 4261307036
+--~ Comment SPACE 0 plus 0 minus 0
+--~ Comment QUAD 1000
+--~ Comment EXTRASPACE 0
+--~ Comment NUM 676.508 393.732 443.731
+--~ Comment DENOM 685.951 344.841
+--~ Comment SUP 412.892 362.892 288.889
+--~ Comment SUB 150 247.217
+--~ Comment SUPDROP 386.108
+--~ Comment SUBDROP 50
+--~ Comment DELIM 2390 1010
+--~ Comment AXISHEIGHT 250
+
+local comment = P("Comment")
+local spacing = patterns.spacer  -- S(" \t")^1
+local lineend = patterns.newline -- S("\n\r")
+local words   = C((1 - lineend)^1)
+local number  = C((R("09") + S("."))^1) / tonumber * spacing^0
+local data    = lpeg.Carg(1)
+
+local pattern = ( -- needs testing ... not used anyway as we no longer need math afm's
+    comment * spacing *
+        (
+            data * (
+                ("CODINGSCHEME" * spacing * words                                      ) / function(fd,a)                                      end +
+                ("DESIGNSIZE"   * spacing * number * words                             ) / function(fd,a)     fd[ 1]                 = a       end +
+                ("CHECKSUM"     * spacing * number * words                             ) / function(fd,a)     fd[ 2]                 = a       end +
+                ("SPACE"        * spacing * number * "plus" * number * "minus" * number) / function(fd,a,b,c) fd[ 3], fd[ 4], fd[ 5] = a, b, c end +
+                ("QUAD"         * spacing * number                                     ) / function(fd,a)     fd[ 6]                 = a       end +
+                ("EXTRASPACE"   * spacing * number                                     ) / function(fd,a)     fd[ 7]                 = a       end +
+                ("NUM"          * spacing * number * number * number                   ) / function(fd,a,b,c) fd[ 8], fd[ 9], fd[10] = a, b, c end +
+                ("DENOM"        * spacing * number * number                            ) / function(fd,a,b  ) fd[11], fd[12]         = a, b    end +
+                ("SUP"          * spacing * number * number * number                   ) / function(fd,a,b,c) fd[13], fd[14], fd[15] = a, b, c end +
+                ("SUB"          * spacing * number * number                            ) / function(fd,a,b)   fd[16], fd[17]         = a, b    end +
+                ("SUPDROP"      * spacing * number                                     ) / function(fd,a)     fd[18]                 = a       end +
+                ("SUBDROP"      * spacing * number                                     ) / function(fd,a)     fd[19]                 = a       end +
+                ("DELIM"        * spacing * number * number                            ) / function(fd,a,b)   fd[20], fd[21]         = a, b    end +
+                ("AXISHEIGHT"   * spacing * number                                     ) / function(fd,a)     fd[22]                 = a       end
+            )
+          + (1-lineend)^0
+        )
+  + (1-comment)^1
+)^0
+
+local function scan_comment(str)
+    local fd = { }
+    lpegmatch(pattern,str,1,fd)
+    return fd
+end
+
+-- On a rainy day I will rewrite this in lpeg ... or we can use the (slower) fontloader
+-- as in now supports afm/pfb loading but it's not too bad to have different methods
+-- for testing approaches.
+
+local keys = { }
+
+function keys.FontName    (data,line) data.metadata.fontname     = strip    (line) -- get rid of spaces
+                                      data.metadata.fullname     = strip    (line) end
+function keys.ItalicAngle (data,line) data.metadata.italicangle  = tonumber (line) end
+function keys.IsFixedPitch(data,line) data.metadata.isfixedpitch = toboolean(line,true) end
+function keys.CharWidth   (data,line) data.metadata.charwidth    = tonumber (line) end
+function keys.XHeight     (data,line) data.metadata.xheight      = tonumber (line) end
+function keys.Descender   (data,line) data.metadata.descender    = tonumber (line) end
+function keys.Ascender    (data,line) data.metadata.ascender     = tonumber (line) end
+function keys.Comment     (data,line)
+ -- Comment DesignSize 12 (pts)
+ -- Comment TFM designsize: 12 (in points)
+    line = lower(line)
+    local designsize = match(line,"designsize[^%d]*(%d+)")
+    if designsize then data.metadata.designsize = tonumber(designsize) end
+end
+
+local function get_charmetrics(data,charmetrics,vector)
+    local characters = data.characters
+    local chr, ind = { }, 0
+    for k,v in gmatch(charmetrics,"([%a]+) +(.-) *;") do
+        if k == 'C'  then
+            v = tonumber(v)
+            if v < 0 then
+                ind = ind + 1 -- ?
+            else
+                ind = v
+            end
+            chr = {
+                index = ind
+            }
+        elseif k == 'WX' then
+            chr.width = tonumber(v)
+        elseif k == 'N'  then
+            characters[v] = chr
+        elseif k == 'B'  then
+            local llx, lly, urx, ury = match(v,"^ *(.-) +(.-) +(.-) +(.-)$")
+            chr.boundingbox = { tonumber(llx), tonumber(lly), tonumber(urx), tonumber(ury) }
+        elseif k == 'L'  then
+            local plus, becomes = match(v,"^(.-) +(.-)$")
+            local ligatures = chr.ligatures
+            if ligatures then
+                ligatures[plus] = becomes
+            else
+                chr.ligatures = { [plus] = becomes }
+            end
+        end
+    end
+end
+
+local function get_kernpairs(data,kernpairs)
+    local characters = data.characters
+    for one, two, value in gmatch(kernpairs,"KPX +(.-) +(.-) +(.-)\n") do
+        local chr = characters[one]
+        if chr then
+            local kerns = chr.kerns
+            if kerns then
+                kerns[two] = tonumber(value)
+            else
+                chr.kerns = { [two] = tonumber(value) }
+            end
+        end
+    end
+end
+
+local function get_variables(data,fontmetrics)
+    for key, rest in gmatch(fontmetrics,"(%a+) *(.-)[\n\r]") do
+        local keyhandler = keys[key]
+        if keyhandler then
+            keyhandler(data,rest)
+        end
+    end
+end
+
+local function get_indexes(data,pfbname)
+    data.resources.filename = resolvers.unresolve(pfbname) -- no shortcut
+    local pfbblob = fontloader.open(pfbname)
+    if pfbblob then
+        local characters = data.characters
+        local pfbdata = fontloader.to_table(pfbblob)
+        if pfbdata then
+            local glyphs = pfbdata.glyphs
+            if glyphs then
+                if trace_loading then
+                    report_afm("getting index data from %a",pfbname)
+                end
+                for index, glyph in next, glyphs do
+                    local name = glyph.name
+                    if name then
+                        local char = characters[name]
+                        if char then
+                            if trace_indexing then
+                                report_afm("glyph %a has index %a",name,index)
+                            end
+                            char.index = index
+                        end
+                    end
+                end
+            elseif trace_loading then
+                report_afm("no glyph data in pfb file %a",pfbname)
+            end
+        elseif trace_loading then
+            report_afm("no data in pfb file %a",pfbname)
+        end
+        fontloader.close(pfbblob)
+    elseif trace_loading then
+        report_afm("invalid pfb file %a",pfbname)
+    end
+end
+
+local function readafm(filename)
+    local ok, afmblob, size = resolvers.loadbinfile(filename) -- has logging
+    if ok and afmblob then
+        local data = {
+            resources = {
+                filename = resolvers.unresolve(filename),
+                version  = afm.version,
+                creator  = "context mkiv",
+            },
+            properties = {
+                hasitalics = false,
+            },
+            goodies = {
+            },
+            metadata   = {
+                filename = file.removesuffix(file.basename(filename))
+            },
+            characters = {
+                -- a temporary store
+            },
+            descriptions = {
+                -- the final store
+            },
+        }
+        afmblob = gsub(afmblob,"StartCharMetrics(.-)EndCharMetrics", function(charmetrics)
+            if trace_loading then
+                report_afm("loading char metrics")
+            end
+            get_charmetrics(data,charmetrics,vector)
+            return ""
+        end)
+        afmblob = gsub(afmblob,"StartKernPairs(.-)EndKernPairs", function(kernpairs)
+            if trace_loading then
+                report_afm("loading kern pairs")
+            end
+            get_kernpairs(data,kernpairs)
+            return ""
+        end)
+        afmblob = gsub(afmblob,"StartFontMetrics%s+([%d%.]+)(.-)EndFontMetrics", function(version,fontmetrics)
+            if trace_loading then
+                report_afm("loading variables")
+            end
+            data.afmversion = version
+            get_variables(data,fontmetrics)
+            data.fontdimens = scan_comment(fontmetrics) -- todo: all lpeg, no time now
+            return ""
+        end)
+        return data
+    else
+        if trace_loading then
+            report_afm("no valid afm file %a",filename)
+        end
+        return nil
+    end
+end
+
+--[[ldx--
+<p>We cache files. Caching is taken care of in the loader. We cheat a bit
+by adding ligatures and kern information to the afm derived data. That
+way we can set them faster when defining a font.</p>
+--ldx]]--
+
+local addkerns, addligatures, addtexligatures, unify, normalize -- we will implement these later
+
+function afm.load(filename)
+    -- hm, for some reasons not resolved yet
+    filename = resolvers.findfile(filename,'afm') or ""
+    if filename ~= "" then
+        local name = file.removesuffix(file.basename(filename))
+        local data = containers.read(afm.cache,name)
+        local attr = lfs.attributes(filename)
+        local size, time = attr.size or 0, attr.modification or 0
+        --
+        local pfbfile = file.replacesuffix(name,"pfb")
+        local pfbname = resolvers.findfile(pfbfile,"pfb") or ""
+        if pfbname == "" then
+            pfbname = resolvers.findfile(file.basename(pfbfile),"pfb") or ""
+        end
+        local pfbsize, pfbtime = 0, 0
+        if pfbname ~= "" then
+            local attr = lfs.attributes(pfbname)
+            pfbsize = attr.size or 0
+            pfbtime = attr.modification or 0
+        end
+        if not data or data.size ~= size or data.time ~= time or data.pfbsize ~= pfbsize or data.pfbtime ~= pfbtime then
+            report_afm("reading %a",filename)
+            data = readafm(filename)
+            if data then
+                if pfbname ~= "" then
+                    get_indexes(data,pfbname)
+                elseif trace_loading then
+                    report_afm("no pfb file for %a",filename)
+                end
+                report_afm("unifying %a",filename)
+                unify(data,filename)
+                if afm.addligatures then
+                    report_afm("add ligatures")
+                    addligatures(data)
+                end
+                if afm.addtexligatures then
+                    report_afm("add tex ligatures")
+                    addtexligatures(data)
+                end
+                if afm.addkerns then
+                    report_afm("add extra kerns")
+                    addkerns(data)
+                end
+                normalize(data)
+                report_afm("add tounicode data")
+                fonts.mappings.addtounicode(data,filename)
+                data.size = size
+                data.time = time
+                data.pfbsize = pfbsize
+                data.pfbtime = pfbtime
+                report_afm("saving %a in cache",name)
+                data = containers.write(afm.cache, name, data)
+                data = containers.read(afm.cache,name)
+            end
+        end
+        return data
+    else
+        return nil
+    end
+end
+
+local uparser = fonts.mappings.makenameparser()
+
+unify = function(data, filename)
+    local unicodevector = fonts.encodings.agl.unicodes -- loaded runtime in context
+    local unicodes, names = { }, { }
+    local private = constructors.privateoffset
+    local descriptions = data.descriptions
+    for name, blob in next, data.characters do
+        local code = unicodevector[name] -- or characters.name_to_unicode[name]
+        if not code then
+            code = lpegmatch(uparser,name)
+            if not code then
+                code = private
+                private = private + 1
+                report_afm("assigning private slot %U for unknown glyph name %a",code,name)
+            end
+        end
+        local index = blob.index
+        unicodes[name] = code
+        names[name] = index
+        blob.name = name
+        descriptions[code] = {
+            boundingbox = blob.boundingbox,
+            width       = blob.width,
+            kerns       = blob.kerns,
+            index       = index,
+            name        = name,
+        }
+    end
+    for unicode, description in next, descriptions do
+        local kerns = description.kerns
+        if kerns then
+            local krn = { }
+            for name, kern in next, kerns do
+                local unicode = unicodes[name]
+                if unicode then
+                    krn[unicode] = kern
+                else
+                    print(unicode,name)
+                end
+            end
+            description.kerns = krn
+        end
+    end
+    data.characters = nil
+    local resources = data.resources
+    local filename = resources.filename or file.removesuffix(file.basename(filename))
+    resources.filename = resolvers.unresolve(filename) -- no shortcut
+    resources.unicodes = unicodes -- name to unicode
+    resources.marks = { } -- todo
+    resources.names = names -- name to index
+    resources.private = private
+end
+
+normalize = function(data)
+end
+
+--[[ldx--
+<p>These helpers extend the basic table with extra ligatures, texligatures
+and extra kerns. This saves quite some lookups later.</p>
+--ldx]]--
+
+local addthem = function(rawdata,ligatures)
+    if ligatures then
+        local descriptions = rawdata.descriptions
+        local resources    = rawdata.resources
+        local unicodes     = resources.unicodes
+        local names        = resources.names
+        for ligname, ligdata in next, ligatures do
+            local one = descriptions[unicodes[ligname]]
+            if one then
+                for _, pair in next, ligdata do
+                    local two, three = unicodes[pair[1]], unicodes[pair[2]]
+                    if two and three then
+                        local ol = one.ligatures
+                        if ol then
+                            if not ol[two] then
+                                ol[two] = three
+                            end
+                        else
+                            one.ligatures = { [two] = three }
+                        end
+                    end
+                end
+            end
+        end
+    end
+end
+
+addligatures    = function(rawdata) addthem(rawdata,afm.helpdata.ligatures   ) end
+addtexligatures = function(rawdata) addthem(rawdata,afm.helpdata.texligatures) end
+
+--[[ldx--
+<p>We keep the extra kerns in separate kerning tables so that we can use
+them selectively.</p>
+--ldx]]--
+
+-- This is rather old code (from the beginning when we had only tfm). If
+-- we unify the afm data (now we have names all over the place) then
+-- we can use shcodes but there will be many more looping then. But we
+-- could get rid of the tables in char-cmp then. Als, in the generic version
+-- we don't use the character database. (Ok, we can have a context specific
+-- variant).
+
+addkerns = function(rawdata) -- using shcodes is not robust here
+    local descriptions = rawdata.descriptions
+    local resources    = rawdata.resources
+    local unicodes     = resources.unicodes
+    local function do_it_left(what)
+        if what then
+            for unicode, description in next, descriptions do
+                local kerns = description.kerns
+                if kerns then
+                    local extrakerns
+                    for complex, simple in next, what do
+                        complex = unicodes[complex]
+                        simple = unicodes[simple]
+                        if complex and simple then
+                            local ks = kerns[simple]
+                            if ks and not kerns[complex] then
+                                if extrakerns then
+                                    extrakerns[complex] = ks
+                                else
+                                    extrakerns = { [complex] = ks }
+                                end
+                            end
+                        end
+                    end
+                    if extrakerns then
+                        description.extrakerns = extrakerns
+                    end
+                end
+            end
+        end
+    end
+    local function do_it_copy(what)
+        if what then
+            for complex, simple in next, what do
+                complex = unicodes[complex]
+                simple = unicodes[simple]
+                if complex and simple then
+                    local complexdescription = descriptions[complex]
+                    if complexdescription then -- optional
+                        local simpledescription = descriptions[complex]
+                        if simpledescription then
+                            local extrakerns
+                            local kerns = simpledescription.kerns
+                            if kerns then
+                                for unicode, kern in next, kerns do
+                                    if extrakerns then
+                                        extrakerns[unicode] = kern
+                                    else
+                                        extrakerns = { [unicode] = kern }
+                                    end
+                                end
+                            end
+                            local extrakerns = simpledescription.extrakerns
+                            if extrakerns then
+                                for unicode, kern in next, extrakerns do
+                                    if extrakerns then
+                                        extrakerns[unicode] = kern
+                                    else
+                                        extrakerns = { [unicode] = kern }
+                                    end
+                                end
+                            end
+                            if extrakerns then
+                                complexdescription.extrakerns = extrakerns
+                            end
+                        end
+                    end
+                end
+            end
+        end
+    end
+    -- add complex with values of simplified when present
+    do_it_left(afm.helpdata.leftkerned)
+    do_it_left(afm.helpdata.bothkerned)
+    -- copy kerns from simple char to complex char unless set
+    do_it_copy(afm.helpdata.bothkerned)
+    do_it_copy(afm.helpdata.rightkerned)
+end
+
+--[[ldx--
+<p>The copying routine looks messy (and is indeed a bit messy).</p>
+--ldx]]--
+
+local function adddimensions(data) -- we need to normalize afm to otf i.e. indexed table instead of name
+    if data then
+        for unicode, description in next, data.descriptions do
+            local bb = description.boundingbox
+            if bb then
+                local ht, dp = bb[4], -bb[2]
+                if ht == 0 or ht < 0 then
+                    -- no need to set it and no negative heights, nil == 0
+                else
+                    description.height = ht
+                end
+                if dp == 0 or dp < 0 then
+                    -- no negative depths and no negative depths, nil == 0
+                else
+                    description.depth  = dp
+                end
+            end
+        end
+    end
+end
+
+local function copytotfm(data)
+    if data and data.descriptions then
+        local metadata     = data.metadata
+        local resources    = data.resources
+        local properties   = derivetable(data.properties)
+        local descriptions = derivetable(data.descriptions)
+        local goodies      = derivetable(data.goodies)
+        local characters   = { }
+        local parameters   = { }
+        local unicodes     = resources.unicodes
+        --
+        for unicode, description in next, data.descriptions do -- use parent table
+            characters[unicode] = { }
+        end
+        --
+        local filename   = constructors.checkedfilename(resources)
+        local fontname   = metadata.fontname or metadata.fullname
+        local fullname   = metadata.fullname or metadata.fontname
+        local endash     = unicodes['space']
+        local emdash     = unicodes['emdash']
+        local spacer     = "space"
+        local spaceunits = 500
+        --
+        local monospaced  = metadata.isfixedpitch
+        local charwidth   = metadata.charwidth
+        local italicangle = metadata.italicangle
+        local charxheight = metadata.xheight and metadata.xheight > 0 and metadata.xheight
+        properties.monospaced  = monospaced
+        parameters.italicangle = italicangle
+        parameters.charwidth   = charwidth
+        parameters.charxheight = charxheight
+        -- same as otf
+        if properties.monospaced then
+            if descriptions[endash] then
+                spaceunits, spacer = descriptions[endash].width, "space"
+            end
+            if not spaceunits and descriptions[emdash] then
+                spaceunits, spacer = descriptions[emdash].width, "emdash"
+            end
+            if not spaceunits and charwidth then
+                spaceunits, spacer = charwidth, "charwidth"
+            end
+        else
+            if descriptions[endash] then
+                spaceunits, spacer = descriptions[endash].width, "space"
+            end
+            if not spaceunits and charwidth then
+                spaceunits, spacer = charwidth, "charwidth"
+            end
+        end
+        spaceunits = tonumber(spaceunits)
+        if spaceunits < 200 then
+            -- todo: warning
+        end
+        --
+        parameters.slant         = 0
+        parameters.space         = spaceunits
+        parameters.space_stretch = 500
+        parameters.space_shrink  = 333
+        parameters.x_height      = 400
+        parameters.quad          = 1000
+        --
+        if italicangle then
+            parameters.italicangle  = italicangle
+            parameters.italicfactor = math.cos(math.rad(90+italicangle))
+            parameters.slant        = - math.round(math.tan(italicangle*math.pi/180))
+        end
+        if monospaced then
+            parameters.space_stretch = 0
+            parameters.space_shrink  = 0
+        elseif afm.syncspace then
+            parameters.space_stretch = spaceunits/2
+            parameters.space_shrink  = spaceunits/3
+        end
+        parameters.extra_space = parameters.space_shrink
+        if charxheight then
+            parameters.x_height = charxheight
+        else
+            -- same as otf
+            local x = unicodes['x']
+            if x then
+                local x = descriptions[x]
+                if x then
+                    parameters.x_height = x.height
+                end
+            end
+            --
+        end
+        local fd = data.fontdimens
+        if fd and fd[8] and fd[9] and fd[10] then -- math
+            for k,v in next, fd do
+                parameters[k] = v
+            end
+        end
+        --
+        parameters.designsize = (metadata.designsize or 10)*65536
+        parameters.ascender   = abs(metadata.ascender  or 0)
+        parameters.descender  = abs(metadata.descender or 0)
+        parameters.units      = 1000
+        --
+        properties.spacer        = spacer
+        properties.encodingbytes = 2
+        properties.format        = fonts.formats[filename] or "type1"
+        properties.filename      = filename
+        properties.fontname      = fontname
+        properties.fullname      = fullname
+        properties.psname        = fullname
+        properties.name          = filename or fullname or fontname
+        --
+        if next(characters) then
+            return {
+                characters   = characters,
+                descriptions = descriptions,
+                parameters   = parameters,
+                resources    = resources,
+                properties   = properties,
+                goodies      = goodies,
+            }
+        end
+    end
+    return nil
+end
+
+--[[ldx--
+<p>Originally we had features kind of hard coded for <l n='afm'/>
+files but since I expect to support more font formats, I decided
+to treat this fontformat like any other and handle features in a
+more configurable way.</p>
+--ldx]]--
+
+function afm.setfeatures(tfmdata,features)
+    local okay = constructors.initializefeatures("afm",tfmdata,features,trace_features,report_afm)
+    if okay then
+        return constructors.collectprocessors("afm",tfmdata,features,trace_features,report_afm)
+    else
+        return { } -- will become false
+    end
+end
+
+local function checkfeatures(specification)
+end
+
+local function afmtotfm(specification)
+    local afmname = specification.filename or specification.name
+    if specification.forced == "afm" or specification.format == "afm" then -- move this one up
+        if trace_loading then
+            report_afm("forcing afm format for %a",afmname)
+        end
+    else
+        local tfmname = findbinfile(afmname,"ofm") or ""
+        if tfmname ~= "" then
+            if trace_loading then
+                report_afm("fallback from afm to tfm for %a",afmname)
+            end
+            return -- just that
+        end
+    end
+    if afmname ~= "" then
+        -- weird, isn't this already done then?
+        local features = constructors.checkedfeatures("afm",specification.features.normal)
+        specification.features.normal = features
+        constructors.hashinstance(specification,true) -- also weird here
+        --
+        specification = definers.resolve(specification) -- new, was forgotten
+        local cache_id = specification.hash
+        local tfmdata  = containers.read(constructors.cache, cache_id) -- cache with features applied
+        if not tfmdata then
+            local rawdata = afm.load(afmname)
+            if rawdata and next(rawdata) then
+                adddimensions(rawdata)
+                tfmdata = copytotfm(rawdata)
+                if tfmdata and next(tfmdata) then
+                    local shared = tfmdata.shared
+                    if not shared then
+                        shared         = { }
+                        tfmdata.shared = shared
+                    end
+                    shared.rawdata   = rawdata
+                    shared.features  = features
+                    shared.processes = afm.setfeatures(tfmdata,features)
+                end
+            elseif trace_loading then
+                report_afm("no (valid) afm file found with name %a",afmname)
+            end
+            tfmdata = containers.write(constructors.cache,cache_id,tfmdata)
+        end
+        return tfmdata
+    end
+end
+
+--[[ldx--
+<p>As soon as we could intercept the <l n='tfm'/> reader, I implemented an
+<l n='afm'/> reader. Since traditional <l n='pdftex'/> could use <l n='opentype'/>
+fonts with <l n='afm'/> companions, the following method also could handle
+those cases, but now that we can handle <l n='opentype'/> directly we no longer
+need this features.</p>
+--ldx]]--
+
+local function read_from_afm(specification)
+    local tfmdata = afmtotfm(specification)
+    if tfmdata then
+        tfmdata.properties.name = specification.name
+        tfmdata = constructors.scale(tfmdata, specification)
+        local allfeatures = tfmdata.shared.features or specification.features.normal
+        constructors.applymanipulators("afm",tfmdata,allfeatures,trace_features,report_afm)
+        fonts.loggers.register(tfmdata,'afm',specification)
+    end
+    return tfmdata
+end
+
+--[[ldx--
+<p>Here comes the implementation of a few features. We only implement
+those that make sense for this format.</p>
+--ldx]]--
+
+local function prepareligatures(tfmdata,ligatures,value)
+    if value then
+        local descriptions = tfmdata.descriptions
+        for unicode, character in next, tfmdata.characters do
+            local description = descriptions[unicode]
+            local dligatures = description.ligatures
+            if dligatures then
+                local cligatures = character.ligatures
+                if not cligatures then
+                    cligatures = { }
+                    character.ligatures = cligatures
+                end
+                for unicode, ligature in next, dligatures do
+                    cligatures[unicode] = {
+                        char = ligature,
+                        type = 0
+                    }
+                end
+            end
+        end
+    end
+end
+
+local function preparekerns(tfmdata,kerns,value)
+    if value then
+        local rawdata = tfmdata.shared.rawdata
+        local resources = rawdata.resources
+        local unicodes = resources.unicodes
+        local descriptions = tfmdata.descriptions
+        for u, chr in next, tfmdata.characters do
+            local d = descriptions[u]
+            local newkerns = d[kerns]
+            if newkerns then
+                local kerns = chr.kerns
+                if not kerns then
+                    kerns = { }
+                    chr.kerns = kerns
+                end
+                for k,v in next, newkerns do
+                    local uk = unicodes[k]
+                    if uk then
+                        kerns[uk] = v
+                    end
+                end
+            end
+        end
+    end
+end
+
+local list = {
+ -- [0x0022] = 0x201D,
+    [0x0027] = 0x2019,
+ -- [0x0060] = 0x2018,
+}
+
+local function texreplacements(tfmdata,value)
+    local descriptions = tfmdata.descriptions
+    local characters   = tfmdata.characters
+    for k, v in next, list do
+        characters  [k] = characters  [v] -- we forget about kerns
+        descriptions[k] = descriptions[v] -- we forget about kerns
+    end
+end
+
+local function ligatures   (tfmdata,value) prepareligatures(tfmdata,'ligatures',   value) end
+local function texligatures(tfmdata,value) prepareligatures(tfmdata,'texligatures',value) end
+local function kerns       (tfmdata,value) preparekerns    (tfmdata,'kerns',       value) end
+local function extrakerns  (tfmdata,value) preparekerns    (tfmdata,'extrakerns',  value) end
+
+registerafmfeature {
+    name         = "liga",
+    description  = "traditional ligatures",
+    initializers = {
+        base = ligatures,
+        node = ligatures,
+    }
+}
+
+registerafmfeature {
+    name         = "kern",
+    description  = "intercharacter kerning",
+    initializers = {
+        base = kerns,
+        node = kerns,
+    }
+}
+
+registerafmfeature {
+    name         = "extrakerns",
+    description  = "additional intercharacter kerning",
+    initializers = {
+        base = extrakerns,
+        node = extrakerns,
+    }
+}
+
+registerafmfeature {
+    name         = 'tlig',
+    description  = 'tex ligatures',
+    initializers = {
+        base = texligatures,
+        node = texligatures,
+    }
+}
+
+registerafmfeature {
+    name         = 'trep',
+    description  = 'tex replacements',
+    initializers = {
+        base = texreplacements,
+        node = texreplacements,
+    }
+}
+
+-- readers
+
+local check_tfm   = readers.check_tfm
+
+fonts.formats.afm = "type1"
+fonts.formats.pfb = "type1"
+
+local function check_afm(specification,fullname)
+    local foundname = findbinfile(fullname, 'afm') or "" -- just to be sure
+    if foundname == "" then
+        foundname = fonts.names.getfilename(fullname,"afm") or ""
+    end
+    if foundname == "" and afm.autoprefixed then
+        local encoding, shortname = match(fullname,"^(.-)%-(.*)$") -- context: encoding-name.*
+        if encoding and shortname and fonts.encodings.known[encoding] then
+            shortname = findbinfile(shortname,'afm') or "" -- just to be sure
+            if shortname ~= "" then
+                foundname = shortname
+                if trace_defining then
+                    report_afm("stripping encoding prefix from filename %a",afmname)
+                end
+            end
+        end
+    end
+    if foundname ~= "" then
+        specification.filename = foundname
+        specification.format   = "afm"
+        return read_from_afm(specification)
+    end
+end
+
+function readers.afm(specification,method)
+    local fullname, tfmdata = specification.filename or "", nil
+    if fullname == "" then
+        local forced = specification.forced or ""
+        if forced ~= "" then
+            tfmdata = check_afm(specification,specification.name .. "." .. forced)
+        end
+        if not tfmdata then
+            method = method or definers.method or "afm or tfm"
+            if method == "tfm" then
+                tfmdata = check_tfm(specification,specification.name)
+            elseif method == "afm" then
+                tfmdata = check_afm(specification,specification.name)
+            elseif method == "tfm or afm" then
+                tfmdata = check_tfm(specification,specification.name) or check_afm(specification,specification.name)
+            else -- method == "afm or tfm" or method == "" then
+                tfmdata = check_afm(specification,specification.name) or check_tfm(specification,specification.name)
+            end
+        end
+    else
+        tfmdata = check_afm(specification,fullname)
+    end
+    return tfmdata
+end
+
+function readers.pfb(specification,method) -- only called when forced
+    local original = specification.specification
+    if trace_defining then
+        report_afm("using afm reader for %a",original)
+    end
+    specification.specification = gsub(original,"%.pfb",".afm")
+    specification.forced = "afm"
+    return readers.afm(specification,method)
+end