Hi Ludo,

On Mon, 13 Apr 2020 15:56:22 +0200
Ludovic Courtès <ludo@gnu.org> wrote:

> > when you mouse-over the function name line, a
> > "permalink to this definition" appears.  
> 
> I’m not sure how to do that.  Isn’t there some JavaScript involved?

The CSS selector ":hover" selects the block only when you are hovering over it:

a[name] img {
  display: none;
}

a[name]:hover img {
  display: inline;
}

Used like that:

<p><a name="anchor1">with class <img src="a.png"></a>
...</p>