Embedding Gemini capsules into a forum post

Why not utilize an ability to provide a custom renderer to do some arbitrary requests on the backend? Let’s get Gemini client and just parse the GMI contents just into a code block.

You can follow the following tutorial to find out how to implement your custom renderer for vpub-plus: https://vpub.mysh.dev/topics/17

Code

We will create custom RenderNode implementation from blackfriday.Renderer to find our gemini link in the forum post and then do something with it.

As for gemini client, we will use Gemax:

type geminiLinkRenderer struct {
	blackfriday.Renderer
}

func (r *geminiLinkRenderer) RenderNode(
	w io.Writer,
	node *blackfriday.Node,
	entering bool,
) blackfriday.WalkStatus {
	if node.Type != blackfriday.Text {
		return r.Renderer.RenderNode(w, node, entering)
	}

	if !bytes.HasPrefix(node.Literal, []byte("gemini://")) {
		return r.Renderer.RenderNode(w, node, entering)
	}

	node.Type = blackfriday.CodeBlock

	cl := gemax.Client{}
	resp, err := cl.Fetch(context.Background(), string(node.Literal))
	if err != nil {
		node.Literal = []byte("Errored when tried to fetch gemini site: " + err.Error())
		return r.Renderer.RenderNode(w, node, entering)
	}

	data, err := io.ReadAll(resp)
	if err != nil {
		node.Literal = []byte("Errored when tried to read from gemax client reader: " + err.Error())
		return r.Renderer.RenderNode(w, node, entering)
	}

	node.Literal = data
	return r.Renderer.RenderNode(w, node, entering)
}

[... somewhere in there is an embed into a renderer ...]

And this is what we ended up with:

Funny. I wonder how it would look like if we transform GMI into HTML nodes?

Last edited on 2026-03-08 11:48:29

After some more experimentation, I think this might be not that crazy of an idea. Stylize it a little bit, actually render gemtext into HTML and this start to look interesting.

Maybe I can add some sort of embed system in place for developers to use? Or maybe not.

Last edited on 2026-03-08 09:58:05