Source
File: wp-includes/class-wp-customize-setting.php
public function preview() {
if ( ! isset( $this->_previewed_blog_id ) ) {
$this->_previewed_blog_id = get_current_blog_id();
}
// Prevent re-previewing an already-previewed setting.
if ( $this->is_previewed ) {
return true;
}
$id_base = $this->id_data['base'];
$is_multidimensional = ! empty( $this->id_data['keys'] );
$multidimensional_filter = array( $this, '_multidimensional_preview_filter' );
/*
* Check if the setting has a pre-existing value (an isset check),
* and if doesn't have any incoming post value. If both checks are true,
* then the preview short-circuits because there is nothing that needs
* to be previewed.
*/
$undefined = new stdClass();
$needs_preview = ( $undefined !== $this->post_value( $undefined ) );
$value = null;
// Since no post value was defined, check if we have an initial value set.
if ( ! $needs_preview ) {
if ( $this->is_multidimensional_aggregated ) {
$root = self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['root_value'];
$value = $this->multidimensional_get( $root, $this->id_data['keys'], $undefined );
} else {
$default = $this->default;
$this->default = $undefined; // Temporarily set default to undefined so we can detect if existing value is set.
$value = $this->value();
$this->default = $default;
}
$needs_preview = ( $undefined === $value ); // Because the default needs to be supplied.
}
// If the setting does not need previewing now, defer to when it has a value to preview.
if ( ! $needs_preview ) {
if ( ! has_action( "customize_post_value_set_{$this->id}", array( $this, 'preview' ) ) ) {
add_action( "customize_post_value_set_{$this->id}", array( $this, 'preview' ) );
}
return false;
}
switch ( $this->type ) {
case 'theme_mod':
if ( ! $is_multidimensional ) {
add_filter( "theme_mod_{$id_base}", array( $this, '_preview_filter' ) );
} else {
if ( empty( self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['previewed_instances'] ) ) {
// Only add this filter once for this ID base.
add_filter( "theme_mod_{$id_base}", $multidimensional_filter );
}
self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['previewed_instances'][ $this->id ] = $this;
}
break;
case 'option':
if ( ! $is_multidimensional ) {
add_filter( "pre_option_{$id_base}", array( $this, '_preview_filter' ) );
} else {
if ( empty( self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['previewed_instances'] ) ) {
// Only add these filters once for this ID base.
add_filter( "option_{$id_base}", $multidimensional_filter );
add_filter( "default_option_{$id_base}", $multidimensional_filter );
}
self::$aggregated_multidimensionals[ $this->type ][ $id_base ]['previewed_instances'][ $this->id ] = $this;
}
break;
default:
/**
* Fires when the WP_Customize_Setting::preview() method is called for settings
* not handled as theme_mods or options.
*
* The dynamic portion of the hook name, `$this->id`, refers to the setting ID.
*
* @since 3.4.0
*
* @param WP_Customize_Setting $this WP_Customize_Setting instance.
*/
do_action( "customize_preview_{$this->id}", $this );
/**
* Fires when the WP_Customize_Setting::preview() method is called for settings
* not handled as theme_mods or options.
*
* The dynamic portion of the hook name, `$this->type`, refers to the setting type.
*
* @since 4.1.0
*
* @param WP_Customize_Setting $this WP_Customize_Setting instance.
*/
do_action( "customize_preview_{$this->type}", $this );
}
$this->is_previewed = true;
return true;
}