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#lang debug racket/base
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(require "helper.rkt"
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"unsafe/freetype.rkt"
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"glyph.rkt"
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"bbox.rkt"
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"glyphrun.rkt"
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"directory.rkt"
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"db.rkt"
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"struct.rkt"
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"table-stream.rkt"
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xenomorph
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racket/match
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sugar/unstable/dict
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sugar/unstable/js
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"unsafe/harfbuzz.rkt"
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"glyph-position.rkt"
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sugar/list
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racket/promise
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crc32c)
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(provide (all-defined-out))
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#|
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approximates
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https://github.com/mbutterick/fontkit/blob/master/src/TTFFont.js
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|#
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(test-module
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(define f (open-font charter-path))
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(define fira (open-font (path->string fira-path)))
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(define otf (open-font (path->string fira-otf-path)))
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(check-equal? (font-postscript-name f) "Charter"))
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(define ft-library (delay (FT_Init_FreeType)))
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(define (+ttf-font port
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[decoded-tables (mhash)]
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[src (path->string (object-name port))]
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[directory (delay (decode Directory port #:parent (mhash '_startOffset 0)))]
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[ft-face (delay (and src (FT_New_Face (force ft-library) src)))]
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[hb-font (delay (and src (hb_ft_font_create (force ft-face))))]
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[hb-buf (delay (hb_buffer_create))]
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[crc (begin0 (crc32c-input-port port) (pos port 0))]
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[get-head-table-proc #f])
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(unless (input-port? port)
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(raise-argument-error '+ttf-font "input port" port))
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(unless (member (peek-bytes 4 0 port) (list #"true" #"OTTO" (bytes 0 1 0 0)))
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(do-probe-fail!))
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(define font
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(ttf-font port decoded-tables src directory ft-face hb-font hb-buf crc get-head-table-proc))
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;; needed for `loca` table decoding cross-reference
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(set-ttf-font-get-head-table-proc! font (delay (dump (get-head-table font))))
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font)
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(define (font-postscript-name font) (FT_Get_Postscript_Name (ft-face font)))
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(define (font-units-per-em font) (· (get-head-table font) unitsPerEm))
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(define (font-ascent font) (· (get-hhea-table font) ascent))
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(define (font-descent font) (· (get-hhea-table font) descent))
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(define (font-linegap font) (· (get-hhea-table font) lineGap))
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(define (font-underline-position font) (· (get-post-table font) underlinePosition))
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(define (font-underline-thickness font) (· (get-post-table font) underlineThickness))
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(define (font-italic-angle font) (· (get-post-table font) italicAngle))
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(define (font-cap-height font)
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(if (has-table? font #"OS/2")
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(· (get-OS/2-table font) capHeight)
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(font-ascent font)))
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(define (font-x-height font)
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(if (has-table? font #"OS/2")
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(· (get-OS/2-table font) xHeight)
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0))
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(test-module
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(check-equal? (font-units-per-em f) 1000)
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(check-equal? (font-ascent f) 980)
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(check-equal? (font-descent f) -238)
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(check-equal? (font-linegap f) 0)
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(check-equal? (font-underline-position f) -178)
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(check-equal? (font-underline-thickness f) 58)
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(check-equal? (font-italic-angle f) 0)
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(check-equal? (font-cap-height f) 671)
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(check-equal? (font-x-height f) 481))
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(define (font-bbox font)
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(define head-table (get-head-table font))
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(+bbox (· head-table xMin) (· head-table yMin) (· head-table xMax) (· head-table yMax)))
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(test-module
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(check-equal? (bbox->list (font-bbox f)) '(-161 -236 1193 963)))
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(define current-layout-caching (make-parameter #false))
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(struct hb-gid (val) #:transparent)
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(struct hb-cluster (chars) #:transparent)
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(struct hb-position (xad yad xoff yoff etc) #:transparent)
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(struct hb-layout (hb-gids hb-clusters hb-positions) #:transparent)
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(define hb-output (+Struct (dictify
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'hb-gids (+Array uint16 uint16)
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'hb-clusters (+Array (+Array uint16 uint16) uint16)
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'hb-positions (+Array (+Array uint16 5) uint16))))
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(define (hb-layout->glyphrun font hbr)
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(match hbr
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[(hash-table ('hb-gids gids)
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('hb-clusters clusters)
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('hb-positions posns))
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(define glyphs (for/list ([gidx (in-list gids)]
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[cluster (in-list clusters)])
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(get-glyph font gidx cluster)))
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(define positions (for/list ([posn (in-list posns)])
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(apply +glyph-position posn)))
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(glyphrun glyphs positions)]))
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(define (harfbuzz-layout font codepoints features script language)
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(define buf (hb-buf font))
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(hb_buffer_reset buf)
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(hb_buffer_add_codepoints buf codepoints)
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(define chars (map hb_glyph_info_t-codepoint (hb_buffer_get_glyph_infos buf)))
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(hb_shape (hb-font font) buf (map tag->hb-feature (or features null)))
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(define gis (hb_buffer_get_glyph_infos buf))
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(dictify 'hb-gids (map hb_glyph_info_t-codepoint gis)
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'hb-clusters (break-at chars (map hb_glyph_info_t-cluster gis))
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'hb-positions (map hb_glyph_position_t->list (hb_buffer_get_glyph_positions buf))))
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(define layout-cache (make-hasheqv))
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(define hb-input (+Struct (dictify
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'font-crc uint32
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'codepoints (+Array uint16)
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'userFeatures (+Array (+String uint8)))))
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(define (layout-cache-key font-crc codepoints user-features . _)
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(crc32c-bytes (encode hb-input (dictify
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'font-crc font-crc
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'codepoints codepoints
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'userFeatures user-features) #f)))
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;; Returns a GlyphRun object, which includes an array of Glyphs and GlyphPositions for the given string.
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(define (layout font string [user-features #f] [script #f] [language #f] #:test [test #f])
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#;((string?) ((option/c (listof symbol?)) (option/c symbol?) (option/c symbol?)) . ->*m . GlyphRun?)
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(define (get-layout string)
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(define codepoints (map char->integer (string->list string)))
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(define args (list codepoints (if user-features (sort user-features symbol<?) null) script language))
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(define key (apply layout-cache-key (ttf-font-crc font) args))
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(hash-ref! layout-cache key
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(λ ()
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#;(encode hb-output (apply harfbuzz-layout font args) #f)
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(match (get-layout-from-db key)
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[(? bytes? res) (dump (decode hb-output res))]
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[_ (define new-layout (apply harfbuzz-layout font args))
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(add-record! (cons key (encode hb-output new-layout #f)))
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(make-hasheq new-layout)])))) ;; `dump` converts to hash
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;; work on substrs to reuse cached pieces
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;; caveat: no shaping / positioning that involve word spaces
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;; todo: why does caching produce slightly different results in test files
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;; theory: because word space is not included in shaping
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(cond
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[(current-layout-caching)
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(define substrs (for/list ([substr (in-list (regexp-match* " " string #:gap-select? #t))]
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#:when (positive? (string-length substr)))
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substr))
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(apply append-glyphruns (map (λ (layout) (hb-layout->glyphrun font layout)) (map get-layout substrs)))]
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[else (if test
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(get-layout string)
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(hb-layout->glyphrun font (get-layout string)))]))
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;; Returns an array of Glyph objects for the given string.
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;; This is only a one-to-one mapping from characters to glyphs.
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;; For most uses, you should use font.layout (described below), which
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;; provides a much more advanced mapping supporting AAT and OpenType shaping.
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(define (glyphs-for-string font string)
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#;(string? . ->m . (listof glyph?))
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;; todo: make this handle UTF-16 with surrogate bytes
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;; for now, just use UTF-8
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(define codepoints (map char->integer (string->list string)))
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(for/list ([cp (in-list codepoints)])
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(glyph-for-codepoint font cp)))
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;; Maps a single unicode code point to a Glyph object.
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;; Does not perform any advanced substitutions (there is no context to do so).
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(define (glyph-for-codepoint font codepoint)
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(define glyph-idx (FT_Get_Char_Index (· font ft-face) codepoint))
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(get-glyph font glyph-idx (list codepoint)))
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(define (measure-char-width font char)
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(define glyph-idx (FT_Get_Char_Index (ft-face font) (char->integer char)))
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(FT_Load_Glyph (ft-face font) glyph-idx FT_LOAD_NO_RECURSE)
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(define width (FT_Vector-x (FT_GlyphSlotRec-advance (FT_FaceRec-glyph (ft-face font)))))
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(* width 1.0))
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(define (measure-string font str size)
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(/ (* size
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(for/sum ([c (in-string str)])
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(measure-char-width font c))) (font-units-per-em font)))
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#|
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approximates
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https://github.com/mbutterick/fontkit/blob/master/src/index.js
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|#
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;; Register font formats
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(define font-formats (list +ttf-font))
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;;fontkit.registerFormat(WOFFFont); ;; todo
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;;fontkit.registerFormat(WOFF2Font); ;; todo
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;;fontkit.registerFormat(TrueTypeCollection); ;; todo
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;;fontkit.registerFormat(DFont); ;; todo
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#|
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approximates
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https://github.com/mbutterick/fontkit/blob/master/src/base.js
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|#
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(define (open-font str-or-path)
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(define filename (if (path? str-or-path) (path->string str-or-path) str-or-path))
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(create-font (open-input-file filename)))
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(struct probe-fail exn ())
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(define (do-probe-fail!)
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(raise (probe-fail "fail" (current-continuation-marks))))
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(define (create-font port)
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(or
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;; rather than use a `probe` function,
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;; just try making a font with each format and see what happens
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(for/first ([font-format (in-list font-formats)])
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(with-handlers ([probe-fail? (λ (exn) #f)])
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(font-format port)))
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(error 'create-font "unknown font format")))
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(test-module
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(check-equal? (measure-string f "f" (font-units-per-em f)) 321.0)
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(check-true (has-table? f #"cmap"))
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(check-exn exn:fail:contract? (λ () (get-table f 'nonexistent-table-tag)))
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(check-true
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(let ([h (layout fira "Rifle" #:test #t)])
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(and (equal? (hash-ref h 'hb-gids) '(227 480 732 412))
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(equal? (hash-ref h 'hb-clusters) '((82) (105) (102 108) (101)))
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(equal? (hash-ref h 'hb-positions) '((601 0 0 0 0) (279 0 0 0 0) (580 0 0 0 0) (547 0 0 0 0)))))))
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