Text and maths

[charlesroddie]

Tracking progress towards creating TeX views allowing both maths and text.

I can start on this when there is a skiasharp view. This project will also depend on inline maths support. Currently I believe only display maths is supported.

[charlesroddie]

TODO

• A. Check Inline maths suport and allow specifying a default (display or inline), either when converting a latex string into an atom, or an atom into a box.
• B. Parse a string representing text including latex. This should be parsed into a list of words, spaces, paragraph breaks, and latex maths (display or inline).
• C. Add syntax for styling, including color.

B and C can be here or in a separate repo. I can help with B and C if they are done in F#.

[Happypig375]

A. According to Stack Overflow,
Inline maths = Small operator symbols and limits side-set for all operators
Display maths = Large operator symbols and for \sum, \prod, \coprod, etc: Limits set above and below operator, for \int: Limits are set to the side of integral symbol
The first behaviour is what \textstyle does, and the second one is what \displaystyle does.
The default behaviour is already configurable by setting the LineStyle property to LineStyle.Text and LineStyle.Display respectively.

> Documentation of LineStyle <

B. Do you mean parsing text out of math? Something like Text \(Inline + Maths\) \[Dsiplay - Maths\] Text? That certainly would be something great to support.

C. Color is supported via the TextColor property and can be overridden with the \color command. Its usage is: \color{HEX}{TEXT}, e.g. \color{#FF0000}{red text}. More styles are also supported, e.g. \mathrm. I will have to write documentation about that.

[charlesroddie]

B. Yes, so getting something equivalent to MathJax.

I am thinking that the input would be parsed into a TextAndMath, where:

type Span =
    | Text of string
    | Math of Atom
    | Space
    | ParagraphBreak

type TextAndMath = Span list

To put in styles like color, we could do:

type Style = {
    FontSize: float
    Italic: bool
    Bold: bool
    Color: System.Drawing.Color }

type TextAndMath = (Span * Style) list

Then for example "Lorem ip<red>sum</red> $2+2=5$." would get parsed into

[
    Text "Lorem", defaultStyle
    Space, defaultStyle
    Text "ip", defaultStyle
    Text "sum", redStyle
    Space, defaultStyle
    Math ..., defaultStyle
    Text "."
]

Thoughts?

[charlesroddie]

Default reflowing is pretty easy if we mimic default web behaviour. Just put in as many groups of non-separator elements as can fit into each line. Word processors are more advanced than this, allowing intra-word line breaks, but we don't need that in v1.

[Happypig375]

I will look into Typography.TextBreak etc. since those projects seem to do automatic line breaks.
Maybe we can even support these via new "math" atom types instead of entirely new types because text like these are basically non-math mode LaTeX.

[charlesroddie]

@Happypig375 I will look into Typography.TextBreak etc. since those projects seem to do automatic line breaks.

Great.

Maybe we can even support these via new "math" atom types instead of entirely new types because text like these are basically non-math mode LaTeX.

I don't think the new types are really atoms. A paragraph break, for example, can't go inside an atom in a math formula, as far as I'm aware. LaTeX as a whole is huge and it makes sense to have a self-contained component that just deals with the math part, with a layer on top to deal with ordinary text.

[Happypig375]

@charlesroddie Today I thought about this a bit more.
Under the current CSharpMath architecture, there are four stages of math rendering:
LaTeX -> math atoms -> math displays -> draw operations

(Math atoms vs math displays: atoms are logically separated, e.g. (sqrt)(2)(space)(+)(3), and displays are given positions and widths, ready to be drawn.)

Maybe we can break only when constructing the math displays since the drawing positions are calculated at that stage. There won't be paragraph breaks embedded in the atoms themselves but will be auto-inserted when constructing the displays since the drawing bounds will be known at that time. Thoughts?

[Happypig375]

I am currently implementing LaTeX spacing commands to e.g. support ~, the non-breaking space.

[charlesroddie]

The ability of math displays to break and reflow is not part of LaTeX, and not even implemented by extensions. It would add a lot of complexity to the math atom -> math display function, which would also need extra inputs to be aware of page width. And it doesn't solve the basic problem of allowing for paragraphs with reflowing text.

A more orthodox approach, which just uses the three methods above without changing them, would be quite easy to implement. I can sketch this when I next have a bit of time.

[Happypig375]

However, LaTeX text commands will not be supported (in the current LaTeX -> math atoms converter, the \text command is supported, which I thought that some of it can be reused.)

[charlesroddie]

The \text command embeds text in math mode. It doesn't leave math mode. Within math mode, it can't reflow. It should be easy to verify this in any latex system.

[Happypig375]

Wow! You are right! I haven't thought about this before. So okay, these two will be separated 😉