I was aways setting Gnome Power Manager to stop the display from going to sleep or screensaver when I was going to watch movies. But it is annoying to launch
System -> Preferneces -> power management and repeat the setting everytime.
Fortunately, I found a Gnome panel applet which disable and enable screen auto-sleep as easy as one click. It’s
Inhibit Applet and is by default installed in Ubuntu.
Add the applet to panel
Right-click on top panel and click “Add to Panel…”, find out
Inhibit Applet and add it to the panel. Move it to an appropriate location.
The default icon on the picture means automatic sleep enabled.
When you’re going to stop the display going to sleep/screensaver, just single-click on the icon and it becomes:
Now, you can enjoy movies without a break.