You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
typesetting/pitfall/fontkit/subset.rkt

89 lines
2.3 KiB
Racket

This file contains invisible Unicode characters!

This file contains invisible Unicode characters that may be processed differently from what appears below. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to reveal hidden characters.

#lang fontkit/racket
(require "clone.rkt" "ttfglyphencoder.rkt")
(provide Subset CFFSubset TTFSubset)
#|
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
[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)
(error 'cff-subset-unimplemented))
#|
approximates
https://github.com/mbutterick/fontkit/blob/master/src/subset/TTFSubset.js
|#
(define-subclass Subset (TTFSubset)
(field [glyphEncoder (make-object TTFGlyphEncoder)])
(field [glyf #f]
[offset #f]
[loca #f]
[hmtx #f])
(as-methods
_addGlyph
encode)
)
(define-stub-go _addGlyph)
;; tables required by PDF spec:
;; head, hhea, loca, maxp, cvt, prep, glyf, hmtx, fpgm
;; additional tables required for standalone fonts:
;; name, cmap, OS/2, post
(define/contract (encode this)
(->m input-port?)
(set-field! glyf this empty)
(set-field! offset this 0)
(set-field! loca this (mhash 'offsets empty))
(set-field! hmtx this (mhash 'metrics empty 'bearings empty))
;; include all the glyphs used in the document
(for ([gid (in-list (· this glyphs))])
(send this _addGlyph gid))
(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)
)