rescue_shortcodes_from_wpautop.php

<?php

// Populate this array with your shortcode tag names (not including brackets).
$shortcodes = array( 'contextbox' );

// Leave this array alone; it's what we'll use to stash shortcode content in until wpautop has safely passed.
$shortcode_replacements = array();

// See wp-includes/default-filters.php for core WordPress filter priorities
// 9 comes right before wpautop at 10
add_filter('the_content', 'mw_rescue_shortcodes_from_wpautop', 9);
// Same level as wp_autop, executed after (because ours is added later) but before do_shortcode at 11
add_filter('the_content', 'mw_restore_shortcodes_after_wpautop', 10);

// Returns empty array if no match found, else:
//  $result[0] == shortcode_tag_found
//  $result[1] == string index
function find_next_shortcode_open_tag( $shortcode, $content, $offset ) {
    $matches = array();
    $result = preg_match( '/\[' . $shortcode . '( [^]]+)?\]/', $content, $matches, PREG_OFFSET_CAPTURE, $offset );

    return $result === 1 ? array( $matches[0][0], $matches[0][1] ) : array();
}

function find_first_shortcode_pos( $content, $offset ) {
    global $shortcodes;

    $earliest_pos = -1;
    $first_shortcode = null;

    foreach ( $shortcodes as $shortcode ) {
        $result = find_next_shortcode_open_tag( $shortcode, $content, $offset );

        if ( count( $result ) === 0 ) {
            continue;
        }

        if ( $earliest_pos == -1 || $result[1] < $earliest_pos ) {
            $earliest_pos = $result[1];
            $first_shortcode = $shortcode;
        }
    }

    return array( $earliest_pos, $first_shortcode );
}

function mw_rescue_shortcodes_from_wpautop( $content ) {
    global $shortcode_replacements;

    $opening_index = 0;

    while ( $opening_index < strlen( $content ) ) {
        $result = find_first_shortcode_pos( $content, $opening_index );
        $opening_index = $result[0];
        $tag_name = $result[1];

        if ( $opening_index == -1 ) {
            break;
        }

        // Found an opening tag? Continue searching until we find the matching closing tag.
        // There is the possibility of nested opening tags before reaching the matching close.
        $closing_tag = '[/' . $tag_name . ']';
        $open_tag_count = 1;
        $closing_index = $opening_index;

        while ( $open_tag_count > 0 && $closing_index < strlen( $content )) {
            $closing_pos = strpos( $content, $closing_tag, $closing_index );

            if ( $closing_pos === false ) {
                // This is a problem; we have no closing tag. Just take the rest of the content.
                $open_tag_count = 0;
                $closing_index = strlen( $content );
                break;
            }

            $open_tag_matches = find_next_shortcode_open_tag ( $tag_name, $content, $closing_index );
            $open_tag_found = count( $open_tag_matches ) > 0;

            if ( $open_tag_found ) {
                $matched_open_tag = $open_tag_matches[0];
                $next_opening_pos = $open_tag_matches[1];
            }

            if ( !$open_tag_found || $closing_pos < $next_opening_pos ) {
                $closing_index = $closing_pos + strlen( $closing_tag );
                $open_tag_count--;
            } else {
                $closing_index = $next_opening_pos + strlen( $matched_open_tag );
                $open_tag_count++;
            }
        }

        // Replace everything from $opening_index to $closing_index with a placeholder and stash that placeholder.
        // Don't forget to wrap it in <p> so that wpautop doesn't. :P
        do {
            $key = '<p>' . md5(rand()) . '</p>';
        } while ( array_key_exists( $key, $shortcode_replacements ) );

        $shortcode_replacements[$key] = substr( $content, $opening_index, $closing_index - $opening_index );
        $content = substr_replace( $content, $key, $opening_index, $closing_index - $opening_index );

        $opening_index = $opening_index + strlen( $key );
    }

    return $content;
}

function mw_restore_shortcodes_after_wpautop( $content ) {
    global $shortcode_replacements;

    foreach ( $shortcode_replacements as $key => $value ) {
        $content = str_replace( $key, $value, $content );
    }

    return $content;
}

?>