<s>
An	O
X	B-Application
window	I-Application
manager	I-Application
is	O
a	O
window	B-Application
manager	I-Application
that	O
runs	O
on	O
top	O
of	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
a	O
windowing	B-Application
system	I-Application
mainly	O
used	O
on	O
Unix-like	B-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
Unlike	O
MacOS	B-Application
Classic	I-Application
,	O
macOS	B-Application
,	O
and	O
Microsoft	B-Application
Windows	I-Application
platforms	O
(	O
excepting	O
Microsoft	B-Application
Windows	I-Application
explorer.exe	B-Protocol
shell	B-Application
replacements	I-Application
)	O
,	O
which	O
have	O
historically	O
provided	O
a	O
vendor-controlled	O
,	O
fixed	O
set	O
of	O
ways	O
to	O
control	O
how	O
windows	O
and	O
panes	O
display	O
on	O
a	O
screen	B-Device
,	O
and	O
how	O
the	O
user	O
may	O
interact	O
with	O
them	O
,	O
window	B-Application
management	I-Application
for	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
was	O
deliberately	O
kept	O
separate	O
from	O
the	O
software	O
providing	O
the	O
graphical	O
display	O
.	O
</s>
<s>
The	O
user	O
can	O
choose	O
between	O
various	O
third-party	O
window	B-Application
managers	I-Application
,	O
which	O
differ	O
from	O
one	O
another	O
in	O
several	O
ways	O
,	O
including	O
:	O
</s>
<s>
When	O
a	O
window	B-Application
manager	I-Application
is	O
running	O
,	O
some	O
kinds	O
of	O
interaction	O
between	O
the	O
X	B-Protocol
server	I-Protocol
and	O
its	O
clients	O
are	O
redirected	O
through	O
the	O
window	B-Application
manager	I-Application
.	O
</s>
<s>
In	O
particular	O
,	O
whenever	O
an	O
attempt	O
to	O
show	O
a	O
new	O
window	O
is	O
made	O
,	O
this	O
request	O
is	O
redirected	O
to	O
the	O
window	B-Application
manager	I-Application
,	O
which	O
decides	O
the	O
initial	O
position	O
of	O
the	O
window	O
.	O
</s>
<s>
Additionally	O
,	O
most	O
modern	O
window	B-Application
managers	I-Application
are	O
reparenting	B-Device
,	O
which	O
usually	O
leads	O
to	O
a	O
banner	O
being	O
placed	O
at	O
the	O
top	O
of	O
the	O
window	O
and	O
a	O
decorative	O
frame	O
being	O
drawn	O
around	O
the	O
window	O
.	O
</s>
<s>
These	O
two	O
elements	O
are	O
controlled	O
by	O
the	O
window	B-Application
manager	I-Application
rather	O
than	O
the	O
program	O
.	O
</s>
<s>
Therefore	O
,	O
when	O
the	O
user	O
clicks	O
or	O
drags	O
these	O
elements	O
,	O
it	O
is	O
the	O
window	B-Application
manager	I-Application
that	O
takes	O
the	O
appropriate	O
actions	O
(	O
such	O
as	O
moving	O
or	O
resizing	O
the	O
window	O
)	O
.	O
</s>
<s>
Window	B-Application
managers	I-Application
are	O
also	O
responsible	O
for	O
icons	O
.	O
</s>
<s>
Indeed	O
,	O
icons	O
do	O
not	O
exist	O
at	O
the	O
X	B-Device
Window	I-Device
System	I-Device
core	I-Device
protocol	I-Device
level	O
.	O
</s>
<s>
When	O
the	O
user	O
requests	O
a	O
window	O
to	O
be	O
iconified	O
,	O
the	O
window	B-Application
manager	I-Application
unmaps	O
it	O
(	O
makes	O
it	O
non-visible	O
)	O
and	O
takes	O
the	O
appropriate	O
actions	O
to	O
show	O
an	O
icon	O
in	O
its	O
place	O
.	O
</s>
<s>
Most	O
modern	O
window	B-Application
managers	I-Application
do	O
not	O
literally	O
show	O
icons	O
to	O
represent	O
iconified	O
windows	O
anymore	O
.	O
</s>
<s>
While	O
the	O
main	O
aim	O
of	O
a	O
window	B-Application
manager	I-Application
is	O
to	O
manage	O
the	O
windows	O
,	O
many	O
window	B-Application
managers	I-Application
have	O
additional	O
features	O
such	O
as	O
handling	O
mouse	O
clicks	O
in	O
the	O
root	B-Device
window	I-Device
,	O
presenting	O
panes	O
and	O
other	O
visual	O
elements	O
,	O
handling	O
some	O
keystrokes	O
(	O
e.g.	O
,	O
Alt-F4	O
may	O
close	O
a	O
window	O
)	O
,	O
deciding	O
which	O
application	O
to	O
run	O
at	O
start-up	O
,	O
etc	O
.	O
</s>
<s>
Standardized	O
protocols	O
exist	O
to	O
allow	O
normal	O
clients	O
to	O
communicate	O
with	O
the	O
window	B-Application
manager	I-Application
.	O
</s>
<s>
The	O
original	O
one	O
is	O
Inter-Client	B-Operating_System
Communication	I-Operating_System
Conventions	I-Operating_System
Manual	I-Operating_System
(	O
ICCCM	B-Operating_System
)	O
but	O
this	O
has	O
been	O
superseded	O
by	O
the	O
Extended	B-Application
Window	I-Application
Manager	I-Application
Hints	I-Application
(	O
EWMH	B-Application
)	O
.	O
</s>
<s>
These	O
protocols	O
allow	O
clients	O
to	O
request	O
titles	O
for	O
windows	O
and	O
icons	O
,	O
check	O
if	O
a	O
window	O
is	O
iconified	O
which	O
might	O
be	O
docked	O
or	O
minimized	O
,	O
and	O
possibly	O
customize	O
windows	O
decorations	O
,	O
what	O
virtual	B-Application
desktop	I-Application
the	O
window	O
occupies	O
.	O
</s>
<s>
Additional	O
information	O
from	O
the	O
window	B-Application
manager	I-Application
is	O
available	O
through	O
the	O
core	O
protocol	O
including	O
the	O
visibility	O
of	O
windows	O
such	O
as	O
if	O
a	O
window	O
is	O
hidden	O
on	O
a	O
different	O
Virtual	B-Application
desktop	I-Application
,	O
and	O
figuring	O
out	O
the	O
adjustments	O
for	O
the	O
window	B-Application
manager	I-Application
frames	O
.	O
</s>
<s>
A	O
stacking	O
window	B-Application
manager	I-Application
renders	O
the	O
windows	O
one-by-one	O
onto	O
the	O
screen	B-Device
at	O
specific	O
co-ordinates	O
.	O
</s>
<s>
In	O
contrast	O
to	O
compositing	O
window	B-Application
managers	I-Application
(	O
see	O
below	O
)	O
,	O
the	O
lack	O
of	O
separate	O
off-screen	B-Algorithm
buffers	I-Algorithm
can	O
mean	O
increased	O
efficiency	O
,	O
but	O
effects	O
such	O
as	O
translucency	O
are	O
not	O
possible	O
.	O
</s>
<s>
Stacking	O
window	B-Application
managers	I-Application
include	O
Amiwm	B-Device
,	O
Blackbox	B-Device
,	O
Enlightenment	B-Application
,	O
Fluxbox	B-Language
,	O
FLWM	B-Language
,	O
FVWM	B-Device
,	O
IceWM	B-Language
,	O
MWM	B-Device
,	O
Openbox	B-Language
and	O
Window	B-Application
Maker	I-Application
.	O
</s>
<s>
A	O
tiling	B-Algorithm
window	B-Application
manager	I-Application
is	O
a	O
window	B-Application
manager	I-Application
with	O
an	O
organization	O
of	O
the	O
screen	B-Device
into	O
mutually	O
non-overlapping	O
frames	O
(	O
hence	O
the	O
name	O
tiling	B-Algorithm
)	O
,	O
as	O
opposed	O
to	O
the	O
traditional	O
approach	O
of	O
coordinate-based	O
stacking	O
of	O
objects	O
(	O
windows	O
)	O
that	O
tries	O
to	O
emulate	O
the	O
desk	O
paradigm	O
.	O
</s>
<s>
Tiling	B-Algorithm
window	B-Application
managers	I-Application
include	O
awesome	B-Language
,	O
dwm	B-Language
,	O
ion	B-Application
,	O
larswm	O
,	O
ratpoison	B-Language
,	O
Stumpwm	B-Language
,	O
wmii	B-Language
,	O
i3	B-Language
,	O
xmonad	B-Device
,	O
and	O
XWEM	O
.	O
</s>
<s>
A	O
compositing	O
window	B-Application
manager	I-Application
may	O
appear	O
to	O
the	O
user	O
similar	O
to	O
a	O
stacking	O
window	B-Application
manager	I-Application
.	O
</s>
<s>
However	O
,	O
the	O
individual	O
windows	O
are	O
first	O
rendered	O
in	O
individual	O
buffers	O
,	O
and	O
then	O
their	O
images	O
are	O
composited	O
onto	O
the	O
screen	B-Algorithm
buffer	I-Algorithm
;	O
this	O
two-step	O
process	O
means	O
that	O
visual	O
effects	O
(	O
such	O
as	O
shadows	O
,	O
translucency	O
)	O
can	O
be	O
applied	O
.	O
</s>
<s>
It	O
also	O
means	O
that	O
compositing	O
window	B-Application
managers	I-Application
are	O
inherently	O
more	O
resource-hungry	O
than	O
an	O
equivalently-powerful	O
stacking	O
window	B-Application
manager	I-Application
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
some	O
window	B-Application
managers	I-Application
for	O
X	B-Operating_System
do	O
not	O
support	O
compositing	O
by	O
default	O
,	O
such	O
as	O
Openbox	B-Language
.	O
</s>
<s>
Historically	O
,	O
the	O
Amiga	O
in	O
1985	O
,	O
OSX	O
in	O
2001	O
,	O
Java	O
Looking	O
Glass	O
in	O
2003	O
,	O
and	O
the	O
Windows	O
Longhorn	O
demo	O
in	O
2003	O
(	O
delayed	O
until	O
Vista	O
in	O
2007	O
)	O
preceded	O
compositing	O
efforts	O
under	O
X11	B-Operating_System
.	O
</s>
<s>
Compositing	O
window	B-Application
managers	I-Application
for	O
X	B-Operating_System
include	O
:	O
</s>
<s>
GNOME	B-Application
's	O
Mutter	B-Language
née	O
Metacity	B-Language
(	O
first	O
dev-branch	O
compositor	O
in	O
2.7	O
or	O
2.8	O
of	O
2004	O
—	O
original	O
stable-branch	O
compositor	O
since	O
2.14	O
in	O
2005	O
or	O
2006	O
—	O
current	O
compositor	O
architecture	O
since	O
2.22	O
in	O
2008	O
—	O
Metacity+Clutter	O
begat	O
Mutter	B-Language
in	O
2011	O
)	O
,	O
</s>
<s>
Xfce	B-Language
's	O
Xfwm	B-Device
(	O
since	O
4.2	O
of	O
2004	O
or	O
2005	O
)	O
,	O
</s>
<s>
KDE	B-Application
's	O
KWin	B-Language
(	O
since	O
4.0	O
of	O
2008	O
)	O
.	O
</s>
<s>
Compositing	O
support	O
can	O
be	O
added	O
to	O
non-compositing	O
window	B-Application
managers	I-Application
,	O
through	O
the	O
use	O
of	O
compositors	O
such	O
as	O
compton	O
.	O
</s>
<s>
A	O
virtual	B-Application
window	I-Application
manager	I-Application
is	O
a	O
window	B-Application
manager	I-Application
that	O
uses	O
virtual	B-Application
screens	I-Application
,	O
whose	O
resolution	O
can	O
be	O
higher	O
than	O
the	O
resolution	O
of	O
one	O
's	O
monitor/display	O
adapter	O
thus	O
resembling	O
a	O
two	O
dimensional	O
virtual	B-Application
desktop	I-Application
with	O
its	O
viewport	O
.	O
</s>
<s>
A	O
number	O
of	O
virtual	B-Application
window	I-Application
managers	I-Application
have	O
been	O
made	O
,	O
including	O
FVWM	B-Device
,	O
Tvtwm	B-Device
,	O
HaZe	B-Device
and	O
others	O
.	O
</s>
<s>
Some	O
window	B-Application
managers	I-Application
are	O
extensible	O
,	O
or	O
programmable	O
,	O
by	O
user	O
scripts	O
.	O
</s>
<s>
In	O
these	O
window	B-Application
managers	I-Application
,	O
users	O
can	O
define	O
new	O
actions	O
or	O
override	O
the	O
default	O
,	O
or	O
reactions	O
to	O
various	O
events	O
,	O
like	O
window	O
size	O
and	O
position	O
changes	O
,	O
window	O
creation	O
and	O
deletion	O
,	O
key	O
and	O
mouse	O
input	O
,	O
timer	O
,	O
etc	O
.	O
</s>
<s>
Some	O
examples	O
of	O
such	O
window	B-Application
managers	I-Application
and	O
the	O
used	O
languages	O
are	O
:	O
</s>
