<s>
screensavers	B-General_Concept
for	O
Unix	B-Operating_System
,	O
macOS	B-Application
,	O
iOS	B-Application
and	O
Android	B-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
It	O
was	O
created	O
by	O
Jamie	B-Operating_System
Zawinski	I-Operating_System
in	O
1992	O
and	O
is	O
still	O
maintained	O
by	O
him	O
,	O
with	O
new	O
releases	O
coming	O
out	O
several	O
times	O
a	O
year	O
.	O
</s>
<s>
The	O
free	B-Application
software	I-Application
and	O
open-source	B-Application
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
running	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
(	O
such	O
as	O
Linux	B-Application
and	O
FreeBSD	B-Operating_System
)	O
use	O
XScreenSaver	B-General_Concept
almost	O
exclusively	O
.	O
</s>
<s>
On	O
Macintosh	B-Application
systems	I-Application
,	O
XScreenSaver	B-General_Concept
works	O
with	O
the	O
built-in	O
macOS	B-Application
screen	B-General_Concept
saver	I-General_Concept
.	O
</s>
<s>
On	O
iOS	B-Application
systems	O
,	O
XScreenSaver	B-General_Concept
is	O
a	O
stand-alone	O
app	O
that	O
can	O
run	O
any	O
of	O
the	O
hacks	O
full-screen	O
.	O
</s>
<s>
On	O
Android	B-Application
systems	I-Application
,	O
the	O
XScreenSaver	B-General_Concept
display	O
modes	O
work	O
either	O
as	O
normal	O
screen	B-General_Concept
savers	I-General_Concept
(	O
which	O
Android	B-Application
sometimes	O
refers	O
to	O
as	O
"	O
Daydreams	O
"	O
)	O
or	O
as	O
live	O
wallpapers	O
.	O
</s>
<s>
There	O
is	O
no	O
official	O
version	O
for	O
Microsoft	B-Application
Windows	I-Application
,	O
and	O
the	O
developer	O
discourages	O
anyone	O
from	O
porting	O
it	O
.	O
</s>
<s>
and	O
says	O
that	O
,	O
as	O
one	O
of	O
the	O
original	O
authors	O
of	O
Netscape	B-Protocol
Navigator	I-Protocol
,	O
he	O
holds	O
a	O
"	O
personal	O
grudge	O
"	O
against	O
Microsoft	O
because	O
of	O
its	O
behavior	O
during	O
the	O
First	O
Browser	O
War	O
.	O
</s>
<s>
The	O
XScreenSaver	B-General_Concept
daemon	B-Operating_System
is	O
responsible	O
for	O
detecting	O
idle-ness	O
,	O
blanking	O
and	O
locking	O
the	O
screen	O
,	O
and	O
launching	O
the	O
display	O
modes	O
.	O
</s>
<s>
It	O
also	O
means	O
that	O
a	O
third-party	O
screen	B-General_Concept
saver	I-General_Concept
can	O
be	O
written	O
in	O
any	O
language	O
or	O
with	O
any	O
graphics	O
library	O
,	O
so	O
long	O
as	O
it	O
is	O
capable	O
of	O
rendering	O
onto	O
an	O
externally	O
provided	O
window	O
.	O
</s>
<s>
For	O
historical	O
and	O
portability	O
reasons	O
,	O
the	O
included	O
hacks	O
are	O
all	O
written	O
in	O
ANSI	O
C	O
.	O
About	O
half	O
of	O
them	O
use	O
the	O
X11	B-Operating_System
API	O
,	O
and	O
about	O
half	O
use	O
the	O
OpenGL	B-Application
1.3	O
API	O
.	O
</s>
<s>
Rather	O
than	O
forking	O
the	O
code-base	O
and	O
re-writing	O
the	O
hacks	O
to	O
target	O
different	O
platforms	O
,	O
XScreenSaver	B-General_Concept
contains	O
a	O
number	O
of	O
compatibility	O
layers	O
.	O
</s>
<s>
To	O
allow	O
the	O
X11-based	O
hacks	O
to	O
run	O
natively	O
on	O
macOS	B-Application
and	O
iOS	B-Application
,	O
XScreenSaver	B-General_Concept
contains	O
a	O
complete	O
implementation	O
of	O
the	O
X11	B-Operating_System
API	O
built	O
on	O
top	O
of	O
Cocoa	B-Operating_System
(	O
"	O
jwxyz	O
"	O
)	O
.	O
</s>
<s>
To	O
allow	O
the	O
OpenGL	B-Application
1.3-based	O
hacks	O
to	O
run	O
natively	O
on	O
iOS	B-Application
and	O
Android	B-Application
systems	I-Application
,	O
which	O
only	O
support	O
OpenGL	B-Application
ES	I-Application
,	O
XScreenSaver	B-General_Concept
contains	O
an	O
implementation	O
of	O
the	O
OpenGL	B-Application
1.3	O
API	O
built	O
in	O
top	O
of	O
OpenGL	B-Application
ES	I-Application
1.0	O
(	O
"	O
jwzgles	O
"	O
)	O
.	O
</s>
<s>
And	O
to	O
allow	O
the	O
X11-based	O
hacks	O
to	O
run	O
natively	O
on	O
iOS	B-Application
and	O
Android	B-Application
,	O
XScreenSaver	B-General_Concept
also	O
contains	O
an	O
implementation	O
of	O
the	O
X11	B-Operating_System
API	O
in	O
terms	O
of	O
OpenGL	B-Application
ES	I-Application
1.0	O
.	O
</s>
<s>
In	O
addition	O
to	O
sandboxing	O
the	O
display	O
modes	O
,	O
the	O
XScreenSaver	B-General_Concept
daemon	B-Operating_System
links	O
with	O
as	O
few	O
libraries	O
as	O
possible	O
.	O
</s>
<s>
In	O
particular	O
,	O
it	O
does	O
not	O
link	O
against	O
GUI	O
frameworks	O
like	O
GTK	B-Application
or	O
KDE	B-Application
,	O
but	O
uses	O
only	O
raw	O
Xlib	B-Language
for	O
rendering	O
the	O
unlock	O
dialog	O
box	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
some	O
Linux	B-Application
distributions	I-Application
have	O
begun	O
using	O
the	O
gnome-screensaver	B-Language
or	O
kscreensaver	B-Application
screen-blanking	O
frameworks	O
by	O
default	O
instead	O
of	O
the	O
framework	O
included	O
with	O
XScreenSaver	B-General_Concept
.	O
</s>
<s>
In	O
2011	O
,	O
gnome-screensaver	B-Language
was	O
forked	O
as	O
both	O
mate-screensaver	B-Language
and	O
cinnamon-screensaver	B-Language
.	O
</s>
<s>
Earlier	O
versions	O
of	O
these	O
frameworks	O
still	O
depended	O
upon	O
the	O
XScreenSaver	B-General_Concept
collection	O
of	O
screen	B-General_Concept
savers	I-General_Concept
,	O
which	O
is	O
over	O
90%	O
of	O
the	O
package	O
.	O
</s>
<s>
However	O
,	O
in	O
2011	O
,	O
gnome-screensaver	B-Language
version	O
3	O
dropped	O
support	O
for	O
screensavers	B-General_Concept
completely	O
,	O
supporting	O
only	O
simple	O
screen	O
blanking	O
,	O
</s>
<s>
and	O
as	O
of	O
2018	O
,	O
Linux	B-Application
Mint	I-Application
's	O
cinnamon-screensaver	B-Language
4.0.8	O
no	O
longer	O
supports	O
the	O
XScreenSaver	B-General_Concept
hacks	O
.	O
</s>
<s>
Those	O
Linux	B-Application
distributions	I-Application
that	O
have	O
replaced	O
XScreenSaver	B-General_Concept
with	O
other	O
screen-locking	O
frameworks	O
have	O
suffered	O
notable	O
security	O
problems	O
.	O
</s>
<s>
In	O
2004	O
,	O
Zawinski	B-Operating_System
had	O
written	O
about	O
the	O
architectural	O
decisions	O
made	O
in	O
XScreenSaver	B-General_Concept
with	O
the	O
goal	O
of	O
avoiding	O
this	O
very	O
class	O
of	O
bug	O
,	O
</s>
<s>
leading	O
him	O
to	O
quip	O
in	O
2015	O
,	O
"	O
If	O
you	O
are	O
not	O
running	O
XScreenSaver	B-General_Concept
on	O
Linux	B-Application
,	O
then	O
it	O
is	O
safe	O
to	O
assume	O
that	O
your	O
screen	O
does	O
not	O
lock.	O
"	O
</s>
<s>
Atlantis	O
an	O
OpenGL	B-Application
animation	O
showing	O
whales	O
and	O
dolphins	O
.	O
</s>
<s>
BSOD	O
shows	O
fake	O
fatal	O
screen	O
of	O
death	O
variants	O
from	O
many	O
computer	O
systems	O
,	O
including	O
Microsoft	B-Application
Windows	I-Application
Blue	O
Screen	O
of	O
Death	O
,	O
a	O
Linux	B-Operating_System
kernel	I-Operating_System
panic	I-Operating_System
,	O
a	O
Darwin	B-Operating_System
crash	O
,	O
an	O
Amiga	B-Device
"	O
Guru	B-Device
Meditation	I-Device
"	O
error	O
,	O
a	O
sad	O
Mac	B-Device
,	O
and	O
more	O
.	O
</s>
<s>
Apple2	O
simulates	O
an	O
Apple	B-Device
II	I-Device
computer	O
,	O
showing	O
a	O
user	O
entering	O
a	O
simple	O
BASIC	O
program	O
and	O
running	O
it	O
.	O
</s>
<s>
When	O
run	O
from	O
the	O
command-line	O
,	O
it	O
is	O
a	O
fully	O
functional	O
terminal	B-Application
emulator	I-Application
(	O
as	O
is	O
Phosphor	O
.	O
)	O
</s>
<s>
Flying	B-Operating_System
toasters	I-Operating_System
3D	O
toasters	O
fly	O
around	O
,	O
inspired	O
by	O
the	O
classic	O
After	B-Operating_System
Dark	I-Operating_System
screensaver	B-General_Concept
.	O
</s>
<s>
Gears	O
an	O
OpenGL	B-Application
animation	O
of	O
inter-meshing	O
gears	O
and	O
planetary	O
gears	O
.	O
</s>
<s>
GLMatrix	O
an	O
OpenGL	B-Application
animation	O
similar	O
to	O
the	O
"	O
digital	O
rain	O
"	O
title	O
sequence	O
seen	O
in	O
the	O
Matrix	O
trilogy	O
.	O
</s>
<s>
Molecule	O
an	O
OpenGL	B-Application
animation	O
showing	O
space-filling	O
or	O
ball-and-stick	O
models	O
of	O
a	O
series	O
of	O
common	O
drugs	O
and	O
other	O
molecules	O
,	O
of	O
which	O
thirty-eight	O
(	O
38	O
)	O
are	O
built	O
in	O
.	O
</s>
<s>
Sproingies	O
an	O
animation	O
in	O
the	O
style	O
of	O
the	O
video	O
game	O
Q*bert	B-Application
.	O
</s>
<s>
XAnalogTV	O
simulates	O
an	O
analog	O
cathode	B-Device
ray	I-Device
tube	I-Device
television	O
set	O
,	O
including	O
visual	O
artifacts	O
and	O
reception	O
issues	O
.	O
</s>
<s>
Boing	O
based	O
on	O
the	O
1984	O
program	O
regarded	O
as	O
the	O
first	O
Amiga	B-Device
demo	I-Device
ever	O
,	O
showing	O
the	O
bouncing	O
red	O
and	O
white	O
ball	O
.	O
</s>
<s>
Moire2	O
moving	O
interference	O
circles	O
similar	O
to	O
those	O
common	O
in	O
older	O
Amiga	B-Device
demos	I-Device
.	O
</s>
<s>
ShadeBobs	O
another	O
effect	O
common	O
in	O
older	O
Amiga	B-Device
demos	I-Device
.	O
</s>
