oEmbed dynamic aspect ratio handling in block themes without $content_width

[sanchothefat]

oEmbed handling in block themes is good for well known players like YouTube with the embed block aspect ratio class handling, but some embeds are just coming out at 500px per the default wp_embed_defaults() settings, especially now that block themes don't necessary set $content_width - the theme.json content width replaces it many ways but it can have a unit other than px.

I think that block themes should set default embed max widths to the same dimension as the large image width, and then if the oembed data response contains width and height values, generate a class name and add supporting styles to set the aspect-ratio and auto height, or output inline styles on the iframe.

This will improve the output and behaviour to match user expectations for more built in, custom and discoverable embeds.

One example is using the player.vimeo.com video embed endpoint - used for non publicly listed videos, try embedding ​https://player.vimeo.com/video/1138248349 and make the block full width.

In summary:

• Setting $content_width is no longer viable as a simple pixel value for settings embed width and may be missing
• theme.json can use number + units for the contentWidth and wideWidth so can't reliably set $content_width from it
• The default embed size from wp_embed_defaults() is 500px wide without $content_width set to something else
• Passing width or maxwidth to the provider URL via the oembed_fetch_url filter gets a larger embed within the iframe, but it isn't responsive e.g. height remains fixed