wp_get_child_layout_style_rules( string $selector, array $child_layout, array $parent_layout = array(), array|null $viewport_overrides = null ): array

109function wp_get_child_layout_style_rules( $selector, $child_layout, $parent_layout = array(), $viewport_overrides = null ) {110	$base_child_layout              = is_array( $child_layout ) ? $child_layout : array();111	$viewport_overrides             = is_array( $viewport_overrides ) ? $viewport_overrides : null;112	$child_layout                   = null === $viewport_overrides ? $base_child_layout : array_replace( $base_child_layout, $viewport_overrides );113	$child_layout_declarations      = array();114	$child_layout_styles            = array();115	$has_viewport_property_override = static function ( $property ) use ( $viewport_overrides ) {116		return array_key_exists( $property, $viewport_overrides );117	};118 119	$self_stretch      = $child_layout['selfStretch'] ?? null;120	$base_self_stretch = $base_child_layout['selfStretch'] ?? null;121 122	/*123	 * These are the serialized `selfStretch` values. `max` used to be called124	 * "Fixed" in the UI, but was renamed and replaced by `fixedNoShrink`.125	 */126	$flex_child_layout_values = array(127		'fit'   => 'fit',128		'grow'  => 'fill',129		'max'   => 'fixed',130		'fixed' => 'fixedNoShrink',131	);132	$flex_size_values         = array(133		$flex_child_layout_values['max'],134		$flex_child_layout_values['fixed'],135	);136 137	if ( null === $viewport_overrides || $has_viewport_property_override( 'selfStretch' ) || $has_viewport_property_override( 'flexSize' ) ) {138		if (139			null !== $viewport_overrides &&140			( $flex_child_layout_values['fit'] === $self_stretch || $flex_child_layout_values['grow'] === $self_stretch ) &&141			in_array( $base_self_stretch, $flex_size_values, true ) &&142			isset( $base_child_layout['flexSize'] )143		) {144			$child_layout_declarations['flex-basis'] = 'unset';145			if ( $flex_child_layout_values['fixed'] === $base_self_stretch ) {146				$child_layout_declarations['flex-shrink'] = 'unset';147			}148		}149		if ( in_array( $self_stretch, $flex_size_values, true ) && isset( $child_layout['flexSize'] ) ) {150			$child_layout_declarations['flex-basis'] = $child_layout['flexSize'];151			if ( $flex_child_layout_values['fixed'] === $self_stretch ) {152				$child_layout_declarations['flex-shrink'] = '0';153			} elseif ( null !== $viewport_overrides && $flex_child_layout_values['fixed'] === $base_self_stretch ) {154				$child_layout_declarations['flex-shrink'] = 'unset';155			}156			$child_layout_declarations['box-sizing'] = 'border-box';157		} elseif ( $flex_child_layout_values['grow'] === $self_stretch ) {158			$child_layout_declarations['flex-grow'] = '1';159		}160	}161 162	$column_start = $child_layout['columnStart'] ?? null;163	$column_span  = $child_layout['columnSpan'] ?? null;164	if ( null === $viewport_overrides || $has_viewport_property_override( 'columnStart' ) || $has_viewport_property_override( 'columnSpan' ) ) {165		if ( $column_start && $column_span ) {166			$child_layout_declarations['grid-column'] = "$column_start / span $column_span";167		} elseif ( $column_start ) {168			$child_layout_declarations['grid-column'] = "$column_start";169		} elseif ( $column_span ) {170			$child_layout_declarations['grid-column'] = "span $column_span";171		}172	}173 174	$row_start = $child_layout['rowStart'] ?? null;175	$row_span  = $child_layout['rowSpan'] ?? null;176	if ( null === $viewport_overrides || $has_viewport_property_override( 'rowStart' ) || $has_viewport_property_override( 'rowSpan' ) ) {177		if ( $row_start && $row_span ) {178			$child_layout_declarations['grid-row'] = "$row_start / span $row_span";179		} elseif ( $row_start ) {180			$child_layout_declarations['grid-row'] = "$row_start";181		} elseif ( $row_span ) {182			$child_layout_declarations['grid-row'] = "span $row_span";183		}184	}185 186	if ( ! empty( $child_layout_declarations ) ) {187		$child_layout_styles[] = array(188			'selector'     => $selector,