vggio

Documentation

Overview

Package vggio provides a vg.Canvas implementation backed by Gioui.

Index

• Constants
• func UseBackgroundColor(c color.Color) option
• func UseDPI(dpi int) option
• type Canvas
  • func New(gtx layout.Context, w, h vg.Length, opts ...option) *Canvas
  • func (c *Canvas) Paint(e system.FrameEvent)

Examples

• Canvas

Constants

const DefaultDPI = 96

DefaultDPI is the default dot resolution for image drawing in dots per inch.

Functions

func UseBackgroundColor

func UseBackgroundColor(c color.Color) option

UseBackgroundColor specifies the image background color. Without UseBackgroundColor, the default color is white.

func UseDPI

func UseDPI(dpi int) option

UseDPI sets the dots per inch of a canvas. It should only be used as an option argument when initializing a new canvas.

Types

type Canvas

type Canvas struct {
	*vgimg.Canvas
	// contains filtered or unexported fields
}

Canvas implements the vg.Canvas interface, drawing to an image.Image using vgimg and painting that image into a Gioui context.

Example

package main

import (
	"log"
	"os"
	"time"

	"gioui.org/app"
	"gioui.org/io/key"
	"gioui.org/io/system"
	"gioui.org/layout"
	"gioui.org/op"
	"gioui.org/unit"

	"gonum.org/v1/plot"
	"gonum.org/v1/plot/vg"
	"gonum.org/v1/plot/vg/draw"
	"gonum.org/v1/plot/vg/vggio"
)

func main() {
	const (
		w   = 20 * vg.Centimeter
		h   = 15 * vg.Centimeter
		dpi = 96
	)
	go func(w, h vg.Length) {
		win := app.NewWindow(
			app.Title("Gonum"),
			app.Size(
				unit.Px(float32(w.Dots(dpi))),
				unit.Px(float32(h.Dots(dpi))),
			),
		)
		defer win.Close()

		done := time.NewTimer(2 * time.Second)
		defer done.Stop()

		for {
			select {
			case e := <-win.Events():
				switch e := e.(type) {
				case system.FrameEvent:
					p, err := plot.New()
					if err != nil {
						log.Fatalf("could not create plot: %+v", err)
					}
					p.Title.Text = "My title"
					p.X.Label.Text = "X"
					p.Y.Label.Text = "Y"

					gtx := layout.NewContext(new(op.Ops), e)
					cnv := vggio.New(gtx, w, h, vggio.UseDPI(dpi))
					p.Draw(draw.New(cnv))
					cnv.Paint(e)

				case system.DestroyEvent:
					os.Exit(0)

				case key.Event:
					switch e.Name {
					case "Q", key.NameEscape:
						os.Exit(0)
					}
				}
			case <-done.C:
				os.Exit(0)
			}
		}
	}(w, h)

	app.Main()

}

func New

func New(gtx layout.Context, w, h vg.Length, opts ...option) *Canvas

New returns a new image canvas with the provided dimensions and options. The currently accepted options are UseDPI and UseBackgroundColor. If the resolution or background color are not specified, defaults are used.

func (*Canvas) Paint

func (c *Canvas) Paint(e system.FrameEvent)

Paint paints the canvas' content on the screen.