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Media: Ensure images have dimensions to reduce layout shift and facilitate lazy-loading. 

This changeset ensures that attachment images which are inserted without `width` and `height` attributes still receive them in the frontend, to reduce cumulative layout shift. Adding the dimensions happens as part of the logic for adding `srcset` and `sizes` attributes, which already assume the specific width and height of the respective image.

Images are now only lazy-loaded if they have `width` and `height` attributes present. While missing these attributes itself is what causes layout shifts, lazy-loading such images can make this problem more apparent to the user.

Props adamsilverstein, westonruter.
Fixes #50367. See #44427.

Built from https://develop.svn.wordpress.org/trunk@48170


git-svn-id: http://core.svn.wordpress.org/trunk@47939 1a063a9b-81f0-0310-95a4-ce76da25c4cd
This commit is contained in:
Felix Arntz 2020-06-25 18:45:08 +00:00
parent b83d6bd777
commit f18870ae4e
2 changed files with 23 additions and 9 deletions
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24
wp-includes/media.php
View File

@ -1495,6 +1495,7 @@ function wp_calculate_image_sizes( $size, $image_src = null, $image_meta = null,
* Adds 'srcset' and 'sizes' attributes to an existing 'img' element.
*
* @since 4.4.0
* @since 5.5.0 `width` and `height` are now added if not already present.
*
* @see wp_calculate_image_srcset()
* @see wp_calculate_image_sizes()
@ -1525,6 +1526,8 @@ function wp_image_add_srcset_and_sizes( $image, $image_meta, $attachment_id ) {
return $image;
}
$attr = '';
$width = preg_match( '/ width="([0-9]+)"/', $image, $match_width ) ? (int) $match_width[1] : 0;
$height = preg_match( '/ height="([0-9]+)"/', $image, $match_height ) ? (int) $match_height[1] : 0;
@ -1547,12 +1550,15 @@ function wp_image_add_srcset_and_sizes( $image, $image_meta, $attachment_id ) {
}
}
}
}
if ( ! $width || ! $height ) {
return $image;
}
// Add width and height if not present.
$attr .= ' ' . trim( image_hwstring( $width, $height ) );
}
$size_array = array( $width, $height );
$srcset = wp_calculate_image_srcset( $size_array, $image_src, $image_meta, $attachment_id );
@ -1567,17 +1573,19 @@ function wp_image_add_srcset_and_sizes( $image, $image_meta, $attachment_id ) {
if ( $srcset && $sizes ) {
// Format the 'srcset' and 'sizes' string and escape attributes.
$attr = sprintf( ' srcset="%s"', esc_attr( $srcset ) );
$attr .= sprintf( ' srcset="%s"', esc_attr( $srcset ) );
if ( is_string( $sizes ) ) {
$attr .= sprintf( ' sizes="%s"', esc_attr( $sizes ) );
}
// Add 'srcset' and 'sizes' attributes to the image markup.
$image = preg_replace( '/<img ([^>]+?)[\/ ]*>/', '<img $1' . $attr . ' />', $image );
}
if ( empty( $attr ) ) {
return $image;
}
// Add extra attributes to the image markup.
return preg_replace( '/<img ([^>]+?)[\/ ]*>/', '<img $1' . $attr . ' />', $image );
}
/**
@ -1714,6 +1722,12 @@ function wp_img_tag_add_loading_attr( $image, $context ) {
$value = 'lazy';
}
// Images should have dimension attributes for the `loading` attribute
// to be added.
if ( false === strpos( $image, ' width=' ) || false === strpos( $image, ' height=' ) ) {
return $image;
}
$quote = null;
// Check if the img tag is valid (has `src` attribute) and get the quote character.

2
wp-includes/version.php
View File

@ -13,7 +13,7 @@
*
* @global string $wp_version
*/
$wp_version = '5.5-alpha-48169';
$wp_version = '5.5-alpha-48170';
/**
* Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.