Links

Chrome turns every <a href> it prints into a PDF link annotation, so anchors in your markup arrive as real clickable links without any work on your side. External URLs, mailto: addresses and in-page #anchor jumps all come through.

What decides whether they survive is which output path you use.

pages, err := doc.GetPdfPages(ctx)
if err != nil {
    return err
}
for _, p := range pages {
    if err := c.AddPage(p); err != nil {
        return err
    }
}

c.Draw drops them

Measured on a document with three anchors, an https URL, a mailto: and an in-page #top:

c.Draw wraps each rendered page with creator.NewBlockFromPage, which turns the page into a content stream. Annotations live beside the content stream rather than in it, so they are left behind. Nothing errors, and the failure is invisible until someone clicks.

Adding a document to a creator.Chapter uses the same machinery, so links are lost there too.

If the markup has links, use GetPdfPages or Document.WriteToFile. There is no way to keep them on the c.Draw path.

What comes through

That last row is the one to watch when converting a multi-file site. A relative link becomes a link to a relative path, and there is no other document for it to resolve against once the PDF is separated from the directory it came from. Turn cross-page links into in-page anchors before converting, or accept that they are dead.

Limitations

Link styling is CSS, not a PDF setting. The blue underline comes from the browser’s default stylesheet, so restyle it in the markup rather than looking for an API.

There is no way to add a link to a region of the rendered output afterwards from the UniHTML side. Once you hold []*model.PdfPage you can attach annotations with UniPDF’s model package, but you have to work out the coordinates yourself.

Anchors created by JavaScript after the DOM has loaded need wait for rendering, like any other late content.

Run the example

links/main.go converts link.html on A5, sets each margin with a different unit type, takes the pages with GetPdfPages, adds them to a creator, then sets the document’s author, title, subject and dates through UniPDF’s model package.

One wrinkle worth knowing: its SetMarginBottom(sizes.Inch(0.5)) rounds to zero on the wire, so the output has no bottom margin. See margins.

git clone https://github.com/unidoc/unihtml-examples.git
cd unihtml-examples/links
go run main.go localhost:8080

If this is your first time using UniHTML, follow the getting started guide to create an API key and set up your development environment.

Sample input

Sample output