Source
File: wp-includes/theme.php
function _custom_background_cb() {
// $background is the saved custom image, or the default image.
$background = set_url_scheme( get_background_image() );
// $color is the saved custom color.
// A default has to be specified in style.css. It will not be printed here.
$color = get_background_color();
if ( get_theme_support( 'custom-background', 'default-color' ) === $color ) {
$color = false;
}
$type_attr = current_theme_supports( 'html5', 'style' ) ? '' : ' type="text/css"';
if ( ! $background && ! $color ) {
if ( is_customize_preview() ) {
printf( '<style%s id="custom-background-css"></style>', $type_attr );
}
return;
}
$style = $color ? "background-color: #$color;" : '';
if ( $background ) {
$image = ' background-image: url("' . esc_url_raw( $background ) . '");';
// Background Position.
$position_x = get_theme_mod( 'background_position_x', get_theme_support( 'custom-background', 'default-position-x' ) );
$position_y = get_theme_mod( 'background_position_y', get_theme_support( 'custom-background', 'default-position-y' ) );
if ( ! in_array( $position_x, array( 'left', 'center', 'right' ), true ) ) {
$position_x = 'left';
}
if ( ! in_array( $position_y, array( 'top', 'center', 'bottom' ), true ) ) {
$position_y = 'top';
}
$position = " background-position: $position_x $position_y;";
// Background Size.
$size = get_theme_mod( 'background_size', get_theme_support( 'custom-background', 'default-size' ) );
if ( ! in_array( $size, array( 'auto', 'contain', 'cover' ), true ) ) {
$size = 'auto';
}
$size = " background-size: $size;";
// Background Repeat.
$repeat = get_theme_mod( 'background_repeat', get_theme_support( 'custom-background', 'default-repeat' ) );
if ( ! in_array( $repeat, array( 'repeat-x', 'repeat-y', 'repeat', 'no-repeat' ), true ) ) {
$repeat = 'repeat';
}
$repeat = " background-repeat: $repeat;";
// Background Scroll.
$attachment = get_theme_mod( 'background_attachment', get_theme_support( 'custom-background', 'default-attachment' ) );
if ( 'fixed' !== $attachment ) {
$attachment = 'scroll';
}
$attachment = " background-attachment: $attachment;";
$style .= $image . $position . $size . $repeat . $attachment;
}
?>
<style<?php echo $type_attr; ?> id="custom-background-css">
body.custom-background { <?php echo trim( $style ); ?> }
</style>
<?php
}