pdfcraft/crates/fonts/README.md

pdfcraft-fonts

Layer L2. Font helpers for the appearance streams PdfCraft generates (comments, form fields).

Today it holds what generated appearances need without a font program:

• helvetica_width: an approximation of Helvetica's proportions by character class. No metrics file or font program from any vendor is bundled; widths are PdfCraft's own estimates, good enough for line breaking and alignment, not for typesetting.
• wrap: greedy line breaking with that measure (paragraphs on newlines, long words split).
• win_ansi: Unicode → WinAnsiEncoding bytes (? for characters it can't represent), and literal to write bytes as a PDF literal string.

It also holds the fonts of the optional craft-fonts build input. build.rs embeds them as CRAFT_FONTS when the build sets CRAFT_FONTS_DIR=<checkout> (and fails if it can't while CRAFT_FONTS_REQUIRED=1, as releases set). Without that variable CRAFT_FONTS is empty and everything below copes:

• ui_japanese_fonts: the Jpan faces for the interface, BIZ UDPGothic first.
• ui_chinese_fonts: the Hans faces for the interface, in manifest order (without one, Chinese characters the Japanese faces lack show the replacement glyph).
• ui_cjk_fonts(prefer_hans): both in fallback order for the UI language (Chinese group first in Chinese mode, so one line never mixes faces with different vertical metrics).
• document_japanese_font / japanese_glyph: the face (Shippori Mincho, then BIZ UDMincho) whose outlines become the Type 3 fallback font for Japanese text written into PDFs. Without it, japanese_glyph returns GlyphError::NoFont and the editor reports a clear error.
• SHIPPORI_MINCHO: Shippori Mincho's bytes, or None.

wasm32 builds embed only BIZ UDPGothic Regular, to keep the web build small: the web build currently has no Chinese face, so Chinese there still shows the replacement glyph. Font files are never committed here (AGENTS.md §1.4; team members: craftrules standards/fonts.md, internal).

The full font subsystem (parsing, shaping, subsetting and embedding) arrives with M2.2/M7.