diff --git a/pitfall/pdfkit/lib/font/embedded.coffee b/pitfall/pdfkit/lib/font/embedded.coffee
index 83203f34..b6004495 100644
--- a/pitfall/pdfkit/lib/font/embedded.coffee
+++ b/pitfall/pdfkit/lib/font/embedded.coffee
@@ -16,6 +16,9 @@ class EmbeddedFont extends PDFFont
 
   encode: (text, features) ->
     {glyphs, positions} = @font.layout text, features
+    for glyph, i in glyphs
+      console.log("glyphid="+glyph.id)
+      console.log("position="+positions[i].toString())
 
     res = []
     for glyph, i in glyphs
diff --git a/pitfall/pitfall/embedded.rkt b/pitfall/pitfall/embedded.rkt
index 9485ffd3..b42278d6 100644
--- a/pitfall/pitfall/embedded.rkt
+++ b/pitfall/pitfall/embedded.rkt
@@ -4,8 +4,10 @@
 
 (define-subclass PDFFont (EmbeddedFont document font id)
   (super-new)
-  (field #;[subset (· this font createSubset)]
+  (field [subset (· this font createSubset)]
+         ;; always include the missing glyph (gid = 0)
          [unicode '((0))]
+         ;; always include the width of the missing glyph (gid = 0)
          [widths (list (send (send (· this font) getGlyph 0) advanceWidth))]
          
          [name (· font postscriptName)]
@@ -46,7 +48,7 @@ For now, we'll just measure width of the characters.
   (check-equal? (· ef lineGap) 0)
   (check-equal? (· ef bbox) '(-161 -236 1193 963))
   (define H-gid 41)
-  (· ef widths)
+  (check-equal? (· ef widths) '(278))
   (check-equal? (send (send (· ef font) getGlyph H-gid) advanceWidth) 738)
-
+(· ef subset)
   )
\ No newline at end of file
diff --git a/pitfall/pitfall/subset.rkt b/pitfall/pitfall/subset.rkt
index ebc923f1..07cfc346 100644
--- a/pitfall/pitfall/subset.rkt
+++ b/pitfall/pitfall/subset.rkt
@@ -1,15 +1,41 @@
 #lang pitfall/racket
 (provide Subset CFFSubset TTFSubset)
 
-(define-subclass object% (Subset)
-  (super-new))
+(define index? (and/c (not/c negative?) integer?))
 
+;; approximates
+;; https://github.com/devongovett/fontkit/blob/master/src/subset/Subset.js
 
-(define-subclass Subset (CFFSubset font)
+(define-subclass object% (Subset font)
+  (super-new)
+  (field [glyphs empty] ; list of glyphs in the subset
+         [mapping (mhash)] ; mapping of glyph ids to indexes in `glyphs`
+         )
+
+  (send this includeGlyph 0) ; always include the missing glyph in subset
+
+  (as-methods
+   includeGlyph))
+
+(define/contract (includeGlyph this glyph)
+  ((or/c object? index?) . ->m . index?)
+  (let ([glyph (if (object? glyph) (· glyph id) glyph)])
+    (hash-ref! (· this mapping) glyph
+               (λ ()
+                 ;; put the new glyph at the end of `glyphs`,
+                 ;; and put its index in the mapping
+                 (push-end-field! glyphs this glyph)
+                 (sub1 (length (· this glyphs)))))))  
+
+
+(define-subclass Subset (CFFSubset)
   (super-new)
   (error 'cff-subset-unimplemented))
 
 
-(define-subclass Subset (TTFSubset font)
+;; approximates
+;; https://github.com/devongovett/fontkit/blob/master/src/subset/TTFSubset.js
+
+(define-subclass Subset (TTFSubset)
   (super-new)
-  (error 'ttf-subset-unimplemented))
\ No newline at end of file
+  )
\ No newline at end of file
diff --git a/pitfall/pitfall/test/test12.pdf b/pitfall/pitfall/test/test12.pdf
index 4a6a5187..d6e51015 100644
Binary files a/pitfall/pitfall/test/test12.pdf and b/pitfall/pitfall/test/test12.pdf differ
diff --git a/pitfall/pitfall/test/test12.rkt b/pitfall/pitfall/test/test12.rkt
index 8fca9113..27819d30 100644
--- a/pitfall/pitfall/test/test12.rkt
+++ b/pitfall/pitfall/test/test12.rkt
@@ -23,4 +23,5 @@
   (define doc (make-object PDFDocument))
   (send doc registerFont "Charter" (path->string charter-path))
   (send* doc [font "Charter"])
-  #;doc)
+  (send doc pipe (open-output-string))
+  (send doc end))