How to load inline SVG in Go using GOTK3 and librsvg?

php editor Youzi will introduce how to use GOTK3 and librsvg to load inline SVG in Go language. GOTK3 is a Go language binding library for creating cross-platform GUI applications, while librsvg is a library for rendering SVG images. By using these two libraries together, we can easily load and display inline SVG images in Go language. Next, let’s take a look at the specific implementation steps!

Question content

I am developing an application written in go. It uses gotk3, librsvg is installed, and I can create (and then display) svg images using gtk.imagenewfromfile(file-path-to-svg).

Now I want to programmatically create an image from an svg inline in the source code... like this:

color := "#FF0000"
redSvg := 
  "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n" +
  "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n" +
  "<svg version=\"1.1\" id=\"Layer_1\" xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" x=\"0px\" y=\"0px\" width=\"32px\" height=\"32px\" viewBox=\"0 0 32 32\" enable-background=\"new 0 0 32 32\" xml:space=\"preserve\">\n" +
  "    <rect fill=\"" + color + "\" width=\"32\" height=\"32\"/>\n" +
  "</svg>"

image, err := ImageNewFromSvg(redSvg)
.
.
.


func ImageNewFromSvg(svg string) (*gtk.Image, error) {
  ?
}

...I need some help with the implementation of imagenewfromsvg(). gotk3 doesn't have imagenewfromsvg() api, but it does have imagenewfrompixbuf().

I tried creating a pixbuf from a string (with svg tag) but I couldn't do it.

Is it possible to create an image from an inline svg defined in source code? If so, what is the implementation of imagenewfromsvg()?

Workaround

You can use gdk.pixbufnewfromdataonly to load an inline svg by passing it the svg string as a byte fragment and then get the pixbuf from it and Put it into gtk.imagenewfrompixbuf to get *gtk.image to use it in the window. This is one of the correct implementations of the imagenewfromsvg function you mentioned:

func imagenewfromsvg(svg string) (*gtk.image, error){
  pixbuf, err := gdk.pixbufnewfromdataonly([]byte(svg))
  if err !=  nil {
    return nil, err
  }
  
  img, err := gtk.imagenewfrompixbuf(pixbuf)
  
  if err !=  nil {
    return nil, err
  }
  
  return img, nil
}

Usage examples in actual gtk programs:

package main

import (
    "log"

    "github.com/gotk3/gotk3/gtk"
    "github.com/gotk3/gotk3/gdk"
)

func main() {
    gtk.Init(nil)

    win, err := gtk.WindowNew(gtk.WINDOW_TOPLEVEL)
    if err != nil {
        log.Fatal("Unable to create window:", err)
    }
    win.SetTitle("Svg Example")
    win.Connect("destroy", func() {
        gtk.MainQuit()
    })


    color := "#FF0000"
    svgdata := "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n" +
               "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n" +
               "<svg version=\"1.1\" id=\"Layer_1\" xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" x=\"0px\" y=\"0px\" width=\"32px\" height=\"32px\" viewBox=\"0 0 32 32\" enable-background=\"new 0 0 32 32\" xml:space=\"preserve\">\n" +
               "    <rect fill=\"" + color + "\" width=\"32\" height=\"32\"/>\n" +
               "</svg>"

    svgImage, err  := ImageNewFromSvg(svgdata)
    
    if err != nil {
        log.Fatal(err)
    }
    
    win.Add(svgImage)
    win.ShowAll()


    gtk.Main()
}  

func ImageNewFromSvg(svg string) (*gtk.Image, error){
  pixbuf, err := gdk.PixbufNewFromDataOnly([]byte(svg))
  if err !=  nil {
    return nil, err
  }
  
  img, err := gtk.ImageNewFromPixbuf(pixbuf)
  
  if err !=  nil {
    return nil, err
  }
  
  return img, nil
}

Output:

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