Group duotone outputs and refactor rendering

[ajlende]

What?

Part 3 in a set of duotone php refactoring to fix small issues in duotone rendering.

• Part 1: Port colord to PHP
• Part 2: Deprecate remaining global duotone functions
• Part 3: Group all duotone outputs (this PR)
• Part 4: Polish duotone rendering code
• Part 5: Refactor duotone class to allow for multiple instances

This part is the refactoring that changes the most duotone rendering logic. It moves the stylesheet genration (style engine) code into its own action that happens after all blocks have rendered.

Also included is a small fix for classic themes that would always try outputting a stylesheet even if no duotone filters were present.

Why?

• Grouping the outputs will reduce the number of calls to the style engine that we have.
• In the future, SVG output can be optimized to wrap all definitions in a single <defs> group instead of having nested SVGs.
• Refactoring should help make the code more understandable, especially with the updates in part 4.
• Classic themes shouldn't include an empty duotone stylesheet if no duotone filters are present.

How?

• Creates a new output_block_styles as a companion to output_global_styles that handles the style engine rendering for all blocks in a single go.
• Refactors the code to reduce duplication. This is most apparent for SVG generation between editor.
• Adds a check for duotone filters before outputting anything.

Testing Instructions

1. Ensure that duotone filters in all of the example content render the same in the post editor, site editor, and frontend.
2. Test that the custom filters render in classic themes. You can use the same example content which includes some.

Example content for TT3 block-out, canary, and pilgrimage variations

<!-- wp:heading -->
<h2 class="wp-block-heading">Image core preset</h2>
<!-- /wp:heading -->

<!-- wp:image {"style":{"color":{"duotone":"var:preset|duotone|midnight"}}} -->
<figure class="wp-block-image"><img src="https://loremflickr.com/640/360" alt="placeholder image" class=""/><figcaption class="wp-element-caption">Preset slug: midnight</figcaption></figure>
<!-- /wp:image -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Image theme preset</h2>
<!-- /wp:heading -->

<!-- wp:image {"style":{"color":{"duotone":"var:preset|duotone|default-filter"}}} -->
<figure class="wp-block-image"><img src="https://loremflickr.com/640/360" alt="placeholder image" class=""/><figcaption class="wp-element-caption">Preset slug: default-filter</figcaption></figure>
<!-- /wp:image -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Image custom filter</h2>
<!-- /wp:heading -->

<!-- wp:image {"style":{"color":{"duotone":["rgb(92, 51, 10)","#fcf2e8"]}}} -->
<figure class="wp-block-image"><img src="https://loremflickr.com/640/360" alt="placeholder image" class=""/><figcaption class="wp-element-caption">Custom sepia filter</figcaption></figure>
<!-- /wp:image -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Image unset</h2>
<!-- /wp:heading -->

<!-- wp:image {"style":{"color":{"duotone":"unset"}}} -->
<figure class="wp-block-image"><img src="https://loremflickr.com/640/360" alt="placeholder image" class=""/><figcaption class="wp-element-caption">This should never have a filter applied</figcaption></figure>
<!-- /wp:image -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Image theme.json styles (plain block)</h2>
<!-- /wp:heading -->

<!-- wp:image {"style":{"color":{}}} -->
<figure class="wp-block-image"><img src="https://loremflickr.com/640/360" alt="placeholder image" class=""/><figcaption class="wp-element-caption"><code>settings.styles.blocks['core/image'].filter.duotone</code></figcaption></figure>
<!-- /wp:image -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Cover core preset</h2>
<!-- /wp:heading -->

<!-- wp:cover {"url":"https://loremflickr.com/640/360","dimRatio":0,"style":{"color":{"duotone":"var:preset|duotone|midnight"}}} -->
<div class="wp-block-cover"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-0 has-background-dim"></span><img class="wp-block-cover__image-background" alt="placeholder image" src="https://loremflickr.com/640/360" data-object-fit="cover"/><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Preset slug: midnight</p>
<!-- /wp:paragraph --></div></div>
<!-- /wp:cover -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Cover theme preset</h2>
<!-- /wp:heading -->

<!-- wp:cover {"url":"https://loremflickr.com/640/360","dimRatio":0,"style":{"color":{"duotone":"var:preset|duotone|default-filter"}}} -->
<div class="wp-block-cover"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-0 has-background-dim"></span><img class="wp-block-cover__image-background" alt="placeholder image" src="https://loremflickr.com/640/360" data-object-fit="cover"/><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Preset slug: default-filter</p>
<!-- /wp:paragraph --></div></div>
<!-- /wp:cover -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Cover custom filter</h2>
<!-- /wp:heading -->

<!-- wp:cover {"url":"https://loremflickr.com/640/360","dimRatio":0,"style":{"color":{"duotone":["rgb(92, 51, 10)","#fcf2e8"]}}} -->
<div class="wp-block-cover"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-0 has-background-dim"></span><img class="wp-block-cover__image-background" alt="placeholder image" src="https://loremflickr.com/640/360" data-object-fit="cover"/><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Custom sepia filter</p>
<!-- /wp:paragraph --></div></div>
<!-- /wp:cover -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Cover unset</h2>
<!-- /wp:heading -->

<!-- wp:cover {"url":"https://loremflickr.com/640/360","dimRatio":0,"style":{"color":{"duotone":"unset"}}} -->
<div class="wp-block-cover"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-0 has-background-dim"></span><img class="wp-block-cover__image-background" alt="placeholder image" src="https://loremflickr.com/640/360" data-object-fit="cover"/><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">This should never have a filter applied.</p>
<!-- /wp:paragraph --></div></div>
<!-- /wp:cover -->

<!-- wp:heading -->
<h2 class="wp-block-heading">Cover theme.json styles (plain block)</h2>
<!-- /wp:heading -->

<!-- wp:cover {"url":"https://loremflickr.com/640/360","dimRatio":0,"style":{"color":{}}} -->
<div class="wp-block-cover"><span aria-hidden="true" class="wp-block-cover__background has-background-dim-0 has-background-dim"></span><img class="wp-block-cover__image-background" alt="placeholder image" src="https://loremflickr.com/640/360" data-object-fit="cover"/><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…"} -->
<p class="has-text-align-center">This depends on <code>settings.styles.blocks['core/cover'].filter.duotone being set</code> to the CSS custom property for a preset.</p>
<!-- /wp:paragraph --></div></div>
<!-- /wp:cover -->

[github-actions]

Flaky tests detected in ad8f98c.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/4734482802
📝 Reported issues:

• [Flaky Test] shouldn't conflict with server-side autosave #35176 in specs/editor/various/autosave.test.js

[scruffian]

LGTM

[ajlende]

This changed from being keyed by slug to being keyed by id so that the id didn't have to get recomputed again later. The key in the second part of the example (wp-duotone-000000-ffffff-2) was wrong before, but it's right now which is why it didn't change.