AskashaCMS "built-in" plugin documentation - Foundational support for constructing any HTML

AkashaRender includes a "built-in" plugin with custom tags useful for any target use. The AkashaCMS toolchain supports rendering both websites and EPUB's, and could support rendering for other target uses of HTML. The EPUB format includes constraints where, while EPUB3 uses HTML5, a sizeable list of HTML5 features are not allowed. Both the built-in plugin and the akashacms-base plugin both aspire to provide features useful to everyone, the latter includes those features useful only for websites, whereas the built-in plugin features are useful for everyone.

Installation and Configuration

There's nothing to do, the built-in plugin is, well, built-in to AkashaRender.

Simplification for figure/img tags

This construct is recommended in the HTML5 world for its microformat goodness

<figure>
<img src="an-image.jpg"/>
<figcaption>Image caption</figcaption>
</figure>

While you can surely write these tags yourself, the <fig-img> tag offers a simplification.

<fig-img href="an-image.jpg" 
        class="class-name" 
        id="id-name" 
        style="...CSS..." 
        width="...width..." 
        template="template-partial.html.ejs">
Optional caption text
</fig-img>

Using the default template (ak_figimg.html.ejs) the tag converts into the structure shown above. The attributes are interpreted as so:

  • class is added as a class attribute to the <figure>
  • id is added as a id attribute to the <figure>
  • style is added as a style attribute to the <figure>
  • width is added as a width attribute to the <figure>
  • template overrides the default template

Create figure/img constructs from images

We have a tag <fig-img> to aid constructing the combination of a <figure> containing an <img>. But after some time of using that tag it seems better to use the <img> tag, and add attributes to control the construction of the figure/img construct.

To trigger this behavior include the figure property on the image.

<img id="change1" figure src="img/Human-Skeleton.jpg">

With the figure property, we replace the <img> with a <figure> containing an <img>.

The recognized attributes are:

  • id becomes the id of the <figure>
  • class becomes the class of the <figure>
  • width becomes the width of the <figure>
  • style becomes the style of the <figure>
  • dest becomes an <a> tag surrounding the <img> within the <figure>
  • caption becomes a <figcaption> tag within the <figure>

This is processed through the ak_figimg.html.ejs template just as for <fig-img>.

Resizing images

Sometimes you want to store a full-size image in the documents directory, but the deployed website will use a reasonable size image for web browsers. For example a marketing department might provide highly detailed product images accompanying a press release, but of course it is useful to keep images to 100-300kb for delivery on a public website.

For this purpose a filter exists to resize images. This feature may be extended in the future to include general image manipulation.

It is triggered by adding a resize-width property to an <img>. The value of this property declares the width of the resulting image in pixels. The image height is automatically calculated to maintain the same width/height scale (e.g. a 600x400 image resized to 300 width would be 200 pixels high).

The usage is as follows:

<img id="resizeto150" 
        src="img/Human-Skeleton.jpg"
        resize-width="150"
        resize-to="img/Human-Skeleton-150.jpg">

The recognized properties are:

  • src The file within the documents or assets directories that is copied into the render output
  • resize-to The file name used within the render output directory
  • resize-width The resulting image width as discussed above.

In the rendered HTML, if resize-to is given, the src attribute of the <img> will be rewritten to the value of the resize-to attribute.

The rendered version of this tag will be:

<img id="resizeto150" src="img/Human-Skeleton-150.jpg">

The resize-width and resize-to attributes are removed in the final output.

<img id="png2jpg"  src="rss_button.png" resize-width="50" resize-to="rss_button.jpg">

In this case the image type in src differs from resize-to. In this case an image format conversion is performed.

Stylesheets

The <ak-stylesheets> tag generates links to CSS stylesheets, as declared in config.js or in the document metadata.

In config.js add something like this:

config
    .addStylesheet({ href: "/vendor/bootstrap/css/bootstrap.min.css" })
    .addStylesheet({ href: "/vendor/bootstrap/css/bootstrap-theme.min.css" })
    .addStylesheet({ href: "/vendor/bootswatch-readable/bootstrap.min.css" })
    .addStylesheet({ href: "/style.css" });

The options include the href option shown here, and media to declare the media type. These correspond to these attributes

<link rel="stylesheet" type="text/css" href="${style.href}" media="${style.media}"/>

In document metadata include this for per-page stylesheets:

---
...
headerStylesheetsAdd:
  - href: "/vendor/bootstrap/css/bootstrap.min.css"
  - href: "/style-for-this-page.css"
...
---

JavaScript

JavaScript tags can be added either at the top of the page, in the <head> section, or at the bottom of the page, depending on your preferences. AkashaRender supports declaring the JavaScript files to be put in which section.

Place the <ak-headerJavaScript> tag where you want header JavaScript to appear, and the <ak-footerJavaScript> tag where you want the footer JavaScript to appear.

In config.js add something like this:

config
    .addFooterJavaScript({ href: "/vendor/jquery/jquery.min.js" })
    .addFooterJavaScript({ href: "/vendor/bootstrap/js/bootstrap.min.js"  })

Substitute Header for Footer and the JavaScript will appear in the <head> section.

The object can contain these fields:

  • lang (optional) specifies the language of the script, corresponding to the type= attribute
  • href corresponds to the src= attribute
  • script becomes an in-line JavaScript placed within the <script>..</script> tag

It is not allowed to have both href and script fields.

To specify these on a per-document basis in the metadata:

---
...
headerJavaScriptAddTop:
  - href: "/vendor/jquery/jquery.min.js"
  - href: "/vendor/bootstrap/js/bootstrap.min.js"
...
---

This specifies JavaScript at the top of the page, use headerJavaScriptAddBottom for JavaScript at the bottom of the page.

Teaser content

Some writers swear by creating a teaser for every document. The idea is a small bit of text teasing the reader to go ahead and read the whole document.

The <ak-teaser> tag supports inserting the content of a teaser metadata object. It uses the ak_teaser.html.ejs partial to do so.

Embedding code snippets from files in the document directory

Sometimes we want to embed code snippets. While Markdown makes this easy, we could also have code in files and then embed the files. To do that:

<code-embed file-name='path/to/file.ext' lang='lang-code'></code-embed>

The file-name argument must be either a relative path, or absolute path, within a documents directory. Relative path's are computed relative to the file this is within.

The lang argument is refers to what language code is to be used with this file. For example css for a CSS file.

Not shown is the id argument that creates an id in the output code.

This element is integrates with the (www.npmjs.com) Highlight.js library and therefore the lang codes must be from their list of supported programming languages.

The contents of the file must be textual for this to work. That's because the file contents will be inserted into the output wrapped within this structure:

<pre id='id'>
<code class='lang'>
... CONTENTS OF FILE
</code>
</pre>

Clearly for this to work correctly the file must have textual content.

Select N elements from a group

Sometimes you want to randomly select one or more elements from a group of items. Consider:

<select-elements id='advert-group'>
    <div><div id='advert1'>... HTML for advert 1</div></div>
    <div><div id='advert2'>... HTML for advert 2</div></div>
    <div><div id='advert3'>... HTML for advert 3</div></div>
    <div><div id='advert4'>... HTML for advert 4</div></div>
</select-elements>

The idea is to support displaying only one of them, selecting at random the child to display.

It selects among the direct children which element or elements to display. The outer element for the child is discarded, and only its contents are displayed in the output HTML. For example the result of the above example might be:

<div id='advert-group'><div id='advert3'>... HTML for advert 3</div></div>

The attributes accepted by select-elements are:

  • id - The ID value to use on the outputted HTML element
  • class - The class value to use on the outputted HTML element
  • count - The number of child elements to display - defaults to 1

Anchor tag cleanups

This feature automagically fixes <a> tags, referencing a local document, and which lack text or an image. Normally an empty tag would show up as nothing in the web browser. AkashaRender makes it into something useful.

It reads the metadata of the referenced document, and inserts that documents title as the anchor text.

For example the code <a href="/hello-world.html"></a> might be rewritten to: <a href="/hello-world.html">Hello, world!</a>. If you're using Markdown the equivalent works: [](/hello-world.html) because Markdown converts that to a normal <a> tag.

The URL passed in the href attribute should of course be the URL of the rendered file. You might have created a file hello-world.html.md which is then rendered to hello-world.html. The link of course needs to reference the rendered file even though the metadata is in the source file. AkashaRender figures out which is which under the covers.

Relative local URL's versus absolute local URL's

It is encouraged to write your content using absolute local URL's like:

<a href="/index.html"></a>
<img src="/images/logo.jpg">
<link rel="stylesheet" type="text/css" href="/vendor/bootstrap/css/bootstrap.min.css">
<script src="/vendor/jquery/jquery.min.js">

But for deployment this has a couple issues:

  • If the content is to be rendered as an EPUB all URL's must be relative, and therefore we must rewrite the URL's
  • If the content is deployed to a subdirectory .. that is, if config.root_url is something like http://example.com/path/to/subdir/ .. the URL's must be rewritten either to include the subdirectory, or to be relative

For the purpose of deployment to a subdirectory, rewriting the URL's to include the subdirectory made it difficult to preview the site using a local web server. That is, if the above is rewritten to:

<a href="/path/to/subdir/index.html"></a>
<img src="/path/to/subdir/images/logo.jpg">
<link rel="stylesheet" type="text/css" href="/path/to/subdir/vendor/bootstrap/css/bootstrap.min.css">
<script src="/path/to/subdir/vendor/jquery/jquery.min.js">

And then we run a local webserver to preview the rendered site, none of these links will work. The biggest problem is CSS and JavaScript for theming will not load.

As a result the built-in plugin now rewrites those to use relative links instead of absolute links.