Bookdown runs plain-PHP templates through Aura.View, using Aura.Html helpers, to render HTML pages.
The default templates are located in the core Bookdown library; you can see them at {$REPO}/_bookdown/vendor/bookdown/bookdown/templates/. The project-specific override templates are located in the {$REPO}/_bookdown/templates directory.
You can override the default templates individiually or entirely to control Bookdown output. To do so:
Copy the template you want to override from {$REPO}/_bookdown/vendor/bookdown/bookdown/templates/ to {$REPO}/_bookdown/templates.
Modify the project-specific main.php template to point to the override version.
Edit the override template as you see fit.
Regenerate the HTML.
For example, let's modify the navheader.php template.
First, we copy the default template to the project-specific template location:
cd {$REPO}/_bookdown
cp vendor/bookdown/templates/navheader.php templates/navheader.php
Next, we open the project-specific copy of main.php and point to the new navheader.php location. Change the line that reads ...
$templates->set("navheader", "{$library}/navheader.php");
... to:
$templates->set("navheader", "{$project}/navheader.php");
(Note that $library and $project are defined at the top of main.php.)
Then we edit the navheader.php template and change it to whatever we like. Try something obvious, like replacing all the HTML and PHP code with <p>HI THERE</p>.
Finally, regenerate the HTML. You should see HI THERE at the top of every page, but no navigation elements at all.
If you like, you can point Bookdown to a completely different master template. In the root bookdown.json config file, specify a "template" value as the path to your new master PHP template:
{
...
"template": "../my-master.php"
}
That template will be passed through an Aura.View instance.
You can also completely rewrite the existing templates/main.php template to whatever you like.
In some cases, you may find it necessary to temporarily override the template value from the top-level bookdown.json file. To do so, you can specify --template= when invoking the bookdown command:
./vendor/bin/bookdown book/bookdown.json --template=../../other-template.php