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.


git-svn-id: https://develop.svn.wordpress.org/trunk@48170 602fd350-edb4-49c9-b593-d223f7449a82
This commit is contained in:
Felix Arntz
2020-06-25 18:43:25 +00:00
parent 886b254ec5
commit 9568134d7b
2 changed files with 43 additions and 18 deletions
+21 -10
View File
@@ -1963,6 +1963,7 @@ EOF;
/**
* @ticket 33641
* @ticket 50367
*/
function test_wp_filter_content_tags() {
$image_meta = wp_get_attachment_metadata( self::$large_id );
@@ -1982,10 +1983,12 @@ EOF;
$img_xhtml = str_replace( ' />', '/>', $img );
$img_html5 = str_replace( ' />', '>', $img );
$hwstring = image_hwstring( $size_array[0], $size_array[1] );
// Manually add srcset and sizes to the markup from get_image_tag().
$respimg = preg_replace( '|<img ([^>]+) />|', '<img $1 ' . $srcset . ' ' . $sizes . ' />', $img );
$respimg_no_size_in_class = preg_replace( '|<img ([^>]+) />|', '<img $1 ' . $srcset . ' ' . $sizes . ' />', $img_no_size_in_class );
$respimg_no_width_height = preg_replace( '|<img ([^>]+) />|', '<img $1 ' . $srcset . ' ' . $sizes . ' />', $img_no_width_height );
$respimg_no_width_height = preg_replace( '|<img ([^>]+) />|', '<img $1 ' . $hwstring . $srcset . ' ' . $sizes . ' />', $img_no_width_height );
$respimg_with_sizes_attr = preg_replace( '|<img ([^>]+) />|', '<img $1 ' . $srcset . ' />', $img_with_sizes_attr );
$respimg_xhtml = preg_replace( '|<img ([^>]+)/>|', '<img $1 ' . $srcset . ' ' . $sizes . ' />', $img_xhtml );
$respimg_html5 = preg_replace( '|<img ([^>]+)>|', '<img $1 ' . $srcset . ' ' . $sizes . ' />', $img_html5 );
@@ -1997,7 +2000,7 @@ EOF;
<p>Image, no size class. Should have srcset and sizes.</p>
%2$s
<p>Image, no width and height attributes. Should have srcset and sizes (from matching the file name).</p>
<p>Image, no width and height attributes. Should have width, height, srcset and sizes (from matching the file name).</p>
%3$s
<p>Image, no attachment ID class. Should NOT have srcset and sizes.</p>
@@ -2530,12 +2533,18 @@ EOF;
/**
* @ticket 44427
* @ticket 50367
*/
function test_wp_lazy_load_content_media() {
$img = get_image_tag( self::$large_id, '', '', '', 'medium' );
$img_xhtml = str_replace( ' />', '/>', $img );
$img_html5 = str_replace( ' />', '>', $img );
$iframe = '<iframe src="https://www.example.com"></iframe>';
$image_meta = wp_get_attachment_metadata( self::$large_id );
$size_array = $this->_get_image_size_array_from_meta( $image_meta, 'medium' );
$img = get_image_tag( self::$large_id, '', '', '', 'medium' );
$img_xhtml = str_replace( ' />', '/>', $img );
$img_html5 = str_replace( ' />', '>', $img );
$img_no_width_height = str_replace( ' width="' . $size_array[0] . '"', '', $img );
$img_no_width_height = str_replace( ' height="' . $size_array[1] . '"', '', $img_no_width_height );
$iframe = '<iframe src="https://www.example.com"></iframe>';
$lazy_img = wp_img_tag_add_loading_attr( $img, 'test' );
$lazy_img_xhtml = wp_img_tag_add_loading_attr( $img_xhtml, 'test' );
@@ -2551,13 +2560,15 @@ EOF;
%2$s
<p>Image, HTML 5.0 style.</p>
%3$s
<p>Image, with pre-existing "loading" attribute.</p>
<p>Image, with pre-existing "loading" attribute. Should not be modified.</p>
%4$s
<p>Image, without dimension attributes. Should not be modified.</p>
%5$s
<p>Iframe, standard. Should not be modified.</p>
%4$s';
%6$s';
$content_unfiltered = sprintf( $content, $img, $img_xhtml, $img_html5, $iframe, $img_eager );
$content_filtered = sprintf( $content, $lazy_img, $lazy_img_xhtml, $lazy_img_html5, $iframe, $img_eager );
$content_unfiltered = sprintf( $content, $img, $img_xhtml, $img_html5, $img_eager, $img_no_width_height, $iframe );
$content_filtered = sprintf( $content, $lazy_img, $lazy_img_xhtml, $lazy_img_html5, $img_eager, $img_no_width_height, $iframe );
// Do not add srcset and sizes.
add_filter( 'wp_img_tag_add_srcset_and_sizes_attr', '__return_false' );