Learning the World

Patrick H. Lauke wrote an excellent article about keyboard-accessible Google Maps on the Opera Developer website. Still I was able to improve it slightly when I implemented an accessible map myself. I would like to share these modifications with you:

• A link to Google Maps when JavaScript is disabled.
• Support for the Google AJAX API Loader.
• Using the small map control.
• Keyboard accessibility for all control elements within the map.

As a fallback without JavaScript — because people disable it, because their mobile device doesn’t support it, or because it gets filtered by corporate proxies — Patrick used the little known Google Static Maps API, but for some reason he missed adding the link to Google. Here is the fix:

1. <div id="map">
2. <a href="http://maps.google.com/maps ?f=q&amp;output=html &amp;q=50.110950+8.684666" title="Google Maps">
3. <img src="http://maps.google.com/staticmap?hl=en &amp;center=50.112267,8.678384 &amp;markers=50.110950,8.684666,red &amp;zoom=15&amp;size=500x300 &amp;key=[Your API Key]" alt="City map of Frankfurt" width="500" height="300" />
4. </a>
5. </div>

Then I changed how the map is embedded. As it seems that the API loader is more current, I preferred that way:

1. <script type="text/javascript" src="http://www.google.com/jsapi?key=[Your API Key]"></script>
2. <script type="text/javascript" src="/js/accgmap.js"></script>
3. <script type="text/javascript">
4. google.load( 'maps', '2', { 'language' : 'en' } );
5. google.setOnLoadCallback( GMAP.initMap );
6. </script>

Using the small control elements is trivial: SmallMapControl(). The next thing I wanted to change was keyboard access to all controls, in particular for the map type, i.e. Map | Satellite | Hybrid. Patrick refers to an id, but I found that all relevant controls have a title, so I just checked for that attribute. I also dropped setting the style attribute in JavaScript as that belongs in the CSS file. His original function GKeyboardPatch() now looks like this (note the while loop for a slightly better performance):

1. GKeyboardPatch: function( map ) {
2. var button, divs = map.getContainer().getElementsByTagName( 'div' );
3. var i = 0;
4. while ( divs[i] ) {
5. if ( divs[i].getAttribute( 'log' ) || ( divs[i].getAttribute( 'title' ) && divs[i].getAttribute( 'title' ) != '' ) ) {
6. button = document.createElement( 'button' );
7. button.setAttribute( 'value', divs[i].getAttribute( 'title' ));
8. divs[i].appendChild( button );
9. if ( divs[i].getAttribute( 'log' )) { // only control buttons
10. // override the IE opacity filter that Google annoyingly sets
11. divs[i].style.filter = '';
12. // should really set to 'transparent'
13. divs[i].style.background = 'url( http://www.google.com/ intl/en_ALL/mapfiles/transparent.png )';
14. }
15. }
16. i++;
17. }
18. }

Now remember I said I’d rather separate style and behaviour, so here are a some lines of CSS with the setting of width and height for the #map being most relevant, otherwise it will collapse:

1. #map {
2. height: 300px;
3. overflow: hidden;
4. position: relative;
5. width: 500px;
6. }
7. #maps-static, #maps-static img {
8. display: block;
9. }
10. #map span.note {
11. display: none;
12. }
13. #map button {
14. background: transparent;
15. border-style: solid;
16. border-width: 0;
17. cursor: pointer;
18. height: 100%;
19. left: -2px;
20. margin: 2px;
21. overflow: hidden;
22. padding: 2px;
23. position: absolute;
24. text-indent: -100em;
25. top: -2px;
26. width: 100%;
27. }
28. #map a:focus, #map a:active, #map button:focus, #map button:active {
29. outline: 2px dashed #61bf1a;
30. }

And that’s it, thanks again to Patrick for the solid foundation I built upon. Now download the JavaScript code and try to tab through the map below.

Actually on the other website I extracted hCard microformats from the page as well and displayed the addresses on the map, but I was lazy and used jQuery. I thought it doesn’t look well here mixed with Patrick’s clean DOM scripting, but feel free to take it from the original website.