The original filter location is `wp_maybe_add_fetchpriority_high_attr()` in `wp-includes/media.php`.
This commit updates the instance in `wp_get_loading_optimization_attributes()` to point to the correct file.
Follow-up to [56037], [56143], [56347].
Props tmatsuur, rajinsharwar, khokansardar.
Fixes#59067.
git-svn-id: https://develop.svn.wordpress.org/trunk@56386 602fd350-edb4-49c9-b593-d223f7449a82
While the `wp_get_loading_optimization_attributes()` function was only recently introduced in 6.3, its code was mostly ported over from the now deprecated `wp_get_loading_attr_default()` function introduced in 5.5.
That function started out in a simple way, but over time was expanded with more and more conditionals on when to avoid lazy-loading, which ended up making the logic extremely complex and hard to follow.
This changeset refactors the logic to simplify it, in a way that allows to follow it more sequentially, and without making any functional changes, ensuring that the extensive existing unit test coverage still passes. This will facilitate future enhancements to the function to be less error-prone and make it more accessible to new contributors.
Props flixos90, joemcgill.
Fixes#58891.
git-svn-id: https://develop.svn.wordpress.org/trunk@56347 602fd350-edb4-49c9-b593-d223f7449a82
This resolves a WPCS warning:
{{{
Found precision alignment of 1 space.
}}}
Follow-up to [55988].
Props jrf.
See #58831.
git-svn-id: https://develop.svn.wordpress.org/trunk@56283 602fd350-edb4-49c9-b593-d223f7449a82
This resolves a few WPCS warnings:
{{{
Equals sign not aligned with surrounding statements
}}}
so that the output of `composer format` is clean.
Follow-up to [55971], [56033], [56056], [56143], [56214].
Props jrf.
See #58831.
git-svn-id: https://develop.svn.wordpress.org/trunk@56273 602fd350-edb4-49c9-b593-d223f7449a82
`str_contains()` was introduced in PHP 8.0 to perform a case-sensitive check indicating if the string to search in (haystack) contains the given substring (needle).
WordPress core includes a polyfill for `str_contains()` on PHP < 8.0 as of WordPress 5.9.
This commit replaces `false !== strpos( ... )` with `str_contains()` in core files, making the code more readable and consistent, as well as better aligned with modern development practices.
Follow-up to [55988], [55990], [56014], [56021], [56031], [56032], [56065], [56241].
See #58206.
git-svn-id: https://develop.svn.wordpress.org/trunk@56245 602fd350-edb4-49c9-b593-d223f7449a82
This fixes an issue where images dynamically created during shortcode rendering (e.g., shortcode image galleries), were not getting image optimizations like `loading="lazy"` or `fetchpriority="hight"` applied. Note that even after this commit, shortcodes are processed after the main content images, which can affect the order in which optimizations are applied in content areas.
Follow-up to [56037].
Props spacedmonkey, flixos90, thekt12, swissspidy, joemcgill.
Fixes#58681.
git-svn-id: https://develop.svn.wordpress.org/trunk@56214 602fd350-edb4-49c9-b593-d223f7449a82
Follow-up to [56037], as that changeset accidentally did not consider the changes made in [55825]: Images that are programmatically injected into post content (e.g. through a block, or shortcode, or any hook calling a function like `wp_get_attachment_image()`) must be treated as part of the whole post content blob since otherwise the heuristics for applying `fetchpriority="high"` and `loading="lazy"` are skewed by parsing certain images before others rather than sequentially parsing the entire post content. [55825] addressed that for lazy-loading, but when [56037] introduced `fetchpriority` support, the related refactor missed making the same consideration for that attribute.
Props flixos90, spacedmonkey, thekt12, mukesh27.
Fixes#58235.
See #58089.
git-svn-id: https://develop.svn.wordpress.org/trunk@56164 602fd350-edb4-49c9-b593-d223f7449a82
This changeset adds support for loading optimization attributes such as `loading="lazy"` and `fetchpriority="high"` to the image widget. A new context `widget_media_image` is introduced for that purpose.
Props spacedmonkey, thekt12, mukesh27, westonruter.
Fixes#58704.
See #58235.
git-svn-id: https://develop.svn.wordpress.org/trunk@56154 602fd350-edb4-49c9-b593-d223f7449a82
Following [55318], [55847], and [56142], certain images in the header of the page have received support for potentially receiving `fetchpriority="high"` and having the `loading="lazy"` attribute omitted. However, these images being present did not affect the "content media count" which counts the images towards a certain threshold so that the first ones are not lazy-loaded.
This changeset also increases that count for such header images if they are larger than a certain threshold. The threshold is used to avoid e.g. a header with lots of small images such as icon graphics to skew the lazy-loading behavior.
Props thekt12, spacedmonkey, flixos90.
Fixes#58635.
git-svn-id: https://develop.svn.wordpress.org/trunk@56143 602fd350-edb4-49c9-b593-d223f7449a82
This changeset is a follow up to [56037] and ensures that the `get_header_image_tag()` function receives the benefits of `wp_get_loading_optimization_attributes()` as well. Prior to `fetchpriority` support, this was not needed since the header image should never be lazy-loaded, but the image certainly is a `fetchpriority` candidate, so therefore it is crucial to have it supported.
Props felipeelia, spacedmonkey, mukesh27, westonruter, flixos90.
Fixes#58680.
git-svn-id: https://develop.svn.wordpress.org/trunk@56142 602fd350-edb4-49c9-b593-d223f7449a82
The description of returned values in array was incorrect for `image_get_intermediate_size()`:
- `$file` returns the filename of image, no path information
- `$path` returns path relative to the uploads directory, not absolute
Props crstauf, sccr410.
Fixes#58686.
See #57840.
git-svn-id: https://develop.svn.wordpress.org/trunk@56122 602fd350-edb4-49c9-b593-d223f7449a82
This changeset adds support for the `fetchpriority` attribute, which is typically added to a single image in each HTML response with a value of "high". This enhances load time performance (also Largest Contentful Paint, or LCP) by telling the browser to prioritize this image for downloading even before the layout of the page has been computed. In lab tests, this has shown to improve LCP performance by ~10% on average.
Specifically, `fetchpriority="high"` is added to the first image that satisfies all of the following conditions:
* The image is not lazy-loaded, i.e. does not have `loading="lazy"`.
* The image does not already have a (conflicting) `fetchpriority` attribute.
* The size of of the image (i.e. width * height) is greater than 50,000 squarepixels.
While these heuristics are based on several field analyses, there will always be room for optimization. Sites can customize the squarepixel threshold using a new filter `wp_min_priority_img_pixels` which should return an integer for the value.
Since the logic for adding `fetchpriority="high"` is heavily intertwined with the logic for adding `loading="lazy"`, yet the features should work decoupled from each other, the majority of code changes in this changeset is refactoring of the existing lazy-loading logic to be reusable. For this purpose, a new function `wp_get_loading_optimization_attributes()` has been introduced which returns an associative array of performance-relevant attributes for a given HTML element. This function replaces `wp_get_loading_attr_default()`, which has been deprecated. As another result of that change, a new function `wp_img_tag_add_loading_optimization_attrs()` replaces the more specific `wp_img_tag_add_loading_attr()`, which has been deprecated as well.
See https://make.wordpress.org/core/2023/05/02/proposal-for-enhancing-lcp-image-performance-with-fetchpriority/ for the original proposal and additional context.
Props thekt12, joemcgill, spacedmonkey, mukesh27, costdev, 10upsimon.
Fixes#58235.
git-svn-id: https://develop.svn.wordpress.org/trunk@56037 602fd350-edb4-49c9-b593-d223f7449a82
`str_contains()` was introduced in PHP 8.0 to perform a case-sensitive check indicating if the string to search in (haystack) contains the given substring (needle).
WordPress core includes a polyfill for `str_contains()` on PHP < 8.0 as of WordPress 5.9.
This commit replaces `false !== strpos( ... )` with `str_contains()` in core files, making the code more readable and consistent, as well as better aligned with modern development practices.
Follow-up to [55988], [56021].
See #58206.
git-svn-id: https://develop.svn.wordpress.org/trunk@56031 602fd350-edb4-49c9-b593-d223f7449a82
`str_starts_with()` and `str_ends_with()` were introduced in PHP 8.0 to perform a case-sensitive check indicating if the string to search in (haystack) begins or ends with the given substring (needle).
WordPress core includes a polyfill for these functions on PHP < 8.0 as of WordPress 5.9.
This commit uses `str_starts_with()` and `str_ends_with()` in core files where appropriate:
* `$needle === substr( $string, 0, $length )`, where `$length` is the length of `$needle`, is replaced with `str_starts_with( $haystack, $needle )`.
* `$needle === substr( $string, $offset )`, where `$offset` is negative and the absolute value of `$offset` is the length of `$needle`, is replaced with `str_ends_with( $haystack, $needle )`.
This aims to make the code more readable and consistent, as well as better aligned with modern development practices.
Follow-up to [52039], [52040], [52326], [55703], [55710], [55987], [55988].
Props Soean, spacedmonkey, Clorith, ocean90, azaozz, sabernhardt, SergeyBiryukov.
Fixes#58220.
git-svn-id: https://develop.svn.wordpress.org/trunk@55990 602fd350-edb4-49c9-b593-d223f7449a82
`str_contains()` was introduced in PHP 8.0 to perform a case-sensitive check indicating if the string to search in (haystack) contains the given substring (needle).
WordPress core includes a polyfill for `str_contains()` on PHP < 8.0 as of WordPress 5.9.
This commit replaces `false !== strpos( ... )` with `str_contains()` in core files, making the code more readable and consistent, as well as better aligned with modern development practices.
Follow-up to [52039], [52040], [52326], [55703], [55710], [55987].
Props Soean, spacedmonkey, costdev, dingo_d, azaozz, mikeschroder, flixos90, peterwilsoncc, SergeyBiryukov.
Fixes#58206.
git-svn-id: https://develop.svn.wordpress.org/trunk@55988 602fd350-edb4-49c9-b593-d223f7449a82
This corrects the placement of double quotes around the query and makes sure the alignment is consistent.
Props umeshmcakadi, mukesh27, krupalpanchal, dhrumilk, SergeyBiryukov.
Fixes#58372.
git-svn-id: https://develop.svn.wordpress.org/trunk@55857 602fd350-edb4-49c9-b593-d223f7449a82
When the logic to exclude images that likely appear above the fold from being lazy-loaded was introduced in WordPress 5.9, initially only images that appear within the main query loop were being considered. However, there is a good chance that images above the fold are rendered before the loop starts, for example in the header template part.
It is particularly common for a theme to display the featured image for a single post in the header. Based on HTTP Archive data from February 2023, the majority of LCP images that are still being lazy-loaded on WordPress sites use the `wp-post-image` class, i.e. are featured images.
This changeset enhances the logic in `wp_get_loading_attr_default()` to not lazy-load images that appear within or after the header template part and before the query loop, using a new `WP_Query::$before_loop` property.
For block themes, this was for the most part already addressed in [55318], however this enhancement implements the solution in a more generally applicable way that brings the improvement to classic themes as well.
Props thekt12, flixos90, spacedmonkey, costdev, zunaid321, mukesh27.
Fixes#58211.
See #53675, #56930.
git-svn-id: https://develop.svn.wordpress.org/trunk@55847 602fd350-edb4-49c9-b593-d223f7449a82
In order to skip lazy-loading the first few images on a page, as of WordPress 5.9 there has been logic to count images that are eligible based on certain criteria. One of those groups are images that appear within the content of a post.
This changeset fixes a bug where images created via `get_the_post_thumbnail()` or `wp_get_attachment_image()` that are injected into the post content would skew the count and therefore result in all images to be lazy-loaded, potentially hurting load time performance. This is relevant for example when those functions are called in server-side rendered blocks, or any other filter callbacks hooked into `the_content`.
Props flixos90, antpb, joedolson, spacedmonkey, mukesh27, thekt12, costdev, jrf.
Fixes#58089.
See #53675.
git-svn-id: https://develop.svn.wordpress.org/trunk@55825 602fd350-edb4-49c9-b593-d223f7449a82
Since WordPress 5.9, a "context" value of "wp_get_attachment_image" has been used in the `wp_get_attachment_image()` function to provide context to underlying functions where that is relevant, e.g. `wp_get_loading_attr_default()`. Since that value used to be not customizable, it required a workaround in `get_the_post_thumbnail()` to avoid calling those functions in `wp_get_attachment_image()`, which resulted in unnecessary complexity and was prone to errors.
This changeset introduces a `wp_get_attachment_image_context` filter and leverages it with private filter callback functions that are leveraged by default when `get_the_post_thumbnail()` is called. This avoids the need for the previous workaround and furthermore provides flexibility for other callers of `wp_get_attachment_image()` to provide their own contexts.
Props flixos90, costdev, thekt12, westonruter, spacedmonkey.
Fixes#58212.
git-svn-id: https://develop.svn.wordpress.org/trunk@55821 602fd350-edb4-49c9-b593-d223f7449a82
The previous default threshold for how many content images to skip lazy-loading on (which was just 1) has proven to be too strict: HTTP Archive data shows that >70% of sites have up to 3 equal-sized images in the initial viewport, each of which could be the LCP image and therefore should not be lazy-loaded. Lazy-loading too many images has adverse effects on load time performance, while increasing the default threshold will not negatively affect load time performance even for sites where a threshold of 1 would be the perfect choice.
The change of default value in this changeset will improve performance for more WordPress sites out of the box. The `wp_omit_loading_attr_threshold` filter can still be used to customize and fine tune the value where needed.
Props thekt12, spacedmonkey, westonruter, flixos90.
Fixes#58213.
git-svn-id: https://develop.svn.wordpress.org/trunk@55816 602fd350-edb4-49c9-b593-d223f7449a82
This is a minor performance enhancement:
* If an object is passed, the call to `is_object()` will be redundant.
* If a non-object is passed, the `instanceof` operator (a variant of `is_a()`) will first [https://github.com/php/php-src/blob/f42992f/Zend/zend_builtin_functions.c#L630-L631 check if it is an object] before doing any further processing.
Therefore, no additional processing cycles should be wasted in both cases.
Follow-up to [6779], [48798], [48905], [49194], [55748].
Props Presskopp, costdev.
Fixes#58309.
git-svn-id: https://develop.svn.wordpress.org/trunk@55757 602fd350-edb4-49c9-b593-d223f7449a82
`str_starts_with()` was introduced in PHP 8.0 to perform a case-sensitive check indicating if the string to search in (haystack) begins with the given substring (needle).
WordPress core includes a polyfill for `str_starts_with()` on PHP < 8.0 as of WordPress 5.9.
This commit replaces `0 === strpos( ... )` with `str_starts_with()` in core files, making the code more readable and consistent, as well as improving performance.
While `strpos()` is slightly faster than the polyfill on PHP < 8.0, `str_starts_with()` is noticeably faster on PHP 8.0+, as it is optimized to avoid unnecessarily searching along the whole haystack if it does not find the needle.
Follow-up to [52039], [52040], [52326].
Props spacedmonkey, costdev, sabernhardt, mukesh27, desrosj, jorbin, TobiasBg, ayeshrajans, lgadzhev, SergeyBiryukov.
Fixes#58012.
git-svn-id: https://develop.svn.wordpress.org/trunk@55703 602fd350-edb4-49c9-b593-d223f7449a82
[52065] originally introduced the logic to guess the LCP image based on certain heuristics and to not lazy-load that image. However, with the introduction of block themes, that logic was not functioning correctly, resulting in all featured images to be lazy-loaded, regardless of whether it was the LCP image or not.
Together with an update to the `core/post-featured-image` block included in [55079], this changeset fixes the logic to correctly handle featured images in block themes as well.
Additionally, in combination with an update to the `core/template-part` block from [55246], this changeset includes an enhancement which uses the benefits of block template parts to avoid lazy-loading images in the `header` block template part, making the lazy-loading heuristics even more accurate for sites using a block theme.
Props flixos90, adamsilverstein, mamaduka, antonvlasenko, shahidul95, reduanmasud, costdev, mukesh27, ironprogrammer, manfcarlo, robinwpdeveloper, spacedmonkey.
Fixes#56930.
git-svn-id: https://develop.svn.wordpress.org/trunk@55318 602fd350-edb4-49c9-b593-d223f7449a82
This changeset improves the way quotation marks are handled in the Playlist template.
Follow-up to [27239], [33643 ].
Props hvar, Presskopp, sabernhardt, james-roberts, arrasel403, abidhasan112, robinwpdeveloper, costdev, mukesh27.
Fixes#50865.
git-svn-id: https://develop.svn.wordpress.org/trunk@55251 602fd350-edb4-49c9-b593-d223f7449a82
When adding `decoding="async"` to images was introduced in [53480], it did not provide the ability to customize that behavior specifically for image tags returned from `wp_get_attachment_image()`.
With this changeset it is now possible to explicitly provide a `decoding` value of e.g. boolean `false` in the `$attr` parameter of the function, to ensure the attribute is omitted.
Props maximej, adamsilverstein, flixos90, costdev, peterwilsoncc, mukesh27.
Fixes#57086.
git-svn-id: https://develop.svn.wordpress.org/trunk@55171 602fd350-edb4-49c9-b593-d223f7449a82
Workaround `wp_img_tag_add_decoding_attr()` potentially breaking JavaScript and JSON data by limiting the addition of the decoding attribute to image tags using unescaped double quoted attributes `src` attributes.
Props rodricus, TimothyBlynJacobs, joelmadigan, mw108, adamsilverstein, flixos90, desrosj, mukesh27.
Fixes#56969.
git-svn-id: https://develop.svn.wordpress.org/trunk@54802 602fd350-edb4-49c9-b593-d223f7449a82
When the output format is altered with the `image_editor_output_format` filter, prefer the image engine that supports both input an output types, falling back to the engine that supports the input type.
Correct an issue where the output format filter wasn't respected because the selected engine didn't support the output format.
Props mikeschroder, ironprogrammer.
Fixes#54476.
git-svn-id: https://develop.svn.wordpress.org/trunk@54416 602fd350-edb4-49c9-b593-d223f7449a82
[54248] reversed the wrapping of `do_shortcode` and `apply_shortcodes` and updated all direct internal calls of `do_shortcode` to `apply_shortcodes` after [47004]. After further consideration, the long history of `do_shortcodes` should be favored over any subjective semantic improvements. This change reverts the remaining changes from #55883 not already reverted in [54278].
Follow-up to [47004], [54248], and [54278].
Props azaozz, jorbin.
See #55883.
git-svn-id: https://develop.svn.wordpress.org/trunk@54319 602fd350-edb4-49c9-b593-d223f7449a82
This changeset reverses the wrapping of `apply_shortcodes()` and `do_shortcode()` such that `apply_shortcodes()` is now the recommended function. In addition:
- Calls to `do_shortcode()` have been changed to `apply_shortcodes()`.
- Some default filter callbacks have been changed from `'do_shortcode'` to `'apply_shortcodes'`.
- Applicable documentation has been updated to refer to `apply_shortcodes()` instead.
Follow-up to [47004].
Props SergeyBiryukov, rafiahmedd, namithjawahar, peterwilsoncc, costdev.
Fixes#55883.
git-svn-id: https://develop.svn.wordpress.org/trunk@54248 602fd350-edb4-49c9-b593-d223f7449a82
This change allows for the muted property to be used in video elements which solves for content that wishes to `autoPlay` when a page is viewed. Adding `muted` to video elements adhears to the requirements browsers have to honor `autoPlay` functionality.
Props prokium, peterwilsoncc, costdev, johnbillion, Benouare.
Fixes#54788.
git-svn-id: https://develop.svn.wordpress.org/trunk@54128 602fd350-edb4-49c9-b593-d223f7449a82
The existing filter `image_editor_output_format` receives an additional parameter `$size_name` which is populated whenever it controls the output format for a specific registered image size to create. Otherwise, it remains empty. In order to achieve this, a low level change has been added in bringing a new `$size_name` class property to the `WP_Image_Editor` base class, which is introduced in a backward compatible way that will not cause conflicts with custom implementations.
This parameter is then used in new logic inside the `wp_default_image_output_mapping()` callback function for the filter, controlling whether `image/jpeg` should map to `image/webp` output or not. By default, this is enabled for all WordPress core image sizes by default, and this list can be modified using a new `wp_image_sizes_with_additional_mime_type_support` filter, e.g. to remove core sizes or add custom sizes.
The customization per image size may be further enhanced by providing a more declarative API via a new parameter on the `add_image_size()` function.
Props eugenemanuilov, flixos90, adamsilverstein, joegrainger.
Fixes#56526.
See #55443, #56288.
git-svn-id: https://develop.svn.wordpress.org/trunk@54097 602fd350-edb4-49c9-b593-d223f7449a82
While the `image_editor_output_format` filter is primarily used in WP Admin, it can also be executed in frontend scope, as the related `WP_Image_Editor` class and `wp_unique_filename()` function are being loaded in that scope.
Follow up to [54086].
See #55443, #56526.
git-svn-id: https://develop.svn.wordpress.org/trunk@54094 602fd350-edb4-49c9-b593-d223f7449a82
This changeset adds the capability for core media uploads to generate sub sized images in more than a single mime type. The output formats for each mime type can be controlled through a filter. WebP is used as an additional output format for JPEG images by default to improve front end performance.
When generating additional mime types, only images which are smaller than the respective original are retained. By default, additional mime type images are only generated for the built-in core image sizes and any custom sizes that have opted in.
Image meta is updated with a new 'sources' array containing file details for each mime type. Each image size in the 'sizes' array also gets a new 'sources' array that contains the image file details for each mime type.
This change also increases image upload retries to accommodate additional image sizes. It also adds a `$mime_type` parameter to the `wp_get_missing_image_subsizes` function and filter.
This change adds three new filters to enable full control of secondary mime image generation and output:
* A new filter `wp_image_sizes_with_additional_mime_type_support` that filters the sizes that support secondary mime type output. Developers can use this to control the output of additional mime type sub-sized images on a per size basis.
* A new filter `wp_upload_image_mime_transforms` that filters the output mime types for a given input mime type. Developers can use this to control generation of additional mime types for a given input mime type or even override the original mime type.
* A new filter `wp_content_image_mimes` which controls image mime type output selection and order for frontend content. Developers can use this to control the mime type output preference order for content images. Content images inserted from the media library will use the available image versions based on the order from this filter.
Thanks to the many contributors who helped develop, test and give feedback on this feature.
A haiku to summarize:
Upload a JPEG
Images of all sizes
Output as WebPs
Props flixos90, MatthiasReinholz, studiolxv, markhowellsmead, eatingrules, pbiron, mukesh27, joegrainger, mehulkaklotar, tweetythierry, akshitsethi, peterwilsoncc, eugenemanuilov, mitogh, shetheliving, clarkeemily, codekraft, mikeschroder, clorith, kasparsd, spacedmonkey, trevorpfromsandee, jb510, scofennellgmailcom, seedsca, cagsmith, karinclimber, dainemawer, baxbridge, grapplerulrich, sobatkras, chynnabenton, tonylocalword, barneydavey, kwillmorth, garymatthews919, olliejones, imarkinteractive, jeffpaul, feastdesignco, webbeetle, masteradhoc.
See #55443.
git-svn-id: https://develop.svn.wordpress.org/trunk@53751 602fd350-edb4-49c9-b593-d223f7449a82
- Deprecate `wp_get_attachment_thumb_file()`.
- Make `wp_get_attachment_thumb_url()` an alias of `wp_get_attachment_image_url()`. This fixes it to return the proper thumbnail URL and fall back to returning the URL to `image_meta['thumb']` if only that exists.
Props: markhowellsmead, mukesh27, csesumonpro, SergeyBiryukov, mikeschroder, killua99, joemcgill, mashukushibiki, mfgmicha, swissspidy, romulodl, nacin, JoshuaAbenazer, wonderboymusic, lonnylot, azaozz.
git-svn-id: https://develop.svn.wordpress.org/trunk@53685 602fd350-edb4-49c9-b593-d223f7449a82
* Add a `@since` note for the `decoding` attribute in `wp_get_attachment_image()`.
* Adjust `wp_img_tag_add_decoding_attr()` DocBlocks per the documentation standards.
* Wrap some long `sprintf()` calls in unit tests for better readability. In at least one case, `the_content` was unnecessarily passed to `sprintf()` as an extra (unused) parameter.
Follow-up to [53480].
See #53232.
git-svn-id: https://develop.svn.wordpress.org/trunk@53481 602fd350-edb4-49c9-b593-d223f7449a82
Dynamically add `decoding="async"` to image tags on the front end of a site to instruct browsers to download them in parallel.
Modifies `wp_get_attachment_image()`, `get_avatar()` to include the attribute by default. Modifies `wp_filter_content_tags()` to add the attribute during the front-end render of the site.
Introduces `wp_img_tag_add_decoding_attr()` to take an image tag and modify it to include the attribute. Introduces the filter `wp_img_tag_add_decoding_attr` used to define the default value for the attribute.
Props adamsilverstein, ayeshrajans, costdev, flixos90, hellofromtonya, isaumya, michaelbourne, mihai2u, mitogh, sergiomdgomes, spacedmonkey, westonruter, peterwilsoncc.
Fixes#53232.
git-svn-id: https://develop.svn.wordpress.org/trunk@53480 602fd350-edb4-49c9-b593-d223f7449a82
