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Media: Enhance wp_get_loading_optimization_attributes() to support …
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…arbitrary context values.

The `wp_get_loading_optimization_attributes()` function, which was introduced in 6.3, based on the now deprecated `wp_get_loading_attr_default()` function introduced in 5.5, relies on a `$context` parameter based on which it may alter its behavior and the attributes returned. So far, it has only supported context values used within WordPress core.

This changeset decouples the behaviors of the function from specific contexts, allowing for more flexibility. Theme and plugin developers will be able to rely on their own context values when rendering images in non-standard ways, rather than being forced to use a core context, to get the loading optimization benefits the function provides.

As part of this change, a `wp_loading_optimization_force_header_contexts` filter is introduced, which allows filtering the map of context values and whether they should be considered header contexts, i.e. i.e. any image having one of these contexts will be assumed to appear above the fold.

Props mukesh27, costdev, flixos90.
Fixes #58894.


git-svn-id: https://develop.svn.wordpress.org/trunk@56612 602fd350-edb4-49c9-b593-d223f7449a82
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@felixarntz
felixarntz committed Sep 18, 2023
1 parent 6a264d2 commit 414a123
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Showing 2 changed files with 231 additions and 74 deletions.
118 changes: 53 additions & 65 deletions src/wp-includes/media.php
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5652,13 +5652,9 @@ function wp_get_loading_optimization_attributes( $tag_name, $attr, $context ) {
* can result in the first post content image being lazy-loaded or an image further down the page being marked as a
* high priority.
*/
switch ( $context ) {
case 'the_post_thumbnail':
case 'wp_get_attachment_image':
case 'widget_media_image':
if ( doing_filter( 'the_content' ) ) {
return $loading_attrs;
}
// TODO: Handle shortcode images together with the content (see https://core.trac.wordpress.org/ticket/58853).
if ( 'the_content' !== $context && 'do_shortcode' !== $context && doing_filter( 'the_content' ) ) {
return $loading_attrs;
}

/*
Expand Down Expand Up @@ -5709,64 +5705,56 @@ function wp_get_loading_optimization_attributes( $tag_name, $attr, $context ) {
}

if ( null === $maybe_in_viewport ) {
switch ( $context ) {
// Consider elements with these header-specific contexts to be in viewport.
case 'template_part_' . WP_TEMPLATE_PART_AREA_HEADER:
case 'get_header_image_tag':
$maybe_in_viewport = true;
$maybe_increase_count = true;
break;
// Count main content elements and detect whether in viewport.
case 'the_content':
case 'the_post_thumbnail':
case 'do_shortcode':
// Only elements within the main query loop have special handling.
if ( ! is_admin() && in_the_loop() && is_main_query() ) {
/*
* Get the content media count, since this is a main query
* content element. This is accomplished by "increasing"
* the count by zero, as the only way to get the count is
* to call this function.
* The actual count increase happens further below, based
* on the `$increase_count` flag set here.
*/
$content_media_count = wp_increase_content_media_count( 0 );
$increase_count = true;

// If the count so far is below the threshold, `loading` attribute is omitted.
if ( $content_media_count < wp_omit_loading_attr_threshold() ) {
$maybe_in_viewport = true;
} else {
$maybe_in_viewport = false;
}
}
/*
* For the 'the_post_thumbnail' context, the following case
* clause needs to be considered as well, therefore skip the
* break statement here if the viewport has not been
* determined.
*/
if ( 'the_post_thumbnail' !== $context || null !== $maybe_in_viewport ) {
break;
}
// phpcs:ignore Generic.WhiteSpace.ScopeIndent.Incorrect
// Consider elements before the loop as being in viewport.
case 'wp_get_attachment_image':
case 'widget_media_image':
if (
// Only apply for main query but before the loop.
$wp_query->before_loop && $wp_query->is_main_query()
/*
* Any image before the loop, but after the header has started should not be lazy-loaded,
* except when the footer has already started which can happen when the current template
* does not include any loop.
*/
&& did_action( 'get_header' ) && ! did_action( 'get_footer' )
) {
$maybe_in_viewport = true;
$maybe_increase_count = true;
}
break;
$header_enforced_contexts = array(
'template_part_' . WP_TEMPLATE_PART_AREA_HEADER => true,
'get_header_image_tag' => true,
);

/**
* Filters the header-specific contexts.
*
* @since 6.4.0
*
* @param array $default_header_enforced_contexts Map of contexts for which elements should be considered
* in the header of the page, as $context => $enabled
* pairs. The $enabled should always be true.
*/
$header_enforced_contexts = apply_filters( 'wp_loading_optimization_force_header_contexts', $header_enforced_contexts );

// Consider elements with these header-specific contexts to be in viewport.
if ( isset( $header_enforced_contexts[ $context ] ) ) {
$maybe_in_viewport = true;
$maybe_increase_count = true;
} elseif ( ! is_admin() && in_the_loop() && is_main_query() ) {
/*
* Get the content media count, since this is a main query
* content element. This is accomplished by "increasing"
* the count by zero, as the only way to get the count is
* to call this function.
* The actual count increase happens further below, based
* on the `$increase_count` flag set here.
*/
$content_media_count = wp_increase_content_media_count( 0 );
$increase_count = true;

// If the count so far is below the threshold, `loading` attribute is omitted.
if ( $content_media_count < wp_omit_loading_attr_threshold() ) {
$maybe_in_viewport = true;
} else {
$maybe_in_viewport = false;
}
} elseif (
// Only apply for main query but before the loop.
$wp_query->before_loop && $wp_query->is_main_query()
/*
* Any image before the loop, but after the header has started should not be lazy-loaded,
* except when the footer has already started which can happen when the current template
* does not include any loop.
*/
&& did_action( 'get_header' ) && ! did_action( 'get_footer' )
) {
$maybe_in_viewport = true;
$maybe_increase_count = true;
}
}

Expand Down
187 changes: 178 additions & 9 deletions tests/phpunit/tests/media.php
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4301,15 +4301,6 @@ public function test_wp_get_loading_optimization_attributes( $context ) {
// Set as main query.
$this->set_main_query( $query );

/*
* For contexts other than for the main content, still return 'lazy' even in the loop
* and in the main query, and do not increase the content media count.
*/
$this->assertSame(
array( 'loading' => 'lazy' ),
wp_get_loading_optimization_attributes( 'img', $attr, 'wp_get_attachment_image' )
);

// First three element are not lazy loaded. However, first image is loaded with fetchpriority high.
$this->assertSame(
array( 'fetchpriority' => 'high' ),
Expand Down Expand Up @@ -4339,6 +4330,184 @@ public function test_wp_get_loading_optimization_attributes( $context ) {
}
}

/**
* Tests that wp_get_loading_optimization_attributes() returns fetchpriority=high and increases the count for arbitrary contexts in the main loop.
*
* @ticket 58894
*
* @covers ::wp_get_loading_optimization_attributes
*
* @dataProvider data_wp_get_loading_optimization_attributes_arbitrary_contexts
*
* @param string $context Context for the element for which the loading optimization attribute is requested.
*/
public function test_wp_get_loading_optimization_attributes_with_arbitrary_contexts_in_main_loop( $context ) {
$attr = $this->get_width_height_for_high_priority();

$this->assertSame(
array( 'loading' => 'lazy' ),
wp_get_loading_optimization_attributes( 'img', $attr, $context ),
'The "loading" attribute should be "lazy" when not in the loop or the main query.'
);

$query = $this->get_new_wp_query_for_published_post();

// Set as main query.
$this->set_main_query( $query );

while ( have_posts() ) {
the_post();

$this->assertSame(
array( 'fetchpriority' => 'high' ),
wp_get_loading_optimization_attributes( 'img', $attr, $context ),
'The "fetchpriority" attribute should be "high" while in the loop and the main query.'
);

// Images with a certain minimum size in the arbitrary contexts of the page are also counted towards the threshold.
$this->assertSame( 1, wp_increase_content_media_count( 0 ), 'The content media count should be 1.' );
}
}

/**
* Tests that wp_get_loading_optimization_attributes() does not return lazy loading attributes when arbitrary contexts are used before the main query loop.
*
* @ticket 58894
*
* @covers ::wp_get_loading_optimization_attributes
*
* @dataProvider data_wp_get_loading_optimization_attributes_arbitrary_contexts
*
* @param string $context Context for the element for which the loading optimization attribute is requested.
*/
public function test_wp_get_loading_optimization_attributes_with_arbitrary_contexts_before_main_query_loop( $context ) {
$attr = $this->get_width_height_for_high_priority();

$query = $this->get_new_wp_query_for_published_post();

// Set as main query.
$this->set_main_query( $query );

$this->assertSame(
array( 'loading' => 'lazy' ),
wp_get_loading_optimization_attributes( 'img', $attr, $context ),
'The "loading" attribute should be "lazy" before the main query loop.'
);

while ( have_posts() ) {
the_post();

$this->assertSame(
array( 'fetchpriority' => 'high' ),
wp_get_loading_optimization_attributes( 'img', $attr, $context ),
'The "fetchpriority" attribute should be "high" while in the loop and the main query.'
);

$this->assertArrayNotHasKey(
'loading',
wp_get_loading_optimization_attributes( 'img', $attr, $context ),
'No "loading" attribute should be present on the second image in the main query loop.'
);
}
}

/**
* Data provider.
*
* @return array[]
*/
public function data_wp_get_loading_optimization_attributes_arbitrary_contexts() {
return array(
array( 'wp_get_attachment_image' ),
array( 'something_completely_arbitrary' ),
);
}

/**
* Tests that wp_get_loading_optimization_attributes() returns empty array for arbitrary context.
*
* @ticket 58894
*
* @covers ::wp_get_loading_optimization_attributes
*/
public function test_wp_get_loading_optimization_attributes_should_return_empty_array_for_any_arbitrary_context() {
remove_all_filters( 'the_content' );

$result = null;
add_filter(
'the_content',
function( $content ) use ( &$result ) {
$attr = $this->get_width_height_for_high_priority();
$result = wp_get_loading_optimization_attributes( 'img', $attr, 'something_completely_arbitrary' );
return $content;
}
);
apply_filters( 'the_content', '' );

$this->assertSame( array(), $result );
}

/**
* @ticket 58894
*
* @covers ::wp_get_loading_optimization_attributes
*
* @dataProvider data_wp_get_loading_optimization_attributes_header_context
*
* @param string $context The context for the header.
*/
public function test_wp_get_loading_optimization_attributes_header_contexts( $context ) {
$attr = $this->get_width_height_for_high_priority();

$this->assertArrayNotHasKey(
'loading',
wp_get_loading_optimization_attributes( 'img', $attr, $context ),
'Images in the header context should not be lazy-loaded.'
);

add_filter( 'wp_loading_optimization_force_header_contexts', '__return_empty_array' );

$this->assertSame(
array( 'loading' => 'lazy' ),
wp_get_loading_optimization_attributes( 'img', $attr, $context ),
'Images in the header context should get lazy-loaded after the wp_loading_optimization_force_header_contexts filter.'
);
}

/**
* Data provider.
*
* @return array[]
*/
public function data_wp_get_loading_optimization_attributes_header_context() {
return array(
array( 'template_part_' . WP_TEMPLATE_PART_AREA_HEADER ),
array( 'get_header_image_tag' ),
);
}

/**
* @ticket 58894
*
* @covers ::wp_get_loading_optimization_attributes
*/
public function test_wp_loading_optimization_force_header_contexts_filter() {
$attr = $this->get_width_height_for_high_priority();

add_filter(
'wp_loading_optimization_force_header_contexts',
function( $context ) {
$contexts['something_completely_arbitrary'] = true;
return $contexts;
}
);

$this->assertSame(
array( 'fetchpriority' => 'high' ),
wp_get_loading_optimization_attributes( 'img', $attr, 'something_completely_arbitrary' )
);
}

/**
* Tests that wp_get_loading_optimization_attributes() returns the expected loading attribute value before loop but after get_header if not main query.
*
Expand Down

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