ttf.c/ttf.h/ttftest.c: TrueType parser core -- sfnt/head/maxp/loca/glyf/cmap (item 4.3.7)
Freestanding C module resolving a Unicode codepoint (cmap format 4) to a glyph index and its outline header (contour count, bounding box), verified against an independent from-scratch Python reference reader via tools/ttftest.c. Not yet wired into the boot path or capsule system. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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Robert Allan James
co-authored by
Claude Sonnet 5
Claude Sonnet 5
parent
b9b7cb2c6a
commit
5f6cc054d4
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/*
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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This file is part of the StarForth project.
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Licensed under the StarForth License, Version 1.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
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This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
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express or implied, including but not limited to the warranties of
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merchantability, fitness for a particular purpose, and noninfringement.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/**
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* ttf.h - TrueType font parser core (Freestanding)
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*
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* FABRIC.md item 4.3.7. Reads a TTF's sfnt directory plus head/maxp/loca/
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* glyf/cmap tables, resolving a Unicode codepoint to a glyph index and its
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* outline header (contour count, bounding box). Does NOT extract outline
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* points or rasterize — that is 4.3.7a/4.3.7c. No floating point; all
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* fields read here are raw integers straight from the font's own
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* big-endian on-disk format (see FABRIC.md §27.7 decision #2 for why the
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* Q48.16-vs-float call was made, and why it doesn't bind this file, which
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* never scales anything).
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*
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* cmap: only format 4 (Windows/Unicode BMP) subtables are resolved. This
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* covers ASCII and all of the BMP, which is what the v1 glyph repertoire
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* (§27.6.4) needs. Format 12 (supplementary planes) is deferred — no
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* v1 glyph requires it.
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*/
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#ifndef STARKERNEL_TTF_H
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#define STARKERNEL_TTF_H
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#include <stdint.h>
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#include <stddef.h>
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#include "q48_16.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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#define TTF_OK 0
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#define TTF_ERR_BAD_SFNT -1
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#define TTF_ERR_TABLE_MISSING -2
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#define TTF_ERR_BAD_TABLE -3
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#define TTF_ERR_BAD_GLYPH_INDEX -4
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#define TTF_ERR_OUT_OF_BOUNDS -5
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/** Glyph index returned for "no mapping" by ttf_codepoint_to_glyph(). */
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#define TTF_GLYPH_MISSING 0
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/**
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* Parsed font handle. Borrows the caller's buffer (does not copy or own
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* it) — the buffer must outlive the ttf_font_t.
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*/
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typedef struct {
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const uint8_t *data;
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uint32_t size;
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uint32_t head_off;
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uint32_t maxp_off;
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uint32_t loca_off;
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uint32_t loca_len;
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uint32_t glyf_off;
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uint32_t glyf_len;
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uint16_t units_per_em;
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int16_t index_to_loc_format; /* 0 = Offset16 (x2), 1 = Offset32 */
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uint16_t num_glyphs;
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/* Selected cmap subtable (format 4 only, see file header comment). */
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uint32_t cmap_subtable_off;
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int has_cmap;
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} ttf_font_t;
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/** Raw glyf record header, per §27.6/4.3.7's "done when" clause. */
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typedef struct {
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int16_t num_contours; /* >= 0 simple glyph, < 0 composite glyph */
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int16_t x_min;
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int16_t y_min;
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int16_t x_max;
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int16_t y_max;
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uint32_t glyf_offset; /* absolute file offset of this glyph's record */
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uint32_t glyf_length; /* bytes; 0 for an empty glyph (e.g. space) */
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} ttf_glyph_header_t;
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/**
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* ttf_parse - Locate and validate the sfnt directory and the head/maxp/
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* loca/glyf tables (cmap is optional; ttf_codepoint_to_glyph() fails
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* cleanly if absent). Does not copy `data` — `out` borrows it.
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*
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* @param data Whole .ttf file contents
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* @param size Length of data in bytes
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* @param out Parsed handle to populate
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* @return TTF_OK, or a TTF_ERR_* code
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*/
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int ttf_parse(const uint8_t *data, uint32_t size, ttf_font_t *out);
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/**
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* ttf_codepoint_to_glyph - Resolve a Unicode codepoint via the font's
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* format-4 cmap subtable.
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*
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* @return glyph index, or TTF_GLYPH_MISSING if unmapped or no cmap
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*/
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uint32_t ttf_codepoint_to_glyph(const ttf_font_t *font, uint32_t codepoint);
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/**
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* ttf_glyph_header - Read a glyph's outline header (contour count,
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* bounding box) via loca + glyf. Does not extract contour points.
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*
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* @param glyph_index As returned by ttf_codepoint_to_glyph()
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* @param out Header to populate
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* @return TTF_OK, or a TTF_ERR_* code
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*/
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int ttf_glyph_header(const ttf_font_t *font, uint32_t glyph_index,
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ttf_glyph_header_t *out);
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#ifdef __cplusplus
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}
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#endif
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#endif /* STARKERNEL_TTF_H */
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