Editing built in Gallery shortcode to filter by categories

Question

So I'm trying to add or change the built in gallery shortcode so that it can display all images of a specific category that we'll call internal medicine with an id of 2, but also able to have the same functionality if I wanted to grab all the images of a different category lets say called downtown with an id of 4, where can I start with this? Here's the code for the built-in shortcode that I'm trying to edit.

    add_shortcode('gallery', 'gallery_shortcode');
/**
 * Builds the Gallery shortcode output.
 *
 * This implements the functionality of the Gallery Shortcode for displaying
 * WordPress images on a post.
 *
 * @since 2.5.0
 *
 * @staticvar int $instance
 *
 * @param array $attr {
 *     Attributes of the gallery shortcode.
 *
 *     @type string       $order      Order of the images in the gallery. Default 'ASC'. Accepts 'ASC', 'DESC'.
 *     @type string       $orderby    The field to use when ordering the images. Default 'menu_order ID'.
 *                                    Accepts any valid SQL ORDERBY statement.
 *     @type int          $id         Post ID.
 *     @type string       $itemtag    HTML tag to use for each image in the gallery.
 *                                    Default 'dl', or 'figure' when the theme registers HTML5 gallery support.
 *     @type string       $icontag    HTML tag to use for each image's icon.
 *                                    Default 'dt', or 'div' when the theme registers HTML5 gallery support.
 *     @type string       $captiontag HTML tag to use for each image's caption.
 *                                    Default 'dd', or 'figcaption' when the theme registers HTML5 gallery support.
 *     @type int          $columns    Number of columns of images to display. Default 3.
 *     @type string|array $size       Size of the images to display. Accepts any valid image size, or an array of width
 *                                    and height values in pixels (in that order). Default 'thumbnail'.
 *     @type string       $ids        A comma-separated list of IDs of attachments to display. Default empty.
 *     @type string       $include    A comma-separated list of IDs of attachments to include. Default empty.
 *     @type string       $exclude    A comma-separated list of IDs of attachments to exclude. Default empty.
 *     @type string       $link       What to link each image to. Default empty (links to the attachment page).
 *                                    Accepts 'file', 'none'.
 * }
 * @return string HTML content to display gallery.
 */
function gallery_shortcode( $attr ) {
    $post = get_post();
    static $instance = 0;
    $instance++;
    if ( ! empty( $attr['ids'] ) ) {
        // 'ids' is explicitly ordered, unless you specify otherwise.
        if ( empty( $attr['orderby'] ) ) {
            $attr['orderby'] = 'post__in';
        }
        $attr['include'] = $attr['ids'];
    }
    /**
     * Filters the default gallery shortcode output.
     *
     * If the filtered output isn't empty, it will be used instead of generating
     * the default gallery template.
     *
     * @since 2.5.0
     * @since 4.2.0 The `$instance` parameter was added.
     *
     * @see gallery_shortcode()
     *
     * @param string $output   The gallery output. Default empty.
     * @param array  $attr     Attributes of the gallery shortcode.
     * @param int    $instance Unique numeric ID of this gallery shortcode instance.
     */
    $output = apply_filters( 'post_gallery', '', $attr, $instance );
    if ( $output != '' ) {
        return $output;
    }
    $html5 = current_theme_supports( 'html5', 'gallery' );
    $atts = shortcode_atts( array(
        'order'      => 'ASC',
        'orderby'    => 'menu_order ID',
        'id'         => $post ? $post->ID : 0,
        'itemtag'    => $html5 ? 'figure'     : 'dl',
        'icontag'    => $html5 ? 'div'        : 'dt',
        'captiontag' => $html5 ? 'figcaption' : 'dd',
        'columns'    => 3,
        'size'       => 'thumbnail',
        'include'    => '',
        'exclude'    => '',
        'link'       => ''
    ), $attr, 'gallery' );
    $id = intval( $atts['id'] );
    if ( ! empty( $atts['include'] ) ) {
        $_attachments = get_posts( array( 'include' => $atts['include'], 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $atts['order'], 'orderby' => $atts['orderby'] ) );
        $attachments = array();
        foreach ( $_attachments as $key => $val ) {
            $attachments[$val->ID] = $_attachments[$key];
        }
    } elseif ( ! empty( $atts['exclude'] ) ) {
        $attachments = get_children( array( 'post_parent' => $id, 'exclude' => $atts['exclude'], 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $atts['order'], 'orderby' => $atts['orderby'] ) );
    } else {
        $attachments = get_children( array( 'post_parent' => $id, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $atts['order'], 'orderby' => $atts['orderby'] ) );
    }
    if ( empty( $attachments ) ) {
        return '';
    }
    if ( is_feed() ) {
        $output = "\n";
        foreach ( $attachments as $att_id => $attachment ) {
            $output .= wp_get_attachment_link( $att_id, $atts['size'], true ) . "\n";
        }
        return $output;
    }
    $itemtag = tag_escape( $atts['itemtag'] );
    $captiontag = tag_escape( $atts['captiontag'] );
    $icontag = tag_escape( $atts['icontag'] );
    $valid_tags = wp_kses_allowed_html( 'post' );
    if ( ! isset( $valid_tags[ $itemtag ] ) ) {
        $itemtag = 'dl';
    }
    if ( ! isset( $valid_tags[ $captiontag ] ) ) {
        $captiontag = 'dd';
    }
    if ( ! isset( $valid_tags[ $icontag ] ) ) {
        $icontag = 'dt';
    }
    $columns = intval( $atts['columns'] );
    $itemwidth = $columns > 0 ? floor(100/$columns) : 100;
    $float = is_rtl() ? 'right' : 'left';
    $selector = "gallery-{$instance}";
    $gallery_style = '';

So the goal of this would be able to put [gallery category="2"] or [gallery id="2"] or however way so that it displays all the images in a specific category, so any help would be very appreciated!

edit so the way I want it to work is to be able to put [gallery category="emergency-medicine"] and have all images or the top 20 most recent appear in the post or another example would be [gallery post_type="gallery" category="medicine"] and what I use to make these custom post types/categories is with the plugin ToolSet Types

function gallery_shortcode( $attr ) {
$post = get_post();
static $instance = 0;
$instance++;
if ( ! empty( $attr['ids'] ) ) {
    // 'ids' is explicitly ordered, unless you specify otherwise.
    if ( empty( $attr['orderby'] ) ) {
        $attr['orderby'] = 'post__in';
    }
    $attr['include'] = $attr['ids'];
}
/**
 * Filters the default gallery shortcode output.
 *
 * If the filtered output isn't empty, it will be used instead of generating
 * the default gallery template.
 *
 * @since 2.5.0
 * @since 4.2.0 The `$instance` parameter was added.
 *
 * @see gallery_shortcode()
 *
 * @param string $output   The gallery output. Default empty.
 * @param array  $attr     Attributes of the gallery shortcode.
 * @param int    $instance Unique numeric ID of this gallery shortcode instance.
 */
$output = apply_filters( 'post_gallery', '', $attr, $instance );
if ( $output != '' ) {
    return $output;
}
$html5 = current_theme_supports( 'html5', 'gallery' );
$atts = shortcode_atts( array(
    'order'      => 'ASC',
    'orderby'    => 'menu_order ID',
    'id'         => null,
    'itemtag'    => $html5 ? 'figure'     : 'dl',
    'icontag'    => $html5 ? 'div'        : 'dt',
    'captiontag' => $html5 ? 'figcaption' : 'dd',
    'columns'    => 3,
    'size'       => 'thumbnail',
    'include'    => '',
    'exclude'    => '',
    'link'       => '',
    'category' => null,
    'post_type' => 'uc-general-gallery',
    'img' => null
), $attr, 'gallery' );
$ids = array();
ob_start();
if ($atts['id'] != null ) {
    $id_str = preg_replace('/\s+/', '', $atts['id']); // strip whitespace
    $ids = explode(',', $id_str);
    ?>
     <?php foreach($ids as $id): ?>
                <?php if(is_numeric($id)): ?>
                                    <?php endif; ?>
            <?php endforeach; ?>
            <?php
} else if($atts['category'] != null) {
    $cat_str = preg_replace('/\s+/', '', $atts['category']); // strip whitespace
    $args = array(
        'post_type'         => $atts['post_type'],
        'order'             => 'DESC',
        'category_name'     => $cat_str,
        'posts_per_page' => 999
        );
    $the_query = new WP_Query( $args );
    if($the_query->have_posts() ) :
        ?>
         <?php while ( $the_query->have_posts() ) : $the_query->the_post(); ?>
         <?php endwhile; ?>
                     <?php
    endif;
}
if ( ! empty( $atts['include'] ) ) {
    $_attachments = get_posts( array( 'include' => $atts['include'], 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $atts['order'], 'orderby' => $atts['orderby'] ) );
    $attachments = array();
    foreach ( $_attachments as $key => $val ) {
        $attachments[$val->ID] = $_attachments[$key];
    }
} elseif ( ! empty( $atts['exclude'] ) ) {
    $attachments = get_children( array( 'post_parent' => $id, 'exclude' => $atts['exclude'], 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $atts['order'], 'orderby' => $atts['orderby'] ) );
} else {
    $attachments = get_children( array( 'post_parent' => $id, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $atts['order'], 'orderby' => $atts['orderby'] ) );
}
if ( empty( $attachments ) ) {
    return '';
}
if ( is_feed() ) {
    $output = "\n";
    foreach ( $attachments as $att_id => $attachment ) {
        $output .= wp_get_attachment_link( $att_id, $atts['size'], true ) . "\n";
    }
    return $output;
}
$itemtag = tag_escape( $atts['itemtag'] );
$captiontag = tag_escape( $atts['captiontag'] );
$icontag = tag_escape( $atts['icontag'] );
$valid_tags = wp_kses_allowed_html( 'post' );
if ( ! isset( $valid_tags[ $itemtag ] ) ) {
    $itemtag = 'dl';
}
if ( ! isset( $valid_tags[ $captiontag ] ) ) {
    $captiontag = 'dd';
}
if ( ! isset( $valid_tags[ $icontag ] ) ) {
    $icontag = 'dt';
}
$columns = intval( $atts['columns'] );
$itemwidth = $columns > 0 ? floor(100/$columns) : 100;
$float = is_rtl() ? 'right' : 'left';
$selector = "gallery-{$instance}";
$gallery_style = '';

So this is what I did to get it working(though kind of ugly) so now I can input [gallery post_type="uc-general-gallery" category="people-residents"] or just [gallery category="etc"] and it'll grab the images and display them, but in the visual editor it'll say no items found but when I actually view the post it does show up in the page, now another issue is I need it to be responsive for mobile users so when the screen shrinks down it'll turn into a slider or slideshow.

Edit

Never mind! my code is buggy and displays every image added instead of going by category, would there be an easy way to fix this?

Answer 1

There are various ways to run another WP_Query with a tax query and collect the ID's into the include attribute of the gallery shortcode.

Let's try another approach, without running a secondary WP_Query.

Native gallery: Support taxonomy and term attributes

We introduce the following custom gallery shortcode attributes:

[gallery taxonomy="media_category" term="people"]

Here's a demo plugin that supports that through the post_gallery, shortcode_atts_gallery filters and the pre_get_posts action:

<?php
/**
 * Plugin Name: Native Gallery Shortcode With Taxonomy And Term Filter Support
 * Description: Add support for [gallery taxonomy='some-taxonomy' term="some-term"]
 * Plugin URI:  http://wordpress.stackexchange.com/a/257801/26350
 */

namespace WPSE\Q257743;

class Gallery
{
    private $term;
    private $taxonomy;

    public function init()
    {
        add_filter( 'post_gallery', [$this, 'post_gallery'], 10, 2 );               
    }

    public function post_gallery( $html, $attr )
    {
        // Check user input for term and taxonomy
        if( empty( $attr['term'] ) || empty( $attr['taxonomy'] ) )
            return $html;

        // Validate taxonomy
        if( ! taxonomy_exists( $attr['taxonomy'] ) )
            return esc_html__( "Taxonomy doesn't exists!", 'wpse-257743' );

        // Validate term
        if( ! term_exists( $attr['term'] , $attr['taxonomy'] ) )
            return esc_html__( "Term doesn't exists!", 'wpse-257743' );

        $this->term     = $attr['term'];
        $this->taxonomy = $attr['taxonomy'];

        // Activate customization
        add_filter( 'shortcode_atts_gallery',   [$this, 'gallery_atts'] );
        add_action( 'pre_get_posts',            [$this, 'pre_get_posts'] );

        return $html;
    }

    public function gallery_atts( $pairs )
    {
        // Set include to a temporary non empty value (that becomes 0)
        $pairs['include'] = ' ';

        // Only run once per gallery
        remove_filter( current_filter(), __FUNCTION__ );

        return $pairs;
    }

    public function pre_get_posts( \WP_Query $q )
    {
        // Make sure it's attachments query
        if( 'attachment' !== $q->get( 'post_type' ) )
            return;

        $post__in = $q->get( 'post__in' );

        // Target queries with post__in (include)       
        if ( empty( $post__in ) )
            return;

        // Check for our temporary 0 value
        if( 1 === count( $post__in ) && 0 != $post__in[0] )
            return;

        $q->set( 'post__in', null );

        // Set the taxonomy query:
        $q->set( 'tax_query', 
            [
                [
                    'taxonomy'  => $this->taxonomy,
                    'field'     => 'slug',
                    'terms'     => $this->term,
                ]
            ]
        );

        // Adjust the number of images to e.g. max 100
        $q->set( 'posts_per_page', 100 );

        // Only run once per gallery
        remove_action( current_action(), __FUNCTION__ );
    }

}

add_action( 'init', [new Gallery, 'init' ] );

Note that here we added a limit of 100 images.

Hope you can test and adjust it further to your needs, and e.g. change it so it can support multiple terms.