'category posts' hack

<?php
/*
Plugin Name: Category Posts Widget
Plugin URI: http://jameslao.com/2011/03/24/category-posts-widget-3-2/
Description: Adds a widget that can display posts from a single category. 2011 Hacked by alchymyth to show posts from the single post's categories. widget restricted to single post by code in line 79 and 133.
Author: James Lao
Version: 3.2
Author URI: http://jameslao.com/
*/

// Register thumbnail sizes.
if ( function_exists('add_image_size') )
{
    $sizes = get_option('jlao_cat_post_thumb_sizes');
    if ( $sizes )
    {
        foreach ( $sizes as $id=>$size )
            add_image_size( 'cat_post_thumb_size' . $id, $size[0], $size[1], true );
    }
}

class CategoryPosts extends WP_Widget {

function CategoryPosts() {
    parent::WP_Widget(false, $name='Category Posts');
}

/**
 * Displays category posts widget on blog.
 */
function widget($args, $instance) {
    global $post;
    $post_old = $post; // Save the post object.

    extract( $args );

    $sizes = get_option('jlao_cat_post_thumb_sizes');

    // If not title, use the name of the category.
    if( !$instance["title"] ) {
//alchymyth edit: set widget title to 'Category Posts' for option 'use post categories'
        if( $instance["cat"] == 0 ) { $instance["title"] = 'Category Posts'; } else {
        $category_info = get_category($instance["cat"]);
        $instance["title"] = $category_info->name;
        } //end alchymyth edit
  }

  $valid_sort_orders = array('date', 'title', 'comment_count', 'random');
  if ( in_array($instance['sort_by'], $valid_sort_orders) ) {
    $sort_by = $instance['sort_by'];
    $sort_order = (bool) $instance['asc_sort_order'] ? 'ASC' : 'DESC';
  } else {
    // by default, display latest first
    $sort_by = 'date';
    $sort_order = 'DESC';
  }

//alchymyth edit: get the single post's categories
if( $instance["cat"] == '0' ) {
global $post;
$posts_categories = wp_get_post_categories($post->ID);
$use_categories = implode(',', $posts_categories);
} else { $use_categories = $instance["cat"]; }
//end of alchymyth edit

    // Get array of post info.
  $cat_posts = new WP_Query(
    "showposts=" . $instance["num"] .
    "&cat=" . $use_categories . //alchymyth edit
    "&orderby=" . $sort_by .
    "&order=" . $sort_order
  );

    // Excerpt length filter
    $new_excerpt_length = create_function('$length', "return " . $instance["excerpt_length"] . ";");
    if ( $instance["excerpt_length"] > 0 )
        add_filter('excerpt_length', $new_excerpt_length);

if( is_single() ) : //alchymyth edit: restrict the widget output to single post

    echo $before_widget;

    // Widget title
    echo $before_title;
    if( $instance["title_link"] )
        echo '<a href="' . get_category_link($instance["cat"]) . '">' . $instance["title"] . '</a>';
    else
        echo $instance["title"];
    echo $after_title;

    // Post list
    echo "<ul>\n";

    while ( $cat_posts->have_posts() )
    {
        $cat_posts->the_post();
    ?>
        <li class="cat-post-item">
            <a class="post-title" href="<?php the_permalink(); ?>" rel="bookmark" title="Permanent link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a>

            <?php
                if (
                    function_exists('the_post_thumbnail') &&
                    current_theme_supports("post-thumbnails") &&
                    $instance["thumb"] &&
                    has_post_thumbnail()
                ) :
            ?>
                <a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>">
                <?php the_post_thumbnail( 'cat_post_thumb_size'.$this->id ); ?>
                </a>
            <?php endif; ?>

            <?php if ( $instance['date'] ) : ?>
            <p class="post-date"><?php the_time("j M Y"); ?></p>
            <?php endif; ?>

            <?php if ( $instance['excerpt'] ) : ?>
            <?php the_excerpt(); ?>
            <?php endif; ?>

            <?php if ( $instance['comment_num'] ) : ?>
            <p class="comment-num">(<?php comments_number(); ?>)</p>
            <?php endif; ?>
        </li>
    <?php
    }

    echo "</ul>\n";

    echo $after_widget;

endif; // end alchymyth edit: end if( is_single() ) : //restrict the widget output to single posts

    remove_filter('excerpt_length', $new_excerpt_length);

    $post = $post_old; // Restore the post object.

    remove_filter('wp_dropdown_cats', 'use_posts_cats');

}

/**
 * Form processing... Dead simple.
 */
function update($new_instance, $old_instance) {
    /**
     * Save the thumbnail dimensions outside so we can
     * register the sizes easily. We have to do this
     * because the sizes must registered beforehand
     * in order for WP to hard crop images (this in
     * turn is because WP only hard crops on upload).
     * The code inside the widget is executed only when
     * the widget is shown so we register the sizes
     * outside of the widget class.
     */
    if ( function_exists('the_post_thumbnail') )
    {
        $sizes = get_option('jlao_cat_post_thumb_sizes');
        if ( !$sizes ) $sizes = array();
        $sizes[$this->id] = array($new_instance['thumb_w'], $new_instance['thumb_h']);
        update_option('jlao_cat_post_thumb_sizes', $sizes);
    }

    return $new_instance;
}

/**
 * The configuration form.
 */
function form($instance) {
?>
        <p>
            <label for="<?php echo $this->get_field_id("title"); ?>">
                <?php _e( 'Title' ); ?>:
                <input class="widefat" id="<?php echo $this->get_field_id("title"); ?>" name="<?php echo $this->get_field_name("title"); ?>" type="text" value="<?php echo esc_attr($instance["title"]); ?>" />
            </label>
        </p>

        <p>
            <label>
                <?php _e( 'Category' ); ?>:
                <?php
                 wp_dropdown_categories( array( 'name' => $this->get_field_name("cat"), 'selected' => $instance["cat"] ) ); ?>
            </label>
        </p>

        <p>
            <label for="<?php echo $this->get_field_id("num"); ?>">
                <?php _e('Number of posts to show'); ?>:
                <input style="text-align: center;" id="<?php echo $this->get_field_id("num"); ?>" name="<?php echo $this->get_field_name("num"); ?>" type="text" value="<?php echo absint($instance["num"]); ?>" size='3' />
            </label>
    </p>

    <p>
            <label for="<?php echo $this->get_field_id("sort_by"); ?>">
        <?php _e('Sort by'); ?>:
        <select id="<?php echo $this->get_field_id("sort_by"); ?>" name="<?php echo $this->get_field_name("sort_by"); ?>">
          <option value="date"<?php selected( $instance["sort_by"], "date" ); ?>>Date</option>
          <option value="title"<?php selected( $instance["sort_by"], "title" ); ?>>Title</option>
          <option value="comment_count"<?php selected( $instance["sort_by"], "comment_count" ); ?>>Number of comments</option>
          <option value="random"<?php selected( $instance["sort_by"], "random" ); ?>>Random</option>
        </select>
            </label>
    </p>

        <p>
            <label for="<?php echo $this->get_field_id("asc_sort_order"); ?>">
        <input type="checkbox" class="checkbox"
          id="<?php echo $this->get_field_id("asc_sort_order"); ?>"
          name="<?php echo $this->get_field_name("asc_sort_order"); ?>"
          <?php checked( (bool) $instance["asc_sort_order"], true ); ?> />
                <?php _e( 'Reverse sort order (ascending)' ); ?>
            </label>
    </p>

        <p>
            <label for="<?php echo $this->get_field_id("title_link"); ?>">
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id("title_link"); ?>" name="<?php echo $this->get_field_name("title_link"); ?>"<?php checked( (bool) $instance["title_link"], true ); ?> />
                <?php _e( 'Make widget title link' ); ?>
            </label>
        </p>

        <p>
            <label for="<?php echo $this->get_field_id("excerpt"); ?>">
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id("excerpt"); ?>" name="<?php echo $this->get_field_name("excerpt"); ?>"<?php checked( (bool) $instance["excerpt"], true ); ?> />
                <?php _e( 'Show post excerpt' ); ?>
            </label>
        </p>

        <p>
            <label for="<?php echo $this->get_field_id("excerpt_length"); ?>">
                <?php _e( 'Excerpt length (in words):' ); ?>
            </label>
            <input style="text-align: center;" type="text" id="<?php echo $this->get_field_id("excerpt_length"); ?>" name="<?php echo $this->get_field_name("excerpt_length"); ?>" value="<?php echo $instance["excerpt_length"]; ?>" size="3" />
        </p>

        <p>
            <label for="<?php echo $this->get_field_id("comment_num"); ?>">
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id("comment_num"); ?>" name="<?php echo $this->get_field_name("comment_num"); ?>"<?php checked( (bool) $instance["comment_num"], true ); ?> />
                <?php _e( 'Show number of comments' ); ?>
            </label>
        </p>

        <p>
            <label for="<?php echo $this->get_field_id("date"); ?>">
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id("date"); ?>" name="<?php echo $this->get_field_name("date"); ?>"<?php checked( (bool) $instance["date"], true ); ?> />
                <?php _e( 'Show post date' ); ?>
            </label>
        </p>

        <?php if ( function_exists('the_post_thumbnail') && current_theme_supports("post-thumbnails") ) : ?>
        <p>
            <label for="<?php echo $this->get_field_id("thumb"); ?>">
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id("thumb"); ?>" name="<?php echo $this->get_field_name("thumb"); ?>"<?php checked( (bool) $instance["thumb"], true ); ?> />
                <?php _e( 'Show post thumbnail' ); ?>
            </label>
        </p>
        <p>
            <label>
                <?php _e('Thumbnail dimensions'); ?>:<br />
                <label for="<?php echo $this->get_field_id("thumb_w"); ?>">
                    W: <input class="widefat" style="width:40%;" type="text" id="<?php echo $this->get_field_id("thumb_w"); ?>" name="<?php echo $this->get_field_name("thumb_w"); ?>" value="<?php echo $instance["thumb_w"]; ?>" />
                </label>

                <label for="<?php echo $this->get_field_id("thumb_h"); ?>">
                    H: <input class="widefat" style="width:40%;" type="text" id="<?php echo $this->get_field_id("thumb_h"); ?>" name="<?php echo $this->get_field_name("thumb_h"); ?>" value="<?php echo $instance["thumb_h"]; ?>" />
                </label>
            </label>
        </p>
        <?php endif; ?>

<?php

}

}

add_action( 'widgets_init', create_function('', 'return register_widget("CategoryPosts");') );

//alchymyth edit: add top option to dropdown
add_filter('wp_dropdown_cats', 'use_posts_cats');
function use_posts_cats($list) {
$list = str_replace("class='postform' >", "class='postform' >\n<option class=\"level-0\" value=\"0\">use post categories</option>\n", $list);
return $list; };
//end alchymyth edit

?>