Font Stash

Font Stash is a light-weight online font texture atlas builder written in Go. It is a pure Go port of the C library fontstash by Mikko Mononen.

It uses golang.org/x/image/font and golang.org/x/image/font/opentype to render fonts on demand to a texture atlas, replacing the original stb_truetype dependency.

Screenshot

This screenshot was generated by the example program in cmd/example/.

Features

• Pure Go implementation (no Cgo).
• Uses standard Go font libraries.
• Immediate mode text rendering API.
• Texture atlas packing (Skyline Bin Packer).
• Backend agnostic (implement Renderer interface).
• Unicode support via Go's rune.

Example

A complete runnable example with a software renderer (outputting to PNG) is available in cmd/example/.

To run the example:

go run cmd/example/main.go

Basic Usage

package main

import (
	"fmt"
	"image"
	"log"

	"github.com/arran4/go-fontstash/fontstash"
)

type MyRenderer struct {
	// ... backend specific fields (e.g. OpenGL texture ID)
}

func (r *MyRenderer) Resize(width, height int) {
	fmt.Printf("Resize atlas to %dx%d\n", width, height)
	// Create or resize texture
}

func (r *MyRenderer) Update(rect image.Rectangle, data []byte, imgWidth int) {
	fmt.Printf("Update atlas rect %v\n", rect)
	// Update texture subimage
}

func (r *MyRenderer) Draw(verts []fontstash.Vertex) {
	fmt.Printf("Draw %d vertices\n", len(verts))
	// Render triangles
}

func main() {
	fs, err := fontstash.New(fontstash.Params{
		Width:  512,
		Height: 512,
		Renderer: &MyRenderer{},
	})
	if err != nil {
		log.Fatal(err)
	}

	// Load font (returns index)
	fontNormal, err := fs.AddFont("sans", "DroidSerif-Regular.ttf")
	if err != nil {
		log.Fatal(err)
	}

	fs.SetFont(fontNormal)
	fs.SetSize(24.0)
	fs.SetColor(0xffffffff) // RGBA packed

	fs.DrawText(10, 10, "Hello Font Stash!")
}

License

The library is licensed under zlib license.