[Fonts API] Allow enqueueing of font face with a chosen weight within range

[zaguiini]

What problem does this address?

Since weights can be a range, it would make sense for any weight within the range of the registered font face to be enqueued.

For example:

wp_register_webfont(
	array(
		'font-family'  => 'Source Serif Pro',
		'font-style'   => 'normal',
		'font-stretch' => 'normal',
		'font-weight'  => '200 900',
		'src'          => get_theme_file_uri( '/assets/fonts/SourceSerif4Variable-Roman.ttf.woff2' ),
	)
);

Font weight range from 200 to 900 gets registered. But right now, if you try passing a font weight within this range, you get an error:

The "Source Serif Pro:400:normal" font face is not registered.

What is your proposed solution?

Passing a font weight within the range (200 to 900) should enqueue that registered face.

In theme.json:

"fontFamilies": [
	{
		"fontFamily": "Source Serif Pro",
		"name": "Source Serif Pro",
		"slug": "source-serif-pro",
		"fontFaces": [
			{
				"fontFamily": "Source Serif Pro",
				"fontWeight": "400",
				"fontStyle": "normal"
			}
		]
	}
]

[hellofromtonya]

Update:

This issue is no longer valid for the Fonts API once the Font Library is merged.

Why?

As shared in Ongoing Roadmap update #41479 (comment), the Fonts API will no publicly expose the means to "register" or "enqueue" fonts. The Font Library and font management will handle the user workflow.

The Fonts API will get / pull the font variations from Theme JSON merged data that need their @font-face generated and printed.

Thank you everyone for your contributions!