inhibit the screensaver when playing a video

Yes, that's a nice feature, but it would require better integration of gnome with browser plugins.
Wishlist.

Is this also not a problem with gnome-screensaver and gnome-power manager?

This is a bug in the upstream flashplayer, which doesn't inhibit gnome-screensaver while it's running.

I've developed a patch that would would work around it to some extent. For want of somewhere better to put it, I've proposed merging into Ubufox:

https://code.launchpad.net/~andrew-bugs-launchpad-net/ubufox/flashsaver/+merge/6768

The patch is far from perfect, and I'm not that sure of my merging etiquette, so please e-mail me if you have suggestions. I'm not a maintainer of any related software, so please don't hassle (for example) the Ubufox guy(s) about this.

There is also an upstream feature request at Adobe's tracker:

https://bugs.adobe.com/jira/browse/FP-997

Maybe this could be added to the 100 paper-cuts program - in case it is still in place....

just figured out that this also happens with .ogv videos in the browser. try http://www.tagesschau.de/ . choose "letzte sendung" and klick "ogg theora video"-download. whe watching this inside the browser (firefox) the screen saver comes up regularly...

can anybody confirm this?

This causes a more serious problem when the computer is left playing a fullscreen flash video (example: youtube) and then walk away. When you return to yourcomputer later, the video is still visible on-screen but the computer seems unresponsive. The mouse cursor moves but clicking doesn't seem to do anything. The keyboard doesn't initially appear to work either.

The problem seems to be that the screensaver password dialog popped up underneath the fullscreen video and was not visible.

I was able to Ctrl-Alt-F1 and login then:

# ps aux | grep "flash"
# kill [pid]
Ctrl-Alt-F7

Then you see the password dialog!!

right. and imagine you were just watching a porn!