Name    : glfont Library                      
Author  : Noah Shibley, http://socialhardware.net                       
Date    : June 16th 2016                                 
Notes   : A modern opengl text rendering library for golang
Dependencies:   freetype, go-gl, glfw

Function List:

func LoadFont

func LoadFont(file string, scale int32, windowWidth int, windowHeight int) (*Font, error)

LoadFont loads the specified font at the given scale. The default character set is ASCII (codepoints 32 to 127).

func LoadTrueTypeFont

func LoadTrueTypeFont(program uint32, r io.Reader, scale int32, low, high rune, dir Direction) (*Font, error)

LoadTrueTypeFont builds buffers and textures based on a ttf files gylphs.

func LoadFontBytes

func LoadFontBytes(buf []byte, scale int32, windowWidth int, windowHeight int) (*Font, error) {

LoadFontBytes loads font directly from bytes (such as goregulat.TTF, https://pkg.go.dev/golang.org/x/image/font/gofont/goregular ) at the given scale. The default character set is ASCII (codepoints 32 to 127).

func (*Font) GenerateGlyphs

func (f *Font) GenerateGlyphs(low, high rune) error

GenerateGlyphs builds additional glyphs for non-ASCII Unicode codepoints.

func (*Font) Printf

func (f *Font) Printf(x, y float32, scale float32, fs string, argv ...interface{}) error

Printf draws a string to the screen, takes a list of arguments like printf

func (*Font) SetColor

func (f *Font) SetColor(red float32, green float32, blue float32, alpha float32)

SetColor allows you to set the text color to be used when you draw the text

func (f *Font) UpdateResolution

func (f *Font) UpdateResolution(windowWidth int, windowHeight int)

UpdateResolution is needed when the viewport is resized

func (f *Font) Width

func (f *Font) Width(scale float32, fs string, argv ...interface{}) float32

Width returns the width of a piece of text in pixels

Example:

package main

import (
	"fmt"
	"log"
	"runtime"

	"github.com/go-gl/gl/all-core/gl"
	"github.com/go-gl/glfw/v3.1/glfw"
	"github.com/nullboundary/glfont"
)

const windowWidth = 1920
const windowHeight = 1080

func init() {
	runtime.LockOSThread()
}

func main() {

	if err := glfw.Init(); err != nil {
		log.Fatalln("failed to initialize glfw:", err)
	}
	defer glfw.Terminate()

	glfw.WindowHint(glfw.Resizable, glfw.True)
	glfw.WindowHint(glfw.ContextVersionMajor, 3)
	glfw.WindowHint(glfw.ContextVersionMinor, 2)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)

	window, _ := glfw.CreateWindow(int(windowWidth), int(windowHeight), "glfontExample", glfw.GetPrimaryMonitor(), nil)

	window.MakeContextCurrent()
	glfw.SwapInterval(1)
	
	if err := gl.Init(); err != nil { 
		panic(err)
	}

	//load font (fontfile, font scale, window width, window height
	font, err := glfont.LoadFont("Roboto-Light.ttf", int32(52), windowWidth, windowHeight)
	if err != nil {
		log.Panicf("LoadFont: %v", err)
	}

	gl.Enable(gl.DEPTH_TEST)
	gl.DepthFunc(gl.LESS)
	gl.ClearColor(0.0, 0.0, 0.0, 0.0)

	for !window.ShouldClose() {
		gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

     //set color and draw text
		font.SetColor(1.0, 1.0, 1.0, 1.0) //r,g,b,a font color
		font.Printf(100, 100, 1.0, "Lorem ipsum dolor sit amet, consectetur adipiscing elit.") //x,y,scale,string,printf args

		window.SwapBuffers()
		glfw.PollEvents()

	}
}

nullboundary / glfont