How to turn off xscreensaver automatically while watching Flash video

Background

There are 2 solutions that were determined for this particular problem. The 1st involved launching xscreensaver, and disabling it so that no screensaver is configured.

The 2nd method involved completely disabling the screensaver in X altogether, through the use of the xset command.

Solution #1

A solution with a narrow scope (by cipricus) is that of adding a fourth step to those included in the answer.

1. Install xscreensaver
2. Remove gnome-screensaver
3. Set Xscreensaver NOT to use any screensaver ('Disable screensaver')

4. Add xscreensaver in the startup programs list. The command to add is:

   xscreensaver -no-splash
   

This solution was suggested by the fact that this message appeared when starting xscreensaver before adding the fourth step:

Further instructions came from this source.

NOTE: To add a program to startup list in eOS, go to System Settings > Stertup Applications > Add

Solution #2

A solution with a wider scope by slm:

xset

Check to see what the xset setting is for screen blanking as well. You can check using this command:

$ xset q

We're specifically interested in this section of the output from the above command:

$ xset q
...
Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  600    cycle:  600
...

Disabling screensaver

You can change these settings like this:

$ xset s off
$ xset s noblank

Confirm by running xset q again:

$ xset q
...
Screen Saver:
  prefer blanking:  no    allow exposures:  yes
  timeout:  0    cycle:  600
...

DPMS

You might also need to disable power management as well, that's the DPMS settings in the xset q output:

$ xset q
...
DPMS (Energy Star):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Enabled
  Monitor is On
...

Disable it like so:

$ xset -dpms

Confirm:

$ xset q
...
DPMS (Energy Star):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Disabled
...

Re-enabling features

You can re-enable these features at any time with these commands

$ xset s blank       # blanking screensaver
$ xset s 600 600     # five minute interval
$ xset +dpms         # enable power management

Confirming changes:

$ xset q
...
Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  600    cycle:  600
...
...
DPMS (Energy Star):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Enabled
  Monitor is On
...

You could try the program I wrote for the very same purpose: https://github.com/grwlf/xscreensaver-run

Just build it and run

./xscreensaver-run /usr/libexec/xscreensaver/apple2 -text -program 'uname -a'

It works by creating a full-screen window and then calling the screensaver with correct -window-id <arg> argument.