Incorrect assumption of hex input by ReaderThemeSupportFeatures::get_relative_luminance_from_hex()

[westonruter]

Bug Description

See support forum topic.

The ReaderThemeSupportFeatures::get_relative_luminance_from_hex() method incorrectly assumes hex input:

amp-wp/src/ReaderThemeSupportFeatures.php

Lines 364 to 383 in a373ac8

	public function get_relative_luminance_from_hex( $hex ) {
	// Remove the "#" symbol from the beginning of the color.
	$hex = ltrim( $hex, '#' );
	// Make sure there are 6 digits for the below calculations.
	if ( 3 === strlen( $hex ) ) {
	$hex = $hex[0] . $hex[0] . $hex[1] . $hex[1] . $hex[2] . $hex[2];
	}
	// Get red, green, blue.
	$red = hexdec( substr( $hex, 0, 2 ) );
	$green = hexdec( substr( $hex, 2, 2 ) );
	$blue = hexdec( substr( $hex, 4, 2 ) );
	// Calculate the luminance.
	$lum = ( 0.2126 * $red ) + ( 0.7152 * $green ) + ( 0.0722 * $blue );
	return (int) round( $lum );
	}
	}

It turns out that in some cases, a theme may be passing a CSS variable like var(--base-2), or presumably rgba(...) could also be passed.

To account for this, the print_editor_color_palette_styles method should skip passing the color value into get_relative_luminance_from_hex when it is not a valid hex.

This could be achieved by adding:

if ( ! preg_match( '/^[0-9a-f]{3}[0-9a-f]{3}?$/i', ltrim( $color_option[ self::KEY_COLOR ], '#' ) ) ) {
    continue;
}

After the following condition (or as part of it):

amp-wp/src/ReaderThemeSupportFeatures.php

Lines 281 to 286 in a373ac8

	private function print_editor_color_palette_styles( array $color_palette ) {
	echo '<style id="amp-wp-theme-support-editor-color-palette">';
	foreach ( $color_palette as $color_option ) {
	if ( ! $this->has_required_feature_props( self::FEATURE_EDITOR_COLOR_PALETTE, $color_option ) ) {
	continue;
	}

Expected Behaviour

If a non-hex color is used, no deprecated error should be raised from hexdec() here:

amp-wp/src/ReaderThemeSupportFeatures.php

Lines 375 to 377 in a373ac8

	$red = hexdec( substr( $hex, 0, 2 ) );
	$green = hexdec( substr( $hex, 2, 2 ) );
	$blue = hexdec( substr( $hex, 4, 2 ) );

Screenshots

No response

PHP Version

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Plugin Version

2.3.0

AMP plugin template mode

Reader

WordPress Version

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Site Health

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Gutenberg Version

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OS(s) Affected

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Browser(s) Affected

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Device(s) Affected

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Acceptance Criteria

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Implementation Brief

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QA Testing Instructions

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Demo

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Changelog Entry

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[pavanpatil1]

QA Passed ✅

Cross-checked the issue with the below snippet and the fix is working as expected.

add_action(
	'after_setup_theme',
	static function() {
		add_theme_support( 'editor-color-palette', array(
			array(
				'name'  => 'bar',
				'slug'  => 'bar',
				'color' => 'var(--bar)',
			)
		) );
	}
);

Before:

debuglog.mp4

After fix:

debuglog1.mp4