ModeMath 0.9.0

ModeMath

Mathematical formula display and editing for .NET, rendered with SkiaSharp.

A formula is an MA: a tree of what is written, not of what it means. Layout places one at a font size, and Painter draws what was placed onto an SKCanvas.

open ModeMath

let formula =
    match Latex.Read @"\frac{-b \pm \sqrt{b^2 - 4ac}}{2a}" with
    | Ok ma -> ma
    | Error error -> failwith error.Message

let placed = (Layout 24f<px>).Of formula
use painter = Painter.Embedded()
painter.Draw(placed, canvas, 0f<px>, placed.Ascent, paint)

examples/ shows what renders, a picture of each formula against its name and size. The formulas themselves are in tools/RenderExamples/Examples.fs.

Editing

Editor holds a formula with a cursor in it, and the states it stood at before. Press answers whether the key was wanted, leaving a caller free to pass on the ones it turns down, and Undo and Redo step through the edits, a run of characters going in one go.

let editor = Editor(Layout 24f<px>, MA.Empty)

for key in [ MathKey.Character 'x'; MathKey.Superscript; MathKey.Character '2' ] do
    editor.Press key |> ignore

editor.Click(x, y)

let bounds = editor.State.Bounds
painter.Draw(editor.State.Cursor, canvas, -bounds.X, bounds.Y + bounds.Thickness, paint)

A formula with a cursor in it is placed by its Bounds rather than by what it draws, since the cursor stands where no atom does: at either end of the line, and above a numerator or below a denominator. They hold both, and hold still as the cursor moves through the formula.

EditorState is the value underneath: every key answers with a new state rather than changing this one, so a caller that would rather keep its own history holds whichever states it likes.

An opening bracket is drawn faint until its closing one is typed, a run of letters spelling a name becomes what it names — a function, the radical sqrt opens, or the mark degree gives — and a formula can be built from MA directly instead.

LaTeX

Latex.Read takes a math-mode string and Latex.Write gives one back, every argument in braces. What is not understood is refused with the position it stands at, rather than guessed at, and a character the font cannot draw is refused there too, so a formula that was read always lays out. One built from MA in code can hold a character the font has no glyph for, and MA.Undrawable is the characters it would fail on.

\color and \textcolor name their colours from a Palette, which a caller may replace to give a name a colour of its own.

let palette = Palette.Default.With("green", Color.FromArgb(255, 130, 212, 20))
let formula = Latex.Read(@"\color{green}{x}", palette)

Fonts

Latin Modern Math, cut down to the glyphs ModeMath draws, and AMS Capital Blackboard Bold are carried inside the assembly along with the licences they are redistributed under. fonts/README.md says where each came from and how the metrics beside them are generated.

Acknowledgements

ModeMath is inspired by CSharpMath. Most of the formulas in examples/ are taken from its rendering tests, and the typesetting is checked against those. ModeMath has no plan to work with any text outside of math mode, so for a LaTeX renderer that includes both text and maths you should use CSharpMath.

Licence

MIT, in LICENSE. The two fonts keep their own: the GUST Font Licence and the SIL Open Font Licence, both carried in fonts/.