gio/apps/hello/hello.go

// SPDX-License-Identifier: Unlicense OR MIT

package main

// A simple Gio program. See https://gioui.org for more information.

import (
	"image"
	"image/color"
	"log"

	"gioui.org/ui"
	"gioui.org/ui/app"
	"gioui.org/ui/layout"
	"gioui.org/ui/measure"
	"gioui.org/ui/text"

	"golang.org/x/image/font/gofont/goregular"
	"golang.org/x/image/font/sfnt"
)

func main() {
	// Never called on mobile, blocks forever on
	// desktop.
	app.Main()
}

// On iOS and Android main will never be called, so
// setting up the window must run in an init function.
func init() {
	regular, err := sfnt.Parse(goregular.TTF)
	if err != nil {
		panic("failed to load font")
	}
	var faces measure.Faces
	black := &image.Uniform{color.Black}
	face := faces.For(regular, ui.Dp(50))
	// On iOS and Android app.NewWindow blocks, waiting
	// for the platform to create a window.
	go func() {
		w, err := app.NewWindow(nil)
		if err != nil {
			log.Fatal(err)
		}
		for w.IsAlive() {
			e := <-w.Events()
			switch e := e.(type) {
			case app.Draw:
				faces.Cfg = e.Config
				cs := layout.ExactConstraints(w.Size())
				root, _ := (text.Label{Src: black, Face: face, Text: "Hello, World!"}).Layout(cs)
				w.Draw(root)
				faces.Frame()
			}
			w.Ack()
		}
		if w.Err() != nil {
			log.Fatal(err)
		}
	}()
}