zoom-to-pinch.php

add_action( 'after_setup_theme', 'definitely_allow_mobile_zooming_add_viewport');
function definitely_allow_mobile_zooming_add_viewport()
{
    /*
     * Set viewport for OceanWP
     */
    if ( class_exists('OCEANWP_Theme_Class') ) {

        add_filter( 'ocean_meta_viewport', 'definitely_allow_mobile_zooming_oceanwp' );

    }
    /*
     * Set viewport by default
     */
    else {

        add_action( 'wp_head', 'definitely_allow_mobile_zooming_default', 9999999 );

    }
}

function definitely_allow_mobile_zooming_default() {
    print '<meta name="viewport" content="width=device-width, user-scalable=yes, initial-scale=1.0, minimum-scale=0.1, maximum-scale=10.0">';
    print "\n";
}

function definitely_allow_mobile_zooming_oceanwp( $viewport ) {
    $viewport   = '<meta name="viewport" content="width=device-width, user-scalable=yes, initial-scale=1.0, minimum-scale=0.1, maximum-scale=10.0">';
    return $viewport;
}