Mercurial > hg > isophonics-drupal-site
view core/lib/Drupal/Core/Asset/CssCollectionRenderer.php @ 0:4c8ae668cc8c
Initial import (non-working)
author | Chris Cannam |
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date | Wed, 29 Nov 2017 16:09:58 +0000 |
parents | |
children | af1871eacc83 |
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<?php namespace Drupal\Core\Asset; use Drupal\Component\Utility\Html; use Drupal\Core\State\StateInterface; /** * Renders CSS assets. * * For production websites, LINK tags are preferable to STYLE tags with @import * statements, because: * - They are the standard tag intended for linking to a resource. * - On Firefox 2 and perhaps other browsers, CSS files included with @import * statements don't get saved when saving the complete web page for offline * use: https://www.drupal.org/node/145218. * - On IE, if only LINK tags and no @import statements are used, all the CSS * files are downloaded in parallel, resulting in faster page load, but if * @import statements are used and span across multiple STYLE tags, all the * ones from one STYLE tag must be downloaded before downloading begins for * the next STYLE tag. Furthermore, IE7 does not support media declaration on * the @import statement, so multiple STYLE tags must be used when different * files are for different media types. Non-IE browsers always download in * parallel, so this is an IE-specific performance quirk: * http://www.stevesouders.com/blog/2009/04/09/dont-use-import/. * * However, IE has an annoying limit of 31 total CSS inclusion tags * (https://www.drupal.org/node/228818) and LINK tags are limited to one file * per tag, whereas STYLE tags can contain multiple @import statements allowing * multiple files to be loaded per tag. When CSS aggregation is disabled, a * Drupal site can easily have more than 31 CSS files that need to be loaded, so * using LINK tags exclusively would result in a site that would display * incorrectly in IE. Depending on different needs, different strategies can be * employed to decide when to use LINK tags and when to use STYLE tags. * * The strategy employed by this class is to use LINK tags for all aggregate * files and for all files that cannot be aggregated (e.g., if 'preprocess' is * set to FALSE or the type is 'external'), and to use STYLE tags for groups * of files that could be aggregated together but aren't (e.g., if the site-wide * aggregation setting is disabled). This results in all LINK tags when * aggregation is enabled, a guarantee that as many or only slightly more tags * are used with aggregation disabled than enabled (so that if the limit were to * be crossed with aggregation enabled, the site developer would also notice the * problem while aggregation is disabled), and an easy way for a developer to * view HTML source while aggregation is disabled and know what files will be * aggregated together when aggregation becomes enabled. * * This class evaluates the aggregation enabled/disabled condition on a group * by group basis by testing whether an aggregate file has been made for the * group rather than by testing the site-wide aggregation setting. This allows * this class to work correctly even if modules have implemented custom * logic for grouping and aggregating files. */ class CssCollectionRenderer implements AssetCollectionRendererInterface { /** * The state key/value store. * * @var \Drupal\Core\State\StateInterface */ protected $state; /** * Constructs a CssCollectionRenderer. * * @param \Drupal\Core\State\StateInterface $state * The state key/value store. */ public function __construct(StateInterface $state) { $this->state = $state; } /** * {@inheritdoc} */ public function render(array $css_assets) { $elements = []; // A dummy query-string is added to filenames, to gain control over // browser-caching. The string changes on every update or full cache // flush, forcing browsers to load a new copy of the files, as the // URL changed. $query_string = $this->state->get('system.css_js_query_string') ?: '0'; // Defaults for LINK and STYLE elements. $link_element_defaults = [ '#type' => 'html_tag', '#tag' => 'link', '#attributes' => [ 'rel' => 'stylesheet', ], ]; $style_element_defaults = [ '#type' => 'html_tag', '#tag' => 'style', ]; // For filthy IE hack. $current_ie_group_keys = NULL; $get_ie_group_key = function ($css_asset) { return [$css_asset['type'], $css_asset['preprocess'], $css_asset['group'], $css_asset['media'], $css_asset['browsers']]; }; // Loop through all CSS assets, by key, to allow for the special IE // workaround. $css_assets_keys = array_keys($css_assets); for ($i = 0; $i < count($css_assets_keys); $i++) { $css_asset = $css_assets[$css_assets_keys[$i]]; switch ($css_asset['type']) { // For file items, there are three possibilities. // - There are up to 31 CSS assets on the page (some of which may be // aggregated). In this case, output a LINK tag for file CSS assets. // - There are more than 31 CSS assets on the page, yet we must stay // below IE<10's limit of 31 total CSS inclusion tags, we handle this // in two ways: // - file CSS assets that are not eligible for aggregation (their // 'preprocess' flag has been set to FALSE): in this case, output a // LINK tag. // - file CSS assets that can be aggregated (and possibly have been): // in this case, figure out which subsequent file CSS assets share // the same key properties ('group', 'media' and 'browsers') and // output this group into as few STYLE tags as possible (a STYLE // tag may contain only 31 @import statements). case 'file': // The dummy query string needs to be added to the URL to control // browser-caching. $query_string_separator = (strpos($css_asset['data'], '?') !== FALSE) ? '&' : '?'; // As long as the current page will not run into IE's limit for CSS // assets: output a LINK tag for a file CSS asset. if (count($css_assets) <= 31) { $element = $link_element_defaults; $element['#attributes']['href'] = file_url_transform_relative(file_create_url($css_asset['data'])) . $query_string_separator . $query_string; $element['#attributes']['media'] = $css_asset['media']; $element['#browsers'] = $css_asset['browsers']; $elements[] = $element; } // The current page will run into IE's limits for CSS assets: work // around these limits by performing a light form of grouping. // Once Drupal only needs to support IE10 and later, we can drop this. else { // The file CSS asset is ineligible for aggregation: output it in a // LINK tag. if (!$css_asset['preprocess']) { $element = $link_element_defaults; $element['#attributes']['href'] = file_url_transform_relative(file_create_url($css_asset['data'])) . $query_string_separator . $query_string; $element['#attributes']['media'] = $css_asset['media']; $element['#browsers'] = $css_asset['browsers']; $elements[] = $element; } // The file CSS asset can be aggregated, but hasn't been: combine // multiple items into as few STYLE tags as possible. else { $import = []; // Start with the current CSS asset, iterate over subsequent CSS // assets and find which ones have the same 'type', 'group', // 'preprocess', 'media' and 'browsers' properties. $j = $i; $next_css_asset = $css_asset; $current_ie_group_key = $get_ie_group_key($css_asset); do { // The dummy query string needs to be added to the URL to // control browser-caching. IE7 does not support a media type on // the @import statement, so we instead specify the media for // the group on the STYLE tag. $import[] = '@import url("' . Html::escape(file_url_transform_relative(file_create_url($next_css_asset['data'])) . '?' . $query_string) . '");'; // Move the outer for loop skip the next item, since we // processed it here. $i = $j; // Retrieve next CSS asset, unless there is none: then break. if ($j + 1 < count($css_assets_keys)) { $j++; $next_css_asset = $css_assets[$css_assets_keys[$j]]; } else { break; } } while ($get_ie_group_key($next_css_asset) == $current_ie_group_key); // In addition to IE's limit of 31 total CSS inclusion tags, it // also has a limit of 31 @import statements per STYLE tag. while (!empty($import)) { $import_batch = array_slice($import, 0, 31); $import = array_slice($import, 31); $element = $style_element_defaults; // This simplifies the JavaScript regex, allowing each line // (separated by \n) to be treated as a completely different // string. This means that we can use ^ and $ on one line at a // time, and not worry about style tags since they'll never // match the regex. $element['#value'] = "\n" . implode("\n", $import_batch) . "\n"; $element['#attributes']['media'] = $css_asset['media']; $element['#browsers'] = $css_asset['browsers']; $elements[] = $element; } } } break; // Output a LINK tag for an external CSS asset. The asset's 'data' // property contains the full URL. case 'external': $element = $link_element_defaults; $element['#attributes']['href'] = $css_asset['data']; $element['#attributes']['media'] = $css_asset['media']; $element['#browsers'] = $css_asset['browsers']; $elements[] = $element; break; default: throw new \Exception('Invalid CSS asset type.'); } } return $elements; } }