1<?php 2 3namespace Drupal\Core\Asset; 4 5/** 6 * Groups CSS assets. 7 */ 8class CssCollectionGrouper implements AssetCollectionGrouperInterface { 9 10 /** 11 * {@inheritdoc} 12 * 13 * Puts multiple items into the same group if they are groupable and if they 14 * are for the same 'media' and 'browsers'. Items of the 'file' type are 15 * groupable if their 'preprocess' flag is TRUE, and items of the 'external' 16 * type are never groupable. 17 * 18 * Also ensures that the process of grouping items does not change their 19 * relative order. This requirement may result in multiple groups for the same 20 * type, media, and browsers, if needed to accommodate other items in between. 21 */ 22 public function group(array $css_assets) { 23 $groups = []; 24 // If a group can contain multiple items, we track the information that must 25 // be the same for each item in the group, so that when we iterate the next 26 // item, we can determine if it can be put into the current group, or if a 27 // new group needs to be made for it. 28 $current_group_keys = NULL; 29 // When creating a new group, we pre-increment $i, so by initializing it to 30 // -1, the first group will have index 0. 31 $i = -1; 32 foreach ($css_assets as $item) { 33 // The browsers for which the CSS item needs to be loaded is part of the 34 // information that determines when a new group is needed, but the order 35 // of keys in the array doesn't matter, and we don't want a new group if 36 // all that's different is that order. 37 ksort($item['browsers']); 38 39 // If the item can be grouped with other items, set $group_keys to an 40 // array of information that must be the same for all items in its group. 41 // If the item can't be grouped with other items, set $group_keys to 42 // FALSE. We put items into a group that can be aggregated together: 43 // whether they will be aggregated is up to the _drupal_css_aggregate() 44 // function or an 45 // override of that function specified in hook_css_alter(), but regardless 46 // of the details of that function, a group represents items that can be 47 // aggregated. Since a group may be rendered with a single HTML tag, all 48 // items in the group must share the same information that would need to 49 // be part of that HTML tag. 50 switch ($item['type']) { 51 case 'file': 52 // Group file items if their 'preprocess' flag is TRUE. 53 // Help ensure maximum reuse of aggregate files by only grouping 54 // together items that share the same 'group' value. 55 $group_keys = $item['preprocess'] ? [$item['type'], $item['group'], $item['media'], $item['browsers']] : FALSE; 56 break; 57 58 case 'external': 59 // Do not group external items. 60 $group_keys = FALSE; 61 break; 62 } 63 64 // If the group keys don't match the most recent group we're working with, 65 // then a new group must be made. 66 if ($group_keys !== $current_group_keys) { 67 $i++; 68 // Initialize the new group with the same properties as the first item 69 // being placed into it. The item's 'data', 'weight' and 'basename' 70 // properties are unique to the item and should not be carried over to 71 // the group. 72 $groups[$i] = $item; 73 unset($groups[$i]['data'], $groups[$i]['weight'], $groups[$i]['basename']); 74 $groups[$i]['items'] = []; 75 $current_group_keys = $group_keys ? $group_keys : NULL; 76 } 77 78 // Add the item to the current group. 79 $groups[$i]['items'][] = $item; 80 } 81 82 return $groups; 83 } 84 85} 86