# Natural display engine with TeX syntax for fx-9860G and fx-CG 50

This library is a customizable 2D math rendering tool for calculators. It can be used to render 2D formulae, either from an existing structure or TeX syntax.

```latex
\frac{x^7 \left[X,Y\right] + 3\left|\frac{A}{B}\right>}
     {\left\{\frac{a_k+b_k}{k!}\right\}^5}
+ \int_a^b \frac{\left(b-t\right)^{n+1}}{n!} dt
+ \left(\begin{matrix} \frac{1}{2} & 5 \\ -1 & a+b \end{matrix}\right)
```

![Sample image](https://www.planet-casio.com/files/forums/TeX-13737.png)

## Features

* Build formulae from TeX syntax or using the structural API
* Highly-customizable graphical and layout parameters
* Drawing uses only a few user primitives (point, line, text size, text)
* Compatible with fxlib and gint

List of currently supported elements:

* Fractions (`\frac`)
* Subscripts and superscripts (`_` and `^`)
* Grouping parentheses, brackets, and braces (`\left` and `\right`)
* Grouping angle brackets, vertical lines, and dots (invisible)
* Sums, products and integrals (`\sum`, `\prod` and `\int`)
* Vectors (`\vec`) and limits (`\lim`)
* Square roots (`\sqrt`)
* Matrices (`\begin{matrix} ... \end{matrix}`)

Features that are partially implemented (and what is left to finish them):

* Support for inline style and display style (expose a parameter)
* Theme that can decently port to fx-CG 50 (suitable parenthesis styles)

See the `TODO.md` file for more features to come.

## Building

First specify the platform you want to use :

* `cli` is for command-line tests, with no visualization (PC)
* `sdl2` is an SDL interface with visualization (PC)
* `fx9860g` builds the library for fx-9860G targets (calculator)
* `fxcg50` builds the library for fx-CG 50 targets (calculator)

For calculator platforms, you can use `--toolchain` to specify a different toolchain than the default `sh3eb` and `sh4eb`. The install directory of the library is guessed by asking the compiler, you can override it with `--prefix`.

Example for an SDL setup:

```sh
% ./configure --platform=sdl2
```

Then you can make the program, and if it's a calculator library, install it. You can later delete `Makefile.cfg` to reset the configuration, or just reconfigure as needed.

```sh
% make
% make install # fx9860g and fxcg50 only
```

## Using in a program

Before using the library in a program, a configuration step is needed. The library does not have drawing functions and instead requires that you provide some, namely:

* Draw a pixel (`TeX_intf_pixel`)
* Draw a line (`TeX_intf_line`)
* Compute the size occupied by a string (`TeX_intf_size`)
* Render a string (`TeX_intf_text`)

The three rendering functions are available in fxlib; for monospaced fonts the fourth can be implemented trivially. In gint, the four can be defined as wrappers for `dpixel()`, `dline()`, `dsize()` and `dtext()`.

The type of formulae is `TeX_Env`. To parse and compute the size of a formula, use the `TeX_parse()` function, which returns a new formula object (or `NULL` if a critical error occurs). The second parameter `display` is set to non-zero to use display mode (similar to `\[ .. \]` in LaTeX) or zero to use inline mode (similar to `$ .. $` in LaTeX).

```c
char *code = "\\frac{x_7}{\\left\\{\\frac{\\frac{2}{3}}{27}\\right\\}^2}";
struct TeX_Env *formula = TeX_parse(code, 1);
```

The size of the formula can be queried through `formula->width` and `formula->height`. To render, specify the location of the top-left corner and the drawing color (which will be passed to all primitives):

```c
TeX_draw(formula, 0, 0, BLACK);
```

The same formula can be drawn several times. When it is no longer needed, free it with `TeX_free()`:

```c
TeX_free(formula);
```