summaryrefslogtreecommitdiff
path: root/Master/texmf-dist/tex/luatex/luaotfload/luaotfload-configuration.lua
blob: 8cdebe063d8633439206b24d2df40c52cadf9268 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
#!/usr/bin/env texlua
-------------------------------------------------------------------------------
--         FILE:  luaotfload-configuration.lua
--  DESCRIPTION:  config file reader
-- REQUIREMENTS:  Luaotfload 2.7 or above
--       AUTHOR:  Philipp Gesang, <phg@phi-gamma.net>
--       AUTHOR:  Dohyun Kim <nomosnomos@gmail.com>
-------------------------------------------------------------------------------
--

if not modules then modules = { } end modules ["luaotfload-configuration"] = {
  version   = "2.7",
  comment   = "part of Luaotfload",
  author    = "Philipp Gesang, Dohyun Kim",
  copyright = "Luaotfload Development Team",
  license   = "GNU GPL v2.0"
}

local status_file             = "luaotfload-status"
local luaotfloadstatus        = require (status_file)

local string                  = string
local stringfind              = string.find
local stringformat            = string.format
local stringstrip             = string.strip
local stringsub               = string.sub

local tableappend             = table.append
local tableconcat             = table.concat
local tablecopy               = table.copy
local table                   = table
local tabletohash             = table.tohash

local math                    = math
local mathfloor               = math.floor

local io                      = io
local ioloaddata              = io.loaddata
local iopopen                 = io.popen
local iowrite                 = io.write

local os                      = os
local osdate                  = os.date
local osgetenv                = os.getenv

local lpeg                    = require "lpeg"
local lpegmatch               = lpeg.match
local commasplitter           = lpeg.splitat ","
local equalssplitter          = lpeg.splitat "="

local kpseexpand_path         = kpse.expand_path

local lfs                     = lfs
local lfsisfile               = lfs.isfile
local lfsisdir                = lfs.isdir

local file                    = file
local filejoin                = file.join
local filereplacesuffix       = file.replacesuffix

local logreport               = print -- overloaded later
local getwritablepath         = caches.getwritablepath


local config_parser -- set later during init
local stripslashes  -- set later during init

-------------------------------------------------------------------------------
---                                SETTINGS
-------------------------------------------------------------------------------

local path_t = 0
local kpse_t = 1

local val_home            = kpseexpand_path "~"
local val_xdg_config_home = kpseexpand_path "$XDG_CONFIG_HOME"

if val_xdg_config_home == "" then val_xdg_config_home = "~/.config" end

local config_paths = {
  --- needs adapting for those other OS
  { path_t, "./luaotfload.conf" },
  { path_t, "./luaotfloadrc" },
  { path_t, filejoin (val_xdg_config_home, "luaotfload/luaotfload.conf") },
  { path_t, filejoin (val_xdg_config_home, "luaotfload/luaotfloadrc") },
  { path_t, filejoin (val_home, ".luaotfloadrc") },
  { kpse_t, "luaotfloadrc" },
  { kpse_t, "luaotfload.conf" },
}

local valid_formats = tabletohash {
  "otf", "ttc", "ttf", "afm", "pfb"
}

local default_anon_sequence = {
  "tex", "path", "name"
}

local valid_resolvers = tabletohash {
  "tex", "path", "name", "file", "my"
}

local feature_presets = {
  arab = tabletohash {
    "ccmp", "locl", "isol", "fina", "fin2",
    "fin3", "medi", "med2", "init", "rlig",
    "calt", "liga", "cswh", "mset", "curs",
    "kern", "mark", "mkmk",
  },
  deva = tabletohash {
    "ccmp", "locl", "init", "nukt", "akhn",
    "rphf", "blwf", "half", "pstf", "vatu",
    "pres", "blws", "abvs", "psts", "haln",
    "calt", "blwm", "abvm", "dist", "kern",
    "mark", "mkmk",
  },
  khmr = tabletohash {
    "ccmp", "locl", "pref", "blwf", "abvf",
    "pstf", "pres", "blws", "abvs", "psts",
    "clig", "calt", "blwm", "abvm", "dist",
    "kern", "mark", "mkmk",
  },
  thai = tabletohash {
    "ccmp", "locl", "liga", "kern", "mark",
    "mkmk",
  },
}

--[[doc--

  We allow loading of arbitrary fontloaders. Nevertheless we maintain a
  list of the “official” ones shipped with Luaotfload so we can emit a
  different log message.

--doc]]--

local default_fontloader = function ()
  return luaotfloadstatus and luaotfloadstatus.notes.loader or "reference"
end

local registered_loaders = {
  default    = default_fontloader (),
  reference  = "reference",
  unpackaged = "unpackaged",
  context    = "context",
}

local pick_fontloader = function (s)
  local ldr = registered_loaders[s]
  if ldr ~= nil and type (ldr) == "string" then
    logreport ("log", 2, "conf", "Using predefined fontloader \"%s\".", ldr)
    return ldr
  end
  local idx = stringfind (s, ":")
  if idx and idx > 2 then
    if stringsub (s, 1, idx - 1) == "context" then
      local pth = stringsub (s, idx + 1)
      pth = stringstrip (pth)
      logreport ("log", 2, "conf", "Context base path specified at \"%s\".", pth)
      if lfsisdir (pth) then
        logreport ("log", 5, "conf", "Context base path exists at \"%s\".", pth)
        return pth
      end
      pth = kpseexpand_path (pth)
      if lfsisdir (pth) then
        logreport ("log", 5, "conf", "Context base path exists at \"%s\".", pth)
        return pth
      end
      logreport ("both", 0, "conf", "Context base path not found at \"%s\".", pth)
    end
  end
  return nil
end

--[[doc--

  The ``post_linebreak_filter`` has been made the default callback for
  hooking the colorizer into. This helps with the linebreaking whose
  inserted hyphens would remain unaffected by the coloring otherwise.

  http://tex.stackexchange.com/q/238539/14066

--doc]]--

local permissible_color_callbacks = {
  default               = "post_linebreak_filter",
  pre_linebreak_filter  = "pre_linebreak_filter",
  post_linebreak_filter = "post_linebreak_filter",
  pre_output_filter     = "pre_output_filter",
}


-------------------------------------------------------------------------------
---                                DEFAULTS
-------------------------------------------------------------------------------

local default_config = {
  db = {
    formats         = "otf,ttf,ttc",
    scan_local      = false,
    skip_read       = false,
    strip           = true,
    update_live     = true,
    compress        = true,
    max_fonts       = 2^51,
    use_fontforge   = false,
  },
  run = {
    anon_sequence  = default_anon_sequence,
    resolver       = "cached",
    definer        = "patch",
    log_level      = 0,
    color_callback = "post_linebreak_filter",
    fontloader     = default_fontloader (),
  },
  misc = {
    bisect         = false,
    version        = luaotfload.version,
    statistics     = false,
    termwidth      = nil,
  },
  paths = {
    names_dir           = "names",
    cache_dir           = "fonts",
    index_file          = "luaotfload-names.lua",
    lookups_file        = "luaotfload-lookup-cache.lua",
    lookup_path_lua     = nil,
    lookup_path_luc     = nil,
    index_path_lua      = nil,
    index_path_luc      = nil,
  },
  default_features = {
    global = { mode = "node" },
    dflt = tabletohash {
      "ccmp", "locl", "rlig", "liga", "clig",
      "kern", "mark", "mkmk", 'itlc',
    },

    arab = feature_presets.arab,
    syrc = feature_presets.arab,
    mong = feature_presets.arab,
    nko  = feature_presets.arab,

    deva = feature_presets.deva,
    beng = feature_presets.deva,
    guru = feature_presets.deva,
    gujr = feature_presets.deva,
    orya = feature_presets.deva,
    taml = feature_presets.deva,
    telu = feature_presets.deva,
    knda = feature_presets.deva,
    mlym = feature_presets.deva,
    sinh = feature_presets.deva,

    khmr = feature_presets.khmr,
    tibt = feature_presets.khmr,
    thai = feature_presets.thai,
    lao  = feature_presets.thai,

    hang = tabletohash { "ccmp", "ljmo", "vjmo", "tjmo", },
  },
}

-------------------------------------------------------------------------------
---                          RECONFIGURATION TASKS
-------------------------------------------------------------------------------

--[[doc--

    Procedures to be executed in order to put the new configuration into effect.

--doc]]--

local reconf_tasks = nil

local min_terminal_width = 40

--- The “termwidth” value is only considered when printing
--- short status messages, e.g. when building the database
--- online.
local check_termwidth = function ()
  if config.luaotfload.misc.termwidth == nil then
      local tw = 79
      if not (   os.type == "windows" --- Assume broken terminal.
              or osgetenv "TERM" == "dumb")
      then
          local p = iopopen "tput cols"
          if p then
              result = tonumber (p:read "*all")
              p:close ()
              if result then
                  tw = result
              else
                  logreport ("log", 2, "db", "tput returned non-number.")
              end
          else
              logreport ("log", 2, "db", "Shell escape disabled or tput executable missing.")
              logreport ("log", 2, "db", "Assuming 79 cols terminal width.")
          end
      end
      config.luaotfload.misc.termwidth = tw
  end
  return true
end

local set_font_filter = function ()
  local names = fonts.names
  if names and names.set_font_filter then
    local formats = config.luaotfload.db.formats
    if not formats or formats == "" then
      formats = default_config.db.formats
    end
    names.set_font_filter (formats)
  end
  return true
end

local set_name_resolver = function ()
  local names = fonts.names
  if names and names.resolve_cached then
    --- replace the resolver from luatex-fonts
    if config.luaotfload.db.resolver == "cached" then
        logreport ("both", 2, "cache", "Caching of name: lookups active.")
        names.resolvespec  = fonts.names.lookup_font_name_cached
    else
        names.resolvespec  = fonts.names.lookup_font_name
    end
  end
  return true
end

local set_loglevel = function ()
  if luaotfload then
    luaotfload.log.set_loglevel (config.luaotfload.run.log_level)
    return true
  end
  return false
end

local build_cache_paths = function ()
  local paths  = config.luaotfload.paths
  local prefix = getwritablepath (paths.names_dir, "")

  if not prefix then
    luaotfload.error ("Impossible to find a suitable writeable cache...")
    return false
  end

  prefix = lpegmatch (stripslashes, prefix)
  logreport ("log", 0, "conf", "Root cache directory is %s.", prefix)

  local index_file      = filejoin (prefix, paths.index_file)
  local lookups_file    = filejoin (prefix, paths.lookups_file)

  paths.prefix          = prefix
  paths.index_path_lua  = filereplacesuffix (index_file,   "lua")
  paths.index_path_luc  = filereplacesuffix (index_file,   "luc")
  paths.lookup_path_lua = filereplacesuffix (lookups_file, "lua")
  paths.lookup_path_luc = filereplacesuffix (lookups_file, "luc")
  return true
end


local set_default_features = function ()
  local default_features = config.luaotfload.default_features
  luaotfload.features    = luaotfload.features or {
                             global   = { },
                             defaults = { },
                           }
  current_features       = luaotfload.features
  for var, val in next, default_features do
    if var == "global" then
      current_features.global = val
    else
      current_features.defaults[var] = val
    end
  end
  return true
end

local set_fontforge = function ()
  local names = fonts.names
  if not names or not names.use_fontforge then
    --- happens normally on the first run
    logreport ("log", 4, "db", "Database not present.")
    return true
  end
  local use_ff = config.luaotfload.db.use_fontforge
  if use_ff == true then
    if not _G.fontloader then
      logreport ("both", 0, "db",
                 "Fontforge loader was requested but the fontloader \z
                  library is missing.")
      return false
    end
    logreport ("log", 0, "db", "Loading font data with FontForge.")
    names.use_fontforge (true)
  else
    logreport ("log", 4, "db", "Loading font data with the Lua loader.")
    names.use_fontforge (false)
  end
  return true
end

reconf_tasks = {
  { "Set the log level"         , set_loglevel         },
  { "Build cache paths"         , build_cache_paths    },
  { "Check terminal dimensions" , check_termwidth      },
  { "Set the font filter"       , set_font_filter      },
  { "Install font name resolver", set_name_resolver    },
  { "Set default features"      , set_default_features },
  { "Set fontforge"             , set_fontforge        },
}

-------------------------------------------------------------------------------
---                          OPTION SPECIFICATION
-------------------------------------------------------------------------------

local string_t    = "string"
local table_t     = "table"
local number_t    = "number"
local boolean_t   = "boolean"
local function_t  = "function"

local tointeger = function (n)
  n = tonumber (n)
  if n then
    return mathfloor (n + 0.5)
  end
end

local toarray = function (s)
  local fields = { lpegmatch (commasplitter, s) }
  local ret    = { }
  for i = 1, #fields do
    local field = stringstrip (fields[i])
    if field and field ~= "" then
      ret[#ret + 1] = field
    end
  end
  return ret
end

local tohash = function (s)
  local result = { }
  local fields = toarray (s)
  for _, field in next, fields do
    local var, val
    if stringfind (field, "=") then
      local tmp
      var, tmp = lpegmatch (equalssplitter, field)
      if tmp == "true" or tmp == "yes" then val = true else val = tmp end
    else
      var, val = field, true
    end
    result[var] = val
  end
  return result
end

local option_spec = {
  db = {
    formats      = {
      in_t  = string_t,
      out_t = string_t,
      transform = function (f)
        local fields = toarray (f)

        --- check validity
        if not fields then
          logreport ("both", 0, "conf",
                     "Expected list of identifiers, got %q.", f)
          return nil
        end

        --- strip dupes
        local known  = { }
        local result = { }
        for i = 1, #fields do
          local field = fields[i]
          if known[field] ~= true then
            --- yet unknown, tag as seen
            known[field] = true
            --- include in output if valid
            if valid_formats[field] == true then
              result[#result + 1] = field
            else
              logreport ("both", 4, "conf",
                         "Invalid font format identifier %q, ignoring.",
                         field)
            end
          end
        end
        if #result == 0 then
          --- force defaults
          return nil
        end
        return tableconcat (result, ",")
      end
    },
    scan_local   = { in_t = boolean_t, },
    skip_read    = { in_t = boolean_t, },
    strip        = { in_t = boolean_t, },
    update_live  = { in_t = boolean_t, },
    compress     = { in_t = boolean_t, },
    max_fonts    = {
      in_t      = number_t,
      out_t     = number_t, --- TODO int_t from 5.3.x on
      transform = tointeger,
    },
    use_fontforge = { in_t = boolean_t, },
  },
  run = {
    anon_sequence = {
      in_t      = string_t,
      out_t     = table_t,
      transform = function (s)
        if s ~= "default" then
          local bits = { lpegmatch (commasplitter, s) }
          if next (bits) then
            local seq = { }
            local done = { }
            for i = 1, #bits do
              local bit = bits [i]
              if valid_resolvers [bit] then
                if not done [bit] then
                  done [bit] = true
                  seq [#seq + 1] = bit
                else
                  logreport ("both", 0, "conf",
                             "ignoring duplicate resolver %s at position %d \z
                              in lookup sequence",
                             bit, i)
                end
              else
                logreport ("both", 0, "conf",
                           "lookup sequence contains invalid item %s \z
                            at position %d.",
                           bit, i)
              end
            end
            if next (seq) then
              logreport ("both", 2, "conf",
                         "overriding anon lookup sequence %s.",
                         tableconcat (seq, ","))
              return seq
            end
          end
        end
        return default_anon_sequence
      end
    },
    live = { in_t = boolean_t, }, --- false for the tool, true for TeX run
    resolver = {
      in_t      = string_t,
      out_t     = string_t,
      transform = function (r) return r == "normal" and r or "cached" end,
    },
    definer = {
      in_t      = string_t,
      out_t     = string_t,
      transform = function (d)
        if   d == "generic"      or d == "patch"
          or d == "info_generic" or d == "info_patch"
        then
          return d
        end
        return "patch"
      end,
    },
    fontloader = {
      in_t      = string_t,
      out_t     = string_t,
      transform = function (id)
        local ldr = pick_fontloader (id)
        if ldr ~= nil then
          return ldr
        end
        logreport ("log", 0, "conf",
                    "Requested fontloader \"%s\" not defined, "
                    .. "use at your own risk.",
                    id)
        return id
      end,
    },
    log_level = {
      in_t      = number_t,
      out_t     = number_t, --- TODO int_t from 5.3.x on
      transform = tointeger,
    },
    color_callback = {
      in_t      = string_t,
      out_t     = string_t,
      transform = function (cb_spec)
        --- These are the two that make sense.
        local cb = permissible_color_callbacks[cb_spec]
        if cb then
          logreport ("log", 3, "conf",
                     "Using callback \"%s\" for font colorization.",
                     cb)
          return cb
        end
        logreport ("log", 0, "conf",
                    "Requested callback identifier \"%s\" invalid, "
                    .. "falling back to default.",
                    cb_spec)
        return permissible_color_callbacks.default
      end,
    },
  },
  misc = {
    bisect          = { in_t = boolean_t, }, --- doesn’t make sense in a config file
    version         = { in_t = string_t,  },
    statistics      = { in_t = boolean_t, },
    termwidth       = {
      in_t      = number_t,
      out_t     = number_t,
      transform = function (w)
        w = tointeger (w)
        if w < min_terminal_width then
          return min_terminal_width
        end
        return w
      end,
    },
  },
  paths = {
    names_dir           = { in_t = string_t, },
    cache_dir           = { in_t = string_t, },
    index_file          = { in_t = string_t, },
    lookups_file        = { in_t = string_t, },
    lookup_path_lua     = { in_t = string_t, },
    lookup_path_luc     = { in_t = string_t, },
    index_path_lua      = { in_t = string_t, },
    index_path_luc      = { in_t = string_t, },
  },
  default_features = {
    __default = { in_t  = string_t, out_t = table_t, transform = tohash, },
  },
}

-------------------------------------------------------------------------------
---                               FORMATTERS
-------------------------------------------------------------------------------

local commented = function (str)
  return ";" .. str
end

local underscore_replacer = lpeg.replacer ("_", "-", true)

local dashed = function (var)
  --- INI spec dictates that dashes are valid in variable names, not
  --- underscores.
  return underscore_replacer (var) or var
end

local indent = "  "
local format_string = function (var, val)
  return stringformat (indent .. "%s = %s", var, val)
end

local format_integer = function (var, val)
  return stringformat (indent .. "%s = %d", var, val)
end

local format_boolean = function (var, val)
  return stringformat (indent .. "%s = %s", var, val == true and "true" or "false")
end

local format_keyval = function (var, val)
  local list = { }
  local keys = table.sortedkeys (val)
  for i = 1, #keys do
    local key    = keys[i]
    local subval = val[key]
    if subval == true then
      list[#list + 1] = stringformat ("%s", key)
    else
      list[#list + 1] = stringformat ("%s=%s", key, val[key])
    end
  end
  if next (list) then
    return stringformat (indent .. "%s = %s",
                         var,
                         tableconcat (list, ","))
  end
end

local format_list = function (var, val)
  local elts = { }
  for i = 1, #val do elts [i] = val [i] end
  if next (elts) then
    return stringformat (indent .. "%s = %s",
                         var, tableconcat (elts, ","))
  end
end

local format_section = function (title)
  return stringformat ("[%s]", dashed (title))
end

local conf_header = [==[
;;-----------------------------------------------------------------------------
;; Luaotfload Configuration
;;-----------------------------------------------------------------------------
;;
;; This file was generated by luaotfload-tool
;; on %s. Configuration variables
;; are documented in the manual to luaotfload.conf(5).
;;
;;-----------------------------------------------------------------------------

]==]

local conf_footer = [==[

;; vim:filetype=dosini:expandtab:shiftwidth=2
]==]

--- Each dumpable variable (the ones mentioned in the man page) receives a
--- formatter that will be used in dumping the variable. Each value receives a
--- “commented” flag that indicates whether or not the line should be printed
--- as a comment.

local formatters = {
  db = {
    compress       = { false, format_boolean },
    formats        = { false, format_string  },
    max_fonts      = { false, format_integer },
    scan_local     = { false, format_boolean },
    skip_read      = { false, format_boolean },
    strip          = { false, format_boolean },
    update_live    = { false, format_boolean },
    use_fontforge  = { false, format_boolean },
  },
  default_features = {
    __default = { true, format_keyval },
  },
  misc = {
    bisect     = { false, format_boolean },
    statistics = { false, format_boolean },
    termwidth  = { true , format_integer },
    version    = { true , format_string  },
  },
  paths = {
    cache_dir    = { false, format_string },
    names_dir    = { false, format_string },
    index_file   = { false, format_string },
    lookups_file = { false, format_string },
  },
  run = {
    anon_sequence   = { false, format_list    },
    color_callback  = { false, format_string  },
    definer         = { false, format_string  },
    fontloader      = { false, format_string  },
    log_level       = { false, format_integer },
    resolver        = { false, format_string  },
  },
}

-------------------------------------------------------------------------------
---                           MAIN FUNCTIONALITY
-------------------------------------------------------------------------------

--[[doc--

  tilde_expand -- Rudimentary tilde expansion; covers just the “substitute ‘~’
  by the current users’s $HOME” part.

--doc]]--

local tilde_expand = function (p)
  if #p > 2 then
    if stringsub (p, 1, 2) == "~/" then
      local homedir = osgetenv "HOME"
      if homedir and lfsisdir (homedir) then
        p = filejoin (homedir, stringsub (p, 3))
      end
    end
  end
  return p
end

local resolve_config_path = function ()
  for i = 1, #config_paths do
    local t, p = unpack (config_paths[i])
    local fullname
    if t == kpse_t then
      fullname = kpse.lookup (p)
      logreport ("both", 6, "conf", "kpse lookup: %s -> %s.", p, fullname)
    elseif t == path_t then
      local expanded = tilde_expand (p)
      if lfsisfile (expanded) then
        fullname = expanded
      end
      logreport ("both", 6, "conf", "path lookup: %s -> %s.", p, fullname)
    end
    if fullname then
      logreport ("both", 3, "conf", "Reading configuration file at %q.", fullname)
      return fullname
    end
  end
  logreport ("both", 2, "conf", "No configuration file found.")
  return false
end

local add_config_paths = function (t)
  if not next (t) then
    return
  end
  local result = { }
  for i = 1, #t do
    local path = t[i]
    result[#result + 1] = { path_t, path }
  end
  config_paths = tableappend (result, config_paths)
end

local process_options = function (opts)
  local new = { }
  for i = 1, #opts do
    local section = opts[i]
    local title = section.section.title
    local vars  = section.variables

    if not title then --- trigger warning: arrow code ahead
      logreport ("both", 2, "conf", "Section %d lacks a title; skipping.", i)
    elseif not vars then
      logreport ("both", 2, "conf", "Section %d (%s) lacks a variable section; skipping.", i, title)
    else
      local spec = option_spec[title]
      if not spec then
        logreport ("both", 2, "conf", "Section %d (%s) unknown; skipping.", i, title)
      else
        local newsection = new[title]
        if not newsection then
          newsection = { }
          new[title] = newsection
        end

        for var, val in next, vars do
          local vspec = spec[var] or spec.__default
          local t_val = type (val)
          if not vspec then
            logreport ("both", 2, "conf",
                       "Section %d (%s): invalid configuration variable %q (%q); ignoring.",
                       i, title,
                       var, tostring (val))
          elseif t_val ~= vspec.in_t then
            logreport ("both", 2, "conf",
                       "Section %d (%s): type mismatch of input value %q (%q, %s != %s); ignoring.",
                       i, title,
                       var, tostring (val), t_val, vspec.in_t)
          else --- type matches
            local transform = vspec.transform
            if transform then
              local dval
              local t_transform = type (transform)
              if t_transform == function_t then
                dval = transform (val)
              elseif t_transform == table_t then
                dval = transform[val]
              end
              if dval then
                local out_t = vspec.out_t
                if out_t then
                  local t_dval = type (dval)
                  if t_dval == out_t then
                    newsection[var] = dval
                  else
                    logreport ("both", 2, "conf",
                               "Section %d (%s): type mismatch of derived value of %q (%q, %s != %s); ignoring.",
                               i, title,
                               var, tostring (dval), t_dval, out_t)
                  end
                else
                  newsection[var] = dval
                end
              else
                logreport ("both", 2, "conf",
                           "Section %d (%s): value of %q could not be derived via %s from input %q; ignoring.",
                           i, title, var, t_transform, tostring (val))
              end
            else --- insert as is
              newsection[var] = val
            end
          end
        end
      end
    end
  end
  return new
end

local apply
apply = function (old, new)
  if not new then
    if not old then
      return false
    end
    return tablecopy (old)
  elseif not old then
    return tablecopy (new)
  end
  local result = tablecopy (old)
  for name, section in next, new do
    local t_section = type (section)
    if t_section ~= table_t then
      logreport ("both", 1, "conf",
                 "Error applying configuration: entry %s is %s, expected table.",
                 section, t_section)
      --- ignore
    else
      local currentsection = result[name]
      for var, val in next, section do
        currentsection[var] = val
      end
    end
  end
  result.status = luaotfloadstatus
  return result
end

local reconfigure = function ()
  for i = 1, #reconf_tasks do
    local name, task = unpack (reconf_tasks[i])
    logreport ("both", 3, "conf", "Launch post-configuration task %q.", name)
    if not task () then
      logreport ("both", 0, "conf", "Post-configuration task %q failed.", name)
      return false
    end
  end
  return true
end

local read = function (extra)
  if extra then
    add_config_paths (extra)
  end

  local readme = resolve_config_path ()
  if readme == false then
    logreport ("both", 2, "conf", "No configuration file.")
    return false
  end

  local raw = ioloaddata (readme)
  if not raw then
    logreport ("both", 2, "conf", "Error reading the configuration file %q.", readme)
    return false
  end

  local parsed = lpegmatch (config_parser, raw)
  if not parsed then
    logreport ("both", 2, "conf", "Error parsing configuration file %q.", readme)
    return false
  end

  local ret, msg = process_options (parsed)
  if not ret then
    logreport ("both", 2, "conf", "File %q is not a valid configuration file.", readme)
    logreport ("both", 2, "conf", "Error: %s", msg)
    return false
  end
  return ret
end

local apply_defaults = function ()
  local defaults      = default_config
  local vars          = read ()
  --- Side-effects galore ...
  config.luaotfload   = apply (defaults, vars)
  return reconfigure ()
end

local dump = function ()
  local sections = table.sortedkeys (config.luaotfload)
  local confdata = { }
  for i = 1, #sections do
    local section    = sections[i]
    local vars       = config.luaotfload[section]
    local varnames   = table.sortedkeys (vars)
    local sformats   = formatters[section]
    if sformats then
      confdata[#confdata + 1] = format_section (section)
      for j = 1, #varnames do
        local var = varnames[j]
        local val = vars[var]
        local comment, sformat = unpack (sformats[var] or { })
        if not sformat then
          comment, sformat = unpack (sformats.__default or { })
        end

        if sformat then
          local dashedvar = dashed (var)
          if comment then
            confdata[#confdata + 1] = commented (sformat (dashedvar, val))
          else
            confdata[#confdata + 1] = sformat (dashedvar, val)
          end
        end

      end
      confdata[#confdata + 1] = ""
    end
  end
  if next(confdata) then
    iowrite (stringformat (conf_header,
                           osdate ("%Y-%m-d %H:%M:%S", os.time ())))
    iowrite (tableconcat (confdata, "\n"))
    iowrite (conf_footer)
  end
end

-------------------------------------------------------------------------------
---                                 EXPORTS
-------------------------------------------------------------------------------

return {
  init = function ()
    config.luaotfload = { }
    logreport         = luaotfload.log.report
    local parsers     = luaotfload.parsers
    config_parser     = parsers.config
    stripslashes      = parsers.stripslashes

    luaotfload.default_config = default_config
    config.actions = {
      read             = read,
      apply            = apply,
      apply_defaults   = apply_defaults,
      reconfigure      = reconfigure,
      dump             = dump,
    }
    if not apply_defaults () then
      logreport ("log", 0, "load",
                 "Configuration unsuccessful: error loading default settings.")
    end
    return true
  end
}