For developers

Anatomy of an edition

<slug>/index.html      the viewer
<slug>/book.json       everything the viewer knows about the edition
<slug>/search.json     the text of each page
<slug>/pages/…         the page images, named with a random string
<slug>/thumbs/…        the thumbnails
<slug>/assets/…        viewer files, copied in
<slug>/<name>.pdf      the file offered for download
<slug>/teaser.json     the shortened description for preview mode

Nothing in there points back into TYPO3. Copy the directory to another server and it runs there — that is the point of the whole construction.

book.json carries title, slug, language, page count, labels, table of contents, colours, flipping behaviour, the list of controls and the pages themselves. An add-on package can put more in there; the viewer ignores what it does not know.

Extension points

The build dispatches four events, the backend module three. They are the seam along which nt_flippdf_pro is attached — and along which anything else can be.

Event	When	Good for
BeforeBuildEvent	before the run	change the settings, even the slug
AfterPagesRenderedEvent	pages rendered, nothing derived yet	change the page images or their number
BeforeBookWrittenEvent	before book.json is written	add anything the viewer should know
AfterBuildEvent	the edition is in place	put something beside it
ModuleFormEvent	the module renders a form	add form sections
ModuleSaveEvent	the module builds or saves	add settings
ModuleColumnsEvent	the module lists editions	add columns

AfterPagesRenderedEvent carries a list saying which page of the source PDF a book page came from. Without it, text and links would drift apart the moment the number of pages changes — which is what happens when double pages are split.

An example

final class MeinListener
{
    public function __invoke(BeforeBookWrittenEvent $ereignis): void
    {
        $buch = $ereignis->getBuch();
        $buch['theme']['accent'] = '#ec6602';
        $ereignis->setBuch($buch);
    }
}

services:
  Vendor\Ext\EventListener\MeinListener:
    tags:
      - name: event.listener
        event: Netthinks\NtFlippdf\Event\BeforeBookWrittenEvent

Building blocks

For an add-on that wants to put a second edition beside the first, a few methods of FlipbookBuilder are public: writeViewer(), swapDirectory(), clearDir(), directoryBytes() and sanitizeSlug().

Counting

The base package does not count. nt_flippdf_pro writes an address into book.json, the viewer pings it on a view, a download or a click on a link — without a cookie and without any identity of the reader, aggregated per day.