Backporting changes in WordPress/gutenberg#45536

- Where no fluid max values are set (e.g., single or custom font size values), the "size" value will act as the maximum value in a clamp() function.
- Do not clamp value if a font size is lower than 14px
- Always honor a supplied fluid.min value, the lower bound of 14px notwidthstanding

src/wp-includes/block-supports/typography.php

@@ -452,6 +452,7 @@ function wp_get_computed_fluid_typography_value( $args = array() ) {
  * formula depending on available, valid values.
  *
  * @since 6.1.0
+ * @since 6.1.1 Adjusted min a
  *
  * @param array $preset                     {
  *     Required. fontSizes preset value as seen in theme.json.
@@ -489,7 +490,6 @@ function wp_get_typography_font_size_value( $preset, $should_use_fluid_typograph
 	$default_maximum_viewport_width   = '1600px';
 	$default_minimum_viewport_width   = '768px';
 	$default_minimum_font_size_factor = 0.75;
-	$default_maximum_font_size_factor = 1.5;
 	$default_scale_factor             = 1;
 	$default_minimum_font_size_limit  = '14px';
 
@@ -508,52 +508,54 @@ function wp_get_typography_font_size_value( $preset, $should_use_fluid_typograph
 	// Font sizes.
 	$preferred_size = wp_get_typography_value_and_unit( $preset['size'] );
 
-	// Protect against unsupported units.
+	// Protects against unsupported units.
 	if ( empty( $preferred_size['unit'] ) ) {
 		return $preset['size'];
 	}
 
-	// If no fluid max font size is available, create one using max font size factor.
-	if ( ! $maximum_font_size_raw ) {
-		$maximum_font_size_raw = round( $preferred_size['value'] * $default_maximum_font_size_factor, 3 ) . $preferred_size['unit'];
-	}
-
-	// If no fluid min font size is available, create one using min font size factor.
-	if ( ! $minimum_font_size_raw ) {
-		$minimum_font_size_raw = round( $preferred_size['value'] * $default_minimum_font_size_factor, 3 ) . $preferred_size['unit'];
-	}
-
-	// Normalizes the minimum font size limit according to the incoming unit, so we can perform checks using it.
+	/*
+	 * Normalizes the minimum font size limit according to the incoming unit,
+	 * in order to perform comparative checks.
+	 */
 	$minimum_font_size_limit = wp_get_typography_value_and_unit(
 		$default_minimum_font_size_limit,
 		array(
 			'coerce_to' => $preferred_size['unit'],
 		)
 	);
 
-	if ( ! empty( $minimum_font_size_limit ) ) {
+	// Don't enforce minimum font size if a font size has explicitly set a min and max value.
+	if ( ! empty( $minimum_font_size_limit ) && ( ! $minimum_font_size_raw && ! $maximum_font_size_raw ) ) {
 		/*
 		 * If a minimum size was not passed to this function
 		 * and the user-defined font size is lower than $minimum_font_size_limit,
-		 * then use the user-defined font size as the minimum font-size.
+		 * do not calculate a fluid value.
 		 */
-		if ( ! isset( $fluid_font_size_settings['min'] ) && $preferred_size['value'] < $minimum_font_size_limit['value'] ) {
-			$minimum_font_size_raw = implode( '', $preferred_size );
+		if ( $preferred_size['value'] <= $minimum_font_size_limit['value'] ) {
+			return $preset['size'];
+		}
+	}
+
+	// If no fluid max font size is available use the incoming value.
+	if ( ! $maximum_font_size_raw ) {
+		$maximum_font_size_raw = $preferred_size['value'] . $preferred_size['unit'];
+	}
+
+	/*
+	 * If no minimumFontSize is provided, create one using
+	 * the given font size multiplied by the min font size scale factor.
+	 */
+	if ( ! $minimum_font_size_raw ) {
+		$calculated_minimum_font_size = round(
+			$preferred_size['value'] * $default_minimum_font_size_factor,
+			3
+		);
+
+		// Only use calculated min font size if it's > $minimum_font_size_limit value.
+		if ( ! empty( $minimum_font_size_limit ) && $calculated_minimum_font_size <= $minimum_font_size_limit['value'] ) {
+			$minimum_font_size_raw = $minimum_font_size_limit['value'] . $minimum_font_size_limit['unit'];
 		} else {
-			$minimum_font_size_parsed = wp_get_typography_value_and_unit(
-				$minimum_font_size_raw,
-				array(
-					'coerce_to' => $preferred_size['unit'],
-				)
-			);
-
-			/*
-			 * If the passed or calculated minimum font size is lower than $minimum_font_size_limit
-			 * use $minimum_font_size_limit instead.
-			 */
-			if ( ! empty( $minimum_font_size_parsed ) && $minimum_font_size_parsed['value'] < $minimum_font_size_limit['value'] ) {
-				$minimum_font_size_raw = implode( '', $minimum_font_size_limit );
-			}
+			$minimum_font_size_raw = $calculated_minimum_font_size . $preferred_size['unit'];
 		}
 	}