KristofferC / MathTeXEngine.jl

A latex math mode engine in pure Julia.

MathTeXEngine

This is a package aimed at providing a pure Julia engine for LaTeX math mode. It is composed of two main parts: a LaTeX parser and a LaTeX engine, both only for LaTeX math mode.

Main features

• Parsing of (possibly nested) LaTeX expression and creation of a layout for them.
• Equivalence between traditional LaTeX commands and their unicode input equivalent.
• Pure julia.

Engine

The main use of the package is through generate_tex_elements taking a LaTeX string as input and return a list of tuples (TeXElement, position, scale) where TeXElement is one of the following:

• TeXChar(char, font) a unicode character to be displayed in a specific font.
• VLine(height, thickness) a vertical line.
• HLine(width, thickness) an horizontal line.

This contains enough information to then draw everything with any plotting package that can draw arbitrary glyph in arbitrary font. The position is the origin of the character according to FreeType.

Positions and scales are given for a font size of 1. For bigger font size they simply need to be multiplied by the font size.

The engine should support every construction the parser does (see below).

Currently the only font set supported is Computer Modern.

Engine examples

Basic examples

julia> using MathTeXEngine

julia> generate_tex_elements(L"\beta_2")
2-element Vector{Any}:
 (TeXChar 'β' [U+00AF in cmmi10 - Regular], [0.0, 0.0], 1.0)
 (TeXChar '2' [U+0032 in cmr10 - Regular], [0.56494140625, -0.20000000298023224], 0.6)

The L"..." macro is reexported from LaTeXStrings.jl and used to convey the information that we want the given string to be interpreted as LaTeX. Note that since we are using Computer Modern, which is a pre-unicode font family, the characters are distributed across a bunch of different fonts.

Also note that Unicode character can be used directly and are equivalent to their command.

julia> generate_tex_elements(L"β_2")
2-element Vector{Any}:
 (TeXChar 'β' [U+00AF in cmmi10 - Regular], [0.0, 0.0], 1.0)
 (TeXChar '2' [U+0032 in cmr10 - Regular], [0.56494140625, -0.20000000298023224], 0.6)

Using the inline math mode with $...$ is supported. However, currently, line breaks or line wraps are not.

julia> generate_tex_elements(L"b $β_2$")
4-element Vector{Any}:
 (TeXChar 'b' [U+0062 in cmr10 - Regular], [0.0, 0.0], 1.0)
 (TeXChar ' ' [U+0020 in cmr10 - Regular], [0.55517578125, 0.0], 1.0)
 (TeXChar 'β' [U+00AF in cmmi10 - Regular], [0.88818359375, 0.0], 1.0)
 (TeXChar '2' [U+0032 in cmr10 - Regular], [1.453125, -0.20000000298023224], 0.6)

VLine and Hline

Some LaTeX constructs, mainly square roots and fractions generate additional lines that are not representing a character. The HLine or VLine object contain all information needed to draw the line correctly.

julia> elements = generate_tex_elements(L"\frac{1}{2}")
3-element Vector{Any}:
 (HLine{Float64}(0.614990234375, 0.009765625), [0.0, 0.210693359375], 1.0)
 (TeXChar '1' [U+0031 in cmr10 - Regular], [0.1405029296875, 0.42626953125], 1.0)
 (TeXChar '2' [U+0032 in cmr10 - Regular], [0.1077880859375, -0.6708984375], 1.0)

julia> hline = elements[1][1]
HLine{Float64}(0.614990234375, 0.009765625)

julia> hline.width
0.614990234375

julia> hline.thickness
0.009765625

Nested expressions

A flat list is always returned even if the LaTeX expression is deeply nested.

julia> generate_tex_elements(L"A_{B_{C_D}}")
4-element Vector{Any}:
 (TeXChar 'A' [U+0041 in cmmi10 - Regular], [0.0, 0.0], 1.0)
 (TeXChar 'B' [U+0042 in cmmi10 - Regular], [0.75, -0.20000000298023224], 0.6)
 (TeXChar 'C' [U+0043 in cmmi10 - Regular], [1.2046875, -0.3200000047683716], 0.36)
 (TeXChar 'D' [U+0044 in cmmi10 - Regular], [1.4616796874999998, -0.3920000058412552], 0.216)

Parser

Parsing is done through the exported function texparse into nested TeXExpr objects forming a tree. The parser does not perform any operation to layout the elements, it only transforms them into a syntax tree.

The readme file in the src/parser folder contains more details about the inner working of the parser.

Supported constructions

The table below contains the list of all supported LaTeX construction and their representation when parsed.

Description	LaTeX example	Expression head	Fields
Accent	\vec{v}	:accent	symbol, core
Char	x	:char
Digit	3	:digit
Delimiter	\left( \right)	:delimited	left_delimiter, content, right_delimiter
Fraction	\frac{}{}	:frac	numerator, denumerator
Function	\sin	:function	name
Generic symbol	ω	:symbol	unicode_char
Group	{ }	:group	elements...
Inline math	$ $	:inline_math	content
Integral	\int_a^b	:integral	symbol, low_bound, high_bound
Math fonts	\mathrm{}	:font	font_modifier, expr
Punctuation	!	:punctuation
Simple delimiter	(	:delimiter
Square root	\sqrt{2}	:sqrt	content
Space	\quad	:space	width
Spaced symbol	+	:spaced	symbol
Subscript and superscript	x_0^2	:decorated	core, subscript, superscript
Symbol with script under and/or over it	\sum_i^k	:underover	symbol, under, over

Parser examples

Basic examples

julia> texparse(raw"\beta_2")
TeXExpr :expr        
└─ TeXExpr :decorated
   ├─ TeXExpr :symbol
   │  └─ 'β'
   ├─ TeXExpr :digit
   │  └─ '2'
   └─ nothing

The Unicode input are supported at the parser level.

julia> expr = texparse(raw"β_2")
TeXExpr :expr
└─ TeXExpr :decorated
   ├─ TeXExpr :symbol
   │  └─ 'β'
   ├─ TeXExpr :digit
   │  └─ '2'
   └─ nothing

TeXExpr have the same head - args structure as the built-in Expr.

julia> expr.args[1].head
:decorated

julia> expr.args[1].args
3-element Vector{Any}:
 TeXExpr :symbol
└─ 'β'

 TeXExpr :digit
└─ '2'

 nothing

Acknowledgement

The font inspector site FontDrop! has been invaluable for this package.