go-fltk

---

A simple wrapper around FLTK 1.4 library, which is a lightweight GUI library which allows creating small, self-contained and fast gui applications.

Requirements

In addition to Go, you will also need a C++11 compiler. The FLTK libraries are bundled with the repo for x86_64 Linux, MacOS and Windows (mingw64). You also need some system libs which are normally available on operating systems with a graphical user interfaces:

• Windows: No external dependencies (for mingw64)
• MacOS: No external dependencies
• Linux: You need:
  • x11
  • Xrender
  • Xcursor
  • Xfixes
  • Xext
  • Xft
  • Xinerama
  • OpenGL

Usage

package main

import "github.com/pwiecz/go-fltk"

func main() {
    win := fltk.NewWindow(400, 300)
    win.SetLabel("Main Window")
    btn := fltk.NewButton(160, 200, 80, 30, "Click")
    btn.SetCallback(func() {
        btn.SetLabel("Clicked")
    })
    win.End()
    win.Show()
    fltk.Run()
}

Widgets are created using the fltk.New<WidgetType> functions, modified for whatever widget you're instantiating. Function and method names resemble the original C++ names, while however, following the Golang convention of PascalCase. Setter methods are also preceded by a Set prefix.

Styling

FLTk offers 4 builtin schemes:

• base (default)
• gtk+
• gleam
• plastic These can be set using fltk.SetScheme("gtk+") for example.

FLTK also allows custom styling of your widgets:

package main

import (
	"strconv"

	"github.com/pwiecz/go-fltk"
)

// FLTK uses an RGBI color representation, the I is an index into FLTK's color map
// Passing 00 as I will use the RGB part of the value
const GRAY = 0x75757500
const LIGHT_GRAY = 0xeeeeee00
const BLUE = 0x42A5F500
const SEL_BLUE = 0x2196F300
const WIDTH = 600
const HEIGHT = 400

func main() {
	curr := 0
	fltk.InitStyles()
	win := fltk.NewWindow(WIDTH, HEIGHT)
	win.SetLabel("Flutter-like")
	win.SetColor(fltk.WHITE)
	bar := fltk.NewBox(fltk.FLAT_BOX, 0, 0, WIDTH, 60, "    FLTK App!")
	bar.SetDrawHandler(func() { // Shadow under the bar
		fltk.DrawBox(fltk.FLAT_BOX, 0, 0, WIDTH, 63, LIGHT_GRAY)
	})
	bar.SetAlign(fltk.ALIGN_INSIDE | fltk.ALIGN_LEFT)
	bar.SetLabelColor(255) // this uses the index into the color map, here it's white
	bar.SetColor(BLUE)
	bar.SetLabelSize(22)
	text := fltk.NewBox(fltk.NO_BOX, 250, 180, 100, 40, "You have pushed the button this many times:")
	text.SetLabelSize(18)
	text.SetLabelFont(fltk.TIMES)
	count := fltk.NewBox(fltk.NO_BOX, 250, 180+40, 100, 40, "0")
	count.SetLabelSize(36)
	count.SetLabelColor(GRAY)
	btn := fltk.NewButton(WIDTH-100, HEIGHT-100, 60, 60, "@+6plus") // this translates into a plus sign
	btn.SetColor(BLUE)
	btn.SetSelectionColor(SEL_BLUE)
	btn.SetLabelColor(255)
	btn.SetBox(fltk.OFLAT_BOX)
	btn.ClearVisibleFocus()
	btn.SetCallback(func() {
		curr += 1
		count.SetLabel(strconv.Itoa(curr))
	})
	win.End()
	win.Show()
	fltk.Run()
}

Label attributes can be seen here

Image support

FLTK supports vector and raster graphics, via several image types:

• SvgImage
• RgbImage
• JpegImage
• PngImage
• BmpImage
• SharedImage

Some of these can be instantiated from an image file or from data:

package main

import (
	"fmt"

	"github.com/pwiecz/go-fltk"
)

func main() {
	win := fltk.NewWindow(400, 300)
	box := fltk.NewBox(fltk.FLAT_BOX, 0, 0, 400, 300, "")
	image, err := fltk.NewJpegImageLoad("image.jpg")
	if err != nil {
		fmt.Printf("An error occured: %s\n", err)
	} else {
		box.SetImage(image)
	}
	win.End()
	win.Show()
	fltk.Run()
}

Resources

• Link to the official FLTK 1.4 documentation.
• Link to go-fltk documentation.