Hmm. One of our salesmen called up today with an interesting problem. We’d published some PowerPoint presentations as slide shows (.pps files). If you open one of these, it should just launch PowerPoint into the presentation. However, he was opening them from our website and they were opening as a normal PowerPoint (.ppt) file. That is they were opening ready for editing, not in presentation mode. Weird.
I remembered having seen this before, but a bit of poking around showed that my fix was still in place. Curious. When I clicked on the link to the presentation I got the ‘Download or Open’ dialog thingy:
First off I noticed that the file extension was .pps – good. I tried opening the file – and it opened it as if it were a .ppt file. Weird. So then I tried the other option – I saved it to my local machine and opened it locally. This time it opened correctly – it opened as a slideshow.
Hmm. So, they’re the same file, but something different is happening when they open. I wondered if it was to do with the HTTP headers, but the same difference occurs when the file is being served with the application/vnd.ms-pps or just text/html (we run MCMS 2002 on a IIS webserver but publish as static content to an Apache server. They serve the file as different mime types, but have the same result – Open opens the file for editing and Save and open shows the slideshow).
Next up, I tried the same experiment using Firefox. If you choose to Open the file rather than save it, it opens the slideshow – correctly! And if you save it, well, it saves the .pps file which, again, opens correctly.
|
text/html mime-type |
application/vnd.ms-pps mimetype |
|
“Open” |
“Save” and open |
“Open” |
“Save” and open |
| IE7 |
WRONG |
OK |
WRONG |
OK |
| Firefox |
OK |
OK |
OK |
OK |
So it looks like Internet Explorer will not open a .pps file as a slideshow irrespective of the mime type sent by the server and the .pps extension (and it’s file association in windows). However, if you save the file locally, it will. Weird.
The only thing that I can think is that this is some sort of security feature, but it’s a bit odd – after all, shouldn’t Firefox do this then?
Andy Burns' Blog 