I'm migrating some code from 3.4 Nexus to 4.x eCommerce.

I don't find any docs like the older 3.4 Nexus docs about mark an invoice paid, create a payment gateway etc...

A specific question: all my payments gateway i need to migrate do something like

public function payScreen()
{
  $html = "my html";
  ...
  return array("html" => $html);
}

The only payment gateway in the default installation that use a paymentScreen is AuthorizeNet, with this kind of code:

public function paymentScreen( \IPS\nexus\Invoice $invoice, \IPS\nexus\Money $amount, \IPS\nexus\Customer $member = NULL, $recurrings = array() )
{
	$return = array();
	$return['card'] = new \IPS\nexus\Form\CreditCard( $this->id . '_card', NULL, FALSE, $options );
	return $return;
}

Any advice about filling the $return with direct html? Thx.

If you can construct what you need to display out of form helpers (they're quite flexible!) then do that. If you absolutely need to use custom HTML though, you can use \IPS\Helpers\Form\Custom. See Stripe for an example:

 

		elseif ( $settings['type'] === 'amex' )
		{
			return array( 'card' => new \IPS\Helpers\Form\Custom( $this->id . '_card', NULL, FALSE, array(
				'rowHtml'	=> function( $field ) use ( $settings ) {
					return \IPS\Theme::i()->getTemplate( 'forms', 'nexus', 'global' )->amexExpressCheckout( $field, $this, $settings['amex_client_id'] );
				}
			) ) );
		}