Fluid typography: use layout.wideSize as max viewport width

[ramonjd]

Let's use the value of settings.layout.wideSize, if set, as the maximum viewport width for fluid font size calculations.

The default value is 1600px.

Checks against invalid settings.layout.wideSize values to ensure resulting clamp values are calculated correctly. This is s defensive measure to prevent bugs.

Added to the Gutenberg plugin in:

• Fluid typography: use layout.wideSize as max viewport width gutenberg#49815
• Fluid typography: custom font-sizes should use max viewport width gutenberg#51516

❗ If #4605 is merged first, this PR will need a rebase and possibly the tests updated

Testing

1. Fire up this branch and use 2023 (a theme that has fluid font sizes enabled)
2. In the site editor play around with setting the wide size for layouts, as well as adding some custom font sizes.
3. In the frontend, check that your font sizes should be at their maximum values when viewport is at least as wide as the value of layout.wideSize

Note: this will only work on the frontend. The editor JS changes will be ready once WordPress/gutenberg#51516 is bundled with the npm packages destined for Core

npm run test:php -- --filter Tests_Block_Supports_Typography

Trac ticket: https://core.trac.wordpress.org/ticket/58522

---

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[tellthemachines]

Code looks good and layout wide size constraint works as expected! I assume the changes from WordPress/gutenberg#51516 aren't testable until the npm packages are updated?

[ramonjd]

Thanks for testing @tellthemachines

I assume the changes from WordPress/gutenberg#51516 aren't testable until the npm packages are updated?

Yes. Thanks for mentioning that. I've updated the test description.

Note to self: if this gets merged, I'll update the tests for #4605 (which will be affected due to the change in the way we calculate max viewport size)

[tellthemachines]

Committed in r55946 / c790ae4.