diff core/lib/Drupal/Core/Asset/CssCollectionRenderer.php @ 0:4c8ae668cc8c

Initial import (non-working)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/lib/Drupal/Core/Asset/CssCollectionRenderer.php	Wed Nov 29 16:09:58 2017 +0000
@@ -0,0 +1,218 @@
+<?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;
+  }
+
+}