Disable screensaver while watching flash videos

Use caffeine, there is absolutely no need to patch flash player, that is way too much work when you can just install caffeine. When you run caffeine it will be in your notification area, a little coffee cup, when you want to watch a video just click on the icon and go to 'disable screen saver'. I use this all the time when I watch videos on the net. When you are done you can just click on the icon again and go to 'enable screen saver'.

https://launchpad.net/~caffeine-developers/+archive/ppa

You'll have to patch the flash-player to send the appropriate signals, like Totem does. Unfortunately, most people have to use Adobe Flash, which is proprietary software.

But did you know that Totem supports watching videos from Youtube? It does deactivate the screensaver when you're playing stuff. You find it in the dropdown list that normally says playlist in the right-panel of Totem. Hope that helps. :)