ttf_words.c: TTF-TEXT entry point, hmtx advance widths (item 4.3.7e)
Punch list §25 item 4.3.7e complete. New src/word_source/ttf_words.c registers TTF-TEXT ( c-addr u x y size color -- ): lazily loads the v1 default font capsule + raster cache once, decodes UTF-8 (C reimplementation mirroring capsules/fabric.4th's DECODE-UTF8 exactly), looks up each glyph's cached bitmap, blits via fb_put_pixel, advances the pen by the glyph's real hmtx advance width scaled to pixels. Necessary plumbing: ttf_parse() now also locates hhea/hmtx, and ttf_glyph_advance_width() reads a glyph's advance width -- required for this item's own "proportional spacing correct" acceptance clause, no advance-width data existed anywhere else in the parser. Verified in tools/ttftest.c: A/a/0/space all read advance_width=600, correctly uniform since JetBrainsMono-Regular.ttf is monospace. (x,y) is raster pixel space (top-left origin, Y-down), deliberately not the stroke font TEXT's Cartesian Y-up convention -- recorded explicitly in ttf_words.h, not conflated. Verified live, amd64, screendump: injected S" Hi 4.3.7e!" 200 200 28 16777215 TTF-TEXT over a serial socket after boot, no error, captured a screendump showing the string rendered legibly with correct mixed-case/digit/punctuation glyphs and even spacing. TTF-TEXT is this item's permanent deliverable, not a throwaway probe. Compile-checked clean on all three architectures. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
This commit is contained in:
Robert Allan James
co-authored by
Claude Sonnet 5
Claude Sonnet 5
parent
2db4603d04
commit
715ebcc57e
@@ -131,6 +131,24 @@ int ttf_parse(const uint8_t *data, uint32_t size, ttf_font_t *out) {
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if (rc != TTF_OK) return rc;
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if (!in_bounds(out, out->glyf_off, out->glyf_len)) return TTF_ERR_OUT_OF_BOUNDS;
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/* hhea (for numberOfHMetrics) + hmtx (advance widths) -- mandatory,
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* needed for ttf_glyph_advance_width() (4.3.7e's proportional
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* spacing). numberOfHMetrics is hhea's 18th field, a fixed 36-byte
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* table per spec. */
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{
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uint32_t hhea_off, hhea_len_unused, hmtx_len;
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rc = find_table(data, size, num_tables, TAG('h', 'h', 'e', 'a'), &hhea_off, &hhea_len_unused);
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if (rc != TTF_OK) return rc;
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if (!in_bounds(out, hhea_off, 36)) return TTF_ERR_BAD_TABLE;
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out->num_h_metrics = rd_u16(data, hhea_off + 34);
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rc = find_table(data, size, num_tables, TAG('h', 'm', 't', 'x'), &out->hmtx_off, &hmtx_len);
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if (rc != TTF_OK) return rc;
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if (out->num_h_metrics == 0
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|| !in_bounds(out, out->hmtx_off, (uint32_t) out->num_h_metrics * 4))
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return TTF_ERR_BAD_TABLE;
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}
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/* cmap is optional to overall parse success; codepoint lookup just
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* fails cleanly (TTF_GLYPH_MISSING) if it's absent or unrecognized. */
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{
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@@ -262,6 +280,16 @@ int ttf_glyph_header(const ttf_font_t *font, uint32_t glyph_index, ttf_glyph_hea
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return TTF_OK;
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}
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uint16_t ttf_glyph_advance_width(const ttf_font_t *font, uint32_t glyph_index) {
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uint32_t idx, off;
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if (!font || font->num_h_metrics == 0) return 0;
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idx = glyph_index < font->num_h_metrics ? glyph_index : (uint32_t) font->num_h_metrics - 1;
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off = font->hmtx_off + idx * 4;
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if (!in_bounds(font, off, 2)) return 0;
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return rd_u16(font->data, off);
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}
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/* ===========================================================================
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* 4.3.7a — glyph outline extraction
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* ===========================================================================
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@@ -75,6 +75,7 @@
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#include "word_source/include/defer_words.h"
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#include "word_source/include/framebuffer_words.h"
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#include "word_source/include/keyboard_words.h"
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#include "word_source/include/ttf_words.h"
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/**
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* @brief Registers a single FORTH word in the virtual machine
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@@ -132,6 +133,7 @@ void register_forth79_words(VM *vm) {
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register_defer_words(vm); /* Module 27: DEFER / IS late binding */
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register_framebuffer_words(vm); /* Module 28: Console fabric -- raw framebuffer primitives */
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register_keyboard_words(vm); /* Module 29: Console fabric -- raw keyboard scancode diagnostic */
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register_ttf_words(vm); /* Module 30: TrueType text entry point */
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log_message(LOG_INFO, "FORTH-79 Standard word set registration complete");
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}
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@@ -0,0 +1,38 @@
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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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Licensed under the StarForth License, Version 1.0
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*/
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#ifndef TTF_WORDS_H
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#define TTF_WORDS_H
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#include "vm.h"
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/**
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* @defgroup ttf_words TrueType Text Words
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* @{
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*
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* @brief `TTF-TEXT`, the TrueType-backed text entry point (FABRIC.md item
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* 4.3.7e). Kernel-only; no-op on hosted builds (no framebuffer/capsule
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* system exists there).
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*
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* @par TTF-TEXT ( c-addr u x y size color -- )
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* Render a UTF-8 string via the v1 default font capsule
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* (`fonts:JetBrainsMono-Regular.ttf`, loaded and cached lazily on first
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* use). (x,y) is raster pixel space (top-left origin, Y-down) -- NOT
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* capsules/fabric.4th's Cartesian Y-up convention used by the stroke
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* font's `TEXT` (4.3.6f); the two are deliberately different coordinate
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* systems, not interchangeable. (x,y) is the first glyph's baseline-left
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* origin. `size` is capped at `TTF_CACHE_MAX_SIZE_PX` (see ttf.h).
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* Advances proportionally per glyph via the font's real hmtx advance
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* width, scaled to pixels.
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* @}
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*/
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void register_ttf_words(VM *vm);
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#endif /* TTF_WORDS_H */
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@@ -0,0 +1,163 @@
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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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Licensed under the StarForth License, Version 1.0
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*/
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/* ttf_words.c — TrueType text entry point (FABRIC.md item 4.3.7e).
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* Kernel-only; no-op on hosted builds. */
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#include "include/ttf_words.h"
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#include "../../include/log.h"
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#include "../../include/word_registry.h"
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#ifdef __STARKERNEL__
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#include "starkernel/framebuffer.h"
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#include "starkernel/ttf.h"
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#include "starkernel/capsule_generated.h"
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#define TTF_WORDS_CACHE_SLOTS 32
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#define TTF_WORDS_DEFAULT_FONT "fonts:JetBrainsMono-Regular.ttf"
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static ttf_font_t g_ttf_font;
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static int g_ttf_font_ready = 0;
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static ttf_raster_cache_slot_t g_ttf_cache_slots[TTF_WORDS_CACHE_SLOTS];
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static ttf_raster_cache_t g_ttf_cache;
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static int ttf_words_ensure_font(void) {
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if (g_ttf_font_ready) return 1;
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if (ttf_load_from_capsule(
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capsule_get_directory(), capsule_get_descriptors(),
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capsule_get_names(), capsule_get_arena(),
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TTF_WORDS_DEFAULT_FONT, &g_ttf_font) != TTF_OK)
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return 0;
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ttf_raster_cache_init(&g_ttf_cache, g_ttf_cache_slots, TTF_WORDS_CACHE_SLOTS);
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g_ttf_font_ready = 1;
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return 1;
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}
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/* Decode one UTF-8 codepoint from VM memory at *a (VM-space address),
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* with *len bytes known remaining. Mirrors capsules/fabric.4th's
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* DECODE-UTF8 exactly: same lead-byte-length table, same U+FFFD
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* fallback (advancing exactly one byte) on an invalid or truncated
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* sequence. Advances *a and *len past the consumed bytes. */
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static uint32_t ttf_words_decode_utf8(VM *vm, vaddr_t *a, cell_t *len) {
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uint8_t lead, b[4];
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uint32_t seqlen, i, cp;
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if (*len <= 0 || !vm_addr_ok(vm, *a, 1)) {
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*len = 0;
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return 0xFFFD;
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}
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lead = vm_load_u8(vm, *a);
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if (lead < 0x80) seqlen = 1;
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else if ((lead & 0xE0) == 0xC0) seqlen = 2;
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else if ((lead & 0xF0) == 0xE0) seqlen = 3;
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else if ((lead & 0xF8) == 0xF0) seqlen = 4;
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else seqlen = 0;
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if (seqlen == 0 || (cell_t) seqlen > *len || !vm_addr_ok(vm, *a, seqlen)) {
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*a += 1;
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*len -= 1;
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return 0xFFFD;
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}
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for (i = 0; i < seqlen; i++) b[i] = vm_load_u8(vm, *a + i);
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switch (seqlen) {
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case 1:
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cp = b[0];
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break;
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case 2:
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cp = ((uint32_t) (b[0] & 0x1F) << 6) | (b[1] & 0x3F);
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break;
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case 3:
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cp = ((uint32_t) (b[0] & 0x0F) << 12) | ((uint32_t) (b[1] & 0x3F) << 6) | (b[2] & 0x3F);
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break;
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default:
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cp = ((uint32_t) (b[0] & 0x07) << 18) | ((uint32_t) (b[1] & 0x3F) << 12)
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| ((uint32_t) (b[2] & 0x3F) << 6) | (b[3] & 0x3F);
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break;
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}
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*a += seqlen;
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*len -= (cell_t) seqlen;
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return cp;
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}
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/* TTF-TEXT ( c-addr u x y size color -- ) */
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static void ttf_word_text(VM *vm) {
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cell_t color, size, y, x, u, addr_cell;
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vaddr_t a;
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cell_t remaining;
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uint32_t pen_x;
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q48_16_t scale;
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if (vm->dsp < 5) {
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log_message(LOG_ERROR, "TTF-TEXT: Stack underflow");
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vm->error = 1;
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return;
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}
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color = vm_pop(vm);
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size = vm_pop(vm);
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y = vm_pop(vm);
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x = vm_pop(vm);
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u = vm_pop(vm);
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addr_cell = vm_pop(vm);
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if (!ttf_words_ensure_font()) {
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log_message(LOG_ERROR, "TTF-TEXT: font capsule load failed");
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vm->error = 1;
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return;
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}
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if (size <= 0 || size > TTF_CACHE_MAX_SIZE_PX) {
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log_message(LOG_ERROR, "TTF-TEXT: size out of range");
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vm->error = 1;
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return;
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}
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a = VM_ADDR(addr_cell);
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remaining = u;
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pen_x = (uint32_t) x;
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scale = q48_div(q48_from_u64((uint32_t) size), q48_from_u64(g_ttf_font.units_per_em));
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while (remaining > 0) {
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uint32_t cp = ttf_words_decode_utf8(vm, &a, &remaining);
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ttf_bitmap_t bmp;
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int rc, was_hit;
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uint32_t gid, adv_units, px, py;
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q48_16_t adv_q;
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rc = ttf_raster_cache_get(&g_ttf_cache, &g_ttf_font, cp, (uint32_t) size, &bmp, &was_hit);
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if (rc == TTF_OK) {
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for (py = 0; py < bmp.height; py++) {
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for (px = 0; px < bmp.width; px++) {
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if (bmp.pixels[py * bmp.width + px]) {
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fb_put_pixel(pen_x + px - TTF_CACHE_MARGIN,
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(uint32_t) y + py - (uint32_t) size - TTF_CACHE_MARGIN,
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(uint32_t) color);
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}
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}
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}
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}
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gid = ttf_codepoint_to_glyph(&g_ttf_font, cp);
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adv_units = ttf_glyph_advance_width(&g_ttf_font, gid);
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adv_q = q48_mul(q48_from_u64(adv_units), scale);
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pen_x += (uint32_t) q48_to_u64(adv_q);
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}
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}
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#endif /* __STARKERNEL__ */
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void register_ttf_words(VM *vm)
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{
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#ifdef __STARKERNEL__
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register_word(vm, "TTF-TEXT", ttf_word_text);
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#else
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(void) vm;
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#endif
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}
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