The Structure

Themes are located in the themes folder where Nikola is installed, and in the themes folder of your site, one folder per theme. The folder name is the theme name.

A Nikola theme consists of the following folders (they are all optional):

assets

This is where you would put your CSS, JavaScript and image files. It will be copied into output/assets when you build the site, and the templates will contain references to them. The default subdirectories are css, js, xml and fonts (Bootstrap).

The included themes use Bootstrap, Colorbox, Flowr.js and Moment.js, so they are in assets, along with CSS files for syntax highlighting, reStructuredText and Jupyter, as well as a minified copy of jQuery.

If you want to base your theme on other frameworks (or on no framework at all) just remember to put there everything you need for deployment. (Not all of the listed assets are used by base)

templates

This contains the templates used to generate the pages. While Nikola will use a certain set of template names by default, you can add others for specific parts of your site.

messages

Nikola tries to be multilingual. This is where you put the strings for your theme so that it can be translated into other languages.

less, sass

Files to be compiled into CSS using LESS and Sass (both require plugins)

This mandatory file:

parent

A text file that, on its first line, contains the name of the parent theme. Any resources missing on this theme, will be looked up in the parent theme (and then in the grandparent, etc).

The parent is so you don’t have to create a full theme each time: just create an empty theme, set the parent, and add the bits you want modified. You must define a parent, otherwise many features won’t work due to missing templates, messages, and assets.

I recommend this:

• If your theme uses Bootstrap 3, inherit the bootstrap3 theme.
• If your theme uses Jinja as a template engine, inherit base-jinja or bootstrap3-jinja
• In any other case, inherit base.

And these optional files:

engine

A text file which, on the first line, contains the name of the template engine this theme needs. Currently supported values are "mako" and "jinja". You must create this file if you’re using Jinja2; otherwise, it’s optional.

bundles

A text file containing a list of files to be turned into bundles using WebAssets. For example:

assets/css/all.css=bootstrap.css,rst.css,code.css,colorbox.css,custom.css

This creates a file called "assets/css/all.css" in your output that is the combination of all the other file paths, relative to the output file. This makes the page much more efficient because it avoids multiple connections to the server, at the cost of some extra difficult debugging.

WebAssets supports bundling CSS and JS files.

Templates should use either the bundle or the individual files based on the use_bundles variable, which in turn is set by the USE_BUNDLES option.

Templates

In templates there is a number of files whose name ends in .tmpl. Those are the theme’s page templates. They are done using the Mako or Jinja2 template languages. If you want to do a theme, you should learn one first. What engine is used by the theme is declared in the engine file.

Both template engines have a nifty concept of template inheritance. That means that, a template can inherit from another and only change small bits of the output. For example, base.tmpl defines the whole layout for a page but has only a placeholder for content so post.tmpl only define the content, and the layout is inherited from base.tmpl.

These are the templates that come with the included themes:

base.tmpl

This template defines the basic page layout for the site. It’s mostly plain HTML but defines a few blocks that can be re-defined by inheriting templates.

It has some separate pieces defined in base_helper.tmpl, base_header.tmpl and base_footer.tmpl so they can be easily overridden.

index.tmpl

Template used to render the multipost indexes. The posts are in a posts variable. Some functionality is in the index_helper.tmpl helper template.

annotation_helper.tmpl (internal)

Code for the optional annotations feature.

archive_navigation_helper.tmpl

Code that implements archive navigation (previous/up/next). Included by archive templates.

archiveindex.tmpl

Used to display archives, if ARCHIVES_ARE_INDEXES is True. By default, it just inherits index.tmpl, with added archive navigation and feeds.

author.tmpl

Used to display author pages.

authorindex.tmpl

Used to display author indexes, if AUTHOR_PAGES_ARE_INDEXES is True. By default, it just inherits index.tmpl, with added feeds.

comments_helper.tmpl (internal)

This template handles comments. You should probably never touch it :-) It uses a bunch of helper templates, one for each supported comment system (all of which start with comments_helper)

crumbs.tmpl, slides.tmpl, pagination_helper.tmpl

These templates help render specific UI items, and can be tweaked as needed.

gallery.tmpl

Template used for image galleries. Interesting data includes:

• post: A post object, containing descriptive post.text() for the gallery.
• crumbs: A list of link, crumb to implement breadcrumbs.
• folders: A list of folders to implement hierarchical gallery navigation.
• enable_comments: To enable/disable comments in galleries.
• thumbnail_size: The THUMBNAIL_SIZE option.
• photo_array: a list of dictionaries, each containing:
  • url: URL for the full-sized image.
  • url_thumb: URL for the thumbnail.
  • title: The title of the image.
  • size: A dict containing w and h, the real size of the thumbnail.
• photo_array_json: a JSON dump of photo_array, used in the bootstrap theme by flowr.js

list.tmpl

Template used to display generic lists of links, which it gets in items, a list of (text, link, count) elements.

list_post.tmpl

Template used to display generic lists of posts, which it gets in posts.

listing.tmpl

Used to display code listings.

math_helper.tmpl (internal)

Used to add MathJax/KaTeX code to pages.

post.tmpl

Template used by default for blog posts, gets the data in a post object which is an instance of the Post class. Some functionality is in the post_helper.tmpl and post_header.tmpl templates.

post_list_directive.tmpl

Template used by the post_list reStructuredText directive.

sectionindex.tmpl

Used to display section indexes, if POST_SECTIONS_ARE_INDEXES is True. By default, it just inherits index.tmpl, with added feeds.

story.tmpl

Used for pages that are not part of a blog, usually a cleaner, less intrusive layout than post.tmpl, but same parameters.

tag.tmpl

Used to show the contents of a single tag or category.

tagindex.tmpl

Used to show the contents of a single tag or category, if TAG_PAGES_ARE_INDEXES is True. By default, it just inherits index.tmpl, with added feeds and some extra features.

tags.tmpl

Used to display the list of tags and categories.

You can add other templates for specific pages, which the user can then use in his POSTS or PAGES option in conf.py. Also, keep in mind that your theme is yours, there is no reason why you would need to maintain the inheritance as it is, or not require whatever data you want (eg. you may depend on specific custom GLOBAL_CONTEXT variables, or post meta attributes)

Also, you can specify a custom template to be used by a post or page via the template metadata, and custom templates can be added in the templates/ folder of your site.

Variables available in templates

The full, complete list of variables available in templates is maintained in a separate document: Template variables

Customizing themes to user color preference and section colors

The user’s preference for theme color is exposed in templates as theme_color set in the THEME_COLOR option.

Each section has an assigned color that is either set by the user or auto selected by adjusting the hue of the user’s THEME_COLOR. The color is exposed in templates through post.section_color(lang). The function that generates the colors from strings and any given color (by section name and theme color for sections) is exposed through the colorize_str_from_base_color(string, hex_color) function

Hex color values, like that returned by the theme or section color can be altered in the HSL colorspace through the function color_hsl_adjust_hex(hex_string, adjust_h, adjust_s, adjust_l). Adjustments are given in values between 1.0 and -1.0. For example, the theme color can be made lighter using this code:

<!-- Mako -->
<span style="color: ${color_hsl_adjust_hex(theme_color, adjust_l=0.05)}">

<!-- Jinja2 -->
<span style="color: {{ color_hsl_adjust_hex(theme_color, adjust_l=0.05) }}">

Identifying and customizing different kinds of pages with a shared template

Nikola provides a pagekind in each template contexts that can be used to modify shared templates based on the context it’s being used. For example, the base_helper.tmpl is used in all pages, index.tmpl is used in many contexts and you may want to add or remove something from only one of these contexts.

Example of conditionally loading different resources on all index pages (archives, author pages, and tag pages), and others again to the front page and in every post pages:

<!-- Mako -->
<head>
    …
    % if 'index' in pagekind:
        <link href="/assets/css/multicolumn.css" rel="stylesheet">
    % endif
    % if 'front_page' in pagekind:
        <link href="/assets/css/fancy_homepage.css" rel="stylesheet">
        <script src="/assets/js/post_carousel.js"></script>
    % endif
    % if 'post_page' in pagekind:
        <link href="/assets/css/article.css" rel="stylesheet">
        <script src="/assets/js/comment_system.js"></script>
    % endif
</head>

<!-- Jinja2 -->
<head>
    …
    {% if 'index' in pagekind %}
        <link href="/assets/css/multicolumn.css" rel="stylesheet">
    {% endif %}
    {% if 'front_page' in pagekind %}
        <link href="/assets/css/fancy_homepage.css" rel="stylesheet">
        <script src="/assets/js/post_carousel.js"></script>
    {% endif %}
    {% if 'post_page' in pagekind %}
        <link href="/assets/css/article.css" rel="stylesheet">
        <script src="/assets/js/comment_system.js"></script>
    {% endif %}
</head>

Promoting visits to the front page when visiting other filtered index.tmpl page variants such as author pages and tag pages. This could have been included in index.tmpl or maybe in base.tmpl depending on what you want to achieve.

<!-- Mako -->
% if 'index' in pagekind:
    % if 'author_page' in pagekind:
        <p>These posts were written by ${author}. See posts by all
           authors on the <a href="/">front page</a>.</p>
    % elif 'tag_page' in pagekind:
        <p>This is a filtered selection of posts tagged “${tag}”, visit
           the <a href="/">front page</a> to see all posts.</p>
    % endif
% endif

<!-- Jinja2 -->
{% if 'index' in pagekind %}
    {% if 'author_page' in pagekind %}
        <p>These posts were written by {{ author }}. See posts by all
           authors on the <a href="/">front page</a>.</p>
    {% elif 'tag_page' in pagekind %}
        <p>This is a filtered selection of posts tagged “{{ tag }}”, visit
           the <a href="/">front page</a> to see all posts.</p>
    {% endif %}
{% endif %}

List of page kinds provided by default plugins:

• front_page
• index
• index, archive_page
• index, author_page
• index, main_index
• index, section_page
• index, tag_page
• list
• list, archive_page
• list, author_page
• list, section_page
• list, tag_page
• list, tags_page
• post_page
• page_page
• story_page
• listing
• generic_page
• gallery_front
• gallery_page

Messages and Translations

The included themes are translated into a variety of languages. You can add your own translation at https://www.transifex.com/projects/p/nikola/

If you want to create a theme that has new strings, and you want those strings to be translatable, then your theme will need a custom messages folder.

LESS and Sass

If you want to use those CSS extensions, you can — just store your files in the less or sass directory of your theme.

In order to have them work, you need to create a list of .less or .scss/.sass files to compile — the list should be in a file named targets in the respective directory (less/sass).

The files listed in the targets file will be passed to the respective compiler, which you have to install manually (lessc which comes from the Node.js package named less or sass from a Ruby package aptly named sass). Whatever the compiler outputs will be saved as a CSS file in your rendered site, with the .css extension.