Skip WordPress embeds (and other iframes which are hidden on pageload due to fallback content) from being lazy-loaded #1133
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…zyload filters when the image or iframe is not eligible in the first place.
…due to fallback content from being lazy-loaded.
felixarntz
commented
Mar 26, 2021
| function test_wp_iframe_tag_add_loading_attr_opt_out() { | ||
| $iframe = '<iframe src="https://www.example.com" width="640" height="360"></iframe>'; | ||
| add_filter( 'wp_iframe_tag_add_loading_attr', '__return_false' ); | ||
| $iframe = wp_iframe_tag_add_loading_attr( $iframe, 'test' ); |
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This call was missing before, so basically this test was testing nothing. :)
swissspidy
approved these changes
Apr 6, 2021
peterwilsoncc
approved these changes
Apr 6, 2021
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wp_filter_oembed_result()checks for any "unknown" oEmbed provider whether there is a fallbackblockquoteelement present for the iframe to load. If so, it hides the iframe visually and adds a generateddata-secretattribute to theiframeandblockquoteto associate them with each other. Then, thewp-embed.jsscript goes through the page looking for such elements. Once the iframe has been loaded (and thus notified thewp-embed.jsscript viapostMessage), the script makes the iframe visible and hides the blockquote.This mechanism can break when the iframe is marked to be lazy-loaded: Since the browser may interpret the hidden iframe as being irrelevant (since it's hidden), it will never load it, hence the iframe will not send the
postMessageevent to become visible.This PR ensures that such iframes do not receive the
loadingattribute and are instead kept unmodified. It also fixes a minor issue so that thewp_img_tag_add_loading_attrandwp_iframe_tag_add_loading_attrfilters no longer fire unnecessarily, and it fixes a pointless iframe test from before.Trac ticket: https://core.trac.wordpress.org/ticket/52768
This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.