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HTMLDecor means full separation of content from presentation. With CSS you can change the styling of a whole site with one stylesheet. With HTMLDecor you can change everything - banner, navbars, ads, page-layout and stylesheets. Not only is it simple to setup and maintain, you'll cut the download time of every page, plus "pushState assisted navi…

README.md

HTMLDecor

HTMLDecor means full separation of content from presentation. With CSS you can change the styling of a whole site with one stylesheet. With HTMLDecor you can change everything - banner, navbars, ads, page-layout and stylesheets. This facilitates API-first / HTML-payload sites which are simple, robust and low-bandwidth, plus "pushState assisted navigation" comes for free.

HTMLDecor is a Javascript page decoration engine which runs in the browser. It allows your site to deliver real page content first and fast (think API-first with HTML-payloads). Your site decor can be placed in its own page and merged in the browser instead of on the server. Auxiliary content could also be conditionally loaded with AJAX (think inside-out iframes).

A site decor page is similar to an external stylesheet in that it can be shared between several pages. Originally it was even referenced with a resource link, just like stylesheets:

<link rel="meeko-decor" type="text/html" href="decor.html" />

(This referencing method has been superceded by external configuration, which is less limiting.)

As a bonus, when your site uses HTMLDecor "pushState assisted navigation" requires no additional setup. When someone viewing your page clicks on a link to another page that uses the same decor then AJAX updates the real content and history.pushState() updates the browser URL.

HTMLDecor.js is around 10kB when minified and gzipped.

To see it in action visit my blog. Make sure you view the page source and check that it is just raw content. The navbar and contact popup are all in the site-decor page.

For more info on the concept of HTMLDecor and its affinity with pushState assisted navigation, read

Also make sure you check the wiki.

Installation

  1. Copy or clone the HTMLDecor project files to a directory on your server, say

    /path/to/HTMLDecor/
    
  2. Open a browser and navigate to the following page

    http://your.domain.com/path/to/HTMLDecor/test/normal.html
    

    Visually inspect the displayed page for the following possible failures:

    • boxes with red background or borders.
    • boxes that claim to be styled with colored borders but just have the default border.
  1. Source the HTMLDecor boot-script into your pages with this line in the <head> of each page

    `<script src="/path/to/HTMLDecor/boot.js"></script>`
    

    The boot-script

    • MUST be in the <head> of the page
    • MUST NOT have @async or @defer
    • SHOULD be before any stylesheets - <link rel="stylesheet" /> or <style>

Quick Start

This is no longer the preferred way of specifying decor, but is conceptually easiest to understand. If you are new to HTMLDecor then read this documentation straight through. Otherwise feel free to skip to the Configuration section first.

Create a HTML document (page.html) with some page specific content - elements that are children of <body> and have @id. Any page specific scripts, styles or meta-data should go in <head>. The <body> may also contain fallback content, which is only displayed if HTMLDecor is NOT enabled.

<!DOCTYPE html>
<html>
<head>
    <!-- source the HTMLDecor boot-script -->
    <script src="/path/to/HTMLDecor/boot.js"></script>
    <!-- create a link to the decor page. All attributes are needed -->
    <link rel="meeko-decor" type="text/html" href="decor.html" />
    <!-- include fallback stylesheets for when HTMLDecor doesn't run.
        @title=nodecor stylesheets are removed !-->
    <link rel="stylesheet" href="nodecor.css" title="nodecor" />
    <!-- page specific style -->
    <style>
    .styled-from-page { border: 2px dashed green; }
    </style>
</head>
<body>
    <header>
    This fallback content will be removed from the page
    </header>

    <article id="mk_content"><!-- Page specific content, identified by @id -->
    #mk_content in page
        <div class="styled-from-decor">
        This content is styled by the decor stylesheet
        </div>  
        <div class="styled-from-page">
        This content is styled by the page stylesheet
        </div>  
    </article>

    <footer>
    This fallback content will be removed from the page
    </footer>
</body>
</html>

Create the decor document (decor.html). This is a normal page of HTML that, when viewed in the browser, will appear as the final page without the page specific content.

<!DOCTYPE html>
<html>
<head>
    <style>
    .styled-from-decor { border: 2px solid blue; }
    </style>
</head>
<body>
    <header>
    #header in decor
    </header>

    <div id="mk_main">
        #mk_main in decor
        <article id="mk_content">
        #mk_content in decor: This will be replaced by #mk_content from the page
        </article>
    </div>

    <footer>
    #footer in decor
    </footer>
</body>
</html>

When page.html is loaded into the browser, HTMLDecor will merge decor.html into it, following these steps:

  1. Set the visibility of the page to "hidden". *
  2. Detect the first <link rel="meeko-decor" href="..." />, fully resolve the @href and use as the decor URL.
  3. Load the decor URL into an iframe.
  4. Fully resolve URLs for all scripts, images and links in the decor page.
  5. Insert <script>, <style>, <link>, and conditionally <meta> and <title> from the <head> of the decor page into the <head> of the content page.
  6. Insert the child nodes of the <body> of the decor page at the start of the <body> in the content page
  7. For each child node of the <body> in the content page, determine whether it should be deleted or moved into the decor. If a child node is an element with an ID, and the ID matches an element in the decor, then the element in the decor is replaced with the element from the content. All other child nodes of the body in the content page are deleted.
  8. When all linked stylesheets for the document have loaded, set the visibility of the page to "visible". This step may occur at any time during or after step 7. *

* Steps 1 & 8 are handled by the boot-script.

This process results in a DOM tree like this:

<!DOCTYPE html>
<html>
<head>
    <style>
    .styled-from-decor { border: 2px solid blue; }
    </style>
    <!-- create a link to the decor page -->
    <link rel="meeko-decor" type="text/html" href="decor.html" />
    <!-- and source the HTMLDecor boot-script -->
    <script src="/path/to/HTMLDecor/boot.js"></script>
    <!-- page specific style -->
    <style>
    .styled-from-page { border: 2px dashed green; }
    </style>
</head>
<body>
    <header>
    #header in decor
    </header>

    <div id="mk_main">
        #mk_main in decor
        <article id="mk_content">
        #mk_content in page
            <div class="styled-from-decor">
            This content is styled by the decor stylesheet
            </div>  
            <div class="styled-from-page">
            This content is styled by the page stylesheet
            </div>  
        </article>
    </div>

    <footer>
    #footer in decor
    </footer>
</body>
</html>

Fallbacks

Sometimes HTMLDecor will not be able to apply the decor document to the page. This can occur because

  • Javascript is disabled
  • the HTMLDecor script failed to download
  • HTMLDecor is configured to NOT autostart
  • the decor document failed to download

In this scenario you would like the page to have some basic styling and auxiliary content - something that can be dispensed with when HTMLDecor runs.

Stylesheets

Any <link rel="stylesheet"> or <style> elements that have @title="nodecor" will be removed from the page before the decor document is applied, e.g.

<style title="nodecor">body { max-width: 72ex; }</style>

NOTE: this is done in the default config.js. If you want to remove or modify this behavior then do so in your site-specific config.js.

Auxiliary content

Children of <body> which have no @id, or which have @id that cannot be found in the decor document will be removed from the page before the decor is applied, e.g.

<body>
    <div>
    This irrelevant content will be DEFINITELY REMOVED from the page
    because it has no @id
    </div>

    <div id="mk_irrelevant">
    This content will be REMOVED from the page
    assuming the decor has no element with matching @id
    </div>

    <div id="mk_content">
    This content will be RETAINED in the page
    assuming the decor has an element with matching @id
    </div>
</body> 

PushState Assisted Navigation

If history.pushState is available then HTMLDecor will conditionally over-ride the default browser behavior when hyperlinks are clicked. If the @href of the hyperlink is a document that specifies the same decor as the current page then it can be merged into the current page in a similar way to the startup merging of decor and document.

Some hyperlinks are not appropriate for this and are ignored by HTMLDecor:

  • hyperlinks to pages on other sites
  • hyperlinks with a different protocol, e.g. javascript:..., ftp:
  • hyperlinks that target a different window or iframe, e.g.

        <a href="some_page.html" target="_blank">...</a>
    
  • anchor hyperlinks - <a href="#skip">

That leaves hyperlinks to other pages within the same site.

If a decor lookup function has been registered then HTMLDecor queries what the decor of the hyperlinked page would be. If it is the same as the current decor then the page is downloaded and used to replace the real content of the current page.

Otherwise normal browser navigation to the next page is triggered.

Note that the HTMLDecor click handling can always be prevented by calling event.preventDefault().

"PushState Assisted Navigation" (PAN) may sometimes be referred to as panning, as in camera panning.

Page Transition Animation

To enable author supplied animation of page transitions, HTMLDecor provides the Meeko.panner.config() method. You could use it by placing something like the following in your decor document

Meeko.panner.config({
    duration: 0, // minimum time (ms) between paging start and end. 
    nodeRemoved: {
        before: hide, // handler for before a content node leaves the page. Called at start of transition.
        after: show // handler for after a content node leaves the page. Cannot be called before duration has expired. 
    },
    nodeInserted: {
        before: hide, // handler for before a node enters the page, after the new url has been downloaded.
        after: show // handler for after a node enters the page. Called after a delay to allow styles set by `before` to be applied. 
    },
    pageOut: {
        before: noop,
        after: noop
    },
    pageIn: {
        before: noop, // indicates that the decor is ready for content to be placed. This would allow decor to be mutated in url dependent way
        after: noop // the equivalent of `window.onload` in non-pushstate enabled environments.
    }
});

function hide(msg) { msg.node.setAttribute("hidden", "hidden"); }
function show(msg) { msg.node.removeAttribute("hidden"); }
function noop() {}

These are actually the options set by the default config.js, so there's no need to repeat these settings. The method can be called at anytime. Key / value pairs in the passed options object overwrite the matching previous settings.

NOTE There is not always a notification after pageOut. For instance, if the next page is ready before the transition duration has expired then the new nodes replace the old nodes directly, rather than transitioning through the decor placeholders.

Example: A simple way to achieve a fade-out / fade-in effect on page transition is to use the following in the decor document:

<script>
Meeko.panner.config({
    duration: 500 // allows our fade-out to complete
});
</script>
<style>
#mk_content { /\* assuming #mk_content is the page-specific content \*/
    -webkit-transition: opacity 0.5s linear;
    -moz-transition: opacity 0.5s linear;
    -ms-transition: opacity 0.5s linear;
    -o-transition: opacity 0.5s linear;
    transition: opacity 0.5s linear;
}
#mk_content[hidden] {
    display: block;
    visibility: visible;
    opacity: 0;
}
</style>

Example: If your pages rely on @class on the <body> or <html> elements, the following will install them in the view-document when the page is panned in:

<script>
Meeko.panner.config({
    pageIn: {
        before: function(msg) {
            var doc = msg.node;
            if (document == doc) return;
            document.documentElement.className = doc.documentElement.className;
            document.body.className = doc.body.className;
        }
    }
});
</script>

Waiting Indicators

If a new page takes longer than one second to load, the user may wonder if the loading has stalled. In this case a waiting indicator is typically used to reassure the user that the page is still loading. HTMLDecor provides a simple way to do this - when the duration has expired (and the next page still hasn't loaded) the decor document is used as the waiting page.

Manual handling

You can stop HTMLDecor handling hyperlink clicks by calling event.preventDefault() in a click handler, e.g.

document.onclick = function(event) { event.preventDefault(); }

You can also request HTMLDecor to navigate manually to a new URL by the following:

Meeko.panner.assign(newURL)

or with history.replaceState() behavior:

Meeko.panner.replace(newURL)

<form> handling

HTMLDecor ONLY handles forms where @method="GET".

All other forms are NOT handled, which means the native browser behavior will apply unless external code prevents the default-action and implements a different behavior.

You are encouraged to handle other forms in a site-specific manner.

@method = GET

The form's @action and input values are processed to generate a query URL which is then used to perform pushState assisted navigaion. This mimics standard browser behavior.

<script> handling

  • Scripts in the landing-page are not handled by HTMLDecor - they execute at the expected time in the browser's script handling. RECOMMENDATION: The page does not need and SHOULD NOT have scripts - they SHOULD all be part of the decor.

  • All scripts which are not in the landing-page (that is, decor content or panned page content) are executed via dynamic script insertion, but behave like scripts that are part of the page content. Page content is not blocked, but earlier scripts block later scripts unless the earlier script has the src and async attributes.

    <script src="..." async></script>

This dynamic script insertion is referred to as enabling in the following rules.

  • Scripts in the <head> of the decor are enabled AFTER all the content in the <head> of the decor is MERGED WITH the page.

  • Scripts in the <body> of the decor are enabled AFTER all the content in the <body> of the decor is INSERTED INTO the page, but BEFORE the page content is MERGED WITH the decor.

  • When panning occurs, scripts in the <head> of the next page are enabled AFTER all the content in the <head> of the next page is MERGED WITH the page. Scripts in the <body> of the next page are enabled AFTER the content in the <body> of the next page is MERGED WITH the page. RECOMMENDATION: You do not need and SHOULD NOT have scripts in any page (other than the decor document).

Capturing

This feature is in beta. It may be removed or redesigned.

The capturing boot option prevents normal browser parsing of the landing page.
This allows HTMLDecor to manage parsing in the same way that AJAXed pages are handled. The main benefits of this would be:

  • normalizing landing-page content occurs before the content is rendered, and

  • because <link> and <img> resources aren't automatically downloaded they can be changed (or removed) with no penalty.

The drawbacks are:

  • parsing and displaying of content doesn't begin until the landing-page has fully down-loaded. On long pages over slow networks this will have quite a noticeable delay before any content is viewable.

The article "Capturing - Improving Performance of the Adaptive Web" provides a short description and discussion of this approach.

Restrictions

  • The boot-script must be the first <script> in the page.
  • The boot-script must be within - or before - <head>.
  • If within <head> the boot-script may only be preceded by <meta http-equiv> elements.

Debugging

By default, HTMLDecor logs error and warning messages to the browser console. The logger can be configured to provide info and debug messages (see Configuration).

External code is called from HTMLDecor (e.g. nodeInserted / nodeRemoved hooks) using event dispatch instead of try / catch blocks. This isolates HTMLDecor from errors in external code, but doesn't prevent errors and stack-traces being logged in the browser console.

Unfortunately, Firefox doesn't log errors in event-listeners. You may find debugging easier in a different browser.

Configuration

Preparation

Assuming the default installation was successful, use these steps to prepare for site specific configuration.

  1. Copy options.js and config.js from the HTMLDecor directory to the root directory of your domain.

    If you have unix shell access to the domain's server

        cd /directory/of/your/domain
        cp path/to/HTMLDecor/options.js path/to/HTMLDecor/config.js .
    
  2. Edit your copy of options.js to change the following lines

        "htmldecor_script": '{bootscriptdir}HTMLDecor.js',
        "config_script": '{bootscriptdir}config.js'
    

    to be

        "htmldecor_script": '/path/to/HTMLDecor/HTMLDecor.js',
        "config_script": '/config.js'
    
  3. Concatenate your modified options.js with boot.js from the HTMLDecor directory and store in boot.js of the root directory.

        cat options.js path/to/HTMLDecor/boot.js > boot.js
    
  4. Source the modified HTMLDecor boot-script into your pages - preferably before any stylesheets - with this line in the <head> of each page

        <script src="/boot.js"></script>
    
  5. Make sure to test the modifications.
    You could symlink to the test directory from the root directory

        ln -s path/to/HTMLDecor/test
    

    then navigate in the browser to

        http://your.domain.com/test/normal.html
    

Now you have a simple setup allowing you to:

  • modify your options without affecting the HTMLDecor installation, and
  • update HTMLDecor without overwriting your options.

When you want to:

  • modify options

    • edit your copy of options.js
    • repeat step 3 to rebuild your boot-script
  • update HTMLDecor

    • overwrite the HTMLDecor directory with the latest version
    • repeat step 3
  • minify HTMLDecor.js

    • minify HTMLDecor.js to HTMLDecor.min.js in the /path/to/HTMLDecor directory
    • change htmldecor_script to /path/to/HTMLDecor/HTMLDecor.min.js in your copy of the options.js file
    • repeat step 3
  • minify boot.js

    • minify boot.js to boot.min.js in the /path/to/HTMLDecor directory
    • repeat step 3 with path/to/HTMLDecor/boot.min.js

Boot options

These options aren't specifically related to the operation of HTMLDecor. The boot-script has the following options (default values in bold).

  • htmldecor_script: "{bootscriptdir}HTMLDecor.js"
  • log_level: "none", "error", "warn", "info", "debug"
  • polling_interval: 50 (milliseconds)
  • autostart: true, false
  • capturing: true, false
  • hidden_timeout: 3000 (milliseconds)
  • html5_block_elements: "article aside figcaption figure footer header hgroup main nav section"
  • html5_inline_elements: "abbr mark output time audio video picture"
  • config_script: "{bootscriptdir}config.js"

Sources for options are detailed below.

From Meeko.options

NOTE this is how options are set in options.js.
Options can be preset by script, like this:

<script>
var Meeko = window.Meeko || (window.Meeko = {});
Meeko.options = {
    log_level: "info",
    autostart: false,
    hidden_timeout: 1000
};
</script>

This tells HTMLDecor to

  • log 'info', 'warn' and 'error' messages
  • prevent automatic startup, and
  • when a manual start is requested to hide the page until all decor-resources are loaded or 1000 milliseconds (1 second) have elapsed, whichever comes first.

If autostart is turned off, HTMLDecor can be manually started by calling Meeko.decor.start().

From localStorage and sessionStorage

When debugging a page you probably don't want to modify the page source to change HTMLDecor options, especially as you may have to change them back after you've found the problem. For this reason HTMLDecor reads sessionStorage and localStorage at startup, looking for config options. sessionStorage options override those found in localStorage, which in turn override those in data-attributes.

Config options are read from JSON stored in the Meeko.options key. Thus the following would prevent autostart and turn on debug logging.

sessionStorage.setItem('Meeko.options', JSON.stringify({ autostart: false, log_level: "debug" }) );

Note that the page would require a refresh after these settings were made.

HTMLDecor configuration

There are two aspects of HTMLDecor:

  1. Decoration - the wrapping of the primary content of the page with site decor

  2. Panning - replacing the primary content of the page while retaining the same decor

These aspects are opposite in purpose, but similar in operation. In particular, they both involve:

  • downloading of external content
  • normalizing this content to prepare for HTMLDecor processing
  • notifications of content insertion / removal, etc

Decorator engine

Options for the decorator are stored in Meeko.decor.options, which can be accessed directly or by calling

Meeko.decor.config(options);

where options is an object containing key / value pairs that will overwrite current values.

Configuration should be done before HTMLDecor starts. This can be achieved by editing the site-specific config.js created during Preparation.

Usually you only want to configure how HTMLDecor determines the appropriate decor-document for a page. Do this by providing one of the following options:

  • detect(doc)
    MUST return the decor-URL by inspecting the current page when HTMLDecor starts (this doesn't allow panning)

  • lookup(url)
    MUST return the decor-URL for any URL in the site, either the current document.URL, or the URL of a different page that is to be panned in.

lookup(url) is the recommended option. detect(doc) is mainly provided for backwards compatibility, as can be seen in the default config.js script.

TODO: request, normalize, notifications

Panner engine

Options for the panner are stored in Meeko.panner.options, which can be accessed directly or by calling

Meeko.panner.config(options);

where options is an object containing key / value pairs that will overwrite current values.

Typically you only want to configure panner animation options. These would be set in the decor-document, as dealt with in Page Transition Animation.

All other configuration should be done before HTMLDecor starts. This can be achieved by editing the site-specific config.js created during Preparation.

Pre-decorated pages

Pages on your site may not be in the format that HTMLDecor and your decor-document are expecting. The most likely scenario for this is that your primary content containers are not direct children of the <body>, or they do not have @id. In this case you need to provide a normalize(doc) function which will manipulate the DOM of doc into the appropriate format, e.g.

    Meeko.panner.config({
        normalize: function(doc) {
            var content = doc.getElementsByTagName('main')[0];
            content.id = 'mk_content';
            doc.body.innerHTML = '';
            doc.body.appendChild(content);
        }
    });

NOTE: configuring the normalize option prevents initial page decoration until the DOMContentLoaded event (or safest equivalent).

Non-HTML payloads

You can also make your landing-page download as HTML and thereafter request, say JSON, and build the primary-content HTML in the browser. Do this by providing a request(url, data, details, callback) function, where

  • method is the HTTP method for the request, which will be 'GET' or 'POST'.
  • url is the URL of the page to be panned in
  • data is any form data (WARNING not implemented yet)
  • details is an object containing at least the URL and method
  • callback is an object with complete(result) and error(err) callback-methods

An example of configuration might be

    Meeko.panner.config({
        request: function(method, url, data, details, callback) { // assumes 'GET'
            if (!/GET/i.test(method)) throw "Only supporting GET requests";
            var rq = new XMLHttpRequest;
            rq.open(method, url, true);
            rq.setRequestHeader('Accept', 'application/json');
            rq.onreadystatechange = onchange;
            rq.send();
            function onchange() {
                if (rq.readyState != 4) return;
                if (rq.status != 200) {
                    callback.error(rq.status);
                    return;
                }
                onload();
            }
            function onload() {
                var json = JSON.parse(rq.responseText);
                var doc = document.implementation.createHTMLDocument(json.title);
                doc.body.innerHTML = processJSON(json); // your json-to-html converter
                callback.complete(doc);
            }
        }
    });

Bonus APIs

HTMLDecor defines various utility classes and functions for internal use. Many of these are also available for external use if appropriate. The most useful of these are in the Meeko.DOM namespace, and include

  • Meeko.DOM.URL This provides overlapping functionality with the proposed URL API. Meeko.DOM.URL(absoluteURL) will return a URL object with the following (read-only) fields:

    • href, protocol, host, hostname, port, pathname, search, hash (Standard)
    • nopathname, basepath, base, nosearch, nohash (Extensions)
      The URL object also has the resolve(relativeURL) method which performs a fast conversion of a relative URL to absolute, using itself for the baseURL.
  • Meeko.DOM.$id This is short-hand for document.getElementById (typically aliased to $id in a code block)

  • Meeko.DOM.$$ This is short-hand for document.getElementsByTagName (typically aliased to $$ in a code block)

Notes and Warnings

  • HTMLDecor may not be compatible with IE behaviors, eg CSS3 PIE.
  • The decor document is loaded via XMLHttpRequest(), parsed to disable scripts, then written into an iframe using document.write().
  • unlike CSS, decor pages should be in the same domain as the content page otherwise the browsers cross-site restrictions will apply. Detection for this hasn't been implemented yet.
  • any stylesheets in the content document and with a title of "nodecor" will be deleted at the start of merging of the decor page. This allows for a fallback styling option of decor-less pages. For example, the following stylesheets would be removed:
    <style title="nodecor">...</style>
    AND
    <link rel="stylesheet" href="style.css" title="nodecor" />
  • in most current browsers, elements from the content can be moved into the decor while the element is still loading. On IE6,7,8 this will throw an error, so for those browsers the decor is inserted and elements moved only after the DOM has fully loaded.
  • the configuration options and mechanism may change in future releases
  • URLs in <style> sections of the decor are not resolved. This means that relative URLs - which are meant to be relative to the decor URL - will probably be wrong when imported into the page. The work-around for this is to use absolute-paths or absolute-URLs (which you should probably be using anyway).
  • There are no compatibility checks and warnings between the content and decor pages (charset, etc)
  • There are no compatibility checks and warnings between the content element and the decor element it replaces (tagName, attrs, etc).

TODO

  • this README is too long - needs to be split up into sub-sections
  • some features would be best explained with demo pages / sites

License

HTMLDecor is available under MPL 2.0. See the MPL 2.0 FAQ for your obligations if you intend to modify or distribute HTMLDecor or part thereof.

Contact

If you have any questions or comments, don't hesitate to contact the author via web, email or twitter.

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