Drupal 6 - make external image_buttons work like D7

mymodule.php

<?php
//you could also add this to your theme's template.php file, by replacing "phptemplate_image_button" with "themename_image_button" in the function name.
function phptemplate_image_button($element) {
  // Make sure not to overwrite classes.
  if (isset($element['#attributes']['class'])) {
    $element['#attributes']['class'] = 'form-'. $element['#button_type'] .' '. $element['#attributes']['class'];
  }
  else {
    $element['#attributes']['class'] = 'form-'. $element['#button_type'];
  }
  
  $src_uri = $element['#src'];
  
  $data = explode('://', $src_uri, 2);
  $scheme = count($data) == 2 ? $data[0] : FALSE;
  
  if (!$scheme) {
    $src_uri = base_path() . '/' . $element['#src'];
  }

  return '<input type="image" name="'. $element['#name'] .'" '.
    (!empty($element['#value']) ? ('value="'. check_plain($element['#value']) .'" ') : '') .
    'id="'. $element['#id'] .'" '.
    drupal_attributes($element['#attributes']) .
    ' src="' . $src_uri . '" ' .
    (!empty($element['#title']) ? 'alt="'. check_plain($element['#title']) .'" title="'. check_plain($element['#title']) .'" ' : '' ) .
    "/>\n";
}

Thanks e1nherjar. I tried disabling javascript in Firefox and click+enter still worked on the image button.

You're right about the coordinates of the click event, in my case it's no biggie.