LaTeXEngine

Engine: pdftex (TeX Live) — pre-built XCFrameworks | Texmf: ~33 MB Latin Modern + amsmath + hyperref + expl3 + firstaid + graphics-def + hyphenation + stringenc + unicode-data | Type: In-process LaTeX compilation, no subprocess | Status: Working — pdflatex foo.tex → foo.pdf end-to-end

In-process LaTeX compilation for iOS. Compiles .tex source to PDF inside the host app — no fork/exec (which iOS forbids), no external pdflatex binary, no network round-trip. Powered by three xcframeworks plus a curated TeX Live texmf tree.

   ┌────────────────────┐
   │ Your Swift / Python│
   │  app code          │
   └─────────┬──────────┘
             │  TeX source string
             ▼
   ┌────────────────────┐         pdftex.framework        ┌────────┐
   │ ios_system bridge  │  ────►  kpathsea (file lookup)  │  PDF   │
   │ (POSIX shim)       │         pdftex (typesetter)     │ bytes  │
   └────────────────────┘         texmf/ (font + macros)  └────────┘

When to add this target

Two main use cases:

Math rendering — render LaTeX math snippets (E = mc^2, \int_0^\infty e^{-x^2} dx, …) inside your app, either as a PDF page or rasterised to a PNG / SVG.
Document compilation — let users author full .tex documents (articles, theses, slides) in your app and produce a PDF on-device with no internet.

.dependencies = [
    .package(url: "https://github.com/yu314-coder/python-ios-lib", from: "1.0.0"),
],
.target(name: "MyApp", dependencies: [
    .product(name: "LaTeXEngine", package: "python-ios-lib"),
])

LaTeXEngine depends on CairoGraphics (for the texmf font rasterisation pipeline) — SPM resolves that automatically.

What's bundled

Sources/LaTeXEngine/latex/
├── ios_system.xcframework      ← POSIX shim providing fork-free CLI surface
├── kpathsea.xcframework        ← TeX Live's file-lookup library
├── pdftex.xcframework          ← The actual pdftex compiler
└── texmf/                      ← 33 MB curated texmf tree
    ├── fonts/                  ← Latin Modern Type 1 (.pfb), .tfm metrics
    │   ├── type1/public/lm/    ← 92 .pfb files
    │   └── tfm/public/lm/      ← 596 .tfm files
    ├── tex/latex/              ← .sty / .cls macro packages
    │   ├── base/               ← article.cls, etc.
    │   ├── amsmath/            ← AMS-math
    │   ├── amsfonts/
    │   ├── tools/              ← multicol, xspace, …
    │   ├── hyperref/           ← clickable links + bookmarks
    │   └── lm/                 ← Latin Modern declarations
    ├── tex/generic/
    │   ├── expl3/              ← expl3 + l3kernel (1.3 MB)
    │   ├── firstaid/           ← compatibility patches
    │   ├── graphics-def/
    │   ├── stringenc/
    │   └── unicode-data/
    └── tex/plain/
        └── hyphenation/        ← Knuth's English + lots of others

The texmf tree is a curated subset of TeX Live full — enough to run modern \documentclass{article} + amsmath + hyperref end-to-end without "missing package" errors. Total static-archive footprint of the three xcframeworks: ~12 MB.

Pure-Swift usage

import LaTeXEngine

// The Swift surface is intentionally tiny — it's just the resource
// bundle accessor. Drive pdftex via the bundled CLI shim.
let bundlePath = PythonIOSLib.resourcePath
print("texmf at:", bundlePath ?? "(unavailable)")

Real integrations call into pdftex via the C API, with the TEXMFCNF / TEXMFROOT environment variables pointing at the bundled texmf/ directory. See OfflinAi's CodeBench/LaTeXEngine.swift for a reference implementation that:

Sets up the texmf paths on first launch
Generates the .fmt (format) file from latex.ltx via the pdftex --ini mode (no pre-built format needed)
Streams .tex strings into a temp file
Calls pdftex_main(argc, argv) directly
Reads the output .pdf from the temp dir

Python usage (via offlinai_latex)

The Manim target ships an offlinai_latex Python module that wraps all of this for you. From the in-app Python shell:

from offlinai_latex import tex_to_svg

svg = tex_to_svg(r"E = mc^2")
print(f"SVG written to: {svg}")

# Math mode with display style
svg2 = tex_to_svg(r"\sum_{n=1}^{\infty} \frac{1}{n^2} = \frac{\pi^2}{6}")

tex_to_svg runs the full pipeline:

Wraps your LaTeX in a minimal preamble (\documentclass{standalone}
- \usepackage{amsmath, amssymb, mathtools})
Calls pdftex to produce a 1-page PDF
Rasterizes the PDF to SVG via Cairo's PDF→cairo→SVG path (or to PNG via Cairo's image surface, used by manim's CJK MathTex fallback)
Returns the output file path

Manim integration

manim's MathTex and Tex mobjects route through this pipeline:

from manim import *

class HelloMath(Scene):
    def construct(self):
        eq = MathTex(r"E = mc^2", font_size=72)
        self.play(Write(eq))
        self.wait()

When you self.play(Write(eq)), manim:

Calls offlinai_latex.tex_to_svg(r"E = mc^2")
pdftex compiles → PDF
Cairo rasterises → SVG paths
manim parses the SVG into VMobject paths
Animates the path drawing

For CJK content (MathTex(r"\text{你好} = ...")), the same pipeline runs but with xelatex-style font fallback — see cairographics.md for the fontconfig setup.

What's INCLUDED in texmf

365 .sty / .cls files across 17 document classes — enough to compile the vast majority of real-world documents. Full list in the Bundled package inventory appendix below.

Highlights by category:

Classes: article, report, book, letter, beamer, amsart, amsbook, amsproc, proc, slides, minimal
Math: amsmath, amssymb, amsthm, amsbsy, amscd, amsfonts, amsopn, amstext, mathtools, bbm, amstex
Drawing: pgf + full tikz library set (arrows, decorations, patterns, plots, shapes, snakes, automata, calendar, …)
Slides: beamer + all beamerbase* modules + beamer themes
Hyperlinks: hyperref + dependencies (pdfescape, kvsetkeys, hypcap, backref, refcount, letltxmacro, atveryend, atbegshi, auxhook)
Layout: geometry, fancyhdr, setspace, microtype, booktabs, float, listings, enumitem, caption / subcaption / bicaption / ltcaption, titlesec-friendly stack
Cross-refs: cleveref, refcount, etoolbox
Graphics: graphicx, color, graphpap
CJK: CJK, CJKutf8, CJKnumb, CJKfntef, CJKulem, CJKspace, CJKvert
Fonts: full Latin Modern Type 1 (92 .pfb files, 596 .tfm metrics, italic / bold / bolditalic / smallcaps), fontenc, inputenc, t1enc
Engine plumbing: expl3, l3kernel, firstaid, graphics-def, pdftexcmds, pdfescape, etoolbox, fp
Hyphenation: English + many other languages

What's NOT included

xelatex / lualatex — only pdftex is wired up in this SPM target. Documents using \usepackage{fontspec} won't compile through LaTeXEngine (no Unicode font loading). For arbitrary Unicode, CodeBench's busytex-WASM path supports xelatex — see docs/offlinai-latex.md.
Computer Modern bitmap fonts — cm-super not shipped; Latin Modern (lmodern) is auto-substituted via the engine's preamble-injection hook so docs requesting cm fonts still compile.
biber — only legacy bibtex (8-bit) reachable in-process. For modern bibliography, pre-compile the .bbl outside the app and ship it alongside the source. backref is bundled so back- references in PDFs still work.
pythontex / minted — both rely on \write18 (shell escape), which iOS forbids. Use listings instead for code blocks; it's bundled and produces good syntax-coloured output.
External tools — dvips, dvipdfmx, epstopdf, latexmk are not bundled. Stick to PDF output and PDF-native graphics.

Limitations

No \write18 / shell escape. iOS forbids subprocess; pdftex was built with -shell-escape permanently disabled.
Single document at a time per process. pdftex's globals aren't thread-safe; serialise compilations.
Format file regeneration on first launch. The first compilation pre-builds latex.fmt (~5 MB) by running pdftex --ini over latex.ltx. Takes 2-3 seconds; cached after that.
PDF post-processing. No qpdf / pdftk for merge / split. Consume the raw PDF in your app or convert to images.

Troubleshooting

`! LaTeX Error: File 'amsmath.sty' not found.`

The texmf tree's path-cache (ls-R) hasn't been built. The host app should run mktexlsr <texmf>/ once on first launch — the xcframework includes the mktexlsr Lua script. Without it, kpathsea linear-scans every directory, which is slow but works; if it fails, the cache wasn't generated AND the directory layout is wrong.

`! Undefined control sequence. l.5 \maketitle`

Same root cause — kpathsea didn't find the class file. Verify TEXMFROOT and TEXMFCNF are set in the environment before calling pdftex_main.

`! pdfTeX error: pdflatex: format file 'latex.fmt' not found.`

The --ini step didn't run (or failed silently). Look for fmtutil / pdftex --ini errors in the host app's NSLog output. Manually:

pdftex --ini --jobname=latex --etex 'pdflatex.ini'

should produce latex.fmt in the current directory; copy it into texmf/web2c/pdftex/.

Output PDF is blank

Almost always a missing font. Check the .log file (sibling of the .pdf that was supposed to be generated) for ! Font \LMR/regular/n/10=lmr10 at 10.0pt not loadable: Metric (TFM) file or installed font not found. The .tfm files for Latin Modern are bundled — if they're missing, the texmf tree didn't get copied. Check the SPM .copy("latex") build phase ran.

Compilation hangs

pdftex's interactive prompt is asking for input ("?"). Make sure you call it with \nonstopmode injected at the top of the TeX source, or pass -interaction=nonstopmode as a CLI arg.

Build provenance

pdftex 1.40.25 from TeX Live 2024
kpathsea built with --disable-shared --enable-static --enable-ipc
ios_system from Nicolas Holzschuch's repo, patched to suppress the .bash_profile parsing path
texmf curated by hand from a texlive-full install, removing unused languages (kept ~50 MB → ~33 MB after pruning)
All three xcframeworks built with Xcode 16, targeting iOS 17+

Bundled package inventory

Generated via find Sources/LaTeXEngine/latex/texmf -name '*.sty' -o -name '*.cls'. Total: 365 packages, 17 document classes.

For each: just \documentclass{...} or \usepackage{...} and it works — no ! LaTeX Error: File ... not found.

Document classes (17)

Class	Purpose
`article`	Standard short documents (most common)
`report`	Multi-chapter reports
`book`	Books with parts / chapters / front-matter
`letter`	Business letters with `\opening` / `\closing`
`beamer`	Full beamer for slide decks
`proc`	Proceedings articles
`slides`	Plain LaTeX slides (legacy)
`minimal`	Empty class for testing
`amsart`, `amsbook`, `amsproc`	AMS journal/book/proceedings
`amsdtx`, `amsldoc`	AMS documentation classes
`l3doc`, `ltxguide`, `ltxnews`, `ltxdoc`	LaTeX kernel documentation classes

Math + AMS

Package	What it gives you
`amsmath`	`align`, `gather`, `matrix`, `cases`, `\dfrac`, `\substack`, …
`amssymb`	`\mathbb{R}`, `\mathfrak`, `\mathcal`, `\hbar`, `\square`, …
`amsthm`	`\newtheorem`, `proof` environment, `\qedhere`
`amsbsy`	Bold math (`\boldsymbol`, `\pmb`)
`amscd`	Commutative diagrams (`CD` environment)
`amsfonts`	`\mathbb`, `\mathfrak` base fonts
`amsgen`, `amsopn`, `amstext`, `amstex`, `amsbooka`, `amsmidx`, `amsxtra`	AMS support packages
`mathtools`	Extends `amsmath` — `\coloneqq`, `\DeclarePairedDelimiter`, mat* envs
`bbm` (+ `bbm-macros`)	`\mathbbm{1}` blackboard-bold double-struck

Graphics, color, drawing

Package	What it gives you
`graphics`, `graphicx`	`\includegraphics{file.pdf}`
`graphics-def`	Engine-specific driver definitions
`color`, `xcolor` (via `graphics-def`)	Named colors, color models
`graphpap`	Graph paper backgrounds
`pgf`	Full PGF — basic drawing primitives
`tikz`	Full TikZ — high-level drawing language
`pgfarrows`, `pgfautomata`, `pgfcalendar`	TikZ libraries (arrow tips, automata, calendar)
`pgfbase{image,layers,matrix,patterns,plot,shapes,snakes}`	TikZ base modules
`pgfcomp-version-{0-65,1-18}`	PGF version-compatibility shims
`pdfescape`, `pdftexcmds`	pdftex string-escape helpers (hyperref dep)

Layout, sectioning, page geometry

Package	What it gives you
`geometry`	`\geometry{a4paper, margin=2cm}`
`setspace`	`\onehalfspacing`, `\doublespacing`
`fancyhdr`	Custom headers/footers (`\fancyhead`, `\fancyfoot`)
`fancyheadings`	Legacy precursor (kept for old docs)
`microtype`	Character protrusion + font expansion → tighter, better-looking paragraphs
`booktabs`	Pro-quality tables: `\toprule`, `\midrule`, `\bottomrule`
`float`	Custom float types via `\newfloat`, `[H]` placement
`listings`	Source-code listings with language syntax highlighting
`enumitem`	Customizable `enumerate` / `itemize` / `description`
`caption`, `caption2`, `caption3`, `subcaption`, `bicaption`, `ltcaption`	Float caption customization
`nohyperref`	Disable hyperref for one section

Hyperlinks, cross-references, bookmarks

Package	What it gives you
`hyperref`	`\href`, `\url`, clickable refs/cites, PDF bookmarks/metadata
`cleveref`	`\cref{eq:foo}` → "equation (3)" (auto-types references)
`refcount`, `etoolbox`, `letltxmacro`	hyperref deps + general macro plumbing
`hypcap`	Anchors at the top of floats, not the caption
`backref`	Back-references from bibliography to citing pages
`atbegshi`, `atveryend`, `auxhook`	Engine event hooks used by hyperref

Bibliography (limited)

Only bibtex (8-bit legacy) reachable in-process. Pre-compile .bbl for modern bibliography:

backref for back-refs in PDFs (clickable from bib entry to citing page)
Native \bibliography{file} works if a pre-built .bbl is present

CJK + Unicode

Package	What it gives you
`CJK`, `CJKutf8`	Chinese/Japanese/Korean (Type1 fonts, UTF-8 encoding)
`CJKnumb`	CJK numeral conversion
`CJKfntef`, `CJKulem`	CJK accent/underline support
`CJKspace`, `CJKvert`	CJK line-spacing, vertical writing
`MULEenc`	Multi-language encoding

(For full Unicode beyond CJK Type1, use CodeBench's busytex+xelatex path.)

Fonts

What	Detail
Latin Modern Type 1	92 `.pfb` font files, 596 `.tfm` metrics
Roman	`lmroman10-{regular,italic,bold,bolditalic,slanted,smallcaps,demi}` + 5/6/7/8/9/12/17pt design sizes
Sans	`lmsans10-{regular,italic,bold,boldoblique,demicondensed}` + design sizes
Mono	`lmmono10-{regular,italic,bold,boldoblique,slanted}` + `lmmonoltcond`
Caps	`lmromancaps10`, `lmromandunh10` (demi unslanted)
`lmodern.sty`	Selects Latin Modern as the default family
`fontenc` (T1)	8-bit T1 encoding
`inputenc`	Reads UTF-8 source
`t1enc`	Legacy T1 encoding shim

Slides (full beamer)

Module	What it does
`beamer.cls`	The main beamer class
`beamerarticle`	Render beamer source as article output
`beamerbase{article,auxtemplates,boxes,color,compatibility,decode,font,frame}`	beamer's internal modules — needed for any non-trivial use
Beamer themes (Default, Boadilla, AnnArbor, Berkeley, etc.)	Pre-set color + layout themes for slides

\documentclass{beamer} with frames, transitions, overlays, themes — all working in-process, no internet, no missing-package errors.

Engine plumbing (not user-facing, but needed)

Package	Purpose
`expl3` / `l3kernel`	Modern LaTeX3 programming layer (~1.3 MB)
`firstaid`	Compatibility patches for older / conflicting packages
`etoolbox`	General-purpose macro plumbing (used everywhere)
`fp`	Fixed-point arithmetic
`tools` package set	`multicol`, `xspace`, `array`, `dcolumn`, `tabularx`, `varioref`
`array`, `array-2016-10-06`	Extended column types for tables
`afterpage`	Defer commands to after current page break
`alltt`	Verbatim-like block with active commands

Hyphenation

English + many other languages in tex/plain/hyphenation/.

Format compatibility shims

Several packages have date-suffixed copies so older documents that reference a specific version still work:

amsmath-2018-12-01.sty
array-2016-10-06.sty
graphics-2017-06-25.sty

Looking up whether a specific package is bundled

From the in-app Python shell:

import os, glob
texmf = "/path/to/texmf"   # see LaTeXEngine.shared.texmfPath
hits = glob.glob(f"{texmf}/**/PACKAGENAME.sty", recursive=True)
print(hits or "not bundled")

Or from the CodeBench terminal:

find /path/to/texmf -name "PACKAGENAME.sty"

If the search returns nothing AND you can't easily rewrite the document to avoid it, two options:

Drop the missing .sty into your document's directory — kpathsea searches the source directory first.
For CodeBench specifically, the busytex-WASM path has a much larger TeX Live overlay (offlinai-texmf adds ~23 MB on top of ubuntu-texlive-{latex-base,latex-recommended,fonts-recommended, latex-extra,science}). Switch via the OFFLINAI_LATEX_ENGINE=busytex env var.

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LaTeXEngine

When to add this target

What's bundled

Pure-Swift usage

Python usage (via offlinai_latex)

Manim integration

What's INCLUDED in texmf

What's NOT included

Limitations

Troubleshooting

`! LaTeX Error: File 'amsmath.sty' not found.`

`! Undefined control sequence. l.5 \maketitle`

`! pdfTeX error: pdflatex: format file 'latex.fmt' not found.`

Output PDF is blank

Compilation hangs

Build provenance

Bundled package inventory

Document classes (17)

Math + AMS

Graphics, color, drawing

Layout, sectioning, page geometry

Hyperlinks, cross-references, bookmarks

Bibliography (limited)

CJK + Unicode

Fonts

Slides (full beamer)

Engine plumbing (not user-facing, but needed)

Hyphenation

Format compatibility shims

Looking up whether a specific package is bundled

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latex-engine.md

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latex-engine.md

File metadata and controls

LaTeXEngine

When to add this target

What's bundled

Pure-Swift usage

Python usage (via offlinai_latex)

Manim integration

What's INCLUDED in texmf

What's NOT included

Limitations

Troubleshooting

! LaTeX Error: File 'amsmath.sty' not found.

! Undefined control sequence. l.5 \maketitle

! pdfTeX error: pdflatex: format file 'latex.fmt' not found.

Output PDF is blank

Compilation hangs

Build provenance

Bundled package inventory

Document classes (17)

Math + AMS

Graphics, color, drawing

Layout, sectioning, page geometry

Hyperlinks, cross-references, bookmarks

Bibliography (limited)

CJK + Unicode

Fonts

Slides (full beamer)

Engine plumbing (not user-facing, but needed)

Hyphenation

Format compatibility shims

Looking up whether a specific package is bundled

`! LaTeX Error: File 'amsmath.sty' not found.`

`! Undefined control sequence. l.5 \maketitle`

`! pdfTeX error: pdflatex: format file 'latex.fmt' not found.`