<s>
A	O
re-parenting	B-Device
window	I-Device
manager	I-Device
is	O
an	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
window	B-Application
manager	I-Application
that	O
adopts	O
all	O
other	O
windows	O
.	O
</s>
<s>
In	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
every	O
window	O
has	O
a	O
parent	O
window	O
,	O
which	O
may	O
be	O
either	O
the	O
root	B-Device
window	I-Device
or	O
another	O
window	O
.	O
</s>
<s>
Windows	O
that	O
are	O
children	O
of	O
the	O
root	B-Device
window	I-Device
are	O
called	O
top-level	O
windows	O
.	O
</s>
<s>
When	O
a	O
top-level	O
window	O
is	O
created	O
,	O
a	O
re-parenting	B-Device
window	I-Device
manager	I-Device
changes	O
that	O
window	O
's	O
parent	O
to	O
be	O
a	O
second	O
new	O
window	O
created	O
by	O
the	O
window	B-Application
manager	I-Application
for	O
this	O
purpose	O
.	O
</s>
<s>
This	O
allows	O
the	O
window	B-Application
manager	I-Application
to	O
decorate	O
the	O
windows	O
with	O
window	O
decorations	O
and	O
title	O
bars	O
as	O
well	O
as	O
allows	O
advanced	O
control	O
over	O
the	O
windows	O
 '	O
operation	O
required	O
,	O
for	O
example	O
,	O
by	O
virtual	B-Application
window	I-Application
managers	I-Application
.	O
</s>
<s>
Technically	O
,	O
a	O
reparenting	B-Device
window	I-Device
manager	I-Device
registers	O
with	O
the	O
X	B-Operating_System
server	I-Operating_System
to	O
be	O
notified	O
when	O
a	O
top-level	O
window	O
is	O
mapped	O
(	O
attempts	O
to	O
become	O
visible	O
)	O
.	O
</s>
<s>
When	O
such	O
an	O
event	B-Application
is	O
generated	O
,	O
the	O
window	B-Application
manager	I-Application
creates	O
a	O
frame	O
window	O
,	O
and	O
in	O
most	O
cases	O
also	O
a	O
title	O
bar	O
window	O
.	O
</s>
<s>
Virtually	O
all	O
modern	O
window	B-Application
managers	I-Application
are	O
re-parenting	O
,	O
although	O
earlier	O
window	B-Application
managers	I-Application
,	O
such	O
as	O
the	O
uwm	B-Device
window	B-Application
manager	I-Application
,	O
were	O
not	O
.	O
</s>
<s>
Exceptions	O
to	O
that	O
rule	O
are	O
dwm	B-Language
,	O
cwm	B-Application
,	O
PLWM	O
,	O
ratpoison	B-Language
and	O
xmonad	B-Device
,	O
due	O
to	O
a	O
lack	O
of	O
any	O
typical	O
window	O
decorations	O
used	O
by	O
these	O
window	B-Application
managers	I-Application
,	O
and	O
also	O
Compiz	B-Language
which	O
drew	O
the	O
decorations	O
separately	O
up	O
until	O
version	O
0.9.0	O
,	O
where	O
it	O
became	O
a	O
re-parenting	B-Device
window	I-Device
manager	I-Device
to	O
allow	O
it	O
to	O
run	O
in	O
a	O
non-composited	O
mode	O
.	O
</s>
<s>
Even	O
though	O
stumpwm	B-Language
does	O
not	O
draw	O
typical	O
window	O
decorations	O
,	O
it	O
reparents	O
windows	O
in	O
a	O
parent	O
frame	O
to	O
display	O
outlines	O
.	O
</s>
