Add filter for the block-template viewport meta tag

[joemaller]

The base block-template.php used for full site editing does not provide a hook for modifying the viewport meta tag. Despite being inserted into wp_head by the _block_template_viewport_meta_tag action hook, the actual tag is basically hard coded and untouchable: ​https://github.com/WordPress/wordpress-develop/blob/00ed25e2c9b20607418cbe8a6103c336d1bf92bd/src/wp-includes/block-template.php#L273-L275.

This ticket introduces a new filter which allows for customization of this meta tag.

This ticket introduces a new filter which allows for customization of the block-template's viewport meta tag.

Despite being inserted into wp_head by the _block_template_viewport_meta_tag action hook, the actual tag is basically ​hard coded and untouchable.

Without this filter, the meta tag can be changed by first removing the _block_template_viewport_meta_tag action:

add_action('pre_get_posts', function() {
    remove_action('wp_head', '_block_template_viewport_meta_tag', 0);
});

And then hooking in a new meta tag:

add_action('wp_head', function() {
        echo '<meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no" />' . "\n";
}, 0);

With the new filter, just this:

add_filter('block_template_viewport_meta_tag', function() {
    return '<meta name="viewport" content="width=device-width" />';
});