Getting started

limu turns Mermaid text into a scene, which records what each part of a diagram is and where it goes. A backend then draws the scene. This page uses the svg package, which needs only Go’s standard library, as limu itself does. To draw diagrams natively instead, see MyGo.

Installing

limu needs Go 1.27 or later.

go get github.com/firede/limu

Drawing a diagram

limu.Layout reads a diagram and lays it out, and svg.Render writes the resulting scene as an SVG document.

package mainimport (	"fmt"	"log"	"github.com/firede/limu"	"github.com/firede/limu/style"	"github.com/firede/limu/svg")func main() {	sc, err := limu.Layout(`flowchart LR  text[Mermaid text] --> layout[Layout] --> scene[Scene]`, nil)	if err != nil {		log.Fatal(err)	}	fmt.Println(svg.Render(sc, &svg.Options{		Look:       style.Look{Theme: style.Kohu()},		FontFamily: "Arial, Helvetica, sans-serif",	}))}

By default, layout measures text with text.Arial, a table of Arial’s character widths, so the SVG should set its text in Arial or a font of the same width. If you draw text in other fonts, measure it with those fonts instead. See Measuring text.

The theme sets the diagram’s colors. The svg package writes them as CSS variables with the theme’s colors as fallbacks, so a page can change them without rendering the diagram again. See Theming.

Errors

When limu can’t read a diagram, limu.Layout returns a *diagram.Error. Its Code says whether the type is unsupported, the text doesn’t parse, or the text is over a limit. Line and Column give the position when there is one.

sc, err := limu.Layout(src, nil)var derr *diagram.Errorif errors.As(err, &derr) {	fmt.Printf("%s at line %d: %s\n", derr.Code, derr.Line, derr.Message)}

Error messages can quote the diagram’s text, so display them as text rather than markup.

Fitting a width

Set layout.Options.MaxWidth to the width you have. Diagrams that can get narrower will, so a wide flowchart may switch from running across to running down. Diagrams that can’t get narrower keep the width they need.

sc, err := limu.Layout(src, &layout.Options{MaxWidth: 480})

The SVG is the size of the scene. To let a page scale it down further, give it max-width: 100% and height: auto in CSS.

Laying out again

If you lay out the same diagram more than once, for example when the available width changes, parse it once with limu.Parse and call Layout on the result as often as you need. Layout doesn’t change the parsed diagram, so it’s safe to call from several goroutines at once.

d, err := limu.Parse(src, diagram.Options{})if err != nil {	return err}wide, err := d.Layout(&layout.Options{MaxWidth: 640})narrow, err := d.Layout(&layout.Options{MaxWidth: 320})

Changing the theme doesn’t need a new layout at all. Draw the same scene in the new theme.

Diagram types

limu supports every diagram type that Pele draws, which covers every type built into Mermaid. limu.Types lists them. limu.Supports checks a text’s declared type without parsing the rest.

if !limu.Supports(src) {	// Show the text as code instead.}

Examples shows each type, and Compatibility lists the keywords that declare them.

Next steps

• API covers parsing and layout options, limits and the scene.
• Theming covers themes, per-role overrides and custom drawing.
• MyGo draws diagrams natively and finds the part under the pointer.
• SVG covers CSS variables, classes and untrusted diagrams.