Thank you for confirming my understanding of your application. I have developed a small custom plugin example that should get you the results you need. The plugin adds a new [mla_gallery] parameter, parent_meta. When this parameter is present, the plugin looks up the custom field value and creates a new parameter based on the content. For example, the shortcode in your example above would be re-coded as:
[mla_gallery size=small link=file columns=4 mla_style=projektova_galerie mla_markup=projektova_galerie_captions mla_rollover_text="{+title+} - {+caption+}" mla_margin=0.5% parent_meta=project_slug]
You can also change the taxonomy by adding the taxonomy slug as the second part of the parent_meta value, e.g., parent_meta="project_slug,attachment_tag".
I have included the complete source code for the plugin below. You can copy it into a file named mla-project-slug-example.php and put the file in your /wp-content/plugins directory. Then, go to your wp-admin “Plugins/Installed Plugins” screen and activate the “MLA Project Slug Example” plugin.
If you would like a copy by e-mail, you can send me your contact information from the Contact Us page at our web site:
Fair Trade Judaica/Contact Us
I will leave this topic unresolved until I hear back from you. Thanks for an interesting question and for your interest in the plugin.
PLUGIN SOURCE CODE
<?php
/**
* Creates a taxonomy=slug parameter from a parent's custom field value
*
* @package MLA Project Slug Example
* @version 1.00
*/
/*
Plugin Name: MLA Project Slug Example
Plugin URI: http://fairtradejudaica.org/media-library-assistant-a-wordpress-plugin/
Description: Provides examples of hooking the filters provided by the [mla_gallery] shortcode
Author: David Lingren
Version: 1.00
Author URI: http://fairtradejudaica.org/our-story/staff/
Copyright 2014 David Lingren
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You can get a copy of the GNU General Public License by writing to the
Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
*/
/**
* Class MLA Project Slug Example hooks all of the filters provided by the [mla_gallery] shortcode
*
* Call it anything you want, but give it an unlikely and hopefully unique name. Hiding everything
* else inside a class means this is the only name you have to worry about.
*
* @package MLA Project Slug Example
* @since 1.00
*/
class MLAProjectSlugExample {
/**
* Initialization function, similar to __construct()
*
* @since 1.00
*
* @return void
*/
public static function initialize() {
/*
* The filters are only useful for front-end posts/pages; exit if in the admin section
*/
if ( is_admin() )
return;
/*
* add_filter parameters:
* $tag - name of the hook you're filtering; defined by [mla_gallery]
* $function_to_add - function to be called when [mla_gallery] applies the filter
* $priority - default 10; lower runs earlier, higher runs later
* $accepted_args - number of arguments your function accepts
*/
add_filter( 'mla_gallery_attributes', 'MLAProjectSlugExample::mla_gallery_attributes_filter', 10, 1 );
}
/**
* MLA Gallery (Display) Attributes
*
* This filter gives you an opportunity to record or modify the arguments passed in to the shortcode
* before they are merged with the default arguments used for the gallery display.
*
* The $shortcode_attributes array is where you will find any of your own parameters that are coded in the
* shortcode, e.g., [mla_gallery my_parameter="my value"].
*
* @since 1.00
*
* @param array the shortcode parameters passed in to the shortcode
*
* @return array updated shortcode attributes
*/
public static function mla_gallery_attributes_filter( $shortcode_attributes ) {
if ( isset( $shortcode_attributes['parent_meta'] ) ) {
global $post;
$values = explode( ',', $shortcode_attributes['parent_meta'] );
$meta_key = $values[0];
$taxonomy = ( isset( $values[1] ) ) ? $values[1] : 'attachment_category';
$values = get_post_meta( $post->ID, $meta_key );
if ( is_array( $values ) ) {
$shortcode_attributes[ $taxonomy ] = implode( ',', $values );
unset( $shortcode_attributes['parent_meta'] );
}
}
//error_log( 'MLAProjectSlugExample::mla_gallery_attributes_filter $shortcode_attributes = ' . var_export( $shortcode_attributes, true ), 0 );
return $shortcode_attributes;
} // mla_gallery_attributes_filter
} // Class MLAProjectSlugExample
/*
* Install the filters at an early opportunity
*/
add_action('init', 'MLAProjectSlugExample::initialize');
?>
