Introduce a filter that short-circuits the avatar URL generation

[johnbillion]

Description of the Change

When a dynamic image resizing service (such as Tachyon or Photon) is in use, Simple Local Avatars provides no way for the URL of an avatar of a given size to be short-circuited so as to avoid its own dynamic resizing that happens via a WP_Image_Editor instance.

This change introduces a filter to short-circuit the URL for an avatar (once it's been determined that a "full" size exists), allowing a dynamic image resizing service to return its own scaled version of the user's image.

How to test the Change

Here's a simplified example of how this filter could be used on a site that uses Tachyon:

add_filter(
	'pre_simple_local_avatar_url',
	function( $url, $user_id, $size, $local_avatars ) {
		return tachyon_url( $local_avatars['full'], [ 'resize' => "{$size},{$size}" ] );
	},
	10,
	4
);

Changelog Entry

Added - pre_simple_local_avatar_url filter to allow an avatar image to be short-circuited before Simple Local Avatars processes it.

Credits

@johnbillion

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[jeffpaul]

Thanks @johnbillion, that usage makes sense to me. Tagging @faisal-alvi for code review/testing to see if there are any concerns here before moving towards merge/release.

[peterwilsoncc]

@faisal-alvi I have a copy of Tachyon set up locally if you need guidance on getting it going/want me to test.

[faisal-alvi]

@peterwilsoncc it would be great if you test + code review this as I do not have Tachyon set up locally. Thanks! ❤️

[peterwilsoncc]

This tests well and works as described.

I've just raised a discussion internally as to whether the plugin should switch to using wp_get_attachment_image_src()[0] and storing dynamically resized images in the image post meta. That will allow the plugin to just work with Tachyon, Photon and other services using the image_downsize filter to dynamically resize images.

[peterwilsoncc]

@johnbillion We've considered the options and decided to put this in for now rather than switch to the proper media functions. The team needs to do a little more investigating of the implications for multisite installations using shared avatars.

I think that would be to be esc_url_raw anyway

Yeah, it probably should be but we use esc_url() elsewhere in the function so it's intended for printing rather than getting.. It's probably too late to make the change now.