zhiayang / sap

not latex

sap

Sap is distinct from latex ...; it is a separate substance, separately produced, and with different components and functions.

— Wikipedia

introduction

sap (not to be confused with Systeme, Anwendungen und Produkte in der Datenverarbeitung) is a document typesetting/preparation system similar in concept to LaTeX (and derivatives), with the following major differences:

1. it is not from 1978 (TeX), 1984 (LaTeX), or 1994 (LaTeX2e)
2. it is not a glorified macro system
3. it is not a fragile amalgamation of packages all trying not to step on each others' toes
4. the programming 'metalanguage' is familiar (and sane)

This is currently a work-in-progress, so features are quite limited. An incomplete list of features can be found at the bottom of this document.

goals

The eventual goal of this project is to completely replace LaTeX as my document typesetting system. To this end, there are some "big features" that will be implemented eventually:

1. Graphics support — at least the (very very) basic features of PGF/TikZ
2. Full document metaprogramming (freely manipulating text)
3. Some basic level of typesetting mathematical expressions
4. ...?

non-goals

Non-goals are split into two categories: things I can't do because this is a one-person effort, and things I won't do because they are not in the scope of this project. For the former, pull requests are very appreciated (:

can't

These are mostly because (a) I won't be writing documents in any of these languages, and (b) I don't know any of these languages.

1. Right-to-left languages
2. "Complex" latin scripts, eg. Vietnamese
3. "Complex" non-latin scripts, eg. Arabic, Urdu

won't

While I appreciate the vast ecosystem that LaTeX has, having any kind of compatibility is simply not possible for obvious reasons.

1. Any sort of TeX/LaTeX compatibility
2. Graphical parity with LaTeX
3. Non-OpenType font support (eg. Type1)
4. Generating LaTeX source as an output

current featureset

This also acts as a sort of TODO; as time goes on completed features may be removed from this list if they are deemed "trivial".

• Unicode substitution (eg. codepoint (de)composition)
• More advanced typography support (BASE, MATH, JSTF, AAT kerx)
• Further size optimisation for embedded fonts
• Optimising bytecode compiler for the scripting language
• Tables
• SVG embedding
• PDF embedding
• Some manipulation of embedded images (eg. rotation)
• Reflection over document contents (not just adding new stuff)
• Various (advanced) scripting language features
• Coloured text (separate from coloured lines...)
• (partial) colour support
• PDF paths (curves and lines)
• PDF Links (annotations)
• Rudimentary and crude bibliography support
• Slightly more advanced layout capabilities (hbox, vbox, zbox)
• Layout integration with scripting language
• Embedding images
• Automatic hyphenation (English only, parsed from hyph-en-gb.tex)
• OpenType font (otf/ttf) loading and embedding
• Embedded font subsetting for TrueType fonts (CFF fonts are a little iffy)
• Glyph positioning (kern & GPOS lookups 1, 2, 7, 8, 9)
• Glyph substitutions (incl. ligatures) (morx & OpenType GSUB lookups 1, 2, 4, 5, 6, 7)
• Text extraction (eg. copy/paste) support — ToUnicode table
• Basic paragraph layout, linebreaking, and pagination
• Some meta language
• Vertical writing
• Variable font support Unlikely to support variable fonts, since it's a pain

alternatives

But what about <insert_tool_here>?

• typst: it wasn't released when i started sap ):
• (g)roff: the language (doesn't seem) powerful enough, seems to require strange things to use unicode, and the syntax is too terse.
• patoline: development seems slow/abandoned, basic things don't work (eg. copying text)
• html/css: no. just no.

license

sap is licensed under the Apache License version 2.0. utf8proc and libdeflate are licensed under their respective licenses.

The hyphenation list is MIT licensed, see the hyphenation file hyph-en-gb.tex or the repo.