Reactor Theme: Prevent Post Thumb on Post

Callback

This is how “Reactor” hooks the callback

add_action( 'reactor_post_header', 'reactor_do_standard_thumbnail', 4 );

Backtrace

The function itself is hooked from where you linked

~/theme_root/library/inc/content/content-post.php

but this file is called by the class Reactor. This class/file is not included during the main callback hooked to after_setup_theme in the functions.php file on priority 10, but before that without a callback. And it gets instantiated right afterwards:

require locate_template('library/reactor.php');
new Reactor();

When the class gets instantiated and the __construct()or gets called, it hooks the callback that registers the callback for the default thumb on priority 14 on the after_setup_theme hook … (FYI: in lame PHP 4 style).

add_action('after_setup_theme', array( &$this, 'content' ), 14);

Then the content() method does nothing else than including another file:

require_once locate_template('/library/inc/content/content-pages.php');

And this file is the one that actually attaches the default thumbnail here.

add_action('reactor_post_header', 'reactor_do_standard_thumbnail', 4);

Exchange

Now simply add the following in your CHILD THEME functions.php file.

/**
 * Remove the original callback, add in a new one
 */
add_action( 'after_setup_theme', 'wpse119843RemoveStandardThumbs', 20 );
function wpse119843RemoveStandardThumbs()
{
    // Removes it for posts AND pages. If you only want posts, use is_single()
    if ( is_singular() )
        remove_action( 'reactor_post_header', 'reactor_do_standard_thumbnail', 4 );

    add_action( 'reactor_post_header', 'wpse119843AddCustomThumbs' );
}
/**
 * The callback that formats the new output
 */
function wpse119843AddCustomThumbs()
{
    $link_titles = reactor_option( 'frontpage_link_titles', 0 );

    if ( has_post_thumbnail() )
    {
        ?>
        // REFACTOR REACTOR
        <?php
    }

}

NOTE

To preserve your changes, use a Child Theme. When you take a closer look at the site, then you’ll see that there already exists one.