id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc	focuses
64597	Client Site Media: PHP backports from Gutenberg	adamsilverstein	adamsilverstein	"== Description

This ticket adds REST API index data and preloaded paths for the client-side media processing feature being developed in Gutenberg.

Client-side media processing allows the browser to handle image resizing, thumbnail generation, and format conversion using WebAssembly (via the vips library), reducing server load and improving upload performance.

=== Changes

1. **REST API Index** (`WP_REST_Server::get_index()`): Adds media processing configuration fields to the REST API root index response for users with the `upload_files` capability.

2. **Preload Paths**: The post editor (`edit-form-blocks.php`) and site editor (`site-editor.php`) now preload these fields.

=== New Fields

The following settings are now available in the REST API index (for authorized users) and preloaded in the editors:

* `image_sizes` - Available image size configurations for thumbnail generation
* `image_size_threshold` - Big image size threshold (default 2560px) for automatic scaling of large images
* `image_output_formats` - Output format mappings for image conversion (e.g., JPEG to WebP)
* `jpeg_interlaced` - Whether to use progressive/interlaced JPEG encoding
* `png_interlaced` - Whether to use interlaced PNG encoding
* `gif_interlaced` - Whether to use interlaced GIF encoding

These preloaded paths prevent additional REST API requests when the editor loads, improving performance.

== Related Gutenberg PRs

* [#74566 - Create sub-sized images](https://github.com/WordPress/gutenberg/pull/74566)
* [#74908 - Add image output formats and interlace settings to REST API client](https://github.com/WordPress/gutenberg/pull/74908)
* [#75112 - Media: Graduate client-side media processing from experimental](https://github.com/WordPress/gutenberg/pull/75112)

== Tracking Issue

* [#75062 - Graduate Client Side Media out of experiments](https://github.com/WordPress/gutenberg/issues/75062)

== Testing

=== REST API Index
1. As an admin user, make a GET request to `/wp-json/` (the REST API root)
2. Verify the response includes `image_sizes`, `image_size_threshold`, `image_output_formats`, `jpeg_interlaced`, `png_interlaced`, and `gif_interlaced`
3. As a subscriber (without `upload_files` capability), verify these fields are NOT present

=== Editor Preloading
1. Open the post editor or site editor
2. Check the Network tab in browser DevTools
3. Look for the preloaded `/?_fields=...` request
4. Verify the response includes the new image settings

== Patch

GitHub PR: https://github.com/WordPress/wordpress-develop/pull/XXXXX
"	enhancement	closed	normal	7.0	Editor	trunk	normal	fixed	has-patch gutenberg-merge