Topic: Cross-Domain Issue? Works in Firefox. Not in IE / Safari.

Hi, firstly let me thank you for a very useful, slick and good looking slide-show flash application.

I have set up my simpleviewer slideshow to pull images from Google's Picasa Web Albums. This works fine from Firefox. But none of the images/thumbs load in Safari (on Mac) or IE (windows). Firefox on both platforms does not seem to have a problem.

I suspect a cross-domain issue. But Google's servers (e.g. lh4.ggpht.com) all seem to have an appropriate crossdomain.xml file. And in addition, the fact that it works from Firefox seems to be confusing the crossdomain issue.

If you could, kindly take a look at: http://ix.cs.uoregon.edu/~anataraj/pics … PikePlace/

This is one such site that works fine from Firefox, but fails on Safari.

Any help in resolving / debugging this issue will be great. I'm not a web-services expert, but have spent sometime trying to debug this / read stuff online, before I'm posting on this forum. Looking forward very much to hearing from you.

Thank you in advance.

Re: Cross-Domain Issue? Works in Firefox. Not in IE / Safari.

The 5th image works in IE for me, but none of the rest do. Try adding <![CDATA[    ]]> to your captions for example <caption><![CDATA[Ready To Eat | 1/60sec f/4.0 100.0mm | Flash:None ISO:160 | 2009-Jun-30]]></caption>

Also you have a HTML error and warnings you can see here:
http://validator.w3.org/check?uri=http% … or%2F1.654

Mike Richards
SimpleViewer Support Team.


Re: Cross-Domain Issue? Works in Firefox. Not in IE / Safari.

Dear miker,

[EDIT: Want to clarify to readers that this is an issue with mashing-up simpleviewer and Picasa Web Albums (not the Picasa image editor software).]

Many thanks for looking into the issue and for trying it out with IE and reporting that one image was loaded. That pretty much ruled out cross-domain issues.

I fixed the errors/warnings that the validator had flagged. I also included the CDATA[] into the captions just as you had advised. Unfortunately none of those fixes worked.

I next tried to understand the difference between the HTTP requests made by Firefox (or its flash-plugin, not sure who exactly makes the actual HTTP request) and Safari. As I mentioned earlier the slideshow works fine on Firefox, but not on Safari (or IE).

On examining the requests as caught by Ethereal, I found one important difference. The Safari requests all had a "Referer" field whereas the Firefox requests did not have this field.

Using telnet I generated image requests to the Picasa backend web-storage servers. When the requests have the "Referer" field a "Not Found" error is returned. But when no such "Referer" field is given, the actual image is successfully returned.

This is apparently a way that Picasa disallows direct interaction with its photo store (it probably requires some other form of interaction through a feed-api).

This may be useful information for others, so I decided to post this long explanation here.

Now I must either try to supress Referer information somehow (not sure how as yet or even if it possible without proxying). Or I must try to work with the Picasa feed api somehow. If you can point me in the right direction for either approach that will be very useful. Do you know if simpleviewer has been used in this manner before with Picasa?

Many thanks for the assistance till date. And a good product you folks have.

Last edited by an (2009-09-12 21:42:39)


Re: Cross-Domain Issue? Works in Firefox. Not in IE / Safari.

Some more progress made in this regard. Looks like Picasa Web Album will accept requests even with a Referer http header field *if* the image request has a maximum-image size encoded in the image path.

For example, the image path:
http://lh6.ggpht.com/_EwBAQb67Bno/SlmM8 … 0709-1.jpg
Does *NOT* have a maximum size. But the same image can be accessed with a modified path (this time with a maximum size of 800 pixels, or s800) as follows:
http://lh6.ggpht.com/_EwBAQb67Bno/SlmM8 … 0709-1.jpg

The only difference between the two paths is that "s800/" is inserted into the second path.

This could be Picasa Web album's way of only serving smaller images (or resized versions of larger images) when requests come through external referrers.

So if all the image paths in the gallery.xml file have the size encoded (such as s800) just before the image file name, then the slideshow works from both Firefox and Safari (even though Safari adds the Referer http header field). I still need to check if it works on IE.

Changed slideshow:
http://ix.cs.uoregon.edu/~anataraj/pics … PikePlace/

Re: Cross-Domain Issue? Works in Firefox. Not in IE / Safari.

IE 8 is now working with the changes to the image path.

Mike Richards
SimpleViewer Support Team.