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Brandon ThomasandClaude Opus 5.5
9953befe28
crates/text/build.rs embeds the fonts of a storytold/craft-fonts checkout named by CRAFT_FONTS_DIR as filmcraft_text::fonts::CRAFT_FONTS (native: all of them; wasm32: only BIZ UDPGothic Regular). Unset, CRAFT_FONTS is empty and nothing changes. A bad CRAFT_FONTS_DIR is a warning, or an error with CRAFT_FONTS_REQUIRED=1. Never a Cargo dependency, no network. - UI: the Japanese faces are the last fallback of every egui font family (BIZ UDPGothic first, Bold first in the semibold/medium families). - Text engine: registered after the bundled faces; fallback_for picks them after the bundled faces and before system faces (Mincho for serif text, Gothic otherwise, nearest weight). - Tests: Japanese glyphs (no tofu) in the UI and title paths, skipped without craft-fonts; the theme works with CRAFT_FONTS empty. - Release: every build job checks out craft-fonts at a pinned commit and builds with CRAFT_FONTS_DIR + CRAFT_FONTS_REQUIRED; packages carry OFL-<family>.txt. NOTICE, ATTRIBUTION.md (optional build input), AGENTS.md, CLAUDE.md, README and docs/contributing.md describe it. FilmCraft main bundles no Japanese font, so no font files move. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
32 lines
3.9 KiB
Markdown
32 lines
3.9 KiB
Markdown
# filmcraft-text
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FilmCraft's text engine (layer L1: depends on `filmcraft-color`, `skrifa`, `harfrust`,
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`unicode-bidi` and `unicode-linebreak`). It draws graphic-clip text and shapes, caption burn-in
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and the Timecode / Clip Name effects. Pure Rust; it builds for `wasm32-unknown-unknown`.
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| Module | What |
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|---|---|
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| `fonts` | Font database. Bundled faces (always present, also on the web): Inter Regular / Medium / SemiBold / Bold / Italic, JetBrains Mono Regular, Noto Serif Regular — all SIL OFL 1.1, unmodified, in `assets/fonts/` with `.attribution` sidecars. More faces come from `FontSource`s: `DirectorySource::system()` scans the platform font folders on first need (only the `name` and `OS/2` tables are read, via `sfnt`); on wasm the scan finds nothing and hosts can call `add_font_data`. `resolve(family, style)` picks a face, synthesises bold/italic when the family lacks them, and falls back to Inter (flagged `missing`). `fallback_for` finds a face for characters the chosen face lacks: bundled faces first, then the optional craft-fonts faces (`CRAFT_FONTS`, embedded by `build.rs` when built with `CRAFT_FONTS_DIR`; Mincho for serif text, Gothic otherwise, nearest weight), then loaded system faces. |
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| `layout` | Paragraph layout: per-character font fallback → bidi levels (UAX #9) → items (runs of one face, direction and size) shaped with harfrust (OpenType kerning, ligatures, marks, complex scripts) → tracking → line breaking at UAX #14 opportunities (area text) → visual reordering per line → alignment (left / centre / right / justify), leading (added to the natural line height), baseline shift, all caps / synthesised small caps (78 %), underline. Every character boundary gets a caret stop (ligatures are split evenly), so editors can place carets, hit-test and draw selections. Layouts are cached by text + style (512 entries, LRU). |
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| `layout_rich` | Per-character style runs (`StyleRun`: a byte range with its own `TextStyle`): runs split shaping items (font, size, tracking, caps, faux styles), baseline shift and underline apply per run, a line holding a larger run is pushed down from the line above (baseline distance = max(base line height, previous descent + this line's ascent + leading)), and every glyph / underline carries its style index so renderers can colour runs (`render::draw_run`). |
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| `raster` | Our anti-aliased rasteriser (non-zero winding, 5 sub-scanlines, exact horizontal coverage, active-edge list), contour paths with transforms, rounded rectangles, ellipses, polygons and outline emboldening. Coverage is linear, so compositing in linear light is correct. |
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| `render` | Glyph outlines (cached per face + glyph) and glyph masks (cached per size in ⅛ px, ¼-px horizontal phase, synthetic style). Axis-aligned uniform transforms use the mask cache with sub-pixel x positioning; rotated / skewed / non-uniform transforms fill the transformed outlines of the whole run in one pass. Synthetic bold grows outlines by 2.5 % of the size; synthetic italic slants by 12°. |
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| `mask` | Outer / centre / inner strokes from an exact Euclidean distance transform (Felzenszwalb–Huttenlocher) with sub-pixel refinement, a three-pass box blur (≈ Gaussian) for shadows, offsets. |
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## Coordinates
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Pixels, y down. Point text: the origin is the alignment point on the first baseline (left edge,
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centre or right edge). Area text (`ParagraphStyle::width`): the origin is the box's top-left.
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## Performance
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A three-line, centred, 96 px bold title at 1080p (`perf::three_line_title_is_fast`), release build
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on an M-series Mac: about 1.6 ms cold (shaping, outline extraction, glyph rasterisation) and
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0.15 ms warm (layout cache + glyph cache). The test fails if the warm path exceeds 40 ms.
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## Not yet
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OpenType
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feature toggles beyond kerning/ligatures, variable-font axes, hinting, colour (emoji) glyphs, and
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hyphenation. Words longer than an area-text line overflow instead of breaking mid-word.
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