From fe237130812485c610d00e33750abf2c70a465bd Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Fri, 9 Jun 2017 16:25:40 -0700
Subject: [PATCH] resume in head table: bitfield

---
 pitfall/fontkit/bbox.rkt             |   2 +-
 pitfall/fontkit/clone.rkt            |   2 +-
 pitfall/fontkit/cmap-processor.rkt   |   2 +-
 pitfall/fontkit/directory.rkt        |  73 ++++++++++---------
 pitfall/fontkit/font.rkt             | 105 ++++++++++++++-------------
 pitfall/fontkit/glyph-position.rkt   |   2 +-
 pitfall/fontkit/glyph.rkt            |   2 +-
 pitfall/fontkit/glyphrun.rkt         |   2 +-
 pitfall/fontkit/head.rkt             |  52 +++++++++++++
 pitfall/fontkit/helper.rkt           |  12 +++
 pitfall/fontkit/hhea.rkt             |  39 ++++++++++
 pitfall/fontkit/layout-engine.rkt    |   2 +-
 pitfall/fontkit/main.rkt             |   2 +-
 pitfall/fontkit/maxp.rkt             |  39 ++++++++++
 pitfall/fontkit/racket.rkt           |  30 ++++++++
 pitfall/fontkit/script.rkt           |   2 +-
 pitfall/fontkit/subset.rkt           |  22 +++++-
 pitfall/fontkit/tables.rkt           |  11 +++
 pitfall/fontkit/ttfglyphencoder.rkt  |   2 +-
 pitfall/pitfall/helper.rkt           |   2 +-
 pitfall/restructure/decodestream.rkt |  10 +--
 pitfall/sugar/port.rkt               |  21 +++++-
 22 files changed, 325 insertions(+), 111 deletions(-)
 create mode 100644 pitfall/fontkit/head.rkt
 create mode 100644 pitfall/fontkit/helper.rkt
 create mode 100644 pitfall/fontkit/hhea.rkt
 create mode 100644 pitfall/fontkit/maxp.rkt
 create mode 100644 pitfall/fontkit/racket.rkt
 create mode 100644 pitfall/fontkit/tables.rkt

diff --git a/pitfall/fontkit/bbox.rkt b/pitfall/fontkit/bbox.rkt
index 2f040183..8ebde8a5 100644
--- a/pitfall/fontkit/bbox.rkt
+++ b/pitfall/fontkit/bbox.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (provide BBox bbox->list)
 
 (define-subclass object% (BBox
diff --git a/pitfall/fontkit/clone.rkt b/pitfall/fontkit/clone.rkt
index 86152e6b..5a1fc990 100644
--- a/pitfall/fontkit/clone.rkt
+++ b/pitfall/fontkit/clone.rkt
@@ -1,4 +1,4 @@
-#lang racket
+#lang fontkit/racket
 (provide cloneDeep)
 
 (define (cloneDeep val)
diff --git a/pitfall/fontkit/cmap-processor.rkt b/pitfall/fontkit/cmap-processor.rkt
index 49b99ba1..d56bbba6 100644
--- a/pitfall/fontkit/cmap-processor.rkt
+++ b/pitfall/fontkit/cmap-processor.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (provide CmapProcessor)
 
 (define-subclass object% (CmapProcessor cmapTable)
diff --git a/pitfall/fontkit/directory.rkt b/pitfall/fontkit/directory.rkt
index dbf96d42..19b7e1c0 100644
--- a/pitfall/fontkit/directory.rkt
+++ b/pitfall/fontkit/directory.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (require restructure)
 
 (provide (all-defined-out))
@@ -32,40 +32,41 @@ https://github.com/mbutterick/fontkit/blob/master/src/tables/directory.js
   (define is (make-object RDecodeStream ip))
   (send Directory decode is))
 
-(module+ test
-  (require rackunit racket/serialize)
-  (define ip (open-input-file "test/assets/Charter.ttf"))
-  (check-equal?
-   (directory-decode ip)
-   (deserialize '((3)
-                  0
-                  ()
-                  0
-                  ()
+
+(test-module
+ (require racket/serialize)
+ (define ip (open-input-file charter-path))
+ (check-equal?
+  (directory-decode ip)
+  (deserialize '((3)
+                 0
+                 ()
+                 0
+                 ()
+                 ()
+                 (h
+                  !
                   ()
-                  (h
+                  (tag u . "\u0000\u0001\u0000\u0000")
+                  (rangeShift . 96)
+                  (searchRange . 128)
+                  (numTables . 14)
+                  (entrySelector . 3)
+                  (tables
+                   h
                    !
-                   ()
-                   (tag u . "\u0000\u0001\u0000\u0000")
-                   (rangeShift . 96)
-                   (searchRange . 128)
-                   (numTables . 14)
-                   (entrySelector . 3)
-                   (tables
-                    h
-                    !
-                    (equal)
-                    (loca h ! () (tag u . "loca") (offset . 38692) (checkSum . 2795817194) (length . 460))
-                    (glyf h ! () (tag u . "glyf") (offset . 4620) (checkSum . 1143629849) (length . 34072))
-                    (OS/2 h ! () (tag u . "OS/2") (offset . 360) (checkSum . 2351070438) (length . 96))
-                    (hhea h ! () (tag u . "hhea") (offset . 292) (checkSum . 132056097) (length . 36))
-                    (post h ! () (tag u . "post") (offset . 41520) (checkSum . 1670855689) (length . 514))
-                    (|cvt | h ! () (tag u . "cvt ") (offset . 4592) (checkSum . 10290865) (length . 26))
-                    (VDMX h ! () (tag u . "VDMX") (offset . 1372) (checkSum . 1887795202) (length . 1504))
-                    (prep h ! () (tag u . "prep") (offset . 4512) (checkSum . 490862356) (length . 78))
-                    (maxp h ! () (tag u . "maxp") (offset . 328) (checkSum . 50135594) (length . 32))
-                    (hmtx h ! () (tag u . "hmtx") (offset . 456) (checkSum . 3982043058) (length . 916))
-                    (cmap h ! () (tag u . "cmap") (offset . 2876) (checkSum . 1723761408) (length . 1262))
-                    (name h ! () (tag u . "name") (offset . 39152) (checkSum . 2629707307) (length . 2367))
-                    (head h ! () (tag u . "head") (offset . 236) (checkSum . 4281190895) (length . 54))
-                    (fpgm h ! () (tag u . "fpgm") (offset . 4140) (checkSum . 106535991) (length . 371))))))))
\ No newline at end of file
+                   (equal)
+                   (loca h ! () (tag u . "loca") (offset . 38692) (checkSum . 2795817194) (length . 460))
+                   (glyf h ! () (tag u . "glyf") (offset . 4620) (checkSum . 1143629849) (length . 34072))
+                   (OS/2 h ! () (tag u . "OS/2") (offset . 360) (checkSum . 2351070438) (length . 96))
+                   (hhea h ! () (tag u . "hhea") (offset . 292) (checkSum . 132056097) (length . 36))
+                   (post h ! () (tag u . "post") (offset . 41520) (checkSum . 1670855689) (length . 514))
+                   (|cvt | h ! () (tag u . "cvt ") (offset . 4592) (checkSum . 10290865) (length . 26))
+                   (VDMX h ! () (tag u . "VDMX") (offset . 1372) (checkSum . 1887795202) (length . 1504))
+                   (prep h ! () (tag u . "prep") (offset . 4512) (checkSum . 490862356) (length . 78))
+                   (maxp h ! () (tag u . "maxp") (offset . 328) (checkSum . 50135594) (length . 32))
+                   (hmtx h ! () (tag u . "hmtx") (offset . 456) (checkSum . 3982043058) (length . 916))
+                   (cmap h ! () (tag u . "cmap") (offset . 2876) (checkSum . 1723761408) (length . 1262))
+                   (name h ! () (tag u . "name") (offset . 39152) (checkSum . 2629707307) (length . 2367))
+                   (head h ! () (tag u . "head") (offset . 236) (checkSum . 4281190895) (length . 54))
+                   (fpgm h ! () (tag u . "fpgm") (offset . 4140) (checkSum . 106535991) (length . 371))))))))
\ No newline at end of file
diff --git a/pitfall/fontkit/font.rkt b/pitfall/fontkit/font.rkt
index 5ca0b4eb..da1c91b7 100644
--- a/pitfall/fontkit/font.rkt
+++ b/pitfall/fontkit/font.rkt
@@ -1,5 +1,5 @@
-#lang pitfall/racket
-(require "freetype-ffi.rkt" ffi/unsafe racket/runtime-path "subset.rkt" "glyph.rkt" "layout-engine.rkt" "bbox.rkt" "glyphrun.rkt" "cmap-processor.rkt" "directory.rkt")
+#lang fontkit/racket
+(require "freetype-ffi.rkt" ffi/unsafe racket/runtime-path "subset.rkt" "glyph.rkt" "layout-engine.rkt" "bbox.rkt" "glyphrun.rkt" "cmap-processor.rkt" "directory.rkt" restructure/decodestream "tables.rkt")
 (provide (all-defined-out))
 
 (define-runtime-path charter-path "../pitfall/test/assets/charter.ttf")
@@ -14,13 +14,12 @@ https://github.com/mbutterick/fontkit/blob/master/src/TTFFont.js
 (define-subclass object% (TTFFont stream)
   (when stream (unless (input-port? stream)
                  (raise-argument-error 'TTFFont "input port" stream)))
-  (unless (member (bytes->string/latin-1 (peek-bytes 4 0 stream))
-                  (list "true" "OTTO" "\u0\u1\u0\u0"))
+  (unless (member (peek-bytes 4 0 stream) (list #"true" #"OTTO" (bytes 0 1 0 0)))
     (raise 'probe-fail))
-  (port-count-lines! stream)
+  
   ;; skip variationCoords
   (field [_directoryPos (port-position stream)]
-         [_tables (mhash)]
+         [_tables (mhash)] ; holds decoded tables (loaded lazily)
          [_glyphs (mhash)]
          [_layoutEngine #f])
 
@@ -28,14 +27,17 @@ https://github.com/mbutterick/fontkit/blob/master/src/TTFFont.js
   (send this _decodeDirectory)
 
   (define/public (_getTable table-tag)
-    (unless (hash-has-key? (hash-ref directory 'tables) table-tag)
-      (raise-argument-error '_getTable "table that exists" table-tag))
-    (hash-ref! _tables table-tag (_decodeTable table-tag))) ; load table from cache, decode if necessary
-
-  (define/public (_decodeTable table)
-    (report table '_decodeTable:starting)
-    (define-values (l c p) (port-next-location stream))
-    (set-port-next-location! stream l c p))
+    (unless (has-table? this table-tag)
+      (raise-argument-error '_getTable "table that exists in font" table-tag))
+    (hash-ref! _tables table-tag (_decodeTable table-tag))) ; get table from cache, load if not there
+
+  (define/public (_decodeTable table-tag)
+    (define table-decoder (hash-ref table-decoders table-tag
+                                    (λ () (raise-argument-error '_decodeTable "decodable table" table-tag))))
+    (define offset (· (hash-ref (· directory tables) table-tag) offset))
+    (define length (· (hash-ref (· directory tables) table-tag) length))
+    (set-port-position! stream offset)
+    (send table-decoder decode (make-object RDecodeStream stream) this length))
 
   (define/public (_decodeDirectory)
     (set! directory (directory-decode stream (mhash '_startOffset 0)))
@@ -84,20 +86,19 @@ https://github.com/mbutterick/fontkit/blob/master/src/TTFFont.js
 ;; The font’s [ascender](https://en.wikipedia.org/wiki/Ascender_(typography))
 (define/contract (ascent this)
   (->m number?)
-  (FT_FaceRec-ascender (· this ft-face)))
+  (hash-ref (send this _getTable 'hhea) 'ascent))
 
 
 ;; The font’s [descender](https://en.wikipedia.org/wiki/Descender)
 (define/contract (descent this)
   (->m number?)
-  (FT_FaceRec-descender (· this ft-face)))
+  (hash-ref (send this _getTable 'hhea) 'descent))
 
 
 ;; The amount of space that should be included between lines
 (define/contract (lineGap this)
   (->m number?)
-  (define hhea-table (cast (FT_Get_Sfnt_Table (· this ft-face) 'ft_sfnt_hhea) _pointer _FT_HoriHeader-pointer))
-  (FT_HoriHeader-lineGap hhea-table))
+  (hash-ref (send this _getTable 'hhea) 'lineGap))
 
 
 (define/contract (underlinePosition this)
@@ -143,11 +144,11 @@ https://github.com/mbutterick/fontkit/blob/master/src/TTFFont.js
 ;; The font’s bounding box, i.e. the box that encloses all glyphs in the font.
 (define/contract (bbox this)
   (->m (is-a?/c BBox))
-  (let ([bbox (FT_FaceRec-bbox (· this ft-face))])
-    (make-object BBox (FT_BBox-xMin bbox)
-      (FT_BBox-yMin bbox)
-      (FT_BBox-xMax bbox)
-      (FT_BBox-yMax bbox))))
+  (define head-table (send this _getTable 'head))
+  (make-object BBox (· head-table xMin)
+    (· head-table yMin)
+    (· head-table xMax)
+    (· head-table yMax)))
 
 
 (define/contract (_cmapProcessor this)
@@ -164,16 +165,16 @@ https://github.com/mbutterick/fontkit/blob/master/src/TTFFont.js
 
 
 
-(define (has-table? this tag)
-  (FT_Load_Sfnt_Table (· this ft-face) (tag->int tag) 0 0 0))
+(define/contract (has-table? this tag)
+  ((or/c bytes? symbol?) . ->m . boolean?)
+  (hash-has-key? (· this directory tables) (if (bytes? tag)
+                                               (string->symbol (bytes->string/latin-1 tag))
+                                               tag)))
   
-(define (has-cff-table? this) (has-table? this #"CFF "))
-
-(define (has-morx-table? this) (has-table? this #"morx"))
-
-(define (has-gpos-table? this) (has-table? this #"GPOS"))
-
-(define (has-gsub-table? this) (has-table? this #"GSUB"))
+(define has-cff-table? (curryr has-table? '|CFF |))
+(define has-morx-table? (curryr has-table? 'morx))
+(define has-gpos-table? (curryr has-table? 'GPOS))
+(define has-gsub-table? (curryr has-table? 'GSUB))
 
 
 ;; Returns a glyph object for the given glyph id.
@@ -262,23 +263,23 @@ https://github.com/mbutterick/fontkit/blob/master/src/TTFFont.js
    (error 'fontkit:create "unknown font format")))
 
 
-(module+ test
-  (require rackunit)
-  (define f (openSync (path->string charter-path)))
-  (check-equal? (postscriptName f) "Charter")
-  (check-equal? (· f unitsPerEm) 1000)
-  (check-equal? (· f ascent) 980)
-  (check-equal? (· f descent) -238)
-  (check-equal? (measure-string f "f" (· f unitsPerEm)) 321.0)
-  (check-false (· f has-cff-table?))
-  (check-false (· f has-morx-table?))
-  (check-false (· f has-gsub-table?))
-  (check-false (· f has-gpos-table?))
-  (check-true (send f has-table? #"cmap"))
-  (check-equal? (· f lineGap) 0)
-  (check-exn exn:fail:contract? (λ () (send f _getTable 'nonexistent-table-tag)))
-  (send f _getTable 'maxp)
-  #;(· f createSubset)
-  
-
-  )
\ No newline at end of file
+(test-module
+ (define f (openSync (path->string charter-path)))
+ (check-equal? (postscriptName f) "Charter")
+ (check-equal? (· f unitsPerEm) 1000)
+ (check-equal? (· f ascent) 980)
+ (check-equal? (· f descent) -238)
+ (check-equal? (bbox->list (· f bbox)) '(-161 -236 1193 963))
+ (check-equal? (measure-string f "f" (· f unitsPerEm)) 321.0)
+ (check-false (· f has-cff-table?))
+ (check-false (· f has-morx-table?))
+ (check-false (· f has-gsub-table?))
+ (check-false (· f has-gpos-table?))
+ (check-true (send f has-table? #"cmap"))
+ (check-equal? (· f lineGap) 0)
+ (check-exn exn:fail:contract? (λ () (send f _getTable 'nonexistent-table-tag)))
+ #;(send f _getTable 'maxp)
+ (define subset (make-object TTFSubset f))
+ (send subset encode)
+
+ )
\ No newline at end of file
diff --git a/pitfall/fontkit/glyph-position.rkt b/pitfall/fontkit/glyph-position.rkt
index 2d40fe57..34b149ff 100644
--- a/pitfall/fontkit/glyph-position.rkt
+++ b/pitfall/fontkit/glyph-position.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (provide GlyphPosition)
 
 ;; Represents positioning information for a glyph in a GlyphRun.
diff --git a/pitfall/fontkit/glyph.rkt b/pitfall/fontkit/glyph.rkt
index 659bf331..5ec34582 100644
--- a/pitfall/fontkit/glyph.rkt
+++ b/pitfall/fontkit/glyph.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (require "freetype-ffi.rkt")
 (provide Glyph CFFGlyph TTFGlyph)
 (module+ test (require rackunit))
diff --git a/pitfall/fontkit/glyphrun.rkt b/pitfall/fontkit/glyphrun.rkt
index 050adfbc..07c7f520 100644
--- a/pitfall/fontkit/glyphrun.rkt
+++ b/pitfall/fontkit/glyphrun.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (require "bbox.rkt" "script.rkt")
 (provide GlyphRun)
 
diff --git a/pitfall/fontkit/head.rkt b/pitfall/fontkit/head.rkt
new file mode 100644
index 00000000..3be8ecf7
--- /dev/null
+++ b/pitfall/fontkit/head.rkt
@@ -0,0 +1,52 @@
+#lang fontkit/racket
+(require restructure)
+(provide (all-defined-out))
+
+(define-subclass RStruct (Rhead))
+
+(define head (make-object Rhead
+               (dictify
+                'version            int32be                   ;; 0x00010000 (version 1.0)
+                'revision           int32be                   ;; set by font manufacturer
+                'checkSumAdjustment uint32be
+                'magicNumber        uint32be                  ;; set to 0x5F0F3CF5
+                'flags              uint16be
+                'unitsPerEm         uint16be                  ;; range from 64 to 16384
+                'created            (make-object RArray int32be 2)
+                'modified           (make-object RArray int32be 2)
+                'xMin               int16be                   ;; for all glyph bounding boxes
+                'yMin               int16be                   ;; for all glyph bounding boxes
+                'xMax               int16be                   ;; for all glyph bounding boxes
+                'yMax               int16be                   ;; for all glyph bounding boxes
+                'macStyle           uint16be
+                #|
+new Bitfield(uint16be [
+                                                           '  'bold' 'italic' 'underline' 'outline'
+                                                                   '  'shadow' 'condensed' 'extended'
+                                                                   '])
+|#
+                'lowestRecPPEM      uint16be                  ;; smallest readable size in pixels
+                'fontDirectionHint int16be
+                'indexToLocFormat   int16be                   ;; 0 for short offsets 1 for long
+                'glyphDataFormat    int16be                    ;; 0 for current format
+                )))
+
+(test-module
+ (require "directory.rkt")
+ (define ip (open-input-file charter-path))
+ (define dir (directory-decode ip))
+ (define offset (· dir tables head offset))
+ (define length (· dir tables head length))
+ (check-equal? offset 236)
+ (check-equal? length 54)
+ (define table-bytes #"\0\1\0\0\0\2\0\0@\247\22 _\17<\365\0\t\3\350\0\0\0\0\316\3\301?\0\0\0\0\316\3\304\363\377_\377\24\4\251\3\303\0\0\0\t\0\2\0\0\0\0")
+ (set-port-position! ip 0)
+ (check-equal? (peek-bytes length offset ip) table-bytes)
+ (define table-data (send head decode (make-object RDecodeStream table-bytes)))
+ (check-equal? (· table-data unitsPerEm) 1000)
+ (check-equal? (· table-data yMin) -236)
+ (check-equal? (· table-data yMax) 963)
+ (check-equal? (· table-data xMax) 1193)
+ (check-equal? (· table-data xMin) -161)
+ (check-equal? (· table-data magicNumber) #x5F0F3CF5))
+
diff --git a/pitfall/fontkit/helper.rkt b/pitfall/fontkit/helper.rkt
new file mode 100644
index 00000000..176f6716
--- /dev/null
+++ b/pitfall/fontkit/helper.rkt
@@ -0,0 +1,12 @@
+#lang racket/base
+(require (for-syntax racket/base) racket/runtime-path br/define)
+(provide (all-defined-out))
+
+(define index? (λ (x) (and (number? x) (integer? x) (not (negative? x)))))
+
+(define-runtime-path charter-path "../pitfall/test/assets/Charter.ttf")
+
+(define-macro (test-module . EXPRS)
+  #`(module+ test
+      (require #,(datum->syntax caller-stx 'rackunit))
+      . EXPRS))
\ No newline at end of file
diff --git a/pitfall/fontkit/hhea.rkt b/pitfall/fontkit/hhea.rkt
new file mode 100644
index 00000000..dc4e4983
--- /dev/null
+++ b/pitfall/fontkit/hhea.rkt
@@ -0,0 +1,39 @@
+#lang fontkit/racket
+(require restructure)
+(provide (all-defined-out))
+
+(define-subclass RStruct (Rhhea))
+
+(define hhea (make-object Rhhea
+               (dictify
+                'version              int32be
+                'ascent               int16be   ;; Distance from baseline of highest ascender
+                'descent              int16be   ;; Distance from baseline of lowest descender
+                'lineGap              int16be   ;; Typographic line gap
+                'advanceWidthMax      uint16be  ;; Maximum advance width value in 'hmtx' table
+                'minLeftSideBearing   int16be   ;; Maximum advance width value in 'hmtx' table
+                'minRightSideBearing  int16be   ;; Minimum right sidebearing value
+                'xMaxExtent           int16be
+                'caretSlopeRise       int16be   ;; Used to calculate the slope of the cursor (rise/run); 1 for vertical
+                'caretSlopeRun        int16be   ;; 0 for vertical
+                'caretOffset          int16be   ;; Set to 0 for non-slanted fonts
+                'reserved             (make-object RArray int16be 4)
+                'metricDataFormat     int16be   ;; 0 for current format
+                'numberOfMetrics      uint16be   ;; Number of advance widths in 'hmtx' table
+                )))
+
+(test-module
+ (require "directory.rkt")
+ (define ip (open-input-file charter-path))
+ (define dir (directory-decode ip))
+ (define offset (· dir tables hhea offset))
+ (define length (· dir tables hhea length))
+ (check-equal? offset 292)
+ (check-equal? length 36)
+ (define table-bytes #"\0\1\0\0\3\324\377\22\0\0\4\311\377_\377`\4\251\0\1\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\345")
+ (set-port-position! ip 0)
+ (check-equal? (peek-bytes length offset ip) table-bytes)
+ (define table-data (send hhea decode (make-object RDecodeStream table-bytes)))
+ (check-equal? (· table-data ascent) 980)
+ (check-equal? (· table-data descent) -238))
+
diff --git a/pitfall/fontkit/layout-engine.rkt b/pitfall/fontkit/layout-engine.rkt
index bd4540cb..08615d91 100644
--- a/pitfall/fontkit/layout-engine.rkt
+++ b/pitfall/fontkit/layout-engine.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (require "script.rkt" "glyph.rkt" "glyphrun.rkt" "glyph-position.rkt")
 (provide LayoutEngine)
 
diff --git a/pitfall/fontkit/main.rkt b/pitfall/fontkit/main.rkt
index 4a9db4b0..f076aaaa 100644
--- a/pitfall/fontkit/main.rkt
+++ b/pitfall/fontkit/main.rkt
@@ -1,4 +1,4 @@
-#lang restructure/racket
+#lang fontkit/racket
 
 (r+p "font.rkt"
      "glyph-position.rkt"
diff --git a/pitfall/fontkit/maxp.rkt b/pitfall/fontkit/maxp.rkt
new file mode 100644
index 00000000..630310da
--- /dev/null
+++ b/pitfall/fontkit/maxp.rkt
@@ -0,0 +1,39 @@
+#lang fontkit/racket
+(require restructure)
+(provide (all-defined-out))
+
+(define-subclass RStruct (Rmaxp))
+
+(define maxp (make-object Rmaxp
+               (dictify 'version                int32be
+                        'numGlyphs              uint16be  ;; The number of glyphs in the font
+                        'maxPoints              uint16be  ;; Maximum points in a non-composite glyph
+                        'maxContours            uint16be  ;; Maximum contours in a non-composite glyph
+                        'maxComponentPoints     uint16be  ;; Maximum points in a composite glyph
+                        'maxComponentContours   uint16be  ;; Maximum contours in a composite glyph
+                        'maxZones               uint16be  ;; 1 if instructions do not use the twilight zone, 2 otherwise
+                        'maxTwilightPoints      uint16be  ;; Maximum points used in Z0
+                        'maxStorage             uint16be  ;; Number of Storage Area locations
+                        'maxFunctionDefs        uint16be  ;; Number of FDEFs
+                        'maxInstructionDefs     uint16be  ;; Number of IDEFs
+                        'maxStackElements       uint16be  ;; Maximum stack depth
+                        'maxSizeOfInstructions  uint16be  ;; Maximum byte count for glyph instructions
+                        'maxComponentElements   uint16be  ;; Maximum number of components referenced at “top level” for any composite glyph
+                        'maxComponentDepth      uint16be  ;; Maximum levels of recursion; 1 for simple components
+                        )))
+
+(test-module
+ (require "directory.rkt")
+ (define ip (open-input-file charter-path))
+ (define dir (directory-decode ip))
+ (define maxp-offset (· dir tables maxp offset))
+ (define maxp-length (· dir tables maxp length))
+ (check-equal? maxp-offset 328)
+ (check-equal? maxp-length 32)
+ (define maxp-bytes #"\0\1\0\0\0\345\0f\0\a\0O\0\4\0\1\0\0\0\0\0\n\0\0\2\0\1s\0\2\0\1")
+ (set-port-position! ip 0)
+ (check-equal? (peek-bytes maxp-length maxp-offset ip) maxp-bytes)
+ (define maxp-data (send maxp decode (make-object RDecodeStream maxp-bytes)))
+ (check-equal? (· maxp-data numGlyphs) 229)
+ (check-equal? (· maxp-data version) 65536))
+
diff --git a/pitfall/fontkit/racket.rkt b/pitfall/fontkit/racket.rkt
new file mode 100644
index 00000000..5bb02fe4
--- /dev/null
+++ b/pitfall/fontkit/racket.rkt
@@ -0,0 +1,30 @@
+#lang racket/base
+(require (for-syntax racket/base br/syntax))
+(provide (for-syntax (all-from-out racket/base br/syntax)))
+(provide (all-from-out racket/base) r+p)
+
+(define-syntax-rule (r+p id ...) (begin (require id ...) (provide (all-from-out id ...))))
+
+(r+p "helper.rkt"
+     sugar/debug
+     racket/class
+     racket/file
+     racket/match
+     racket/string
+     racket/format
+     racket/contract
+     racket/list
+     racket/port
+     racket/function
+     br/define
+     sugar/class
+     sugar/js
+     sugar/dict
+     sugar/stub
+     sugar/port)
+
+(module reader syntax/module-reader
+  #:language 'fontkit/racket
+  #:read @-read
+  #:read-syntax @-read-syntax
+  (require (prefix-in @- scribble/reader)))
\ No newline at end of file
diff --git a/pitfall/fontkit/script.rkt b/pitfall/fontkit/script.rkt
index d404a0be..dfdecfc8 100644
--- a/pitfall/fontkit/script.rkt
+++ b/pitfall/fontkit/script.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (provide (all-defined-out))
 
 ;; approximates
diff --git a/pitfall/fontkit/subset.rkt b/pitfall/fontkit/subset.rkt
index 91e234c6..6a9095ef 100644
--- a/pitfall/fontkit/subset.rkt
+++ b/pitfall/fontkit/subset.rkt
@@ -1,9 +1,11 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (require "clone.rkt" "ttfglyphencoder.rkt")
 (provide Subset CFFSubset TTFSubset)
 
-;; approximates
-;; https://github.com/devongovett/fontkit/blob/master/src/subset/Subset.js
+#|
+approximates
+https://github.com/devongovett/fontkit/blob/master/src/subset/Subset.js
+|#
 
 (define-subclass object% (Subset font)
   (field [glyphs empty] ; list of glyph ids in the subset
@@ -67,8 +69,20 @@ https://github.com/mbutterick/fontkit/blob/master/src/subset/TTFSubset.js
   (for ([gid (in-list (· this glyphs))])
        (send this _addGlyph gid))
 
-  (define maxp (cloneDeep (send (· this font) _getTable maxp)))
+  (define maxp (cloneDeep (send (· this font) _getTable 'maxp)))
+  ;; (hash-set! maxp 'numGlyphs (length (· this glyf))) ; todo
+
+  ;; todo
+  ;;     this.loca.offsets.push(this.offset);
+  ;; Tables.loca.preEncode.call(this.loca);
+
+  (define head (cloneDeep (send (· this font) _getTable 'head)))
+  ;;    head.indexToLocFormat = this.loca.version; ; todo
+
+  (define hhea (cloneDeep (send (· this font) _getTable 'hhea)))
+  ;; hhea.numberOfMetrics = this.hmtx.metrics.length;
 
   (unfinished)
   )
 
+
diff --git a/pitfall/fontkit/tables.rkt b/pitfall/fontkit/tables.rkt
new file mode 100644
index 00000000..c6a1a3d3
--- /dev/null
+++ b/pitfall/fontkit/tables.rkt
@@ -0,0 +1,11 @@
+#lang fontkit/racket
+(provide (all-defined-out))
+
+(define-macro (define-table-decoders ID TABLE-ID ...)
+  (with-pattern ([TABLE-ID-STRINGS (pattern-case-filter #'(TABLE-ID ...)
+                                                        [STX (datum->syntax caller-stx (format "~a.rkt" (syntax->datum #'STX)))])]) 
+                #'(begin
+                    (r+p . TABLE-ID-STRINGS)
+                    (define ID (make-hasheq (map cons (list 'TABLE-ID ...) (list TABLE-ID ...)))))))
+
+(define-table-decoders table-decoders maxp hhea head)
\ No newline at end of file
diff --git a/pitfall/fontkit/ttfglyphencoder.rkt b/pitfall/fontkit/ttfglyphencoder.rkt
index 284da511..e34ed100 100644
--- a/pitfall/fontkit/ttfglyphencoder.rkt
+++ b/pitfall/fontkit/ttfglyphencoder.rkt
@@ -1,4 +1,4 @@
-#lang pitfall/racket
+#lang fontkit/racket
 (provide TTFGlyphEncoder)
 
 (define-subclass object% (TTFGlyphEncoder)
diff --git a/pitfall/pitfall/helper.rkt b/pitfall/pitfall/helper.rkt
index b5866f30..3068a231 100644
--- a/pitfall/pitfall/helper.rkt
+++ b/pitfall/pitfall/helper.rkt
@@ -25,7 +25,7 @@
 (define (layout? x)
   (and (hash? x) (hash-has-key? x 'glyphs) (hash-has-key? x 'positions)))
 
-(define index? (and/c (not/c negative?) integer?))
+(define index? (and/c number? integer? (not/c negative?)))
 
 
   
\ No newline at end of file
diff --git a/pitfall/restructure/decodestream.rkt b/pitfall/restructure/decodestream.rkt
index da307dc4..401e9a36 100644
--- a/pitfall/restructure/decodestream.rkt
+++ b/pitfall/restructure/decodestream.rkt
@@ -24,14 +24,12 @@
                                 [endian '("" BE LE)])
                                (values (string->symbol (format "~a~a" key endian)) value))))
 
-(require racket/port)
 ;; basically just a wrapper for a Racket port
 (define-subclass object% (RDecodeStream [buffer-in #""])
-  (field [buffer (if (input-port? buffer-in)
-                   (port->bytes buffer-in)
-                   buffer-in)]
-         [length (bytes-length buffer)]
-         [_port (open-input-bytes buffer)])
+  (field [_port (cond
+                  [(bytes? buffer-in) (open-input-bytes buffer-in)]
+                  [(input-port? buffer-in) buffer-in]
+                  [else (raise-argument-error 'RDecodeStream "bytes or input port" buffer-in)])])
   (getter-field [pos (port-position _port)])
 
   (define/public (read count)
diff --git a/pitfall/sugar/port.rkt b/pitfall/sugar/port.rkt
index fe4cf839..70f9528b 100644
--- a/pitfall/sugar/port.rkt
+++ b/pitfall/sugar/port.rkt
@@ -3,5 +3,22 @@
 (provide (all-defined-out) (all-from-out racket/port))
 
 (define (port-position ip)
-  (define-values (line col pos) (port-next-location ip))
-  pos)
\ No newline at end of file
+  (file-position ip))
+
+(define (set-port-position! ip where)
+  (file-position ip where))
+
+(module+ test
+  (require rackunit)
+  (define ip (open-input-bytes (bytes 1 2 3 4)))
+  (port-count-lines! ip)
+  (check-equal? (port-position ip) 0)
+  (check-equal? (read-byte ip) 1)
+  (check-equal? (port-position ip) 1)
+  (check-equal? (read-byte ip) 2)
+  (set-port-position! ip 4)
+  (check-equal? (port-position ip) 4)
+  (check-equal? (read-byte ip) eof)
+  (set-port-position! ip 0)
+  (check-equal? (port-position ip) 0)
+  (check-equal? (read-byte ip) 1))
\ No newline at end of file