Parses shortcode in WordPress image captions

shortcode_in_wp-caption.php

<?php

function nested_img_caption_shortcode($nada, $attr, $content = null) {
	extract(
		shortcode_atts(
			array(
				'id'    => '',
				'align' => 'alignnone',
				'width' => '',
				'caption' => ''
			), 
			$attr, 
			'caption'
		)
	);
	
	$caption = do_shortcode($caption); // process nested shortcodes
	
	if ( 1 > (int) $width || empty($caption) )
		return $content;
	
	if ( $id ) $id = 'id="' . esc_attr($id) . '" ';
	
	return '<div ' . $id . 'class="wp-caption ' . esc_attr($align) . '" style="width: ' . (10 + (int) $width) . 'px">' . do_shortcode( $content ) . '<p class="wp-caption-text">' . $caption . '</p></div>';
}
add_filter('img_caption_shortcode', 'nested_img_caption_shortcode', 1, 3);