A sticky footer for the GeneratePress theme which will stick to the bottom when the content isn´t long enough and just scroll like a normal footer otherwise.

gp-sticky-hook.php

// For testing purpose, I added this script to a GP hook (wp_head) and had it run for only the test page named "Stickytest". To be valid for the whole site, you might want to enqueue the script.

<?php if ( is_page( 'stickytest' ) ) : ?>
    <script>
        jQuery(document).ready(function($) {

         $(window).resize(function(){
                var footerHeight = $('.site-info').outerHeight();
                var stickFooterPush = $('.push').height(footerHeight);

                $('.contentwrapper').css({'marginBottom':'-' + footerHeight + 'px'});
            });

            $(window).resize();

});
    </script>
<?php endif; ?>

gp-sticky.css

/* Add to childtheme CSS file or CSS snippets plugin of your choice */

html, body {
    height: 100%;
}

.contentwrapper {
  min-height: 100%;
  height: auto !important;
  height: 100%;
}

gp-sticky.php

// Add to childtheme functions or PHP plugin of your choice

// Add custom opening div tag
add_action( 'generate_before_header', 'opening_div' );
function opening_div() {
echo '<div class="contentwrapper">';
}

// Add custom closing div tag including push container
add_action( 'generate_before_footer', 'closing_div' );
function closing_div() {
echo '<div class="push"></div></div>';
}