HTML::DeferableCSS - Simplify management of stylesheets in your HTML
version v0.2.1
use HTML::DeferableCSS; my $css = HTML::DeferableCSS->new( css_root => '/var/www/css', url_base_path => '/css', inline_max => 512, aliases => { reset => 1, jqui => 'jquery-ui', site => 'style', }, cdn => { jqui => '//cdn.example.com/jquery-ui.min.css', }, ); ... print $css->deferred_link_html( qw[ jqui site ] );
This is an experimental module for generating HTML-snippets for deferable stylesheets.
This allows the stylesheets to be loaded asynchronously, allowing the page to be rendered faster.
Ideally, this would be a simple matter of changing stylesheet links to something like
<link rel="preload" as="stylesheet" href="....">
but this is not well supported by all web browsers. So a web page needs some JavaScript to handle this, as well as a noscript block as a fallback.
noscript
This module allows you to simplify the management of stylesheets for a web application, from development to production by
declaring all stylesheets used by your web application;
specifying remote aliases for stylesheets, e.g. from a CDN;
enable or disable the use of minified stylesheets;
switch between local copies of stylesheets or CDN versions;
automatically inline small stylesheets;
use deferred-loading stylesheets, which requires embedding JavaScript code as a workaround for web browsers that do not support these natively.
This is a required hash reference of names and their relative filenames to "css_root".
It is recommended that the .css and .min.css suffixes be omitted.
If the name is the same as the filename (without the extension) than you can simply use 1. (Likewise, an empty string or 0 disables the alias:
1
0
my $css = HTML::DeferableCSS->new( aliases => { reset => 1, gone => 0, # using "gone" will throw an error one => "1.css", # } ... );
If all names are the same as their filenames, then an array reference can be used:
my $css = HTML::DeferableCSS->new( aliases => [ qw( foo bar } ], ... );
Absolute paths cannot be used.
You may specify URLs instead of files, but this is not recommended, except for cases when the files are not available locally.
This is the required root directory where all stylesheets can be found.
This is the URL prefix for stylesheets.
It can be a full URL prefix.
If true (default), then a file with the .min.css suffix will be preferred, if it exists in the same directory.
Note that this does not do any minification. You will need separate tools for that.
This is a hash reference used internally to translate "aliases" into the actual files or URLs.
If files cannot be found, then it will throw an error, so calling this attribute in void context can be used to check for any errors:
eval { $css->css_files } or die "$@";
This is a hash reference of "aliases" to URLs. (Only one URL per alias is supported.)
When "use_cdn_links" is true, then these URLs will be used instead of local versions.
This is true when there are "cdn_links".
When true, this will prefer CDN URLs instead of local files.
This specifies the maximum size of an file to inline.
Local files under the size will be inlined using the "link_or_inline_html" or "deferred_link_html" methods.
Setting this to 0 disables the use of inline links, unless "inline_html" is called explicitly.
True by default.
This is used by "deferred_link_html" to determine whether to emit code for deferred stylesheets.
When true, a noscript element will be included with non-deffered links.
This defaults to the same value as "defer_css".
This is the pathname of the cssrelpreload.js file that will be embedded in the resulting code.
You do not need to modify this unless you want to use a different script from the one included with this module.
This is a code reference for a subroutine that returns a stylesheet link.
This is a code reference for a subroutine that returns a stylesheet preload link.
This is an optional static asset id to append to local links. It may refer to a version number or commit-id, for example.
This is useful to ensure that changes to stylesheets are picked up by web browsers that would otherwise use cached copies of older versions of files.
True if there is an "asset_id".
my $href = $css->href( $alias );
This returns this URL for an alias.
my $html = $css->link_html( $alias );
This returns the link HTML markup for the stylesheet referred to by $alias.
$alias
my $html = $css->inline_html( $alias );
This returns an embedded stylesheet referred to by $alias.
my $html = $css->link_or_inline_html( @aliases );
This returns either the link HTML markup, or the embedded stylesheet, if the file size is not greater than "inline_max".
Note that a stylesheet will be inlined, even if there is are "cdn_links".
my $html = $css->deferred_link_html( @aliases );
This returns the HTML markup for the stylesheets specified by "aliases", as appropriate for each stylesheet.
If the stylesheets are not greater than "inline_max", then it will embed them. Otherwise it will return the appropriate markup, depending on "defer_css".
This module is written for HTML5.
It does not support XHTML self-closing elements or embedding styles and scripts in CDATA sections.
All files are embedded as raw files.
No URL encoding is done on the HTML links or "asset_id".
It's also spelled "Deferable".
The development version is on github at https://github.com/robrwo/HTML-DeferableCSS and may be cloned from git://github.com/robrwo/HTML-DeferableCSS.git
Please report any bugs or feature requests on the bugtracker website https://github.com/robrwo/HTML-DeferableCSS/issues
When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.
Robert Rothenberg <rrwo@cpan.org>
reset.css comes from http://meyerweb.com/eric/tools/css/reset/.
cssrelpreload.js comes from https://github.com/filamentgroup/loadCSS/.
This software is Copyright (c) 2020 by Robert Rothenberg.
This is free software, licensed under:
The MIT (X11) License
To install HTML::DeferableCSS, copy and paste the appropriate command in to your terminal.
cpanm
cpanm HTML::DeferableCSS
CPAN shell
perl -MCPAN -e shell install HTML::DeferableCSS
For more information on module installation, please visit the detailed CPAN module installation guide.