elementor / modules / image-loading-optimization / module.php

module.php in Elementor Website Builder – more than just a page builder 3.19.0-beta1, at modules/image-loading-optimization/module.php

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1	<?php
2	namespace Elementor\Modules\ImageLoadingOptimization;
3
4	use Elementor\Core\Base\Module as BaseModule;
5	use Elementor\Core\Experiments\Manager as Experiments_Manager;
6
7	if ( ! defined( 'ABSPATH' ) ) {
8	exit; // Exit if accessed directly
9	}
10
11	class Module extends BaseModule {
12	/**
13	* @var string The experiment name.
14	*/
15	const EXPERIMENT_NAME = 'e_image_loading_optimization';
16
17	/**
18	* @var int Minimum square-pixels threshold.
19	*/
20	private $min_priority_img_pixels = 50000;
21
22	/**
23	* @var int The number of content media elements to not lazy-load.
24	*/
25	private $omit_threshold = 3;
26
27	/**
28	* @var array Keep a track of images for which loading optimization strategy were computed.
29	*/
30	private static $image_visited = [];
31
32	/**
33	* Get Module name.
34	*/
35	public function get_name() {
36	return 'image-loading-optimization';
37	}
38
39	/**
40	* Get experimental data.
41	*
42	* @return array Experimental settings.
43	*/
44	public static function get_experimental_data() {
45	return [
46	'name' => static::EXPERIMENT_NAME,
47	'title' => esc_html__( 'Optimize Image Loading', 'elementor' ),
48	'tag' => esc_html__( 'Performance', 'elementor' ),
49	'description' => sprintf(
50	/* translators: 1: fetchpriority attribute, 2: lazy loading attribute. */
51	esc_html__( 'Applying %1$s on LCP image and %2$s on images below the fold to improve performance scores.', 'elementor' ),
52	'<code>fetchpriority="high"</code>',
53	'<code>loading="lazy"</code>'
54	),
55	'generator_tag' => true,
56	'release_status' => Experiments_Manager::RELEASE_STATUS_STABLE,
57	'default' => Experiments_Manager::STATE_ACTIVE,
58	];
59	}
60
61	/**
62	* Constructor.
63	*/
64	public function __construct() {
65	parent::__construct();
66
67	// Stop wp core logic.
68	add_action( 'init', [ $this, 'stop_core_fetchpriority_high_logic' ] );
69	add_filter( 'wp_lazy_loading_enabled', '__return_false' );
70
71	// Run optimization logic on header.
72	add_action( 'get_header', [ $this, 'set_buffer' ] );
73
74	// Ensure buffer is flushed (if any) before the content logic.
75	add_filter( 'the_content', [ $this, 'flush_header_buffer' ], 0 );
76
77	// Run optimization logic on content.
78	add_filter( 'wp_content_img_tag', [ $this, 'loading_optimization_image' ] );
79
80	// Run optimization logic on footer. Flushing of footer buffer will be handled by PHP script end default logic.
81	add_action( 'get_footer', [ $this, 'set_buffer' ] );
82	}
83
84	/**
85	* Stop WordPress core fetchpriority logic by setting the wp_high_priority_element_flag flag to false.
86	*/
87	public function stop_core_fetchpriority_high_logic() {
88	// wp_high_priority_element_flag was only introduced in 6.3.0
89	if ( function_exists( 'wp_high_priority_element_flag' ) ) {
90	wp_high_priority_element_flag( false );
91	}
92	}
93
94	/**
95	* Set buffer to handle header and footer content.
96	*/
97	public function set_buffer() {
98	ob_start( [ $this, 'handle_buffer_content' ] );
99	}
100
101	/**
102	* This function ensure that buffer if any is flushed before the content is called.
103	* This function behaves more like an action than a filter.
104	*
105	* @param string $content the content.
106	* @return string We simply return the content from parameter.
107	*/
108	public function flush_header_buffer( $content ) {
109	$buffer_status = ob_get_status();
110
111	if ( ! empty( $buffer_status ) &&
112	1 === $buffer_status['type'] &&
113	get_class( $this ) . '::handle_buffer_content' === $buffer_status['name'] ) {
114	ob_end_flush();
115	}
116
117	return $content;
118	}
119
120	/**
121	* Callback to handle image optimization logic on buffered content.
122	*
123	* @param string $buffer Buffered content.
124	* @return string Content with optimized images.
125	*/
126	public function handle_buffer_content( $buffer ) {
127	return $this->filter_images( $buffer );
128	}
129
130	/**
131	* Check for image in the content provided and apply optimization logic on them.
132	*
133	* @param string $content Content to be analyzed.
134	* @return string Content with optimized images.
135	*/
136	private function filter_images( $content ) {
137	return preg_replace_callback(
138	'/<img\s[^>]+>/',
139	function ( $matches ) {
140	return $this->loading_optimization_image( $matches[0] );
141	},
142	$content
143	);
144	}
145
146	/**
147	* Apply loading optimization logic on the image.
148	*
149	* @param mixed $image Original image tag.
150	* @return string Optimized image.
151	*/
152	public function loading_optimization_image( $image ) {
153	if ( isset( self::$image_visited[ $image ] ) ) {
154	return self::$image_visited[ $image ];
155	}
156
157	$optimized_image = $this->add_loading_optimization_attrs( $image );
158	self::$image_visited[ $image ] = $optimized_image;
159
160	return $optimized_image;
161	}
162
163	/**
164	* Adds optimization attributes to an `img` HTML tag.
165	*
166	* @param string $image The HTML `img` tag where the attribute should be added.
167	* @return string Converted `img` tag with optimization attributes added.
168	*/
169	private function add_loading_optimization_attrs( $image ) {
170	$width = preg_match( '/ width=["\']([0-9]+)["\']/', $image, $match_width ) ? (int) $match_width[1] : null;
171	$height = preg_match( '/ height=["\']([0-9]+)["\']/', $image, $match_height ) ? (int) $match_height[1] : null;
172	$loading_val = preg_match( '/ loading=["\']([A-Za-z]+)["\']/', $image, $match_loading ) ? $match_loading[1] : null;
173	$fetchpriority_val = preg_match( '/ fetchpriority=["\']([A-Za-z]+)["\']/', $image, $match_fetchpriority ) ? $match_fetchpriority[1] : null;
174
175	// Images should have height and dimension width for the loading optimization attributes to be added.
176	if ( ! str_contains( $image, ' width="' ) \|\| ! str_contains( $image, ' height="' ) ) {
177	return $image;
178	}
179
180	$optimization_attrs = $this->get_loading_optimization_attributes(
181	[
182	'width' => $width,
183	'height' => $height,
184	'loading' => $loading_val,
185	'fetchpriority' => $fetchpriority_val,
186	]
187	);
188
189	if ( ! empty( $optimization_attrs['fetchpriority'] ) ) {
190	$image = str_replace( '<img', '<img fetchpriority="' . esc_attr( $optimization_attrs['fetchpriority'] ) . '"', $image );
191	}
192
193	if ( ! empty( $optimization_attrs['loading'] ) ) {
194	$image = str_replace( '<img', '<img loading="' . esc_attr( $optimization_attrs['loading'] ) . '"', $image );
195	}
196
197	return $image;
198	}
199
200	/**
201	* Return loading Loading optimization attributes for a image with give attribute.
202	*
203	* @param array $attr Existing image attributes.
204	* @return array Loading optimization attributes.
205	*/
206	private function get_loading_optimization_attributes( $attr ) {
207	$loading_attrs = [];
208
209	// For any resources, width and height must be provided, to avoid layout shifts.
210	if ( ! isset( $attr['width'], $attr['height'] ) ) {
211	return $loading_attrs;
212	}
213
214	/*
215	* The key function logic starts here.
216	*/
217	$maybe_in_viewport = null;
218	$increase_count = false;
219	$maybe_increase_count = false;
220
221	/*
222	* Logic to handle a `loading` attribute that is already provided.
223	*
224	* Copied from `wp_get_loading_optimization_attributes()`.
225	*/
226	if ( isset( $attr['loading'] ) ) {
227	/*
228	* Interpret "lazy" as not in viewport. Any other value can be
229	* interpreted as in viewport (realistically only "eager" or `false`
230	* to force-omit the attribute are other potential values).
231	*/
232	if ( 'lazy' === $attr['loading'] ) {
233	$maybe_in_viewport = false;
234	} else {
235	$maybe_in_viewport = true;
236	}
237	}
238
239	// Logic to handle a `fetchpriority` attribute that is already provided.
240	$has_fetchpriority_high_attr = ( isset( $attr['fetchpriority'] ) && 'high' === $attr['fetchpriority'] );
241
242	/*
243	* Handle cases where a `fetchpriority="high"` has already been set.
244	*
245	* Copied from `wp_get_loading_optimization_attributes()`.
246	*/
247	if ( $has_fetchpriority_high_attr ) {
248	/*
249	* If the image was already determined to not be in the viewport (e.g.
250	* from an already provided `loading` attribute), trigger a warning.
251	* Otherwise, the value can be interpreted as in viewport, since only
252	* the most important in-viewport image should have `fetchpriority` set
253	* to "high".
254	*/
255	if ( false === $maybe_in_viewport ) {
256	_doing_it_wrong(
257	__FUNCTION__,
258	esc_html__( 'An image should not be lazy-loaded and marked as high priority at the same time.', 'elementor' ),
259	''
260	);
261	/*
262	* Set `fetchpriority` here for backward-compatibility as we should
263	* not override what a developer decided, even though it seems
264	* incorrect.
265	*/
266	$loading_attrs['fetchpriority'] = 'high';
267	} else {
268	$maybe_in_viewport = true;
269	}
270	}
271
272	if ( null === $maybe_in_viewport && ! is_admin() ) {
273	$content_media_count = $this->increase_content_media_count( 0 );
274	$increase_count = true;
275	if ( $content_media_count < $this->omit_threshold ) {
276	$maybe_in_viewport = true;
277	} else {
278	$maybe_in_viewport = false;
279	}
280	}
281
282	if ( $maybe_in_viewport ) {
283	$loading_attrs = $this->maybe_add_fetchpriority_high_attr( $loading_attrs, $attr );
284	} else {
285	$loading_attrs['loading'] = 'lazy';
286	}
287
288	if ( $increase_count ) {
289	$this->increase_content_media_count();
290	} elseif ( $maybe_increase_count ) {
291	if ( $this->get_min_priority_img_pixels() <= $attr['width'] * $attr['height'] ) {
292	$this->increase_content_media_count();
293	}
294	}
295
296	return $loading_attrs;
297	}
298
299	/**
300	* Helper to get the minimum threshold for number of pixels an image needs to have to be considered "priority".
301	*
302	* @return int The minimum number of pixels (width * height). Default is 50000.
303	*/
304	private function get_min_priority_img_pixels() {
305	/**
306	* Filter the minimum pixel threshold used to determine if an image should have fetchpriority="high" applied.
307	*
308	* @see https://developer.wordpress.org/reference/hooks/wp_min_priority_img_pixels/
309	*
310	* @param int $pixels The minimum number of pixels (with * height).
311	* @return int The filtered value.
312	*/
313	return apply_filters( 'elementor/image-loading-optimization/min_priority_img_pixels', $this->min_priority_img_pixels );
314	}
315
316	/**
317	* Keeps a count of media image.
318	*
319	* @param int $amount Amount by which count must be increased.
320	* @return int current image count.
321	*/
322	private function increase_content_media_count( $amount = 1 ) {
323	static $content_media_count = 0;
324
325	$content_media_count += $amount;
326
327	return $content_media_count;
328	}
329
330	/**
331	* Determines whether to add `fetchpriority='high'` to loading attributes.
332	*
333	* @param array $loading_attrs Array of the loading optimization attributes for the element.
334	* @param array $attr Array of the attributes for the element.
335	* @return array Updated loading optimization attributes for the element.
336	*/
337	private function maybe_add_fetchpriority_high_attr( $loading_attrs, $attr ) {
338	if ( isset( $attr['fetchpriority'] ) ) {
339	if ( 'high' === $attr['fetchpriority'] ) {
340	$loading_attrs['fetchpriority'] = 'high';
341	$this->high_priority_element_flag( false );
342	}
343
344	return $loading_attrs;
345	}
346
347	// Lazy-loading and `fetchpriority="high"` are mutually exclusive.
348	if ( isset( $loading_attrs['loading'] ) && 'lazy' === $loading_attrs['loading'] ) {
349	return $loading_attrs;
350	}
351
352	if ( ! $this->high_priority_element_flag() ) {
353	return $loading_attrs;
354	}
355
356	if ( $this->get_min_priority_img_pixels() <= $attr['width'] * $attr['height'] ) {
357	$loading_attrs['fetchpriority'] = 'high';
358	$this->high_priority_element_flag( false );
359	}
360
361	return $loading_attrs;
362	}
363
364	/**
365	* Accesses a flag that indicates if an element is a possible candidate for `fetchpriority='high'`.
366	*
367	* @param bool $value Optional. Used to change the static variable. Default null.
368	* @return bool Returns true if high-priority element was marked already, otherwise false.
369	*/
370	private function high_priority_element_flag( $value = null ) {
371	static $high_priority_element = true;
372
373	if ( is_bool( $value ) ) {
374	$high_priority_element = $value;
375	}
376
377	return $high_priority_element;
378	}
379	}
380